ROOF TAKE-OFFS MADE EASY
R O O F
Q U A N T I T Y
E S T I M A T E
G U I D E
2
ROOF TYPES
Gable Roof
Bell Cast Roof
Four Hip Roof
Skillion Roof
Cape Cod
(Gable Style) Roof
ROOF ELEMENTS
Pop (Nozzle)
Offset & Downpipe
Ridge Capping
End Span
Internal Spans
Overhang
End Span
Roof battens or purlins
Flue Penetration
Valley
Gutter
Skylight
Internal Spans
End Span
Overhang
Guttering
Downpipe Offset
Downpipe Strap
Downpipe
End Span
Downpipe Shoe
Pop (Nozzle)
Downpipe
Eaves Line
Hip Capping
Ridge
Soaker Flashing
Under & Over Flashings
Chimney
Dutch Gable
Gutter (spouting)
Short Hip
Bullnose Verandah
Gutter (Spouting)
Hip
Valley Gutter
Pop (Nozzle)
Offset & Downpipe
Hip Capping
Ridge
Bullnose Verandah
Ridge Capping
Barge Capping
Gable End
3
R O O F TA K E O F F S MADE EASY
This simplified Roof Take-off Guide
introduces basic techniques that will
help you calculate quantities of roofing,
battens and rainwater products for
houses and small commercial roofs with
a reasonable degree of accuracy.
WHAT IS A TAKE-OFF?
Quantities of roofing materials can be "taken
off" a roof plan. However, remember that
quantities taken off plans are only estimates.
Accurate roof sheeting sizes must be obtained
by measuring the roof structure on site after
the rafters or battens have been pitched.
ROOF TYPES
Take-off examples in this guide are for the most
common roof types (skillion, gable, hip and
bullnose). The principles can be applied to any
roof type by dividing the roof into sections.
ROOF SLOPE
The angle or slope of the roof determines the
length of sheet runs and the area of the roof.
Sheet lengths and roof area can both be
calculated using only the slope and the
horizontal distance between the fascia and the
ridge line on the roof plan. The table of Roof
Slope Factors provides a quick method of
calculating sheet runs and roof areas without
resor ting to trigonometry.
OVERHANGS
ROOF BATTENS
Allowance must be made for overhangs into
gutters at roof sheet ends (usually 50mm). On
gable roofs, an overhang may be added to the
sides of the roof to attach a gable roll. Other
overhangs or underlaps may be needed to
accommodate flashing, ridge capping and
changes in roof slope.
The number of supports or roof battens is one
more than the number of spans. To calculate the
number of spans for each area of roof, divide
the sheeting length by the sheeting span and, if
necessary, round up to the next whole number.
Then add one. The length of each batten is the
same as the roof width for a rectangular roof
area. Battens must also be added on both sides
of hips and valleys. Add 15% to each length to
allow for lapping and overhangs.
PENETRATIONS
When calculating the roof area, do not subtract
for penetrations such as skylights, vents,
dormers and chimneys. Unless the penetration
is extremely large (i.e. much wider than the
sheet) roof sheeting is continuous.
FLASHING
The amount and type of flashing depends on
the roof detailing. Refer to the Stramit
Architectural Detailing Guide for more
information. Stramit Building Products provides
a wide range of flashing for waterproofing roof
ends and joins, including under and over
flashing, ridge and barge capping, valley gutters
and custom shapes that enhance the aesthetic
appearance of the building.
Batten spacings should not exceed 1200mm
centres. Refer to Stramit's technical manual Top
Hats & Battens Capacity Tables for more information.
FASTENERS
The Product Selector table includes the number
of fasteners per sheet for each product. Note
that the first fastener for each sheet is on the
overlap.This fastener secures both sheets and is
only counted once.
Overlap
Overlap
Roof Edge
Multiply the number of fasteners per sheet by
the number of sheets then multiply the answer
by the number of fixing points (battens). Add an
extra row of fasteners for the final sheet, which
has no sheet overlap at the end.
4
R O O F TA K E O F F S M A D E E A S Y
Another method is to divide the sheet cover
by the number of fasteners per sheet (in the
case of Stramit® Corrugated sheeting with
3 fasteners per sheet, 762÷3 = 254mm) then
divide the total length of battens
(in millimetres) by this number. Add an extra
row of fasteners for the final sheet.
Add an extra 10% to allow for flashing, wastage
and loss.
DECKING CLIPS
For concealed fixed decking products, to
calculate the number of fixing clips simply
multiply the number of fixing points (purlins)
by the number of sheets,
e.g. 5 purlins x 12 sheets = 60 clips.
RAINWATER GOODS
You will also need to determine the quantity,
type, size and colour of the rainwater products
applicable to the structure. These may include
guttering (with stop ends, angles, nozzles and
brackets), downpipes (with offsets, shoes and
astragals) and roof edge capping.
NOTE
N1 or
N2 or
N3 or
ON ROOF SPANS
Region A (sheltered suburban)
Region A (exposed suburban) and Region B (sheltered suburban)
Region A (rural) and Region B (exposed suburban)
Region A =
Normal conditions in most of central and southern Australia,
including Tasmania (e.g. Sydney, Melbourne, Perth)
Region B =
Intermediate conditions prevailing in northern coastal zones
(e.g. Brisbane)
Region C & D = Cyclonic areas. Data not applicable.
Contact Stramit for advice.
Wind load regions from AS1170.2 or AS4055.
PRODUCT SELECTOR
STRAMIT®
Cladding Product
Cover Width
(mm)
Rib Height
(mm)
Fasteners
per sheet
Minimum
Roof Pitch
Corrugated
762
16
3 or 5
1 in 11 (5º)
Curved Corrugated
762
16
3 or 5
1 in 11 (5º)
Monoclad®
762
29
4
1 in 29 (2º)
Longspan®
700
27
3, 4 or 5
1 in 38 (1.5º)
Speed Deck Ultra®
700
43
3
1 in 57 (1º)
Speed Deck® 500 (Vic only)
500
41
2
1 in 57 (1º)
ROOF SPANS
STRAMIT
Cladding Product
Steel
GRADE
BMT
(mm)
Corrugated
G550
0.42
0.48
1200/1000
1600/1300
1200/1000
1600/1300
Curved Corrugated
G300
0.60
1200/1000
1200/1000
®
Monoclad
G550
0.42
0.48
1700/1400
2300/1900
1700/1400
2300/1900
Longspan®
G550
0.42
0.48
2100/1750
2700/2250
1900/1550
2300/1950
Speed Deck Ultra®
G550
0.42
0.48
2100/1750
2700/2250
2100/1750
2550/2150
Speed Deck® 500 (Vic only)
G550
0.42
0.48
0.60
0.60
1500/1250
2100/1750
2100/1750 (N1)
2000/1650 (N2)
1150/950
1850/1500
1500/1250
®
Internal/End Roof Spans (mm)
N1 and N2
N3
5
ROOF SLOPE FACTORS
Roof slope (degrees)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Roof Area/
Sheet Length
1.000
1.001
1.001
1.002
1.004
1.006
1.008
1.010
1.012
1.015
1.019
1.022
1.026
1.031
1.035
Hip Length
1.414
1.415
1.415
1.416
1.417
1.418
1.420
1.421
1.423
1.425
1.428
1.430
1.433
1.436
1.439
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Roof Area/
Sheet Length
1.040
1.046
1.051
1.058
1.064
1.071
1.079
1.086
1.095
1.103
1.113
1.122
1.133
1.143
1.155
Hip Length
1.443
1.447
1.451
1.456
1.460
1.465
1.471
1.477
1.483
1.489
1.496
1.503
1.511
1.519
1.528
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
Roof Area/
Sheet Length
1.167
1.179
1.192
1.206
1.221
1.236
1.252
1.269
1.287
1.305
1.325
1.346
1.367
1.390
1.414
Hip Length
1.537
1.546
1.556
1.567
1.578
1.590
1.602
1.616
1.630
1.644
1.660
1.677
1.694
1.712
1.732
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Roof Area/
Sheet Length
1.440
1.466
1.494
1.524
1.556
1.589
1.624
1.662
1.701
1.743
1.788
1.836
1.887
1.942
2.000
Hip Length
1.753
1.775
1.798
1.823
1.849
1.877
1.907
1.939
1.973
2.010
2.049
2.091
2.136
2.184
2.236
Roof slope (degrees)
Roof slope (degrees)
Roof slope (degrees)
6
QUICK ESTIMATES
The table of Roof Slope Factors
allows quick calculations of roof
area, sheet length and hip length.
These methods are for quick estimating
purposes only.
Accurate measurements must be taken
from the actual roof frame before
ordering roofing and rainwater products.
ROOF AREA
SHEET LENGTH
First determine the area of the roof plan by
multiplying the length of the roof by the width.
Before making the calculation, add gutter
overhangs of 50mm. In this case, there are
gutters on all four sides. Then, to find the area
of the hipped roof, simply multiply this plan
area by the Roof Slope Factor.
On the roof plan, measure the distance from
the line of the ridge to the outside edge of the
fascia, which in our example is half the span or
4000mm. Multiply this measurement by the
Roof Slope Factor for 30º (1.155) to find the
length of the sheet required to span from the
ridge to the fascia.
This same method is used for gable roofs (for
an explanation of the roof geometry, see hip
roof take-off example on page 15).
As an example, we will look at a typical
hipped roof where all four roof sections have
the same slope (30º) and all hips are of
equal length.
Using our example roof, we can determine the
roof area as follows:
Roof length (m)
This example illustrates the use of the
table only.
+
50
Total span (mm)
=
4050
Roof Slope Factor for 30º
x
1.155
Sheet length (mm)
=
4678
+
0.1
Total roof length (m)
=
19.1
4m
8m
11m
8
Gutter overhangs (m)
+
0.1
Total roof width(m)
=
8.1
Roof plan length (m)
19m
4000
Gutter overhang (mm)
See roofing examples for detailed take-offs.
Typical hipped roof (roof slope = 30º)
Half span - ridge to fascia (mm)
19
Gutter overhangs (m)
Roof plan width (m)
Note that all roof sheeting must extend at least
50mm beyond the fascia line to provide gutter
overhang.
19.1
Roof plan width (m)
x
8.1
Plan area (m2)
=
154.7
Roof Slope Factor for 30º
x
1.155
Roof area (m2)
=
178.7
Therefore, roughly 179m2 of sheeting will be
needed to cover the roof. On complex roof
shapes, you may need to add for wastage.
QUICK TAKE-OFF
HIP CAPPING
ROOF BATTENS
To find the length of ridge capping required to
cover the hip, measure the distance from the
ridge line to the fascia on the roof plan
(again 4000mm) add the gutter overhang and
multiply by the Hip Length Factor for 30º.
For a ballpark estimate of battens (in metres)
multiply the roof area by 1.5. A better method is
to divide the roof into sections and use the
table below. Multiply the number of battens by
the width of the roof panel. For a triangular roof
section, find batten lengths for a rectangular panel
and divide by 2. Remember that raked sheet
ends (hips and valleys) require batten support.
Half span - ridge to fascia (mm)
4000
Gutter overhang (mm)
+
50
Hip Length Factor for 30º
x
1.528
Hip capping required (mm)
= 6188.4
Capping for one hip (mm)
The hipped roof example can be treated as a
gable roof with 2 panels, each 19m wide. Sheet
length is 4.68m. If sheeting span is 1m,
6 battens are needed (by reading between
the columns in the table).
Battens per panel
x
19
Total for both sides
x
2
Add for hips (6.19m x 8)
+
49.5
Batten lengths (m)
=
277.5
Add 15% for laps, etc.
x
1.15
Total battens (m)
=
319
2
4
6
8
10
12
600
5
8
11
15
18
21
800
4
6
9
11
14
16
1000
3
5
7
9
11
13
1200
3
5
6
8
10
11
1400
3
4
6
7
9
10
1600
3
4
5
6
8
9
1800
3
4
5
6
7
8
2000
2
3
4
5
6
7
19
2200
2
3
4
5
6
7
Battens (mm) - Do not include laps
Multiply by 4
x
4
Total hip capping (m)
=
24.8
RIDGE CAPPING
The length of ridges running parallel to the sides
of the roof can be read straight off the plan.
For hipped roofs where all sides have the same
slope, the length of the top ridge is equal to the
length of the roof plan minus the width,
regardless of slope.
Maximum sheet length (m)
6
Length of battens (m)
Average
sheeting
span
(mm)
6190
Roof plan length (m)
NUMBER OF ROOF BATTENS
For different sheeting spans and lengths
7
FASTENERS
To find the number of roofing fasteners
required, divide the total batten length by the
space between each fastener. Add an extra
10% to the total for flashing, wastage and loss.
In the case of Stramit® Corrugated sheeting,
cover is 762mm. Divide this by the number of
fasteners per sheet (3) to find the distance
between each fastener (254mm).
277500
Roof plan width (m)
–
8
2400
2
3
4
5
6
6
Fastener spacing (mm)
÷
254
Length of top ridge (m)
=
11
2600
2
3
4
5
5
6
Plus 10%
x
1.1
2800
2
3
4
4
5
6
Number of fasteners
=
1202
Add 5% to all capping to allow for laps.
8
DOUBLE CARPORT OR SKILLION ROOF
This is a relatively simple example of a material take-off of a standard double carport or
simple skillion roof extension. If an extension roof, specific flashing is required to seal the join
between the roof and the main building.
First choose an appropriate roof cladding according to factors such as appearance, watercarrying capacity and roof slope.The minimum roof slope allowed by the BCA is 1º
(a fall of 1 in 57). For a 1º slope, a decking product must be used to ensure sufficient
water-carrying capacity.
In this example, the roof slope is 2º (a fall of 1 in 29). According to the Product Selector table
this is suitable for Stramit Monoclad® sheeting, which has an effective cover of 762mm.
Material thickness must also be specified, taking account of design criteria such as support
spacings, wind loads and foot traffic requirements. Simplified data is given in the Product
Selector and Roof Span tables for various roof sheeting options. Refer to the relevant
Stramit® Technical Manual for comprehensive information.
In this example, Stramit Monoclad® sheeting with a base metal thickness of
0.48 mm has been specified, with sheeting spans (batten spacings) of 1500mm.
SHEET QUANTITY
SHEET LENGTH
ROOF BATTENS
To find out how many sheets will be
required, simply divide the width of the
roof by the cover width of the sheet.
When calculating the sheet length,
remember to make allowance for roof
slope and for the gutter overhang,
which in this case is at the lower end of
the roof only.
The number of supports or roof
battens is one more than the number of
spans. The length of each batten is the
same as the roof width. Add 15% to
each length to allow for lapping and
overhangs.
Roof width (mm)
Roof sheet cover width (mm)
÷
7620
762
Number of sheets required
=
10
When the calculated number of sheets
includes a fraction, round up to the
nearest whole number.
Note that the roof will be slightly wider
than indicated above because the
underlap is not included in the sheet
cover width. In this case the final sheet
will extend beyond 7620mm by the
width of the underlap.
Roof length (mm)
Gutter overhang (mm)
Roof Slope Factor for 2º
+
x
6000
50
1.001
Total sheet length (mm)
= 6056
Sheet length (mm)
Sheeting span (mm)
Number of spans
Add for last batten
÷
=
+
6000
1500
4
1
Number of battens
=
5
Length of batten (m)
Number of battens
Total batten lengths (m)
Add 15% for laps, etc.
=
x
7.62
5
38.1
1.15
Required length of battens (m) =
43.8
x
If ordering stock lengths of battens, the
number required can be found by
dividing the total length of the battens
by the length of one stock batten. For
this example, if stock length were 7.5m,
six stock lengths would be required.
DOUBLE CARPORT
7620mm
End Span
1500
1500
Fall = 2º
Internal or
Intermediate
Spans
6000mm
1500
End Span
1500
ROOFING PRODUCTS
QUANTITY
Stramit Monoclad® cladding
Fasteners
Roof Fixings
Batten Fixings
Fascia
Metal Fascia
Rafter Brackets
Fascia Corners
Rainwater Goods
Guttering
Gutter Snap Clips
Gutter Stiffeners
Stop Ends
Downpipe
Downpipe Nozzles
Downpipe Offsets
Downpipe Astragals
Flashing
Edge Flashing
Fascia Capping
Battens
Roof Battens
6050mm
225
80
7620mm
22
2
7700mm
8
8
2
2400mm
1
1
2
7700mm
6000mm
7500mm
x 10 sheets
x 1 / 6000mm x 2
(measure on site)
x2
x6
7620mm
Plan of typical double carport roof (with 2º slope) - joins existing house at top
FASTENERS
OTHER PRODUCTS
From the Product Selector table,
Stramit Monoclad® sheeting requires
4 fasteners per sheet (3 plus 1 on the
sheet overlap). To calculate the number
of fasteners required, multiply this by
the number of sheets, then multiply by
the number of fixing points (battens).
Then add the fasteners required to fix
the roof edge on the final row of
sheeting.
Having determined the quantity and
length of roof sheets, lineal metres of
battens and number of fasteners
required, now determine the quantity,
type, size and colour of the rainwater
products and flashing applicable to the
structure. In this case:
Fasteners per sheet
Number of sheets
Number of battens
Number of battens in last row
x
x
+
4
10
5
5
Number of fasteners
=
205
Add an extra 10% to the number of
fasteners to allow for flashing, wastage
and loss.
Metal Fascia
Rafter Brackets
Fascia Corners
Guttering
Gutter Stop Ends
Gutter Snap Clips
Gutter Stiffeners
Edge Capping
Downpipe
Downpipe Nozzle
Downpipe Offset
Astragals
Stramit® Fascia
& Barge Board
Stramit® Quad Gutter
Stramit® Downpipe
Round
Astragal
Nozzle/Pop
Gutter Stiffener
Snap Clip
Fascia
Joiner
Stop End Plates
Fascia
Corner
Rafter
Bracket
Rectangular
Adjustable
Downpipe
Offset
Downpipe
Shoe
9
10
7620mm
10 Sheets of Stramit Monoclad®
IRREGULAR SKILLION ROOF
Gutter
Overhang
This is a slightly more difficult exercise for an irregular shaped roof extension constructed
with steel battens.
In this example, the roof slope is 2º and Stramit Monoclad® sheeting (0.48 bmt) has been
specified. Effective cover is 762mm.
Calculating quantities for a roof of irregular size with minimum wastage is quite simple
using the following method.
1400
1700
7900mm
1700
Roof Fall = 2º
1700
1400
Plan of typical triangular skillion roof (with 2º slope)
SHEET QUANTITY
SHEET LENGTH
First determine the number of sheets
required. This is a simple matter of
dividing the roof width by the sheet
cover width.
The roof plan tapers from 7900mm
down to nothing. As in the previous
carport roof, allowance must be made
for roof slope and gutter overhang.
Therefore, the length of the longest
sheet will be:
Roof width (mm)
Roof sheet cover width (mm)
÷
7620
762
Number of sheets required
=
10
When the calculated number of sheets
includes a fraction, round up to the
nearest whole number.
Roof length (mm)
Gutter overhang (mm)
Roof Slope Factor for 2º
7900
50
1.001
+
x
Total sheet length (mm)
= 7958
As shown in the diagram, each sheet is
incrementally longer or shorter than
the next one by the same amount. To
find this "reduction factor" simply divide
the length of the longest sheet by the
number of sheets.
When calculating the reduction factor
do not include the gutter overhang. This
should be added later.
Sheet length
(mm)
with 50mm
overhang
1st sheet
791
841
7908
10
2nd sheet
1582
1632
3rd sheet
2372
2422
= 790.8
4th sheet
3163
3213
The first sheet is 791mm long (without
gutter overhang). Each sheet after that
will be 790.8mm longer than the one
before it (plus the 50mm gutter
overhang). Always start with the
shortest sheet.
5th sheet
3954
4004
6th sheet
4745
4795
7th sheet
5536
5586
8th sheet
6326
6376
9th sheet
7117
7167
10th sheet
7908
7958
Sheet length without overhang (mm)
Number of sheets
÷
Reduction factor
When the gutter overhang is added, the
first sheet has a short side of 50mm
(rather than zero).
IRREGULAR SKILLION
7620mm
ROOFING PRODUCTS
1400mm
Raking
batten
(11.03m)
3@
1700mm
Only three transverse battens
are needed - The off-cuts supply the
two remaining battens.
11
QUANTITY
Stramit Monoclad® cladding
Fasteners
Roof Fixings
Batten Fixings
Fascia
Metal Fascia
Rafter Brackets
Fascia Corners
Rainwater Goods
Guttering
Gutter Snap Clips
Gutter Stiffeners
Stop Ends
Downpipe
Downpipe Nozzles
Downpipe Offsets
Downpipe Astragals
Flashing
Edge Flashing
Fascia Capping
Battens
Roof Battens
See sheet length table on page 10
183
70
8000mm x 1 / 7700mm x 1
17
1
7700mm
8
8
2
2400mm
1
1
2
8000mm
8000mm
7500mm x 6
1400mm
NOTE: Width of battens exaggerated for clarity.
ROOF BATTENS
RAKING BATTEN
FASTENERS
OTHER PRODUCTS
In this example there are 5 battens, the
longest being 7.62m. The simplest
method is to use 3 battens, each 7.62m
long, then use the cut-offs for the
remaining two battens, as shown in the
diagram. Note that this is only possible
if the spans are symmetrical.
On a raked roof such as this one, a
raking batten is required to support the
raked ends of the sheets.
The raked edge is the hypotenuse of a
right-angled triangle. The square of the
hypotenuse is equal to the sum of the
squares of the other two sides.
Therefore, the longest side equals
√(7.622 + 7.9 2), or 10.98m. Add 50mm
for gutter overhang.
The approximate number of fasteners
can be determined using a simplified
method, as for the battens. The total
number of fasteners will be the same as
for 10 sheets of Stramit Monoclad®
sheeting fixed on only three supports.
Now determine the quantity, type, size
and colour of the flashing and rainwater
products applicable to the structure, as
well as any insulation required.
Length of single batten (m)
Number required
Total length (m)
7.62
x
3
= 22.86
Transverse battens (m)
Raking batten with overhang (m)
Total batten lengths (m)
Add 15% for laps, etc.
+
=
x
22.86
11.03
33.89
1.15
Required length of battens (m) = 38.97
If batten stock lengths were 7.5m,
six battens would be required.
Fasteners per sheet
Number of sheets
Number of battens
Number of battens in last row
Raking batten fasteners (10x4)
x
x
+
+
4
10
3
6
40
Number of fasteners
=
166
Add 10% for flashing, wastage and loss.
Note that when adding the last row of
screws to fix the edge, six screws must
be added (not three) because there are
six fixing points.
12
GABLE ROOF FOR HOUSE OR GARAGE
Check the roof plan for the specified material. For the purpose of this exercise,
Stramit® Corrugated sheeting (0.42 bmt) has been nominated.
12m
Gable roll allowance:
Note that on a corrugated roof, the full width of the roof will usually
include an extra 100mm (50mm overhang at both ends)
to attach the gable roll.
Gable roll
If standard edge flashing is used,
no allowance is needed.
4.5
Roof slope
30º
m
Batten
Barge board
End Elevation
Side Elevation
7.8m
Plan and elevations of typical gable roof (with 30º slope)
ROOF AREA
SHEET QUANTITY
SHEET LENGTH
To determine the area of the whole
roof, multiply the roof width (including
gable overhangs if required) by the
sheet length (including gutter
overhangs) then double.
To calculate the number of sheets
required, divide the roof plan length by
the effective cover of the sheet. Then
double this to give the number of
sheets required to cover both sides of
the roof, assuming the roof is evensided. If the sides of the roof are
uneven, make two calculations and
add them.
When working from accurate plans,
measure the length of the barge on the
end elevation, from the apex of the roof
to the fascia board, adding at least
50mm for gutter overhang. There is no
need to allow for turning up the ends
of Stramit® Corrugated sheeting as
this does not affect the sheet length.
Alternatively, use the Roof Slope Factor
to determine the sheet length. On the
roof plan, measure the distance from
the line of the ridge to the fascia, which
in this example is half the span or
3900mm. Multiply this measurement by
the appropriate Roof Slope Factor
(1.155) to find the length of the sheet
required to span from the ridge to
the fascia.
Roof widths with overhangs (m)
Sheet length with overhangs (m)
Area of one side (m2)
Double for whole roof
12.1
4.56
55.18
2
x
=
x
Roof area (m2)
= 110.4
Alternatively, multiply the roof plan area
(with overhangs) by the Roof Slope
Factor.
Plan length with overhangs (m)
Plan width with overhangs (m)
Plan area (m2)
Roof Slope Factor for 30º
12.1
7.9
95.6
1.155
x
=
x
Approximate roof area (m2)
= 110.4
Roof length (mm)
Gable roll overhang (mm)
Total roof length (mm)
Sheet cover width (mm)
Sheet to cover one side
Double for whole roof
12000
+
100
= 12100
÷
762
=
16
x
2
Number of sheets required
=
32
All roof sheeting must extend at least
50mm beyond the fascia line to provide
gutter overhang.
Half span - ridge to fascia (mm)
Gutter overhang (mm)
Total span (mm)
Roof Slope Factor for 30º
+
=
x
3900
50
3950
1.155
Sheet length (mm)
= 4562
G A B L E RO O F F O R H O U S E O R G A R AG E
12m
Gutter Overhang
Eaves Overhang
ROOFING PRODUCTS
QUANTITY
Stramit® Corrugated cladding
4550mm x 32
Fasteners
Roof Fixings
645
Batten Fixings
264
Metal Fascia
4600mm x 4 / 6000mm x 4
Fascia
Rainwater Goods
7.8m
Eaves Overhang
Gutter Overhang
Plan View
Flashing
Batten supports are trusses at 900mm centres
Battens
ROOF BATTENS
Calculating the number of battens for a
gable roof is simple. The number of
battens on each side of the roof is one
more than the number of spans. In this
example, batten spacings have been
specified at 900mm.
Batten Spacings = 5 @ 900mm
Sheet length (m)
Sheeting span (m)
Number of spans
Add for last batten
Roof battens per side
Double for both sides
Total number of battens
Roof batten length (m)
Total length (m)
Add 15% for laps, etc.
÷
=
+
=
x
=
x
=
x
4.5
0.9
5
1
6
2
12
12.1
145.2
1.15
Roof Batten length required (m)=
167
If batten stock length were 7.5m, a total
of 23 battens would be required.
Rafter Brackets
42
Fascia Corners
4
Apex Cover Plates
2
Guttering
6100mm x 4
Gutter Snap Clips
22
Gutter Stiffeners
22
Stop Ends
4
Downpipe
2400mm x 2
Downpipe Nozzles
2
Downpipe Offsets
2
Downpipe Astragals
4
Gable roll
4600mm x 4
Ridge Capping
6100mm x 2
Roof Battens
7500mm x 23
13
FASTENERS
OTHER PRODUCTS
Again, calculating the number of
fasteners is simple, but remember to
add for the last row of battens, to fix
the edge of the roof.
Now determine the quantity, type, size
and colour of the flashing and rainwater
products applicable to the structure, as
well as any insulation required.
Fasteners per sheet
Number of sheets
Battens per sheet
Number of battens in last rows
x
x
+
3
32
6
12
Number of fasteners
=
588
Add 10% for flashing, wastage and loss.
14
DOMESTIC HIPPED ROOF
Check the plans for roof type, slope, specified material, etc. In this example
Stramit® Corrugated sheeting (0.42 bmt) has been nominated. Effective cover is 762mm.
22m
Roof slope
30º
47
93
mm
8.2m
Side Elevation
End Elevation
Plan View
Plan and elevations of typical hip roof (with 30º slope)
ROOF AREA
SHEET QUANTITY
SHEET LENGTH
The amount of sheeting required for a
hipped roof is the same as for a gable roof
of the same plan dimensions and roof
slope. Note this rule only applies to
equal-hip roofs, where all four sides have
the same slope.
Therefore, the method of calculating the
roof area of a hipped roof is virtually the
same as for a gable roof. Multiply the
length and width of the plan (including
gutter overhangs) then multiply by the
appropriate Roof Slope Factor. Because a
hipped roof has gutters on all four sides,
an extra 100mm (or 0.1m) must be added
to both the length and the width for
gutter overhangs.
Similarly, calculating the number of sheets
required for a hip roof is the same as for
a gable roof. Divide the roof plan length
by the effective cover of the sheet, then
double the answer to cover both sides of
the roof.
On the roof plan, measure the distance
from the line of the ridge to the fascia,
which is half the span or 4100mm and add
the gutter overhang. Multiply this by the
appropriate Roof Slope Factor (1.155) to
find the required length of the sheets.
All roof sheeting must extend at least
50mm beyond the fascia line to provide
gutter overhang.
Roof plan length (m)
Gutter overhangs (m)
+
22
0.1
Total roof length (m)
=
22.1
Roof plan length (m)
Gutter overhangs (m)
+
8.2
0.1
Total roof length (m)
=
8.3
Roof plan length (m)
Roof plan width (m)
Plan area (m2)
Roof Slope Factor for 30º
x
=
x
22.1
8.3
183.4
1.155
Roof area (m2)
= 211.9
Roof plan length with overhangs (mm) 22100
Sheet cover width (mm)
÷
762
Sheets to cover one side
=
29
Double for whole roof
x
2
Number of sheets required
=
58
Half span - ridge to fascia (mm)
Gutter overhang (mm)
Total span (mm)
Roof Slope Factor for 30º
+
=
x
4100
50
4150
1.155
Sheet length (mm)
= 4793
DOMESTIC HIPPED ROOF
ELIMINATING WASTAGE
15
WHY HIP AND GABLE ROOFS HAVE THE SAME COVER
On an equal-hip roof, where the side roofs and the end roofs have the
same slope, it is possible to order all roof sheets at one length, as for
Order all sheets
at the same
length, as for a
gable roof
Order all sheets at the same length.
Off-cuts from the side roofs are
installed on the opposite corner of
the end roof, with the raked ends
aligned with the hip.
a gable roof. Wastage will be eliminated because, when the sheets
on the side roof are cut along the hip line, the off-cuts can
be installed on the opposite corner of the end roof. The
off-cut sections will include the required gutter
Sheets should be laid against the
direction of prevailing weather
where possible.
overhang for the end roofs.
Sheets are cut
along hip line
Common
Rafter
On a hip roof, the end jack and the common
rafter are the same length.
They form two equal triangles, with the
raked hip line as the longest side.
End
Jack
Off-cuts are installed
on opposite corner of
end roof (raked ends
aligned with hip)
Hip
RIDGE CAPPING
The length of sheets on the tapered
sections of the roof can be calculated
using the method shown for the triangular
skillion roof. However, cutting the raked
ends of the sheets results in significant
wastage.Wastage can be eliminated by
ordering all sheets at the same length and
using the off-cuts to cover the end roofs.
ROOF BATTENS
To find the length of ridge capping
required to cover the hip, measure the
distance from the ridge line to the fascia
on the roof plan (4100mm) add gutter
overhang and multiply by the Hip Length
Factor for 30º from the table.
On an equal-hip roof, the top ridge is
equal to the roof length minus the width.
Half span - ridge to fascia (mm)
Gutter overhang (mm)
Hip Length Factor for 30º
Capping for one hip (mm)
Because of transport limitations, the top
ridge capping will need to be ordered as
two lengths of, say, 7000mm, with an
overlap.Total length of ridge capping
required is:
4100
+
50
x 1.528
= 6341.2
This should be rounded up to 6400mm to
allow both ends to be mitre cut.
Four lengths will be required.
Roof plan length (m)
Roof plan width (m)
–
22
8.2
Total ridge length (m)
=
13.8
Batten spacings have been specified to
meet the sheeting span limits of Stramit®
Corrugated sheeting. End spans are
900mm and internal spans are 978.5mm
(sheet length in the diagram does not
include gutter overhang).
4.1 x 1.155 = 4.7355m
6400mm x 4
7000mm x 2
900
97
mm
mm
900
Hip capping (m)
Ridge capping (m)
mm
8mm
mm
978
978
Sheet length is half the roof span (4.1m)
multiplied by the Sheet Length Factor (1.155)
which equals 4.735m.
As with roof sheeting, the length of roof
battens on an equal-hip roof is the same
as on a gable roof of similar plan.
16
DOMESTIC HIPPED ROOF
ROOFING PRODUCTS
QUANTITY
Stramit® Corrugated cladding
4790mm x 58
Fasteners
Roof Fixings
1426
Batten Fixings
805
Metal Fascia
7350mm x 6 / 8200mm x 2
Fascia
Note that battens
must be added to
both sides of the hips
6
5
4
Rainwater Goods
3
2
6
5
4
3
68
Fascia Corners
4
Guttering
7400mm x 6 / 8200mm x 2
Gutter Snap Clips
68
Gutter Stiffeners
68
Downpipe
2400mm x 4
Downpipe Nozzles
4
Downpipe Offsets
4
Downpipe Astragals
8
Flashing
Ridge Capping
6400mm x 4 / 7000mm x 2
Battens
Roof Battens
7500mm x 49
2
1
Rafter Brackets
Battens on the side roofs are treated as equal lengths. Off-cuts are used on the opposite
side of the end roof. Batten supports are assumed to be trusses at 900mm centres
Treat all battens as the same length, with
the off-cuts from the side roofs being
used on the adjacent end roofs.
The number of battens per side is one
more than the number of spans. Batten
length calculation is the same as for a
gable roof, except that battens must be
added to both sides of the hips.This will
be double the amount of hip capping.
Hip length for all hips (m)
Double for two rows
x
25.4
2
Total Hip battens
=
50.8
Battens per side
Double for both sides
Total number of battens
Batten length (m)
Total length (m)
Add hip battens
Add 15% for laps, etc.
x
=
x
=
+
x
6
2
12
22
264
50.8
1.15
Batten length required (m)
=
362
If stock batten lengths were 7.5m, a total
of 49 battens would be required.
FASTENERS
OTHER PRODUCTS
As with sheeting, the number of fasteners
can be calculated by assuming equal length
sheets, with the off-cuts used on the
end roofs.
Now determine the quantity, type, size
and colour of the flashing and rainwater
products applicable to the structure, as
well as any insulation required.
Fasteners per sheet
Number of sheets
Battens per sheet
Number of battens in last rows
Add for hip battens (6x8)
x
x
+
+
3
58
6
12
48
Number of fasteners
= 1104
Add 10% for flashing, wastage and loss.
Note there are 12 battens in total, so an
extra 12 fasteners must be added to fix the
edges, not 6.
17
BULLNOSE VERANDAH
5º roof slope
angle
of curve
The heritage-style bullnose verandah is the best-known
application of Stramit® Curved Corrugated sheeting.
In this example, standard dimensions have been specified:
85º
400mm radius
5º roof slope
400mm radius on
curved section
1800mm verandah depth
110mm straight wall section
Note that the verandah depth
(from wall to fascia) of 1800mm
requires a mid-span batten.
1800mm verandah depth
1800
Verandah
Roof Pitch
is 5º
Sheet length is best determined by
measuring a template or an actual
roofing sample (when replacing an
existing roof). The template should be
made to actual dimensions, including the
minimum straight roof section.
Templates can either be drawn on a
stable base (such as cardboard or
chipboard) or fabricated from timber,
steel, copper tube, etc.
If no template is supplied, all
information on the sample order form
must be supplied to enable accurate
manufacture.
11.250 14.850
Radius
400mm
The ver tical section (above the gutter) must have a
minimum depth of 110mm.
This is necessary for manufacturing purposes.
However, this section can be cut back after manufacture,
for an additional fee.
SHEET LENGTH
110mm
straight section
1800
1800
1800
26.100
29.700
1800
ADDITION FOR BULLNOSE SEGMENT (mm)
CALCULATING SHEET
LENGTH
Sheet length is the sum of the straight
and curved roof sections, plus the
straight wall section into the gutter
(minimum 110mm). Remember to
include underlap at the top if required.
In the case of a standard bullnose
verandah with a straight wall section at
the front (such as the example shown
here) the length can be calculated using
the following method.
Verandah depth (mm)
Sheet length factor for 5º
Bullnose segment from table (mm)
1800
1.004
337
x
+
Total sheet length (mm)
= 2144
This length includes the 110mm straight
wall section. Add 150mm underlap if
required.
Radius of
curve (mm)
300
400
500
600
700
800
900
1000
1200
1500
2000
5
280
337
394
450
507
564
620
677
791
961
1244
Pitch of straight roof section (degrees)
10
15
20
25
277
273
266
259
333
327
319
309
389
381
371
359
444
435
423
408
500
489
475
458
556
543
527
508
611
598
579
558
667
652
632
607
779
760
736
707
946
923
892
856
1224
1193
1153
1105
30
251
298
345
392
439
486
533
580
674
815
1050
This length includes:
110mm for the straight wall section at front of curve
Length of curved section
Part of straight roof section
Note: The angle of the curve is assumed to be 90º minus the slope of the straight section
(e.g., 85º angle of curve for a 5º roof slope)
18
B U L L N O S E V E R A N DA H
SAVING ON MATERIAL
Some cost saving can be achieved by incorporating the minimum straight roof section
into the curved length, thereby eliminating extra length and docking charges. This
provides a sloped section at the end, rather than a
straight wall section.
CONNECTION DETAILS
There are two basic methods of connecting a verandah to the house:
Main Roof
150mm
Underlap
(min)
Contact Stramit for fur ther advice.
Wall
Under and
over flashing
Wall
Verandah
Post
Verandah
Post
Minimum straight section incorporated
into curved roof section.
1. Butt join directly to the house wall under the guttering, using under-and-over
flashing to provide weather sealing. This is the most common style.
2. Underlap the main roof to give a smooth-flowing look similar to a bell cast or
dual-slope roof. When ordering an underlap style, specify “Main roof to match
bullnose verandah” because it is not possible to match the verandah to the roof.
SHEET QUANTITY
ROOF BATTENS
FASTENERS
To calculate the number of sheets
required, divide the perimeter
dimensions of the verandah by the
effective cover of the sheet.
A simple method of calculating batten
lengths is to assume that the off-cuts
from the long sides can be used on the
short sides at the opposite end.
However, battens must then be added
to the short sides, equal to the width of
the building.
Because of the mid-span support, three
battens are required for each sheet.
A simplified method can be used to
calculate the number of fasteners,
similar to that for battens. The extra
battens on the short sides must also be
accounted for.
Fasteners per sheet
Additional sheets on short side
Battens per sheet
Add number of battens
Fasteners per sheet
Number of sheets on long side
Battens per sheet
Add number of battens
x
x
+
3
39
3
3
Then double the quantities for both
sides and add together for total number
of fasteners.
Number of fasteners on long side =
354
, Side verandah (mm)
Sheet cover width (mm)
Sheets on one side
Double for both sides
29,700
÷
762
=
39
x
2
Sheets required for long sides
=
78
÷
=
x
14,850
762
20
2
Length of battens on long side (m)
29.7
Multiply by 3 & double for both sides x 3 x 2
Add battens for short sides
+ 11.25 x 3 x 2
Total length of battens (m)
= 245.7
Add 15% for laps, etc.
x
1.15
Sheets required for short sides =
40
Total batten length required (m) = 282.6
Sheets required for long sides
Sheets required for short sides
+
78
40
If stock batten lengths were 7.5m, a
total of 38 lengths would be required.
Total number of sheets
=
118
End verandah (mm)
Sheet cover width (mm)
Sheets on one side
Double for both sides
This also accounts for the fasteners on
the triangular end parts of the short
sides. The number of sheets in the
central part of the short side can be
found by dividing the building width
(11.25m) by the cover of the sheet
(0.762m) which equals 15.
x
x
+
3
15
3
3
Number of fasteners on short side =
138
Fasteners on long side x 2
Fasteners on short side x 2
+
708
276
Total number of fasteners
=
984
Add 10% for flashing, wastage and loss.
19
CURVED SHEETING ORDER FORM
BULLNOSE ORDER FORM
DIMENSIONS
CONCAVE
CONVEX
Straight roof section (m)
Straight wall section (m)
Colour side
Radius of curve (mm)
Colour side
E
Angle of pitch
D
A
A
Angle of curve
C
Verandah depth - wall to fascia (m)
C
Other information
B
B
Number of sheets
Topside colour or finish
A
Direction of laying L to R / R to L
Does curved sheet end lap straight sheet? If yes add 150mm
Bullnosing
A
D
E
A Straight section at overhangs __________________________________________________ mm
E
D Wall to fascia __________________________________________________mm
Colour side
C Height __________________________________________________ mm (Required if B not available)
C˚
G Total sheet length __________________________________________________ mm
B
Radius
B Radius __________________________________________________ mm (Required if C not available)
A
D
Type of curve ❑ concave
❑ convex
Number of sheets required __________________________________________________
Colour __________________________________________________
A Straight section into gutter __________________________________________________mm
Other information (eg. docking, endlapping) _________________________________________________
B Radius of curve __________________________________________________ mm
C Angle of roof pitch __________________________________________________ degrees
D Wall to fascia __________________________________________________ mm
(Required if G not available)
E
Sheet length __________________________________________________ mm
(Required if D not available)
Number of sheets required __________________________________________________
Direction of laying
❑ left to right ❑ right to left
Colour __________________________________________________
Other curving information (eg. docking, endlapping) _________________________________
The length of any curved sheet can be calculated by treating it as an arc
(a portion of the circumference of a circle). Divide the angle of the curve by
360 and multiply by the circumference (πd).
The formula is:
radius x 2 x 3.1416 x angle of curve ÷ 360
Radius of curve (mm)
400
Multiply by 2
x
2
Multiply by π
x 3.1416
Multiply by angle of curve (degrees) x
85
Divide by 360 degrees
÷
360
Length of curved section (mm)
=
593
R O O F I N G E S T I M AT E G U I D E
SYDNEY
(02) 9834 0900
ADELAIDE
(08) 8262 4444
NEWCASTLE
(02) 4954 5033
BRISBANE
(07) 3803 9999
CANBERRA
(02) 6297 3533
MACKAY
(07) 4942 3488
COFFS HARBOUR
(02) 6652 6333
ROCKHAMPTON
(07) 4936 2577
MURWILLUMBAH
(02) 6672 8542
TOWNSVILLE
(07) 4779 0844
ORANGE
(02) 6361 0444
CAIRNS
(07) 4045 3069
MELBOURNE
(03) 9237 6200
MARYBOROUGH
(07) 4121 2433
ALBURY
(02) 6041 7600
SUNSHINE COAST
(07) 5456 4083
BENDIGO
(03) 5447 8455
DARWIN
(08) 8947 0780
LAUNCESTON
(03) 6391 9293
PERTH
(08) 9493 8800
HOBART
(03) 6263 5536
BUNBURY
(08) 9721 8046
www.stramit.com.au
The information contained within this brochure is as far as possible accurate at the date of publication, however, before application in a par ticular situation, Stramit Building Products recommends that you obtain qualified exper t
advice confirming the suitability of product(s) and information in question for the application proposed. While Stramit Building Products accepts its legal obligations, be aware however that to the extent permitted by law, Stramit
Building Products disclaims all liability (including liability for negligence) for all loss and damage resulting from the use of the information provided in this brochure.
® TM Trade marks of Stramit Corporation Pty Limited ABN 57 005 010 195 trading as Stramit Building Products. A member of the Fletcher Building Group.
© Stramit Corporation Pty Limited April 2009. This edition supersedes all previous issues.
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