CHAPTER B2
LUMBER: USE IN CONSTRUCTION
This is the most technical chapter in the entire
course. But don’t let that scare you. Look at it as
a challenge. Every time you acquire more
knowledge it will help you do your job better and
you become more valuable. The more things
you can do that others can’t, the more likely you
will satisfy your customers and keep them
coming back.
One group of customers you want to satisfy are
those building or remodelling homes. Their
business represents major building materials
purchases. This customer can be an individual
homeowner, or a builder who builds one to ten
homes a year, or a builder who builds or
remodels many homes. These people are often
looking for technical advice, such as what size
floor joists to use, built-up beam size, window
header or lintel size, etc.
Sometimes this information is provided and all
the customer needs is someone with a little
understanding of design principles.
A caution right here. Never design structural
members unless you are a qualified engineer. It
is foolish to risk the liability associated with
guessing at structural sizes. If you don’t know
what size, species, spacing, etc., is required, do
not offer a guess. Refer the problem to a
qualified engineer.
You can successfully recommend structural
member sizes from tables that are provided by
building codes, associations, or other qualified
agencies if you know how to read them.
That’s part of what this chapter is about.
Reading tables, then practicing them. You’ll also
get a basic background in design considerations
to go along with your “table reading” abilities.
You also will read about quantities for ordering
lumber, calculating board feet and coverage
tables that help you in estimating.
This is more of a reference chapter than a
learning chapter. There is material you’ll
probably use over and over if you work with
building materials used in homes.
This chapter’s primary purpose is to help you
learn to read span tables. The tables in this
chapter are valid, but be reminded that codes
change and the tables shown here may not be
appropriate for all regions. You must locate and
obtain current tables that are used in your local
area.
When you obtain tables from your local or
provincial building code office you will find them
similar to those in this chapter, in which case
you should have no trouble understanding them.
The tables in this chapter are meant to be
accurate and useful, but CRHA and the
author assume no responsibility for any
injury, loss, or damage however caused,
arising from use of any table or information
provided in this course.
CHAPTER OVERVIEW
This chapter is broken into a number of sections
to allow you to develop an understanding of the
basis of Canadian span tables and to develop
your ability to read span tables effectively. The
sections that follow include:
1. Background to Canadian code
requirements.
2. An overview of the wood material design
strength requirements.
3. An overview of the loads used in
designing various structural members.
4. Span tables for a number of end uses
such as floor, ceiling and roof joists, roof
rafters, built-up floor beams and headers
over openings, etc.
To be able to read span tables effectively there
are three background pieces of information that
need be considered.
1. The strength of the material.
2. The loads that are going to be applied to
the material.
3. The construction details that are to be
used.
Typically, the solution is not identifying any one
of the above and then simply selecting the size
of member that you are able to use, but
frequently involves a solution where you
consider two or three options, then select the
best solution for your customer. For example, a
2x8 of a grade that is not commonly stocked
might provide the span that your customer
wants. However, to do this you would have to
make a special order which extends delivery
time and likely increases cost. It is likely better
for you to recommend a larger size of a grade
that you have in stock.
How do you find the span table criteria? There
are several sources such as the various grading
agencies and regional lumber manufacturing
associations and the national association,
Canadian Wood Council. However, the building
criteria published by all of these agencies are
based on requirements contained in Part 9,
Housing and Small Buildings of the National
Building Code of Canada (NBCC). The NBCC
is generally adopted by the various jurisdictions
throughout Canada. However, be aware that
some jurisdictions deviate from NBCC. You
should be aware that and not all jurisdictions
adopt the “latest” edition of NBCC in a timely
manner.
BACKGROUND TO CANADIAN
CODE REQUIREMENTS
An effort has been made to standardize building
codes across Canada so that builders don’t
have to build differently every time they cross
into a new government jurisdiction. Changing
building methods creates additional costs and
confusion.
The NBCC has evolved as the model Canadian
building code. That is, a code that has been well
thought out and put together and is available for
provinces or local governments to “adopt” so
they don’t have to create their own. (We’re not
including mechanical, plumbing, or electrical
codes).
This building code (and others for mechanical,
plumbing and electrical) is prepared under the
rules and procedures of the Canadian
Commission on Building and Fire Codes. The
overall code consists of nine parts and includes
two parts that directly affect the span tables that
you will be using – Part 4 “Structural Design”
and Part 9, “Housing and Small Buildings.” Part
4 identifies the loads that are to be used in the
design process and also specifies the standards
that provide the design requirements for the
structural materials. For example, the design
basis for buildings and structural members made
of wood shall conform to CSA O86.1,
“Engineering Design in Wood (Limit States
Design).” Part 9 identifies the criteria that are
relevant to housing and small buildings.
As the NBCC is the Canadian model code it best
fits our needs for this course. For more complete
information and information on how to obtain the
entire “code book” applicable in your
area/jurisdiction contact your local agency
responsible for issuing “building” permits.
More comments on the NBCC and building
codes in general. The formal requirements found
in the NBCC (and related material specific
standards) are specified using SI metric
terminology. Where construction practices use
the Canadian Imperial measurement system,
conversions need to be made. This means that
some of the converted values “look” funny (e.g.
a 2.0 kPa snow load is equivalent to 41.8 psf.).
In addition, the requirements of Canadian
building codes are developed on a basis that
differs from that of other countries. Span tables
developed for use in Canada differ from span
tables developed for use in the US, even though
the same species and grade of Canadian lumber
is going to be used.
One additional caution. Many areas, particularly
rural areas, may not be under any building code.
Good building practice would usually dictate that
you want to construct homes with at least the
minimums found in the codes. So even if you
don’t have to follow a building code, it’s a good
idea to use it for reference.
With the above as reference, let us continue by
looking at the terms you’ll be seeing in the
various tables. For the most part it is not
necessary to understand all the terms. Usually
you could go right to the appropriate table and
find what you need. You’ll communicate with
your customers better about required structural
member sizes, however, if you have a basic
understanding of these terms. So give it a shot.
FLOOR JOISTS AND TRUSSED ROOF
Structural members, of course, carry the weight
of the building materials and building contents
ultimately to the ground. So a series of bearing
walls, joists, rafters, (or trusses) headers,
girders, etc., is designed to do that.
The amount of weight that lumber can carry is
dependent on its strength. The strength of
lumber varies with species, as well as within
species. Its strength is also dependent on the
amount and kind of defects. This is reflected in
the grade given to it by the lumber grader (or
machine and grader if MSR lumber).
These strength values are further adjusted to
reflect lumber size, 2x4 or 2x10 for example and
what it is being used for: a floor joist, a rafter,
etc. Also whether it is being used as a single
piece, such as a beam, or with a group, such as
floor and ceiling joists, or rafters.
This sounds complicated but the situations just
described are taken care of when using the span
tables.
FLOOR JOISTS, CEILING JOISTS AND RAFTERS
MATERIAL DESIGN
PROPERTIES
The table on the following page is typical of the
tables identifying specified strengths for visually
stress-graded lumber. The table is for structural
joists and planks of lumber as appropriate for
use in Canada. Similar tables are available for
the other grades of stud, light framing, beams
and stringers, posts and timbers and MSR
(Machine Stress Rated) lumber.
You will note that the value for each property
has not been listed in the table. The table has
been presented in this way as, in the design
process, the value needs to be modified for a
number of factors such as: load duration, service
condition, treatment, type of construction, size,
etc. Span tables incorporate these factors where
appropriate. So, when you read span tables it is
important that you also read the notes etc., to
ensure that the spans reflect the conditions
under which the building is going to be built.
In addition, be aware that spans for use in
Canada are not the same as for spans in other
countries and that spans for No. 1 grade are the
same as for No. 2 grade. In other words, spans
developed for use in the US are not the same as
those for use in Canada.
SPECIFIED STRENGTHS AND MODULUS OF ELASTICITY FOR STRUCTURAL JOISTS AND
PLANKS OF LUMBER (MPa)
Compression
Grade
Bending
at
extreme
fibre
fb
fv
fc
fcp
ft
E
SS
No. 1/No. 2
No. 3
SS
No.1/No. 2
No. 3
SS
No.1/No. 2
No. 3
SS
No.1/No. 2
No. 3
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
Species
Identification
DFir-L
Hem-Fir
S-P-F
Northern
Notes:
Longitudinal
shear
Parallel
to grain
Perpendicular
to grain
Tension
parallel
to grain
A specified strength or modulus of elasticity will
be listed (shown as xxx) for each species group,
grade and property. Beware that in Canada the
numerical value for No. 1 and No. 2 grades are
equal. The values are not identified in this table
as a number of modification factors are applied to
the value in the overall design process.
xxx
xxx
xxx
xxx
Modulus
of
elasticity
Tabulated values are based on the following standard conditions:
(a) 286 mm larger dimension
(b) dry service conditions
(c) standard term duration of load
COMMON STRESS TYPES
There are several types of stresses that develop
in loaded members. In the design process the
designer checks that none of the specified
strengths are exceeded when a load is applied
to the member.
However, generally the importance of the type of
stress is dependant on how the member is being
used. For example, rafters will usually fail first,
by bending too much and breaking. Therefore,
the fb value is usually the limiting factor in rafter
design. The rest of the stresses are present but
the lumber is usually strong enough to withstand
them.
We will now look at each of the stress types that
develop in members under load.
BENDING MEMBERS
Extreme Fibre Stress In Bending - “fb”
Three primary types of stresses are introduced
into a member that bends under load. The
greatest (or extreme) stress occurs along the
very top edge and bottom edge of the lumber.
At the top edge the lumber wants to get shorter
or “compress”. This stress is called
compression parallel to grain, it is frequently
referred to simply as compression. It’s the
tendency to push together or shorten.
Along the bottom the lumber wants to lengthen,
or pull apart.This stress is called tension. The
nearer to the centre you get, the less bending
stress there is. Right at the middle there is no
bending stress. This middle is sometimes called
the neutral axis (this middle is where
longitudinal (or horizontal) shear is the
greatest, but right now we are discussing
extreme fibre stress in bending).
Modulus of Elasticity - “MOE” or “E”
The limiting factor for floor and ceiling joists (and
many beams) is frequently their elasticity. This
means that they will bend enough to cause
problems in the building, before they get enough
weight on them to break.
The reason this is a problem for floor and ceiling
joists is that they are carrying drywall. If the
ceiling sags enough the joints will come apart,
nails will pop and problems will occur. The floor
joists may not have drywall directly applied to
them, but if they sag so do the walls on top of
them creating the same problems.
The amount of “sag” or “deflection” is set by the
building code. Generally the deflection limit for
floor joists is set at 1/360 of the span (usually
stated on the span table). That is a maximum
sag of 1" for every 360" (30') of joist length. To
see what the actual allowed deflection for any
span is, convert the span length into inches then
divide by 360.
For example, if a joist has a span of 14', then 14'
= 168". Divided by 360 = 0.467” or just less than
1
/2". That doesn't mean the joist will sag 0.467”,
but that is the maximum it can deflect, by code.
The joist is likely not stretched out to its
maximum span, and is probably not the lowest
possible grade or species piece in the world so
we’ll never have the total designed load on this
joist at its weakest point (centre span).
Ceiling joists are usually allowed a little more
deflection by code as the ceiling joists do not
carry bearing walls. A common amount is
1/240th of the span. (Using the 14' span as an
example: 14' = 168". Divided by 240 = 0.700", or
almost 3/4".
Rafter tables allow even more deflection if the
underside of the rafter is not carrying drywall
(and it usually doesn’t). Usually it is 1/180th of
the rafter span.
You don’t have to worry about this, just read the
tables properly and they’ll stop you from using
members that break too soon or deflect too
much.
One reason for knowing about this is you may
use joists in an agricultural or commercial
building where drywall nail popping and opening
of corners is not a problem. You can ignore the
restriction of deflection and use the fb value as
the limiting factor.
The modulus of elasticity “E” is a measure of the
elasticity of the material. In the SI system it is
expressed in MPa where as in the Canadian
Imperial measurement system it is expressed in
pounds per square inch (psi). “E” value is often
shortened by dividing by one million so that an E
value of 1,500,000 is often called 1.5E.
OTHER STRESS TYPES
The modulus of elasticity (E) and the extreme
fibre stress in bending (fb) are the two design
parameters covered so far. They are the major
controlling factors in joist and rafter spans. Let’s
now look at the remaining main stress types.
Fibre Stress in Tension - “ft”
This is important in a post when forces
are trying to pull it apart. Except for prefabricated trusses the “ft” value rarely is
ever a controlling factor in house building.
Compression Parallel to Grain - “fc”
This is the more normal loading of a post,
column, stud, etc. Rarely is this a
problem in normal house construction
since most lumber is very strong in
resisting compression.
Compression Perpendicular to Grain “fcp”
Wherever the floor joist, ceiling joist, beam, etc.,
rests on a support, the weights tend to crush, or
compress, the fibres at the bearing point. The
bearing area has to be large enough so this
doesn’t happen.
The building codes take care of this by setting
“minimum” bearings for the various members.
Minimum Bearing
Minimum bearing for wood floor and ceiling
joists and rafters is typically 11/2" and for beams
is 31/2". If you follow these minimums in house
construction, compression perpendicular to grain
probably will never enter your mind again!
Longitudinal (Horizontal) Shear - “fv”
This is where the wood fibres tend to slide over
themselves horizontally right at the top to bottom
mid-point of a member loaded in bending (refer
to the figure as related to the extreme fibre
stress in bending discussion). This is not usually
a problem either, except possibly in short,
heavily loaded beams, that are quite “deep”.
For practical purposes the only stresses are
typically of concern in common house
construction are “E” and “fb”.
The rest are included for background information
and to help you understand other information
you may come across.
LOADS
When engineers develop span tables they
decide what will be the maximum load the
various members may have to carry. There are
two primary kinds of loads: dead and live loads.
DEAD LOADS
Dead loads are weights of building materials and
objects installed in or on the structure. Walls,
ceilings, roofs, furnaces, etc.
Dead loads can be calculated right down to the
ounce, but for design purposes there are several
“standard” dead loads. For floors and ceilings,
it’s common to use 10 pounds per square foot
(psf) and for roofs, 7 psf is common. This
information is generally noted on the tables.
But there are numbers reflecting the highest
probable live loads for different conditions.
These live loads are found in building codes. For
example, all rooms in a house except sleeping
rooms would have a live load of 1.9 kPa (40
psf). Sleeping rooms and attics with limited
storage: 1.4 kPa (30 psf). Auditoriums have a
common live load of 4.8 kPa (100 psf). You will
need to use the correct local code requirements.
Other live loads that are important are s n o w
loads, w i n d loads and in some regions
earthquake loads.
Snow loads affect several components of the
building structure. You’ll most likely have a
choice in snow loads of 1.0 to 4.0 kPa (20.9 psf
to 83.5 psf) or heavier. The one to pick depends
on the conditions in your area. If you have a
building official ask them which one to use.
TOTAL LOADS
When reading span tables for house
construction the “normal” live and dead loads
are already added together. If your situation is
the same as described in the heading or footers
of the tables go ahead and use them.
Sometimes your specific situation may differ. If
your loads are heavier or more restrictions
apply, you cannot use the tables. You should
then use a qualified engineer or architect.
AN EXAMPLE - A 28' WIDE
HOUSE
We are now going to work through a number of
tables by first introducing a table and then using
a number of examples of how you find the size
of framing members for a make-believe 28' wide
house. We will assume that there is a bearing
wall in the centre and that the clear span will be
14'.
LIVE LOADS
We’ll look at the table headings and describe the
terms in those tables, so it’ll take a while.
Live loads are all loads that are not dead loads.
For the most part it includes people and
furniture. Things that come and go and are fairly
easy to move.
Once you know the species and grade of wood
you’ll be using, you need to find its span values.
These loads are impossible to figure accurately.
You don’t know how many people may live in
the house, or stand in the same area at one
time, or the amount and kind of furniture, etc.
How do you know the species and grade you’ll
be using? For this lesson we’ll give you that
information. However on the job you’ll simply
know, or ask, what species and grade of lumber
you stock in 2x8 or 2x10, which is the common
floor joist sizes. Or what species and grade you
stock in 2x6, which is the common ceiling joist
and rafter size. Of course you don’t know that
those sizes will work for your particular situation,
that’s why you should look it up in the tables.
For this review we will be using information
similar to that found in the NBCC’s Part 9
“Housing and Small Buildings” and Canadian
Wood Council’s “The Span Book” which is a
supplement to the wood joist, rafter and beam
spans found in NBCC. As before, you should
determine what information is acceptable to the
building authority in your area.
Two additional points. The tables in this chapter
present information applicable to No. 1 and No.
2 grades of Structural Light Framing (2x4) and
Structural Joists and Planks (2x5 and wider)
categories of lumber. NBCC, the CWC span
book and the code in your jurisdiction provide
spans for several other grades such as: Select
Structural, No. 3, Stud, Construction, etc. In
addition, the chapter provides spans for a limited
number of snow loads. Again NBCC, the CWC
span book and the code of your jurisdiction
provide spans for a broader range of snow
loads.
Several figures and much of the tabular
information in this chapter is based on
information generally available from the
Canadian Wood Council.
a number of construction practices that reduce
vibration and as a result, improves floor
performance.
Before referring to the span tables let’s look at
what we mean by joist span and at some of the
various construction practices.
Joist span is the clear distance between
supports.
Strapping is a piece of lumber nailed to the
bottom of the joists. The NBCC requires that the
minimum strap be a 1x3 located at not more
than 2.1 m (6'-10") from each support or other
rows of strapping fastened at the ends to sill or
header. Panel-type ceiling finish attached
directly to the joists may be considered as
equivalent in some jurisdictions.
FLOOR JOISTS
NBCC provides tables listing maximum spans
for floor joists for general cases as well as for
special cases. The table on the following page
provides the information for the general cases
of: “with strapping”, “with bridging” and “with
strapping and bridging” (see column headings)
and the table following this table provides the
information for the special cases of: “joists with
ceilings attached to wood furring, without
bridging” and “with bridging” and “joists with
concrete topping, with or without bridging”.
Floors constructed without strapping, bridging,
etc., tend to be “bouncy.” This does not mean
that they will collapse but that they will bounce
as a person walks on the floor. To minimize
bouncy floors (or more technically referred to as
vibration) the NBCC requires that the design of
floor spans consider strength, deflection and
vibration. As vibration is considered in the
Canadian design solution, the NBCC introduced
Bridging consists of “solid blocking” (2x joist
depth) or “cross-bridging” (1x3 or 2x2 minimum)
located not more than 2.1 m (6'-10") from each
support or other rows of bridging.
Strapping and bridging is where both are
combined on the same floor. Minimum 1x3 or
2x2 cross bridging (or 2x joist depth solid
blocking) located not more than 2.1 m (6'-10")
from each support or other rows of bridging,
together with strapping. For increased stiffness,
additional rows of strapping or bridging may be
used. Where more than one row of strapping or
bridging is used, greater stiffness results from
placement near the centre of the floor.
Floor joists with ceilings attached to wood
furring, no bridging relies on the furring and
gypsum board to stiffen the floor above. The
minimum thickness of gypsum board and sizes
of furring strips are shown on the figure below.
Where bridging is applied in combination with
the above, it should meet the bridging
requirements described earlier.
FLOOR JOISTS EXAMPLE PROBLEMS
Now let’s have a look at reading the floor span
tables.
For all examples assume (unless the chapter
asks you to consider something different) that
your store stocks a complete range of sizes of
No. 2 grade S-P-F.
MAXIMUM SPANS FOR FLOOR JOISTS: GENERAL CASES
Species
Group
DFir-L
Hem-Fir
S-P-F
Northern
Species
Maximum Span (ft.-in.)
With Strapping
With Bridging
Joist
Joist Spacing (in.)
Joist Spacing (in.)
Grade
Size
12
16
24
12
16
24
2x6
10-2
9-7
8-7
10-10
9-10
8-7
No. 1
2x8
12-2
11-7
11-0
13-1
12-4
11-3
and
2x10
14-4
13-8
13-0
15-3
14-4
13-6
No. 2
2x12
16-5
15-7
14-10
17-2
16-2
15-3
2x6
10-2
9-7
8-7
10-10
9-10
8-7
No. 1
2x8
12-2
11-7
11-0
13-1
12-4
11-3
and
2x10
14-4
13-8
13-0
15-3
14-4
13-6
No. 2
2x12
16-5
15-7
14-10
17-2
16-2
15-3
2x6
9-7
8-11
8-2
10-4
9-4
8-2
No. 1
2x8
11-7
11-0
10-6
12-5
11-9
10-9
and
2x10
13-8
13-0
12-4
14-6
13-8
12-10
No. 2
2x12
15-7
14-10
14-1
16-4
15-5
14-6
2x6
8-3
7-8
7-1
9-3
8-5
7-5
No. 1
2x8
10-6
10-0
9-4
11-3
10-7
9-8
and
2x10
12-4
11-9
11-2
13-1
12-4
11-7
No. 2
2x12
14-1
13-5
12-9
14-9
13-11
13-1
5
Notes:
(a) Nailed /8" subfloor
(b) Live Load = 40 psf
(c) Dead Load = 10 psf
(d) Deflection = Span/360
(e) Spans include consideration of vibration criteria.
With Strapping and Bridging
Joist Spacing (in.)
12
16
24
10-10
9-10
8-7
13-9
12-10
11-3
15-10
14-10
13-10
17-10
16-7
15-6
10-10
9-10
8-7
13-9
12-10
11-3
15-10
14-10
13-10
17-10
16-7
15-6
10-4
9-4
8-2
13-1
12-2
10-9
15-1
14-1
13-2
17-0
15-10
14-9
9-4
8-5
7-5
11-10
11-0
9-8
13-8
12-9
11-10
15-4
14-4
13-4
Example Problem 1
What is the maximum floor joist span for a 2x8
spaced 16" o/c when built using strapping only?
Solution: (Find the information in the tables as
we go along.)
1. Find the table containing the construction
detail to be used. The appropriate table is
“Maximum Spans for Floor Joists: General
Cases.”
2. Review the notes to ensure that the table is
based on the criteria that is appropriate.
3. Find the row dealing with S-P-F species, the
row dealing with No. 2 grade and the row for
2x8.
4. Find the column dealing with “with strapping”
and the column dealing with a joist spacing 16"
o/c.
5. Read the span where the row and column
intersect i.e. 11'-0". Great!
Example Problem 2
What is the maximum floor joist span for a 2x8
spaced 16" o/c when built using bridging only?
When built with strapping and bridging?
Solution: This is an extension of the first
problem. The table and row is the same for both
of the construction details. The only change is
the column. Therefore for Part 1:
1. Find the column dealing with “with bridging”
and the column dealing with a joist spacing 16"
o/c.
2. Read the span where the row and column
intersect i.e. 11'-9".
and for Part 2 of the question:
3. Find the column dealing with “with strapping
and bridging” and the column dealing with a joist
spacing 16" o/c.
4. Read the span where the row and column
intersect i.e. 12'-2"
Spend a bit of time examining the table. You will
note that if we had exactly the same conditions
as in Example Problem 1 and 2 except that the
joist spacing is 24" o/c rather than 16" o/c the
maximum spans would be 10'-6" with strapping,
10'-9" with bridging and 10'-9" with strapping
and bridging. Yes! That is right! For this size and
grade of joist and under this particular set of
loads and construction details, there is no real
advantage in building with both strapping and
bridging.
Example Problem 3
Now let’s have a problem using our mythical 28'
wide house having clear spans of 14'. Your
customer wants to know the size of lumber that
should be used for the 14' span.
Solution. Continue to use the “Maximum Spans
for Floor Joists General Cases” table.
1. Ask your customer some questions to be
sure that the Notes to the table apply. In other
words, additional or unusual loads are not going
to be part of the building plans.
2. Find the row dealing with S-P-F species and
the row dealing with No. 2 grade. Now all spans
exceeding 14'-0" are appropriate.
3. You now should try to zero in on the type of
construction that your customer would prefer to
use. For example, all of the 2x12 spans exceed
the 14'-0" required and some of the 2x10 spans
also exceed the 14'-0".
4. Your customer will likely want to use the
smaller size. So, you should identify that a
S-P-F, No. 2 grade, 2x10 will meet the 14'-0"
required span using the following construction
details:
• with bridging and 12" o/c joist spacing
(14'-6"),
• with strapping and bridging and 12" o/c
joist spacing (15'-1") and
• with strapping and bridging and 16" o/c
joist spacing (14'-1").
Your customer will likely be impressed with your
advice. You have identified some options and
from an overall cost effective point of view it is
likely that the third option (with strapping and
bridging and 16" o/c joist spacing (14'-1") will be
selected.
Example Problem 4
Now let’s assume your customer asks you if the
floor of the second story can be built differently?
Solution: As this is the second floor the ceiling
underneath will be finished. Therefore,
1. Select the table reflecting the construction
detail to be used. The appropriate table is
“Maximum Spans for Floor Joists: Special
Cases”.
2. Review the notes to ensure that the table is
based on the criteria that is appropriate.
3. Find the row dealing with S-P-F species, the
row dealing with No. 2 grade and the row for
2x10. In this row you will identify four
construction details (not including the “concrete
topping” solutions) meeting your customers
needs, i.e. 14'-11", 14'-1", 16'-4" and 15'-7".
Again you have provided your customer a
number of solutions with the most cost effective
one likely being the solution using 16" o/c joist
spacing without bridging (14'-1").
CEILING JOISTS
Spans for ceiling joists where the attic is not
accessible by a stairway are the easiest to
deal with as there is only the dead weight of the
joists, ceiling material and insulation to deal with.
As there is no live load and the dead load is
constant these joist tables only have one span
per combination of species / grade / size / joist
spacing.
MAXIMUM SPANS FOR CEILING JOISTS
(Attic not Accessible by a Stairway)
Species
Group
Grade
DFir-L
No. 1
and
No. 2
Hem-Fir
No. 1
and
No. 2
S-P-F
No. 1
and
No. 2
Northern
Species
No. 1
and
No. 2
Joist
Size
2x4
2x6
2x8
2x10
2x4
2x6
2x8
2x10
2x4
2x6
2x8
2x10
2x4
2x6
2x8
2x10
Maximum Span (ft.-in.)
Joist Spacing (in.)
12
16
24
10-9
9-9
8-6
16-10
15-4
13-5
22-2
20-2
17-7
28-4
25-9
22-6
10-9
9-9
8-6
16-10
15-4
13-5
22-2
20-2
17-7
28-4
25-9
22-6
10-3
9-3
8-1
16-1
14-7
12-9
21-1
19-2
16-9
27-0
24-6
21-5
9-3
8-5
7-4
14-6
13-2
11-6
19-1
17-4
15-2
24-4
22-2
19-4
Notes: (a) Attic not accessible by a stairway
(b) Deflection = Span/360
MAXIMUM SPANS FOR FLOOR JOISTS: SPECIAL CASES
Maximum Span (ft.-in.)
Joists with Ceilings Attached to Wood Furring
Species
Group
Grade
DFir-L
No. 1
and
No. 2
Hem-Fir
No. 1
and
No. 2
S-P-F
No. 1
and
No. 2
Northern
Species
No. 1
and
No. 2
Notes:
Without Bridging
Joist Spacing (in.)
12
16
24
10-10
9-10
8-7
13-4
12-7
11-3
15-8
14-9
13-6
17-10
16-10
15-4
10-10
9-10
8-7
13-4
12-7
11-3
15-8
14-9
13-6
17-10
16-10
15-4
10-4
9-4
8-2
12-8
11-11
10-9
14-11
14-1
12-10
17-0
16-0
14-7
9-4
8-5
7-5
11-6
10-10
9-8
13-6
12-8
11-7
15-4
14-5
13-2
Joist
Size
2x6
2x8
2x10
2x12
2x6
2x8
2x10
2x12
2x6
2x8
2x10
2x12
2x6
2x8
2x10
2x12
5
With Bridging
Joist Spacing (in.)
12
16
24
10-10
9-10
8-7
14-2
12-11
11-3
17-2
16-4
14-2
19-5
18-6
16-5
10-10
9-10
8-7
14-2
12-11
11-3
17-2
16-4
14-5
19-5
18-6
17-3
10-4
9-4
8-2
13-6
12-4
10-9
16-4
15-7
13-9
18-6
17-7
16-7
9-4
8-5
7-5
12-3
11-1
9-8
14-9
14-1
12-4
16-9
15-11
14-4
(a) Nailed /8" subfloor
(b) Live Load = 40 psf
(c) Dead Load = 10 psf
1
(d) Dead load of concrete topping = 20 psf (1 /4" to 2" of concrete)
(e) Deflection = Span / 360
(f) Spans include consideration of vibration criteria.
Joists with Concrete
Topping
With or Without Bridging
Joist Spacing (in.)
12
16
24
10-10
9-10
8-5
14-2
12-6
10-2
17-8
15-3
12-6
20-6
17-9
14-6
10-10
9-10
8-7
14-2
12-11
10-8
18-2
16-0
13-1
21-6
18-7
15-2
10-4
9-4
8-2
13-6
12-4
10-9
17-3
15-8
13-7
20-5
19-1
15-9
9-4
8-5
7-4
12-3
10-11
8-11
15-4
13-4
10-10
17-10
15-5
12-7
Example Problem 5
What size of ceiling joist should be used for our
28' wide house where the ceiling joist clear span
is 14' and is attic is not accessible by a
stairway?
Solution:
1. Select the appropriate table (“Maximum
Spans for Ceiling Joists”) and check the notes re
attic accessibility.
2. Find the row dealing with S-P-F species, the
row dealing with No. 2 grade. You now
recognize that several sizes and joists spacings
will meet the span requirements. As the other
elements in the house are at 16" o/c it will likely
be the preferred spacing. This “works” as a 2x6
at 16" o/c spans 14'-7" which is greater than the
needed 14'.
ROOF JOISTS AND RAFTERS
Roof joists (where a ceiling is applied i.e. a flat
roof, cathedral ceiling, etc.) and rafters (no finish
applied to the underside of the rafter i.e. an
unfinished attic, etc.) are more complicated than
the previous members we have looked at as we
now must consider the affect of snow. From a
simple point of view the span tables are no more
complicated to read except you must make sure
you are referring to the column that identifies the
snow load requirement for your area. You
should contact your local building official to
identify what snow load is applicable in your
area. Or better yet, what snow loads are
applicable in the areas that your store serves.
For example, in mountainous areas, or in areas
where a “boundary” exists between two snow
load requirements, snow loads may vary greatly
even though the distances between the local
areas may be small.
In addition to the
snow load issue we
have the “sloping
length” issue. Roof
rafters and possibly
roof joists, are
sloped. Span tables
reflect the “clear
distance between
supports”. So, the
clear span needs
to be converted from the horizontal span to the
sloping distance plus the bearing lengths,
overhangs, etc.
Fortunately, this is not difficult but does require
you to make some additional calculations. The
table below provides you with the conversion
factors.
CONVERSION FACTORS FOR SLOPING
JOISTS/RAFTERS
Slope
(in 12)
3
4
5
6
7
8
9
Slope
Factor
1.031
1.054
1.083
1.118
1.158
1.202
1.250
Slope
(in 12)
10
11
12
13
14
15
16
Slope
Factor
1.302
1.357
1.414
1.474
1.537
1.601
1.667
How are these factors applied?
Assume the horizontal span is 14' and the slope
is 4:12, then, from the above conversion factor
table, the slope factor is 1.054 and the sloping
length is 14.76' (14 x 1.054). If the slope is 10:12
then the sloping length is 18.29' (14 x 1.302).
Now let’s look at some roof and joists rafter
tables.
NBCC and others publish roof and joists and
rafters tables for a number snow load levels.
This chapter will use only three different levels.
And the differences between the levels are fairly
large. So, again it is important that you obtain
tables reflecting the snow loads in your area,
otherwise you may be advising your customers
to use spans that are overly safe, or more
importantly, spans that are not safe. You
certainly don’t want to get the reputation that
your recommendations “cost too much” or do not
reflect the needs of your area.
Now let’s look at the roof span tables.
Roof Joists Example Problem 6
Assume you are in an area with a snow load of
20.9 psf. What is the maximum span for a S-P-F
No. 2 grade 2x10 at 24" o/c?
Solution:
1. Find the table containing the relevant
information. “Maximum Spans for Roof Joists.”
MAXIMUM SPANS FOR ROOF JOISTS
Species
Group
Grade
DFir-L
No. 1
and
No. 2
Hem-Fir
No. 1
and
No. 2
S-P-F
No. 1
and
No. 2
Northern
Species
No. 1
and
No. 2
Notes:
Roof Snow Load
20.9 psf (1.0 kPa)
Joist
Joist Spacing (in.)
Size
12
16
24
2x4
8-6
7-9
6-9
2x6
13-5
12-2
10-8
2x8
17-7
16-0
14-0
2x10
22-6
20-5
17-10
2x12
27-4
24-10
21-0
2x4
8-6
7-9
6-9
2x6
13-5
12-2
10-8
2x8
17-7
16-0
14-0
2x10
22-6
20-5
17-10
2x12
27-4
24-10
21-9
2x4
8-1
7-4
6-5
2x6
12-9
11-7
10-1
2x8
16-9
15-3
13-4
2x10
21-5
19-5
17-0
2x12
26-1
23-8
20-8
2x4
7-4
6-8
5-10
2x6
11-6
10-6
9-2
2x8
15-2
13-9
12-0
2x10
19-4
17-7
15-4
2x12
23-6
21-5
18-4
(a) Dead Load = 10 psf
(b) Deflection = Span / 360
Maximum Span (ft.-in.)
Roof Snow Load
Roof Snow Load
41.8 psf (2.0 kPa)
62.7 psf (3.0 kPa)
Joist Spacing (in.)
Joist Spacing (in.)
12
16
24
12
16
24
6-9
6-2
5-4
5-11
5-4
4-8
10-8
9-8
8-5
9-3
8-5
7-4
14-0
12-8
11-1
12-2
11-1
9-6
17-10
16-2
13-10
15-7
14-2
11-8
21-9
19-8
16-1
19-0
16-7
13-6
6-9
6-2
5-4
5-11
5-4
4-8
10-8
9-8
8-5
9-3
8-5
7-4
14-0
12-8
11-1
12-2
11-1
9-8
17-10
16-2
14-2
15-7
14-2
12-3
21-9
19-9
16-10
19-0
17-3
14-2
6-5
5-10
5-1
5-7
5-1
4-6
10-1
9-2
8-0
8-10
8-0
7-0
13-4
12-1
10-7
11-7
10-7
9-3
17-0
15-5
13-6
14-10
13-6
11-9
20-8
18-9
16-5
18-1
16-5
14-4
5-10
5-3
4-7
5-1
4-7
4-0
9-2
8-4
7-3
8-0
7-3
6-4
12-0
10-11
9-6
10-6
9-6
8-4
15-4
13-11
12-1
13-5
12-2
10-2
18-8
17-0
14-0
16-4
14-5
11-9
2. Review the notes to ensure that the table is
based on the criteria that is appropriate.
3. Find the row dealing with “S-P-F species,”
the row dealing with “No. 2 grade” and the row
for “2x10.”
4. Find the column dealing with “roof snow load
20.9 psf” and the column for a “joist spacing 24"
o/c.”
5. Read the span where the row and column
intersect i.e. 17'-0".
Remember this is the clear span. A longer
length of lumber will be required to provide for
bearing (and overhang if required).
Example Problem 7
Assume the same conditions as for Example
Problem 6 except that your customer wants to
use No. 1 grade instead of No. 2 grade.
Solution:
The clear span is the same (17'-0") as the
design values for No. 1 grade are the same as
for No. 2 grade.
Roof Snow Load
83.5 psf (4.0 kPa)
Joist Spacing (in.)
12
16
24
5-4
4-10
4-3
8-5
7-8
6-8
11-1
10-1
8-5
14-2
12-7
10-3
16-10
14-7
11-11
5-4
4-10
4-3
8-5
7-8
6-8
11-1
10-1
8-9
14-2
12-10
10-9
17-3
15-3
12-6
5-1
4-8
4-1
8-0
7-4
6-5
10-7
9-7
8-5
13-6
12-3
10-8
16-5
14-11
12-11
4-7
4-2
3-8
7-3
6-7
5-9
9-6
8-8
7-4
12-2
10-11
8-11
14-8
12-8
10-4
Roof Rafters Example Problem 8
Assume you are in an area having a snow load
of 62.7 psf. What is the maximum span for a
S-P-F No. 2 grade 2x10 at 16" o/c?
Solution:
1. Find the table containing the relevant
information. “Maximum Spans for Roof Rafters.”
2. Review the notes to ensure that the table is
based on the criteria that is appropriate. If you
are viewing the correct table you will see that the
deflection for this member is span/180. This is
appropriate as no gypsum will be applied inside
the attic.
3. Find the row dealing with “S-P-F species”,
the row dealing with “No. 2 grade” and the row
for “2x10.”
4. Find the column dealing with “roof snow load
62.7 psf” and the column for a “joist spacing 16"
o/c.”
5. Read the span where the row and column
intersect i.e. 15'-11".
MAXIMUM SPANS FOR ROOF RAFTERS
Species
Group
Grade
DFir-L
No. 1
and
No. 2
Hem-Fir
No. 1
and
No. 2
S-P-F
No. 1
and
No. 2
Northern
Species
No. 1
and
No. 2
Notes:
Roof Snow Load
20.9 psf (1.0 kPa)
Rafter
Rafter Spacing (in.)
Size
12
16
24
2x4
10-9
9-9
8-6
2x6
16-10
15-4
12-11
2x8
22-2
19-4
15-9
2x10
27-3
23-7
19-3
2x12
31-7
27-5
22-4
2x4
10-9
9-9
8-6
2x6
16-10
15-4
13-5
2x8
22-2
20-2
16-6
2x10
28-4
24-9
20-2
2x12
33-2
28-9
23-5
2x4
10-3
9-3
8-1
2x6
16-1
14-7
12-9
2x8
21-1
19-2
16-9
2x10
27-0
24-6
20-11
2x12
32-10
29-9
24-3
2x4
9-3
8-5
7-4
2x6
14-6
13-2
11-3
2x8
19-1
16-10
13-9
2x10
23-9
20-7
16-10
2x12
27-7
23-10
19-6
(a) Dead Load = 7 psf
(b) Deflection = Span/180
Maximum Span (ft.-in.)
Roof Snow Load
Roof Snow Load
41.8 psf (2.0 kPa)
62.7 psf (3.0 kPa)
Rafter Spacing (in.)
Rafter Spacing (in.)
12
16
24
12
16
24
8-6
7-9
6-9
7-5
6-9
5-7
13-5
11-10
9-8
11-4
9-10
8-0
16-7
14-5
11-9
13-10
12-0
9-9
20-4
17-7
14-4
16-11
14-8
11-11
23-7
20-5
16-8
19-7
17-0
13-10
8-6
7-9
6-9
7-5
6-9
5-11
13-5
12-2
10-1
11-8
10-4
8-5
17-5
15-1
12-4
14-6
12-7
10-3
21-4
18-5
15-1
17-9
15-4
12-6
24-9
21-5
17-6
20-7
17-10
14-6
8-1
7-4
6-5
7-1
6-5
5-7
12-9
11-7
10-1
11-2
10-1
8-9
16-9
15-3
12-9
14-8
13-0
10-7
21-5
19-1
15-7
18-4
15-11
13-0
25-7
22-2
18-1
21-4
18-5
15-1
7-4
6-8
5-10
6-5
5-10
4-11
11-6
10-4
8-5
9-11
8-7
7-0
14-6
12-6
10-3
12-1
10-5
8-6
17-8
15-4
12-6
14-9
12-9
10-5
20-6
17-9
14-6
17-1
14-10
12-1
Example Problem 9
In example Problem 8 you found the maximum
span as being 15'-11". (a) If the slope of the roof
was to be 4 in 12 what would the sloping length
be? (b) If there was to be a 2' overhang, what
length of lumber would you recommend to your
customer?
Solution (a):
1. Convert 15'-11" to feet. 11"= 11/12ths of a
foot or 11/12 = 0.92'. Therefore 15'-11" = 15.92'.
2. From the “Conversion Factors for Sloping
Joists/Rafters” table the 4:12 conversion factor
is 1.054.
Roof Snow Load
83.5 psf (4.0 kPa)
Rafter Spacing (in.)
12
16
24
6-9
6-0
4-11
9-11
8-7
7-0
12-1
10-6
8-7
14-9
12-10
10-5
17-2
14-10
12-1
6-9
6-2
5-2
10-5
9-0
7-4
12-8
11-0
9-0
15-6
13-5
10-11
18-0
15-7
12-9
6-5
5-10
5-1
10-1
9-2
7-8
13-1
11-4
9-3
16-1
13-11
11-4
18-7
16-2
13-2
5-10
5-3
4-3
8-8
7-6
6-1
10-6
9-1
7-5
12-11
11-2
9-1
14-11
12-11
10-7
peak (see the figure dealing with sloping rafters).
For ease of calculation assume this is 9" or 0.75'
(9 / 12) which is just about the depth of the 2x10
joist.
2. On this basis the horizontal length will be the
9" from 1 above + span length + the bearing
length on top of the outside wall (assume 3_" -or
approximately 0.25' - for the width of the top wall
plate) + overhang. Therefore the horizontal
length is 0.75 + 15.92 + 0.25 + 2.00 = 18.92'
3. Calculate the rafter length as the horizontal
length x the 4 in 12 conversion factor. 18.92'x
1.054 = 19.94'.
Example Problem 10
3. Hence the sloping length would be 15.92 x
1.054 = 16.78'.
Solution (b):
(Hint. First work with the horizontal lengths and
then convert to the sloping length.)
1. At one end there will be a need to cut off a
small triangular piece of lumber so as to rest
against the “ridge beam” at the top of the roof
Let’s now go back to our 28' wide house where
the clear span is 14'. Assume the roof slope is 1
in 6, there is a 2' overhang and you are in a
snow load region of 41.8 psf. What lumber size,
o/c spacing and overall length of rafter would
you recommend to your customer?
Solution:
First let’s determine the overall length of the
rafter. This is done as the overall length could
influence the final decision.
1. As in Example Problem 9 the overall rafter
length will be “the triangle cut-off” (as the slope
is not excessively steep assume 0.75' as before)
+ clear span + bearing + overhang = 0.75 +
14.00 + 0.25 + 2.00 = 17.00'.
2. From the “Conversion Factors for Rafters”
table the 6 in 12 conversion factor is 1.118.
3. Hence the sloping length would be 17.00 x
1.118 = 19.01'. As lumber is likely delivered to
your store in 2’ increments you will be
recommending 20' length of lumber.
Now let’s determine the size and spacing of the
lumber to be used. Remember the clear span is
14'.
4. From the “Maximum Spans for Roof Rafters”
table find the row dealing with “S-P-F species”,
the row dealing with “No. 2 grade.”
5. Find the column dealing with “roof snow load
41.8 psf.”
6. Where the row and column intersect you find
that: a 2x8 spans 16'-9" at 12" o/c, 15'-3' at 16"
o/c and 12'-9" at 24" o/c; and, a 2x10 spans 21'5" at 12" o/c, 19'-1" at 16" o/c and 15'-7" at 24"
o/c. As you need a span of 14'-0" you can
recommend either a 2x8 spaced at 16" o/c or a
2x10 spaced at 24" o/c. Due to the bearings and
overhang, the sloped rafter will need to be 20'
long.
Reducing Rafter Size
Construction practices can reduce rafter size.
How? Well, the maximum spans for rafters (as
well as for the other tables in this chapter) are
listed as horizontal clear spans. Therefore, any
“interior” support that “interrupts” the overall
span reduces the span.
Example Problem 11
For example, in our 28' wide house, introduce a
brace to reduce the 14'-0" span into two spans
of 4'-8" and 9'-4". We now have a maximum
span of 9'-4". As in Example Problem 10, What
size rafter do we now need?
Solution:
1. From the “Maximum Spans for Roof Rafters”
table find the row dealing with “S-P-F species”,
the row dealing with “No. 2 grade.”
2. Find the column dealing with “roof snow load
41.8 psf.”
3. Where the row and column intersect you find
that a 2x6 spans 10'-1" at 24" o/c. This exceeds
the 9'-4" we require when using the bracing. So,
you can recommend, providing the framing
method uses the bracing, a 2x6 at 24" o/c rather
than a 2x8 spaced at 16" o/c or a 2x10 spaced
at 24" o/c.
BUILT-UP FLOOR BEAMS
You just learned how to select the proper size of
floor joists that will hold up the finished floor, etc.
Now we’ll take a look at how to select a wood
built-up beam or girder to hold up the floor joists.
The beam that holds up the floor joists is usually
a built-up wood beam made by nailing a number
of pieces (usually 3) of dimension lumber
(usually 2x10s) together. Another choice, though
not too common except in post and beam
houses, is a solid wood beam of 4x8 up to 6x12.
Steel beams are also common. They are usually
designed by the steel supplier where the builder
has identified the house width, the number
storeys, space between posts or supports, etc.
The supplier has a manual listing sizes needed
to meet those conditions.
A wood built-up beam, however, may have to be
selected by the draftsperson or estimator at the
building materials store. Many times the builder
will tell you what size and type wood girder they
want and all you have to do is to price it out
and/or see that the builder gets it. Once in a
while you may be in a position to help somebody
figure out what size wood girder is required.
If you can find your situation described in a
reliable table it should be okay to suggest a size.
However, as we’ve said before:
“Never design a structural member. It is not
worth the liability. And it’s not the right thing
to do anyway!”
Read the built-up beam sizes from the
appropriate table, but never design them.
A typical built-up floor beam table, for beams not
supporting more than two floors, is shown
below. Agencies publishing such tables usually
provide a number of similar tables for supporting
not more than one, two and/or three floors. This
chapter only provides the “two floor case” as the
format of the table will be the same for all tables.
In addition, beware that the tables do not allow
for carrying of a roof (snow) load. In other words
the building is framed using a truss system that
carries the roof load to the outside walls and the
walls carry the load down through the walls to
the foundation. The built up floor beam tables
are not difficult to read. But make sure that you
always use the appropriate table. And some
agencies also provide tables that incorporate
snow loads.
Example Problem 12
Again use our 28' wide house. Assume we want
to support two floors and use DFir-L, No. 2
grade for the built-up floor beam. What is the
maximum span we can achieve with a 4-ply
beam?
Solution:
1. Find the table containing the information we
require. (“Maximum Spans For Built-Up Floor
Beams Supporting Not More Than Two Floors”).
MAXIMUM SPANS FOR BUILT-UP FLOOR BEAMS SUPPORTING NOT MORE THAN TWO FLOORS
Maximum Span (ft.-in.)
Size of Beam
Species
Group
Grade
DFir-L
No. 1
and
No. 2
Hem-Fir
No. 1
and
No. 2
S-P-F
No. 1
and
No. 2
Northern
Species
No. 1
and
No. 2
Notes:
Supported
2x8
2x10
Length
(ft.)
3-ply
4-ply
5-ply
3-ply
4-ply
5-ply
3-ply
8
7-5
8-6
9-6
9-0
10-5
11-8
10-6
10
6-7
7-8
8-6
8-1
9-4
10-5
9-4
12
6-0
7-0
7-9
7-4
8-6
9-6
8-7
14
5-7
6-5
7-2
6-10
7-11
8-10
7-11
16
5-3
6-0
6-9
6-5
7-4
8-3
7-5
18
4-11
5-8
6-4
6-0
6-11
7-9
7-0
20
4-8
5-5
6-0
5-9
6-7
7-4
6-8
8
7-9
8-11
10-0
9-6
10-11
12-3
11-0
10
6-11
8- 0
8-11
8-6
9-9
10-11
9-10
12
6-4
7-4
8-2
7-9
8-11
10-0
8-11
14
5-10
6-9
7-7
7-0
8-3
9-3
7-11
16
5-3
6-4
7-1
6-4
7-9
8-8
7-2
18
4-10
6-0
6-8
5-9
7-2
8-2
6-7
20
4-6
5-7
6-4
5-4
6-7
7-9
6-1
8
8-0
9-3
10-4
9-10
11-4
12-8
11-5
10
7-2
8-3
9-3
8-9
10-2
11-4
10-2
12
6-7
7-7
8-5
8-0
9-3
10-4
9-4
14
6-1
7-0
7-10
7-5
8-7
9-7
8-7
16
5-8
6-7
7-4
6-10
8-0
8-11
7-9
18
5-3
6-2
6-11
6-3
7-7
8-5
7-1
20
4-10
5-10
6-7
5-9
7-2
8-0
6-7
8
6-5
7-5
8-4
7-10
9-1
10-2
9-2
10
5-9
6-8
7-5
7-0
8-2
9-1
8-2
12
5-3
6-1
6-9
6-5
7-5
8-4
7-5
14
4-10
5-7
6-3
5-11
6-10
7-8
6-11
16
4-7
5-3
5-11
5-7
6-5
7-2
6-6
18
4-3
4-11
5-6
5-3
6-1
6-9
6-1
20
4-1
4-8
5-3
5-0
5-9
6-5
5-9
(a) Spans apply only where the floors serve residential areas.
(b) Spans are clear spans between supports. For total span
1
(c) Provide a minimum of 3 /2" of bearing at each support.
(d) Supported length means one half the sum of the joists on both sides of the beam.
(e) Straight line interpolation may be used for other supported lengths.
2x12
4-ply
12-1
10-10
9-11
9-2
8-7
8-1
7-8
12-8
11-4
10-4
9-7
8-11
8-1
7-6
13-2
11-9
10-9
9-11
9-4
8-9
8-1
10-7
9-5
8-7
8-0
7-5
7-0
6-8
5-ply
13-6
12-1
11-1
10-3
9-7
9-0
8-7
14-2
12-8
11-7
10-9
10-0
9-5
8-11
14-8
13-2
12-0
11-1
10-5
9-10
9-4
11-9
10-7
9-8
8-11
8-4
7-10
7-5
2. Review the notes to ensure that the table is
based on the criteria that is appropriate. You will
note that “supported length” is defined as the
one half the sum of the joists on both sides of
the beam. We are using our 28' wide house that
has floor joists having a clear span of 14'. So,
one-half of 14' is 7'. However, the beam
supports the ends of two floor joists, so
7' +7' = 14'. Therefore, the supported length we
are interested in is 14'. The figure below
provides a visual dealing with supported length.
In addition, in looking up the span information
requested by your customer, you likely noticed
that a 4-ply 2x12 built-up beam had a clear span
of 9'-11". As the house is 50' long and each
beam requires 31/2" bearing at each end, you
can advise your customer that by spacing the
columns at 10' apart (i.e. five spaces at 10' =
50') the built up beam could be sized at 4-ply
2x12. Your familiarity with the tables and
extending the question asked has allowed you to
provide your customer with some options.
Congratulations!
HEADERS / LINTELS
Openings in walls are necessary for doors,
windows and other elements. When an opening
is put in a wall, it cuts off some supports carrying
loads down to the foundation and from there to
the footings and ultimately the soil.
3. Find the row dealing with DFir-L, the row
dealing with No. 2 grade and the row for 14'
supported length.
The supporting members “cut off” are generally
the wall studs though it could be posts in a post
and beam type house.
4. Find the columns dealing with 4-ply beams.
The loads that were being carried by these “cut
off” members have to be transferred to other
load carrying members nearby. Headers, or
frequently referred to as lintels, are the terms
given to supporting members that transfer these
loads.
5. Read the spans where the row and columns
intersect. i.e. 6'-5" for 4 - 2x8s, 7'-11" for 4 2x10s and 9'-2" for 4 - 2x12s. Therefore, the
longest span is 9'-2" for a 4-ply 2x12 built-up
beam.
Example Problem 12
Let’s return to using the No. 2 grade S-P-F. Our
customer with the 28' wide house tells us the
house is 50' long and that he/she wants a
minimum number of posts in the basement
supporting the built-up beam carrying two floors.
What can you advise?
Solution:
1. You know the supported length is 14'. So,
find the row dealing with S-P-F, the row dealing
with No. 2 grade and the row for 14' supported
length.
2. Look at the spans across this row, where you
can identify that a 5-ply 2x12 built-up beam
provides the maximum span of 11'-1".
The header/lintel size depends on many things
just as the size of joists, rafters and built-up
beams did, including how much weight they
have to carry. However, this depends on the
house width, height, location of header, etc.
The header size also depends on the strength of
the wood, the size of the wood and the number
of pieces being used to make the header.
HEADERS / LINTELS
Again, several agencies publish header/lintel
tables. Once again, then, if you know how to
read these tables accurately you can make sure
your customers are using properly designed
headers/lintels that are large enough to carry the
loads safely, but not oversized to increase the
material costs. We’ll be demonstrating and
practicing reading one of these tables shortly.
sheathing is used, lintel spans may be increased
as the sheathing helps spread the load out over
a larger area. In fact, if you examine the notes of
the table you will of see exactly that. Note (e)
identifies a 15% increase in spans when
structural panels of a minimum thickness,
conforming to a specific standard and fastened
in a specified way are used.
When the header has to carry a load it must be
accurately designed. However, there are quite a
number of headers that don’t carry any
significant load at all. Normally these headers
can be a single 2x4 turned flat. Used just to
"frame out" the opening.
A further review of the notes also identifies that
under certain conditions (floor joists spanning
the full width of the building without support)
spans are to be reduced by 15%.
A window placed on the gable end of a one story
house, for example, has no significant load over
it as the roof loads are transferred to the side
walls rather than the end (gable) wall. The main
purpose of the studs in that case is to provide
nailing and backing for exterior sheathing and
siding and for interior wall finish.
So when the studs are cut off to make the
window rough opening, no load carrying header
is required.
All the interior walls on the top floor of a trussed
roof building are normally non-load bearing (the
truss carries all the loads to the outside walls).
So when the studs are cut off to make the rough
openings for interior doors, there is no weight
that has to be transferred anywhere. Again then,
2x4s turned flat can be used to frame out the
opening. Even with a conventionally framed roof,
only bearing wall(s) need a load bearing header.
All the rest of the partitions are non-load
bearing.
So study your specific house, then apply what
you are learning and you can design proper
header sizes for many homes.
Now, before we do some Header/Lintel Example
Problems let’s look at the table (on the next
page) “Maxi m u m
Spans
for
2-Ply
Headers/Lintels with Non-Structural Sheathing
Supporting One Storey and Roof Snow Loads.”
The title identifies that the table is for
“headers/lintels with non-structural sheathing.”
This means that the sheathing, or the manner it
is fastened to the building frame is such that it
does not help to carry the load around the wall
opening. In some cases when structural
The notes to this table reinforce the importance
of reviewing and understanding all the
information: title, column and row headings,
notes, etc., on any table that you are going to
use to provide information to a customer.
A final comment before moving to a couple of
examples.
The header/lintel table in this chapter is only one
way in which information can be presented.
Other agencies may provide separate tables for
most cases encountered in regular construction.
They may also rely on notes to cover off
construction details not listed in the table they
have chosen to publish. A good first step in
getting the tables you want, is to discuss the
need for tables with your local building official.
Now an example problem.
Example Problem 14
Assume a 32 foot wide house where you are
using insulation sheathing board and you have a
10' rough opening on the wall carrying the roof
load and one storey. You are in a snow load
area of 41.8 psf. What is the smallest Hem-Fir,
No. 2 grade, 2-ply header you can use? (You
have already located the table and are familiar
with the notes.)
Solution:
1. Find the row dealing with Hem-Fir, No. 2
grade and the row of supported length of 10'.
2. Find the column dealing with the snow load
of 41.8 psf.
3. Read the spans where the row and column
intersect (5'-1", 6'-3", 7'-7" and 8'-10"). So, the
table you have doesn’t provide a solution.
And you will have to locate another table, refer
your customer to an engineer, or provide some
other solutions.
required by your customer.
You could tell your customer that the window
size could be reduced to under the 8'-10" or,
what about changing the type of sheathing?
Now, you have three suggestions for your
customer.
1. Reduce the opening to less that 8' -10".
2. Refer the solution to a design engineer.
3. Use a 2-ply 2x12 lintel along with
approved structural sheathing and
appropriate nailing.
The notes to the table allow for an increase in
span of 15% providing specified sheathing is
used. For the 2-ply 2x12 the maximum span is
8'-10". 8'-10" = 8' + 10/12' = 8' + 0.83' = 8.83'.
Now increase this by 15 %. 15% = 1.15. 8.83 x
1.15 = 10.15', which is greater than the 10'
All this with only the information contained in the
table of this chapter. If you have followed up by
obtaining a complete set of available tables from
agencies providing them you likely will have a
number of solutions using the material you are
regularly stocking in your store.
Here are some suggestions.
MAXIMUM SPANS FOR 2-PLY HEADERS/LINTELS WITH NON-STRUCTURAL SHEATHING SUPPORTING ONE
STOREY AND ROOF SNOW LOADS
Maximum Span (ft.-in.)
SupSnow Load
Snow Load
Snow Load
ported
20.9 psf (1.0 kPa)
41.8 psf (2.0 kPa)
62.7 psf (3.0 kPa)
Species
Grade
Length
Group
Beam Size of 2-ply at
Beam Size of 2-ply at
Beam Size of 2-ply at
(ft.)
2x6
2x8
2x10
2x12
2x6
2x8
2x10
2x12
2x6
2x8
2x10
2x12
8
6-5
7-9
9-6
11-0
5-5
6-7
8-1
9-5
4-10
5-10
7-2
8-4
10
5-9
6-11
8-6
9-10
4-10
5-11
7-3
8-5
4-4
5-3
6-5
7-5
12
5-3
6-4
7-9
9-0
4-5
5-5
6-7
7-8
3-11
4-9
5-10
6-10
No. 1
DFir-L
and
14
4-10
5-11
7-2
8-4
4-1
5-0
6-1
7-1
3-8
4-5
5-5
6-4
No. 2
16
4-6
5-6
6-9
7-10
3-10
4-8
5-9
6-8
3-5
4-2
5-1
5-11
18
4-3
5-2
6-4
7-4
3-8
4-5
5-5
6-3
3-3
3-11
4-9
5-7
20
4-1
4-11
6-0
7-0
3-5
4-2
5-1
5-11
3-1
3-9
4-6
5-3
8
6-8
8-2
10-0
11-7
5-9
6-11
8-6
9-10
5-1
6-2
7-6
8-9
10
6-0
7-4
8-11
10-4
5-1
6-3
7-7
8-10
4-6
5-6
6-9
7-9
12
5-6
6-8
8-2
9-5
4-8
5-8
6-11
8-1
4-2
5-0
6-0
6-9
No. 1
Hem-Fir
and
14
5-1
6-2
7-6
8-9
4-4
5-3
6-5
7-3
3-10
4-6
5-4
6-1
No. 2
16
4-9
5-9
7-1
8-2
4-0
4-10
5-9
6-7
3-5
4-1
4-10
5-7
18
4-6
5-5
6-8
7-8
3-9
4-5
5-4
6-1
3-2
3-9
4-6
5-2
20
4-3
5-2
6-3
7-1
3-6
4-1
4-11
5-8
2-11
3-6
4-2
4-10
8
6-10
8-5
10-4
12-0
5-11
7-2
8-10
10-3
5-3
6-4
7-10
9-1
10
6-2
7-7
9-3
10-9
5-3
6-5
7-10
9-2
4-8
5-8
7-0
8-1
12
5-8
6-11
8-5
9-9
4-10
5-11
7-2
8-4
4-3
5-2
6-4
7-4
No. 1
S-P-F
and
14
5-3
6-5
7-10
9-1
4-6
5-5
6-8
7-9
4-0
4-10
5-9
6-7
No. 2
16
4-11
6-0
7-4
8-6
4-2
5-1
6-3
7-1
3-8
4-4
5-3
6-0
18
4-8
5-8
6-11
8-0
3-11
4-9
5-9
6-6
3-5
4-0
4-10
5-6
20
4-5
5-4
6-6
7-7
3-9
4-5
5-4
6-1
3-2
3-9
4-6
5-2
8
5-7
6-9
8-3
9-7
4-9
5-9
7-1
8-2
4-2
5-1
6-3
7-3
10
5-0
6-1
7-5
8-7
4-3
5-2
6-4
7-4
3-9
4-7
5-7
6-6
12
4-7
5-6
6-9
7-10
3-11
4-9
5-9
6-8
3-5
4-2
5-1
5-11
No. 1
Northern
and
14
4-3
5-1
6-3
7-3
3-7
4-4
5-4
6-2
3-2
3-10
4-9
5-6
Species
No. 2
16
3-11
4-10
5-10
6-10
3-4
4-1
5-0
5-10
3-0
3-7
4-5
5-2
18
3-9
4-6
5-6
6-5
3-2
3-10
4-8
5-6
2-10
3-5
4-2
4-10
20
3-6
4-3
5-3
6-1
3-0
3-8
4-6
5-2
2-8
3-3
3-11
4-7
Notes:
(a) Supported length means half the span of the longest supported member.
(b) If floor joists span the full width of the building without support, spans shall be reduced by 15%.
1
(c) For ends of lintels fully supported by wall, provide a minimum 1 /2" of bearing for spans up to 10'; or 3" of bearing for lintel
spans greater than 10'.
1
1
(d) A single piece of 3 /2" thick lumber (of the same species and grade) may be used in lieu of 2 pieces of 1 /2" lumber on edge.
3
(e) When structural sheathing is used, lintel spans may be increased by 15%. Structural sheathing consists of a minimum /8"
thick structural panel conforming to CSA O121, CSA O151, CSA O437 or CSA O325 fastened with at least two rows of
fasteners to the exterior face of the lintel and a single row to the top plates and studs.
OTHER KINDS OF FRAMING
MEMBERS
Manufactured lumber and “alternate” types of
framing members are becoming more popular.
There are studs made of a combination of
particle board and lumber. Of course steel studs,
joists, etc., are available.
Joists and beams can be made from laminated
wood, combinations of plywood, lumber and/or
laminated materials.
Each of these “engineered” products has span
and strength information available. Get and use
information that is specific to the product your
store stocks.
It would be impractical to cover all these
“patented” products in a course such as this. But
the concepts covered in this chapter, if
understood, will help you decide when and how
to use new products, as they come along.
Some of these products may be superior to the
standard wood products and are “catching on”
so don’t be afraid to consider using them when
and if appropriate.
TRUSS ROOF SYSTEMS
A special caution. Truss roof systems are
designed entirely differently. The previous
information on finding rafters cannot be used to
find truss sizes. The concept of a truss is much
different as far as member sizes are concerned.
The span, slope, dead and live loads, etc., are
given to the truss manufacturer and they have
engineered trusses available to meet your
requirements. Contact the truss manufacturer in
your area for their information and literature.
RECAP
You should now be able to figure out sizes of
floor joists, ceiling joists, rafters headers / lintels,
etc. Many people are guessing or going by
tradition to find sizes. In many cases this has
been working out fine, still, if you can figure
these member sizes using a solid basis such as
the building code approved in your area, it
should give you confidence and could be a big
help to the customers and contractors you work
with.
The main point of this chapter was to familiarize
you with reading span tables. Your building code
official will be able to suggest the tables and
loads in effect in your area. Don’t hesitate to
contact this official.
Once you have obtained the tables approved for
use in your jurisdiction, why not challenge one or
more of your colleagues by taking turns and
asking each other questions that require use of
the span table to find answers. All of you can
then become familiar with using the span table
which will be beneficial when a customer asks
for your advice.
LUMBER ORDERING INFORMATION
This page gives approximate lumber quantities
contained in truckload and railcar lumber
shipments. Of course regional customs vary.
That’s why there is room for you to fill in
information specific to your store. When ordering
lumber it is helpful to know what quantities make
up standard units. It is usually advantageous to
order full units. The price is better, banded units
are easier to load and unload (with the right
equipment) and delivery is usually faster to you
because of easier handling. The main reason for
changing quantities with size is to try to keep all
the units approximately the same size to simplify
warehousing. The table below shows the most
common unit quantities listed first in each size
category, next are unit quantities used by some
lumber mills and/or wholesalers which may or
may not be available in your area. There is also
an empty line for you to fill in the quantities
commonly available to you, if different than any
of those listed.
TRUCKLOADS
Common truckload quantities are from 23,000
Board feet (Bd.Ft.) to 30,000 Bd. ft.
RAILCAR LOADS
A boxcar might be from 40,000 to 50,000 Bd. ft.
A flat car from 70,000 to 100,000 Bd. ft.
SIZE
PIECES
PER UNIT
NUMBER
OF PIECES
(wide x
high)
APPROX.
UNIT
DIMENSIONS
(inches)
2x4
2x4
2x4
2x4
208
192
180
13 x 16
12 x 16
12 x 15
45 x 25
42 x 25
42 x 23
2x4 Studs
2x4 Studs
2x4 Studs
2x4 Studs
300
208
192
13 x 16
12 x 16
45 x 25
42 x 25
2x6 Studs
2x6 Studs
2x6 Studs
128
120
8 x 16
8 x 15
44 x 25
44 x 23
2x6
2x6
2x6
128
120
8 x 16
8 x 15
44 x 25
44 x 23
2x8
2x8
2x8
96
90
6 x 16
6 x 15
43 /2 x 25
1
43 /2 x 23
2x10
2x10
2x10
80
75
5 x 16
5 x 15
46 x 25
46 x 23
2x12
2x12
2x12
64
60
4 x 16
4 x 15
45 x 25
45 x 23
1
A good portion of your lumber cost can be the
freight charges from the mill to your store.
Freight charges are sometimes a determining
factor in the kind of lumber you stock. Certain
minimum weight amounts give you the best
freight rate. Check with the railroad, lumber mill
or broker.
You are given a certain amount of time, such as
48 hours, to unload a car after the railroad has
notified you the car is in position to be unloaded.
You are charged “demurrage” if you take too
long to unload a railcar.
If you order lumber in “unit” quantities (called
bunks, skids, etc.) and it’s banded together and
is easy and fast to unload by forklift.
If your lumber is delivered in a boxcar “loose”,
such as boards might be, it can be a major
project to get it unloaded in the allotted time.
Much lumber is delivered by truck, of course and
is usually easy to unload.
LUMBER LENGTHS
Lumber is generally available in lengths of 8' to
16' in 2' increments. Longer lengths to 26' may
be available in the coastal species. And even
longer lengths may be available from a few mills,
though there is usually a price premium after
lengths of 16' or 18'.
BOARD FEET
Most lumber today is sold “by the piece”. It was
common to sell lumber by the “board foot” in the
”old” days. Some transactions still take place “by
the board foot.” So it’s still a good idea to learn
about board feet.
These next two pages contain a table on board
feet, plus board foot formulas, examples and
practice problems to reinforce your board foot
knowledge.
A board foot is 144 cubic inches of lumber. It’s
often pictured as a piece of lumber 12" square
and 1" thick, though it can be a 2"x6" 1 foot long
(12"), or any combination that equals 144 cubic
inches.
To use the Board Feet Per Piece Table “Nom.
Size” column to find the lumber size, then read
across to the correct column. The numbers have
always been rounded up. The two most frequent
numbers are 0.333, which goes on forever, this
is rounded to 0.34 or 0.3334; and 0.666, which
is rounded to 0.67 or 0.6667.
BOARD FOOT PER PIECE
Lineal
Feet
per
Board
Foot
6.00
4.00
3.00
Board
Feet
per
Lineal
Foot
0.1667
0.2500
0.3334
2.00
0.5000
1.50
0.6667
1.20
1.00
0.8334
1.0000
0.75
1.3340
0.60
0.50
1.6667
2.0000
0.34
3.0000
Length
Nom.
Size
1x2
1x3
1x4
2x2
1x6
2x3
1x8
2x4
1x10
1x12
2x6
2x8
4x4
2x10
2x12
4x6
6x6
8 Ft
10 Ft
12 Ft
14 Ft
16 Ft
18 Ft
20 Ft
22 Ft
24 Ft
26 Ft
1.34
2.00
1.67
2.50
2.00
3.00
2.34
3.50
2.67
4.00
3.00
4.50
3.34
5.00
3.67
5.50
4.00
6.00
4.34
6.50
2.67
3.34
4.00
4.67
5.34
6.00
6.67
7.34
8.00
8.67
4.00
5.00
6.00
7.00
8.00
9.00
10.00
11.00
12.00
13.00
5.34
6.67
8.00
9.34
10.67
12.00
13.34
14.67
16.00
17.34
6.67
8.34
10.00
11.67
13.34
15.00
16.67
18.34
20.00
21.67
8.00
10.00
12.00
14.00
16.00
18.00
20.00
22.00
24.00
26.00
10.67
13.34
16.00
18.67
21.34
24.00
26.67
29.34
32.00
34.67
13.34
16.67
20.00
23.34
26.67
30.00
33.34
36.67
40.00
43.34
16.00
20.00
24.00
28.00
32.00
36.00
40.00
44.00
48.00
52.00
24.00
30.00
36.00
42.00
48.00
54.00
60.00
66.00
72.00
78.00
READING THE BOARD FOOT TABLE
EXAMPLES
You can find out how many lineal feet (LFT) are
in a certain number of board feet of a certain
size piece of lumber by using the left column.
Example: To find how many LFT of 2x4 in 300
Bd. Ft. of 2x4, look up the LFT in one Bd. Ft. of
2x4. It shows 1.50. Multiply 1.50 x 300 and you
find 450 LFT of 2x4 in 300 Bd. Ft.
To find how many board feet in a certain amount
of lineal footage, multiply the board feet per
lineal foot (found in the second column from the
left) of the given size times the lineal footage.
Example: The reverse of the example above.
How many Bd. Ft. in 450 LFT of 2x4? There is
0.6667 Bd. Ft per LFT in a 2x4 (from table
above), 0.6667 x 450 = 300 Bd. Ft in 450 LFT of
2x4.
To find board feet per piece, look down the
"Nom. Size" column for the size you want, then
read to the right, under the length. That number
is the Bd. Ft. per piece.
Example: A 22' long 2x12 = 44 Bd. Ft.
BOARD FEET (cont.)
FORMULA FOR FINDING BOARD FEET
[NUMBER OF PIECES x THICKNESS (in) x WIDTH (in) x LENGTH per piece (ft)] / 12 = BOARD FEET
or
[LINEAL FEET (ft) x THICKNESS (in) x WIDTH (in)] / 12 = BOARD FEET
Example: Find how many board feet in 20 Pcs. of 2x6 - 16'.
Answer: 320 Bd. Ft.
Solution: 20 x 2 x 6 x 16 = 3840. Divided by 12 = 320
Example: Find how many board feet in 500 LFT of 2x10.
Answer 833.34 Bd. Ft.
Solution: 500 x 2 x 10 = 10,000. Divided by 12 = 833-1/3
CHANGING BOARD FEET TO LINEAL FEET
Lineal feet is like placing the lumber end to end and just counting the total length (sometimes called
running feet). For example, 10 pieces of 2x4 - 10' would be 100 Lineal feet (LFT).
Sometimes you may have to change board feet into LFT. Here’s how:
1. Find how many board feet are in one LFT of the given size (you could calculate it with the board
foot formula, or look in the Board Feet per Piece Figure.
2. Divide that number into the board feet given.
Example: How many LFT of 1x3 lumber in 1000 board feet?
Answer: 4000 LFT
Solution: 1 pc. of 1x3 - 1' long contains 0.25 Bd. Ft.; 1000 Bd. Ft. divided by 0.25 = 4000
CHANGING BOARD FEET TO NUMBER OF PIECES
A list of materials may have been priced out “by the thousand board feet”. Now the customer wants the
material delivered. The bid may show 2000 Bd. Ft. of 2x8 at a certain price. The customer wants you to
deliver that much, but in 14' lengths.
Example: How many 2x8s - 14' should be delivered?
Answer: 107 or 108
Solution:
1. Find out how many Bd. Ft. in one piece of the desired size.
2. Divide that number into the allotted amount.
3. Round up or down depending on situation. 1 pc 2x8 - 14' = 18.667 Bd. Ft.; 2000 + 18.667 = 107.14
pcs.
BOARD FEET (cont.)
PRICING LUMBER “BY THE THOUSAND” BOARD FEET
Lumber is often priced “by the thousand” board feet. It’s often written like this example. $600 per M (M
being the Roman Numeral for 1,000.) Or $600/M; or $600/MBF ($600 per 1,000 Board Feet) and more.
To price lumber ”per M”, multiply the price per M x the number of board feet, then divide by 1,000 (to
divide by 1,000 simply move the decimal point three places to the left). A couple of alternate methods are
to divide the board feet by 1,000 then multiply by the per M price, or divide the price by 1,000 then multiply by the board feet. It all works out the same.
Example: How much does 350 Bd. Ft. of 2 x 10 cost if the price is $500/M?
Answer: $175
Solution: 350 x $500 = 175,000 Dividing by 1,000 (moving the decimal 3 places to the left) = $175.00
Sometimes you have to calculate the board feet first, but you know how to do that!
PRACTICE PROBLEMS Do these problems like
the examples on this page. Then check them by
doing them again using the table in Figure 2-22.
Then check with answers given at end of page.
Find board feet for problems 1-6
1. 15 PCS 2 x 6 - 10' = __________
2. 3 PCS 2 x 10 - 16' = __________
3. 1000 LFT 2 x 8 = __________
4. 7 PCS 1 x 4 - 4' = ___________
5. 560 LFT 2 x 4 = ___________
6. 25 PCS 2 x 4 - 15' (Special order) =_______
Find lineal feet for problems 7-10
7. 300 Bd. Ft. of 2 x 4 = _________ LFT
8. 1500 Bd. Ft. of 1 x8 = __________ LFT
9. 210 Bd. Ft. of 2 x 4 = _______ LFT
10. 800 Bd. Ft. of 2 x 10 = _________ LFT
Answers: Use your judgement.
1. 150
6. 250
2. 80
7. 450
3. 1333.33
8. 2250
4. 9.33
9. 315
5. 373.33
10. 480
Find number of pieces for problems 11-14
11. 500 Bd. Ft. of 1 x 3 - 10' = _________ PCS
12. 1100 Bd. Ft. of 2 x 4 - 16' = ________ PCS
13. 200 Bd. Ft. of 1 x 2 - 14' = ________ PCS
14. 3000 Bd. Ft. of 4 x 4 - 8' = ________ PCS
Price out problems 15-20, all at $550/M
15. 10 PCS 2 x 10 - 16' = $____________
16. 20 PCS 2 x 4 - 8' = $___________
17. 9 PCS 1 x 4 - 16' = $__________
18.300 PCS 2 x 4 - 16' = $_________
19.1000 Bd. Ft. 2 x 8 = $_________
20.1000 LFT 2 x 8 = $__________
If you’re within one Bd. Ft., or $1.00 you’re probably close enough.
11. 200
16. 107 BF/ $58.85
12. 103+
17. 48 BF/ $26.40
13. 85+
18. 3200 BF/ $1760.00
14. 281+
19. $550.00
15. 267 BF/ $146.85
20. 1334 BF/ $733.70
LUMBER COVERAGE TABLES
Since lumber is sold and board feet is figured on
the nominal size of lumber, some people are
misled as to how much area lumber will cover.
The problem is that a 1x8, for example, is
actually 7_" wide, not a full 8". All lumber has
this same problem. If you have the right tables
available you can easily tell how much to add to
make up for the difference in nominal and actual
lumber sizes.
The amount to add to make up for the difference
in actual and nominal size can be calculated
exactly. When using the products, however,
Lumber Type
S4S Boards
Shiplap
Tongue &
Groove
Bevel siding
1” lap
Drop siding
Nominal
Size
1x4
1x6
1x8
1x10
1x12
1x8
1x10
1x4
1x6
1x8
1/2x4
1/2x6
1/2x8
5/8x10
1x6
1x8
some waste usually occurs. Pieces are cut off
and are too short to be used, there could be
some “bad” spots, etc. The amount of waste
depends on the builder. Our tables will show the
amount extra needed because of the difference
in nominal and actual size and a column that
includes 5% more for waste. Some builders may
require 10% waste, or more. If so, you can adapt
these tables quite easily. There is also a column
in cases of diagonal installation, where an
additional 6 percentage points has been added
to the normal multipliers because of the extra
waste associated with diagonal installation.
ESTIMATING LUMBER COVERAGE
Board Feet
required per
SqFt of
Actual Width
surface
Overall
Face
No waste
(in)
(in)
31/2
31/2
1.14
51/2
51/2
1.09
71/4
71/4
1.10
91/4
91/4
1.08
111/4
111/4
1.07
7
71/4
6 /8
1.16
7
91/4
8 /8
1.13
3
1
3 /8
3 /8
1.28
3
1
5 /8
5 /8
1.17
1
7
7 /8
6 /8
1.16
31/2
31/2
1.60
51/2
51/2
1.33
71/4
71/4
1.28
91/4
91/4
1.21
3
1
5 /8
5 /8
1.17
1
7
7 /8
6 /8
1.16
Board Feet required per
SqFt of surface
5 % waste
1.19
1.14
1.15
1.13
1.12
1.21
1.18
1.33
1.22
1.21
1.65
1.38
1.33
1.26
1.22
1.21
Diagonal
1.21
1.27
1.24
READING COVERAGE TABLES
Select the kind of lumber used. Multiply the square feet of area (length x width) to be covered times the
multiplier from one of the last two columns, depending on whether you want to include waste.
Example: How many Bd. Ft. are required to cover a floor 15' by 20' if you are using 1x8 S4S boards and
want a 5% waste factor?
Answer: 345 Bd. Ft.
Solution: 15x20 = 300 Sq. Ft. times 1.15 (multiplier across from 1x8 S4S Boards, in 5% waste column).
Example: How much 1/2x8 bevel siding to cover 800 Sq. Ft. of wall? (include waste)
Answer: 1064 Bd. Ft.
Solution: Locate multiplier of 1.33 across from 1/2x8 Bevel siding. Multiply 1.33 x 800 = 1064. (1/2" in
lumber is still figured as 1" for finding board feet).
CONVERSION FACTORS FOR SLOPING JOISTS/RAFTERS
READING SLOPING JOISTS/RAFTERS
LENGTH TABLES
Conversion Factor
Slope
(in 12)
3
4
5
6
7
8
9
10
11
12
13
14
15
16
For
Common
Joist/Rafter
1.031
1.054
1.083
1.118
1.158
1.202
1.250
1.302
1.357
1.414
1.474
1.537
1.601
1.667
For
Hip/Valley
Joist/Rafter
1.436
1.453
1.474
1.500
1.530
1.563
1.601
1.641
1.685
1.732
1.781
1.833
1.887
1.944
First find the common rafter (or joist) run
including the overhang. The common rafter run
is the horizontal, or flat distance the rafter
covers. For example, if your house is 26' wide
and has a 2' overhang the common rafter run is
15'. Here’s why. 1/2 the house width of 26' is 13'
(the rafters peak in the middle of the house),
then add the 2' overhang for a total rafter run of
15'. Next find out what the roof slope is to be.
Assume it’s 4:12 (4 in 12). Then go to the
“Conversion Factor” table, read across from 4:12
to "common rafter" column. It is 1.054. Multiply
that times 15 to find the actual rafter length to be
15.81'. That means you’ll be using 16' stock.
To find the length of a hip or a valley rafter for
this same roof, multiply the common rafter run
(15') times the number in the far right column,
which is 1.453 to get a hip or valley rafter length
of 21.8', or use 22' stock.
Now try doing the calculations for buildings 22'
and 28' and 32' wide. All with a 5:12 rise to run
and a 2' overhang and see if you get the
answers shown below.
Answers:
22' bldg = 22 / 2 =11, +2' overhang
= 13 x 1.083
= 14.08'
28' bldg = 17.33'
32' bldg = 19.49'
CANADIAN IMPERIAL AND METRIC MEASUREMENTS
Canadians generally
measurement units.
use
a
mixture
of
Liquid volumes are typically based on the metric
(SI) system. Temperatures and distances are
commonly specified using metric terminology.
Weights, depending on the type of product, use
either the metric or Canadian Imperial system.
Lengths and dimensions of construction
products, particularly for residential use, are
generally in Canadian Imperial measurements.
Canadian building codes are written using metric
units. But the construction trades, particularly
those in residential construction, typically use
the Canadian Imperial system. This mixture of
measurement systems frequently results in
many product manufacturers providing
information using both systems. Unfortunately,
the approaches used in presenting the
“converted” measurements are not consistent.
Some information is based on “exact”
conversion measurements whereas other
information is based on “rounded”
measurements.
From your perspective and in communicating
with your customer it is important to recognize
that in some instances the exact conversion is
necessary and in other instances a more
“rounded” conversion is appropriate.
CONVERSION FACTORS
1 inch (in.)
1 foot (ft.)
1 yard (yd.)
=
=
=
25.4 mm
0.3048 m
0.9144 m
1 fluid ounce - US (oz.)
1 fluid ounce - Canadian (oz.)
1 gallon - US (gal.)
1 gallon - Canadian (gal.)
=
=
=
=
0.0296 L
0.0284 L
3.785 L
4.546 L
1 ounce - avoirdupois (oz.)
1 pound - avoirdupois (lb.)
=
=
28.35 g
0.454 kg
1 pound per square inch (psi)
1 pound per square foot (psf)
=
=
6.895 kN/m
0.04788 kPa
2
Celsius temperature = (Fahrenheit temperature - 32) / 1.8
SOME TYPICAL MEASUREMENTS
FOR LUMBER PRODUCTS
(“rounded” conversions)
Length
in.
mm
ft.
1
38
64
89
114
140
165
184
235
286
337
387
8
10
12
14
16
18
20
22
24
26
1 /2
1
2 /2
1
3 /2
1
4 /2
1
5 /2
1
6 /2
1
7 /4
1
9 /4
1
11 /4
1
13 /4
1
15 /4
26
Length
m
Note: Always consult your provincial and local codes
2.44
3.05
3.66
4.27
4.88
5.49
6.10
6.71
7.32
7.92
B2 LUMBER: USE IN CONSTRUCTION
LUMBER PRODUCTS
IN YOUR STORE
“In Your Store” is a worksheet where you apply the knowledge you have learned in this chapter to the
products you stock in your store. You may be able to find the answers on your own, or you may want to
ask some of the people you work with for help. There are no test questions on this information, as the
answers vary with location and local custom.
Do not send these answers in for correcting. This is a worksheet to help you get more familiar with
your store. It becomes a reference tool for you to review when you need a refresher about what your
store stocks.
DIRECTIONS: Take your copy of this page from your test package. Fill out the blanks as appropriate
for your situation. Sometimes more or less information could be entered. The object of the exercise is not
to fill in blanks, but to learn more about the products covered in this chapter, as applied to the store you
work in. So just use this exercise as a guide.
What transportation lines serve your store?
Rail
Truck
List the species and grade of lumber stocked?
2x4 Studs
2x4s
2x8s
2x6s
2xl0s
2x12s
List the quantity contained in your units of lumber.
2x4 Studs
2x4s
2x8s
2x6s
2xl0s
2x12s
Name of some Lumber brokers/wholesalers/mills your store buys from:
List the “Manufactured” framing members stocked or available? (such as TJI’s, laminated garage door headers, etc.)
What is your governing building code, if any?
Who is your building code official? Location?
What is the Live load required for roofs?
Any other special requirements?
NOTES:
ACKNOWLEDGEMENTS
■ The course was first developed by the North American Retail
Hardware Association (NRHA) and the Home Center Institute (HCI)
under the direction of a project coordinator and a number of
authors. Several U.S. based companies provided industry specific
information.
This second Canadian Edition of the ACHR is based on NRHA/HCI’s
14th Edition. It has been extensively modified and rewritten with
the help of Carl R. Wilson & Associates Ltd. (CRWAL) so as to
reflect Canadian products and construction practices. We also
acknowledge the many Canadian organizations and companies
that provided information for this Canadian edition of the
Advanced Course in Hardware Retailing (ACHR) and the Building
Material Product Knowledge Course (BMPK).
Because local codes and regulations vary greatly, you are reminded to check with local experts and authorities on which codes,
regulations and practices apply in your area.
Copyright© 2004 by NRHA. All rights reserved. No part of this
publication may be reproduced, stored in a retrieval system, or
any system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without prior written permission of the publisher.
Though the information in this course is intended to be
accurate and useful, the authors, editors, publishers,
NRHA and CRWAL and their directors, officers, agents
and employees will not be liable for any damage whatsoever that might occur from any use of this material.
NOTE: ALWAYS CONSULT YOUR PROVINCIAL AND LOCAL CODES