CARPENTRY - HOUSING
PART 2:
GABLE ROOFS
The gable roof is classified as being double-pitched and one of the simplest roof forms, due to
the fact that all rafters in the roof are exactly the same length and have the same bevels.
Gables are best suited for use on buildings or structures with a simple quadrilateral shape,
which is typical of the freestanding car garage, most outbuildings, lichgates (or lychgate),
portico’s, etc.
They may also be used in a modified form, such as a gablet, to enhance the surface of any other
roof type or may also be used as a means of providing light and ventilation to a room or roof
space. Many modern roof designs use dummy gables to enhance plain designs or to break up
large areas of straight roof surface.
In a conventionally pitched gable roof there are many individual members, which have specific
structural roles to perform. Each member is reliant on the next to form an unyielding structure
and at the same time provide a framework for the roof covering
PARTS, PROPORTIONS and DEDINITIONS
Span:
Half span or
Run of rafter:
Centre line
length of
rafter:
Hypotenuse:
Rise:
This is the horizontal width of the roof, measured overall the wall plates.
This is the horizontal distance measured from the centre of the ridge to the
outside of the wall plate. It is also the plan length of the rafter.
This is measured along the top edge of the rafter taken from the centre of
the ridge to plumb over the outside of the wall plate. It is equal to the length
of the hypotenuse of the right-angled triangle formed by the rise and half
span.
This is the sloping length of a right-angled triangle.
This is the vertical distance between the ‘X-Y’ line and where the
hypotenuse meets the centre of the ridge.
X-Y line:
This is an imaginary horizontal line, which passes through the position
where the outside of the walls is plumbed up to meet the hypotenuse or top
edge of the rafter. It is used to identify the centre line positions to calculate
rafter set out length and the rise of the roof.
Plumb bevel:
This is the angle found at the top of the right-angled triangle, formed by the
rise, half span and top of rafter edge. This bevel is used for the angled cut
on the top end of the common rafters.
Level bevel:
This is the angle found at the bottom of the right-angled triangle, formed by
the rise, half span and top of rafter edge. This bevel is used for the angled
cut on the foot of the common rafters, where they rest on the wall plates.
©TAFE NSW Construction and Transport Division
27
BASIC ROOF and CEILING FRAMING
DETAIL AT PLATE
g
an
er h
Ov
Eave width
gth
en
el
of
Birdsmouth
notch not greater
than D/3
lin
entr
Ce
r
fte
ra
Level bevel
Plate line
Ridge
Plumb
bevel
Collar tie
Strut
Ceiling
Fig 22 Section through a gable roof
Eq
ua
l
e
lin
Eq
ua
l
entr
Ce
Common rafter
Top plate
Half span or Run
Rise
Height
Gauge line
depth
DETAIL AT RIDGE BOARD
©TAFE NSW Construction and Transport Division
28
Rise
Height
CARPENTRY - HOUSING
Eaves width:
Eaves
overhang:
This is the horizontal distance measured between the outside face of the
wall frame, for a timber-framed cottage, or the outside face of the
brickwork, for a brick veneer and cavity brick cottage, to the plumb cut on
the rafter end .
This is the distance measured along the top edge of the rafter from the
position plumb up from the outside of the wall frame, where the X-Y line
passes through the hypotenuse, to the short edge of the plumb cut on the
end of the rafter.
Birdsmouth:
This is a right-angled notch taken out of the lower edge of the rafter, where
it rests on the top wall plate. The purpose of the birdsmouth is to locate the
bottom of the rafter over the wall plate and to provide an equal amount
left-on so the top edges of the rafters will all be the same. This is only
necessary when rough sawn timber is used. The depth of the notch should
not be greater than ⅓ the width or depth of the rafter, to prevent it from
being weakened.
Height of the
roof:
This is the vertical distance taken from the top of the wall plates to the top
of the rafters where they butt against the ridge.
Note: this should not be confused with the ‘Rise’ of the roof.
STRUCTURAL ROOF MEMBERS
COMMON RAFTERS
These are the main sloping members, which all have the same length, running from the wall plate
to either side of the ridge. They are spaced at 450 to 600 mm centres for tiled roofs, and up to
900 mm centres for sheet roofs. They support the roof battens, which in turn support the roof
covering.
The rafters may be set out using a variety of methods, which include use of the steel square, full
size set out and by calculating length.
Since the rafters are all the same lengths, they are usually set out from a pattern. This pattern has
the cutting length, plumb cuts and birdsmouth marked on it to allow for consistent accuracy
during repetitive mark transfer.
Note: Section size, timber species and stress grades for rafters may be obtained from AS 1684.
Ce
n
tre
Tru line l
e le eng
th
Tru
ng
o
th
of o e len
of f raft
r af
ver gth
te r e r
han
g
X
Y
Fig. 23 Set out of the common rafter
©TAFE NSW Construction and Transport Division
29
BASIC ROOF and CEILING FRAMING
True length of reduction
for ½ thickness or ridge
Allowance for
plumb cut
Plumb bevel
Level bevel
Birdsmouth notch
½ Thickness of
ridge on plan
PLUMB LEVEL
LEVEL BEVEL
Fig. 24 Bevels for the common rafter
RIDGE
Usually a deep and narrow member, it is the highest member of the roof, which runs
horizontally for the length of the roof. It must be level and parallel to wall plates, for the length
of the roof with the rafters being nail-fixed onto it on opposite sides.
Gable roofs may be very long, therefore the ridge may require one or more joins to create a
continuous length, as shown below:
SCARF JOINTED
Scarf jointed at
abutment of rafter
pair
Ridge
Rafters
CLOSE BUTT JOINTED
Joint spliced with
full depth timber
fish plates each
side, 25 mm thick
Fig. 25 Methods of joining ridge boards
Before the roof is erected, the ridge is set out (usually on one side only) to suit the position of
the rafters. The easiest way to set out the ridge is to lay the ridge on top of the completed
ceiling frame, over the external wall plate, and transfer the rafter positions onto the ridge board.
This ensures the rafters will be parallel and consistent with the positions marked along the wall
plate.
30
©TAFE NSW Construction and Transport Division
CARPENTRY - HOUSING
Rafter positions marked
onto ridge
Ceiling joists
Fig.
S
26
etting out the rafter positions onto the ridge board
WIND BRACING
Wind bracing is designed to prevent any
movement of the roof, or racking out of
plumb. Wind forces on the gable ends
usually cause racking.
Effect of racking of the roof
Fig. 27 Inclined wind bracing
Inclined brace
Bracing of the roof frame may be done by
having two opposite 45º timber braces from
the ridge onto an internal load-bearing
wall, normally using 75 mm square timber.
Ridge
45°
Alternatively, the roof frame may be
permanently braced using metal speed
bracing over the surface of the frame.
Temporary bracing may also be inclined, as
shown, or be diagonally fixed under the
rafters from the ridge to the external wall
plate.
Gable
rafter
Chock
Top plate
Stiffner
©TAFE NSW Construction and Transport Division
31
BASIC ROOF and CEILING FRAMING
PURLINS
Purlins, also called underpurlins, are fixed to the underside of the rafters parallel to the ridge
and wall plates. They provide continuous support under the rafters, similar to bearers under
joists in a floor frame.
They are normally spaced at 2100 mm centres, but this will depend on the section size and
stress grade, including the section size and stress grade of the rafters.
210
0m
ax
2 10
0m
ax
Fig. 28 Spacing of pur
Halved scarfing
Purlins are supported by struts at 2100 mm
centres, depending on the section size and
stress grade, with an additional strut under
any join.
The most common method of joining is to
half-lap and nail together. Joints may also be
cleated to prevent spreading by using timber
or metal connector plates.
Purlin
Strut
Rafter
Fig. 29 Joining purlins over a support
Purlins are positioned by measuring up from
the wall plate, the desired spacing, on the
underside of the end rafters, and marking the
top side of the purlin thickness. A string line
or chalk line is run through and a temporary
75 mm nail driven into the underside of
every third rafter. The purlin is lifted into
position and pulled hard up against the
temporary nail, clamped and double skew
nailed.
Note: Each rafter is sighted for straight
before being nailed to the purlins.
Rafters sighted for straight prior
to nailing off
75mm nail
Desired spacing
up from wall to
centre of purlin
Fig. 30 Joining purlins over a support
32
©TAFE NSW Construction and Transport Division
Purlins cramped
to rafter
CARPENTRY - HOUSING
STRUTS
These members are placed under the purlins to transfer the roof load to the internal load-bearing
walls, strutting beams or between other struts or supports.
There are several strutting systems used for roofing, as follows:
Inclined and Flying or Fan struts
These struts are cut around the purlin and run at 90º, or as near as possible, to the underside of the
purlin to the top of a load-bearing wall or strutting beam. Chocks are placed behind the foot of the
strut to prevent it sliding under load. Flying or Fan struts are chocked at the top as well by fixing
blocks onto the face of the purlin, on the outside edge of the strut.
Alternatively, they may be bolted through the purlin or have a spreader bolted across the face to
prevent them sliding apart under load.
Solid timber struts are normally 75 x 75 mm, however this will depend on the stress grade, length
of strut and imposed roof load. The following table provides a guide for imposed roof loads,
which will assist in the selection of strutting material:
TABLE 1
MASS OF ROOF MATERIALS
TYPE
Steel sheet
MATERIAL
0.76 mm thick
0.55 mm thick
1.2 mm thick
Terra-cotta
Concrete
Pressed metal
Corrugated sheet
Flat shingles
38 x 75 battens at 900 mm c/c
25 x 50 battens at 330 mm c/c
35 x 35 battens at 330 mm c/c
Aluminium sheet
Roof tiles
Fibre cement (F.C.)
Unseasoned hardwood
Seasoned pine
Approx. MASS in kg/m²
10.0
6.0
5.0
58.0
54.0
7.5
16.0
15.0
3.2
3.8
2.0
Average mass of metal roof covering and battens is approx. 15 kg/m²; and
Average mass of tiled roof covering and battens is approx. 60 kg/m².
Note: The size of struts should be based on AS 1684 - 1999 Part 2
Rafters
Rafter
Chock
Chock
Purlins
Alternative
spreader bolted
to struts
Inclined Strut
Chock
Chock
Chock
Flying Struts
Chock
Load-bearing
wall
ELEVATION
SECTION
SINGLE INCLINED STRUT
ELEVATION
Load-bearing
wall
SECTION
FLYING OR FAN STRUTS
Fig. 31 Common strutting methods
©TAFE NSW Construction and Transport Division
33
BASIC ROOF and CEILING FRAMING
Fitting struts to various angles
It may not be possible to fit the struts at exactly 90° to the underside of the purlin, therefore the
following adjustments may be made:
Rafter
Rafter
90°
'x' Small variations
permitted (approx.
or truly
perpendicular)
'Y' Small variation
permitted (approx
or truly vertical)
D
B
Top of strut
must reach at
least to top
edge of purlin
B
A
C
A
C
Struts
Struts
'A' Not less than 44 mm
'B' Not less than 25 mm and not over 38 mm measured at
bottom of purlin
STRUT PERPENDICULAR TO RAFTER
C' Not less than 38 mm
'D' Not over 12 mm
STRUT VERTICAL OR 'PLUMB' TO RAFTER
2/2.5 x75 mm nails
Strut
Low angle
flat strutting
Studs
'Z' Any angle from 0° upwards, provided that the
strut is not flatter than 1 vertical to 2 horizontal units
for a roof slope of 1:2, or 1 vertical to 1.5 horizontal
units for a roof slope of 5:12
Not less than 5 nails
at least twice length
of chock thickness
chock
Stiffener
NOTE: Long chock required to prevent slip caused
by greater thrust
LOW ANGLE FLAT STRUT
Strut
Perpendicular
or steep angle
strutting
Not less than 3 nails
at least twice length
of chock thickness
2/2.7x75 mm nails
E
E
Top wall plate
E' Not less than 38 mm, but not more than ½ width of
strut.
FLAT STRUTTING
NOTE: Short chock required due to a more direct
load to the wall
STEEP ANGLE PERPENDICULAR STRUT
Fig. 32 Methods of fitting struts
34
©TAFE NSW Construction and Transport Division
CARPENTRY - HOUSING
Supporting struts over internal walls
It is preferable to position struts directly over studs, however as this is not always possible the
load must be distributed in an alternative way. This may be achieved by strengthening the plate
either between or over the studs with additional blocking.
Also, where struts are placed at a low or flat angle, it will be necessary to fit a block, referred to
as a chock, behind the foot of the strut to prevent it from sliding under load.
Chock with not
less than 3 nails at
least twice length
of chock thickness
Strut
Top wall plate reinforced
over two studs. Stiffener
50mm thick, full width of
wall plate
Top wall plate
Intermediate blocking to
stiffen top plate
NOTE: Avoid strutting between studs
ALTERNATIVE STIFFENING METHOD
STRUT BEARING BETWEEN STUDS
Top plate locally reinforced to
distribute load over two or
more studs
Braces, 38mm
thick, full stud
width
NOTE: Avoid strutting over openings
STRUTTING OVER DOOR OPENINGS
Lintel deemed to be a
strutting beam. Refer to
AS 1684
ALTERNATIVE STIFFENING METHOD
Strut landing only if
unavoidable
Preferred strut
landing over a
stud
STRUTTING OVER AN OPENING
Fig. 33 Methods of reinforcing top wall plates for struts
©TAFE NSW Construction and Transport Division
35
BASIC ROOF and CEILING FRAMING
Scissor struts
These struts consist of deep-sectioned timber members supported over external walls and
bolted where they cross in the centre of the roof space.
They are designed to transfer the roof load to the external walls where there are no internal
walls for support or the internal walls are non load-bearing.
∅12 Bolt, nut and
washer or well nailed
20 Bolt, nut and washer
Spacer block
Underpurlin
Scissor struts
NOTE: Scissor struts must be
kept clear of hangers
Hanger
Hanger
20 Bolt, nut and washer to
spliced joint of tie member
Fig. 34 Full scissor type strutting
If there is internal support available, but would cause an inclined strut to be too flat to be
effective, then a half scissor may be used.
20 Bolt, nut and washer to top
connection. Use ∅20 for all other
connections.
Half scissor strut
Strut
Tie member required where
ceiling joist can not be used
as bottom chord of truss
Regular purlin
strutting
Fig. 35 Half scissor type strutting
Note: The foot of the scissor struts must be bolted
to a rafter, and preferably a ceiling joist as well,
and bolted together where they cross over in the
centre of the roof. If ceiling joists are not full
length they should also be bolted together where
they lap over a wall, to prevent the external walls
spreading under load.
Section sizes and stress grades should be taken
from AS 1684 - 1999 Part 2
Common rafter
Scissor strut
15
min
20
bolt
Ceiling joist
(tie member)
Fig. 36 Bolt connection detail
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©TAFE NSW Construction and Transport Division
CARPENTRY - HOUSING
Strutting beams
An alternative to using scissor struts over large room spans would be the use of large timber or
steel strutting beams.
They are usually placed parallel to the ceiling frame hangers, but must not rest on any part of
the ceiling frame. To achieve this the ends must be packed up at least 25 mm above the ceiling
joists, which allows for any deflection.
In some situations the hanger and strutting beam may be the one member, but the member
should comply with AS 1684 tables or be designed by a structural engineer to cater for the
additional load.
The following materials may be used for strutting beams:
• Solid timber (hardwood or softwood with the correct stress grade);
• Horizontally laminated timber (similar to Glulam beams);
• Vertically laminated timber (similar to L.V.L. beams);
• Boxed beams (made from plywood); and
• Steel beams (either Universal channels, U.C., or Universal beams, U.B.)
Note: Refer to AS 1684 for section sizes and stress grades of timber members. If deep solid
timber is used, it should be seasoned to reduce the risk of shrinkage. Most timber species over
175 mm deep will shrink excessively.
12mm max
Rafter
Purlin
Purlin
Inclined Strut
38mm min
Chock
Plumb strut
Deep strutting beam
25mm clearance to
allow for deflection
Ceiling joist
STRUTTING BEAM RUNNING
PARALLEL WITH HANGER
STRUTTING BEAM RUNNING
PARALLEL WITH HANGER
Fig. 37 Positions of strutting beams
An alternative position for the strutting beam is directly under the rafters, which are notched
over it as if it were another wall plate. The plumb struts under it would then rest on an internal
load-bearing wall.
See
adjacent
detail
Beam
Strutting
beam
Birdsmouth to
rafter provides
secure seating
to beam
Plumb
strut
Fig. 38 Alternative strutting beam position
©TAFE NSW Construction and Transport Division
37
BASIC ROOF and CEILING FRAMING
PATENT TYPE STRUTTING
Super Barap
This is a patent type of strutting system used where conventional strutting methods cannot be
used or it will be too expensive to use them. These patent struts consist of steel saddle brackets
at either end connected by a 12 mm diameter steel rod and a centrally located adjustable
fulcrum. They may be used under purlins, rafters, hips or valleys to provide the required
support where sagging or excessive deflection of the member has or may occur.
This system operates similar to a truss as it is made up of ties, which are in tension, and a strut,
which is in compression. They may be purchased through hardware stores or direct from the
manufacturer.
Note: See manufacturers brochure and specification for further details and fitting instructions.
Maximum span 2 fulcrums
Purlin
6.700m
Saddle bracket
Adjustable
fulcrums
Strut
Saddle bracket
Tie rod
Strut
Maximum span 1 fulcrum
Purlin
5.500m
Saddle bracket
Adjustabl
e fulcrum
Strut
Saddle bracket
Tie rod
Strut
Fig. 39 Patent type Super barap strut/brace
Cable truss
This is another very effective patent type system, similar to the Super Barap, which uses two
tensile steel cables instead of a solid steel rod. Each cable is made up of 7/ 1.6 mm Ø wire
strands. The truss may also be fitted with an additional adjustable fulcrum or strut for use on
longer members. The ends of the cables must be bolted within 200 mm Max. of the end
supports.
To calculate the length of the truss, measure the distance between the bolted ends and add 80 to
150 mm to allow for the cables to run over the single or double fulcrums.
Note: See manufacturers brochure and specification for further details and fitting instructions.
'Tyloc'
plates and
bolt
Rafter
Purlin
Support
block
Adjustable
fulcrum
Twin wire support
system
Fig. 40 Patent type Cable truss/strutting system
38
©TAFE NSW Construction and Transport Division
CARPENTRY - HOUSING
COLLAR TIES
They are light sectioned horizontal members used
for additional support, like spreaders, to prevent
the rafters from sagging at the purlin position.
These are fixed to alternative pairs of rafters, i.e.
at 900 to 1200 mm spacings, and placed on top of
the purlins running parallel to the ceiling joists.
They may be half scarfed around the face and
edge of the rafters and nail fixed with 2/75 mm
nails.
Common rafter
Collar-tie half
scarfed or bolted
to rafter
Underpurlin
Alternatively, they may be run past the face of the
rafters and be bolted to them at both ends using a
single 10 mm Min. mild steel, cuphead bolt.
Strut
Fig. 41 Collar tie fitted to rafter over purlin
Note: The size of collar ties depends on the stress grade and length of timber used. As a guide,
they are normally 75 x 50 or 125 x 38 F5 to F7 up to 4200 mm long, and 100 x 50 or 125 x 38
F5 to F7 over 4200 mm long. Refer to AS 1684 for specific details.
Placed every 2nd pair of rafters,
900 to 1200 mm apart
Fig. 42 Placement of collar ties in the roof frame
©TAFE NSW Construction and Transport Division
39
BASIC ROOF and CEILING FRAMING
GABLE ENDS
There are three main methods used to finish the ends of gables:
1. Flush gable with no eaves;
2. Flush gable with raked eaves; and
3. Boxed gable.
Flush gables (no eaves)
The end of the gable is flush or in-line with
the outside face of the end wall. The end of
the roof has no overhanging eaves, only a
barge fixed flush with the outside of the end
wall. This finish may be applied to timber
framed cottages, where the walls are clad with
boards or sheeting, or to brick veneer and
cavity brick cottages, where the brickwork
runs to the underside of the roof covering.
The triangular section formed between the top
of the standard wall frame and the underside
of the rafters is framed with stud material,
spaced at the same centres as the wall frames,
fixed on flat or on edge.
Fig. 43 Flush gable
Gable studs for cladding fixing or
trying to brick work.
Fig. 44 Framed flush gable
40
©TAFE NSW Construction and Transport Division
CARPENTRY - HOUSING
Flush gables with raked eaves
The gable finish for this type is similar to that
of a gable with no eaves. The main difference
is the end of the roof frame is extended past
the end wall to form an eaves overhang, which
is lined on the rake.
The ridge and top wall plates may be extended
to provide support for the gable rafters. Where
the overhang is particularly wide or the length
of the gable rafters is excessive, the purlins
may also be extended to provide additional
support.
Where the raked ends are required to adjoin
level side eaves, the ends of the eaves are
usually boxed to allow the raked section to
terminate neatly.
Fig. 45 Flush gable with raked eaves
Rafters
Gable
stud
Trimmers
Trimmer
Top
plate
Wall
stud
Fig. 46 Framing for eaves lined on-the-rake
©TAFE NSW Construction and Transport Division
41
BASIC ROOF and CEILING FRAMING
Framing variations for raking eaves
The top wall plates may be extended to take
the gable rafters.
It is only necessary where the ends of the side
eaves are to be boxed, which will allow the
raked gable eaves to terminate neatly.
Note: It is necessary to extend the ridge for
this method as well.
Stiffener to
support extended
top plate
Fig. 47 Extended top plate
When the eaves width at the gable ends is
excessive, i.e. say greater than 450 mm, or the
unsupported length of the gable rafter is
excessive for the section size of rafter, then it
may be necessary to extend the purlins on both
sides to support the mid length of the gable
rafters.
Also, with some roof design or when the eaves
are lined on top of the rafters, it is desirable to
expose the framing members.
(this was a typical method used for the
‘Bungalow’ style of cottage during the
Federation period)
Trimmers or
outriggers
Fig. 48 Cantilevered gable framing
To provide continuous raked eaves with no
framing members visible, it will be necessary
to place cantilevered trimmers to support the
gable rafters.
Gable rafter
Purlin
These trimmers, also known as outriggers, are
either checked into the rafters on their flat or
will be supported on-edge over the gable end
wall frame, which has raking top plates. Short
rafter trimmers are then cut between them to
provide fixing for tile or roof sheet battens.
Fig. 49 Extended purlin
42
©TAFE NSW Construction and Transport Division
CARPENTRY - HOUSING
Boxed gable
A boxed gable occurs where it is desirable to
have level eaves on both sides and ends of the
roof. The face of the boxed gable may be clad
with the same material as the end wall, but may
also be featured by cladding with an alternative
material finish.
The fascia may be returned level around the
corner or the barge may extend to the outside
of the gutter and have a small timber ‘bellcast’
added to the top edge.
The end of the boxed gable is framed up with
gable studs, eaves trimmers and a full width
bottom chord or tie, to allow for fixing of the
cladding and eaves soffit lining.
Fig. 50 Boxed gable
Soffit lining
Ridge
Fascia
Purlin
Ceiling joist
Ceiling
trimmers
Top plate
Gable cladding
Soffit
bearer
Batten for
fixing
Gable stud
Plates and purlins extended
for support
Fig. 51 Framing for a boxed gable
©TAFE NSW Construction and Transport Division
43
BASIC ROOF and CEILING FRAMING
Verge finishes
The verge is the section at the end of the gable roof where the roof surface meets the barge or
verge board. The type of finish will depend on the roofing material used and the finish required.
Tiled roofs may have a coloured mortar pointed verge, which is laid on a narrow fibre cement
(F.C.) strip, it may be covered with purpose made barge cover tiles or the tiles may be cut against
a pre-formed ‘barge soaker’. In recent times, the Colorbond barge soaker has become the
preferred method of finishing the verge as it does not require any maintenance.
Metal sheet roofs may also have a barge soaker or may be fitted with a covering pre-formed
Colorbond barge capping.
Screw Fixing
Pop
rivet
Clip and/or
bracket fixing
Clip
Vapour
barrier
Fig. 52 Metal barge capping profiles
Steep
angle
ridge
Standard ridge tiles
Tiles bedded and
pointed
Fibrous cement strip
Fig. 53 Pointed verge
Ridge capping
Barge cover tiles
Reflective foil insulation/sarking
Fig. 54 Barge tiled verge
End cap
Vapour
barrier
Barge capping
Fixing clips
NOTE: Metal barge capping may also
be used on the verge of tiled roofs
Fig. 55 Metal barge capping to verge
44
Gutter bracket
Fig. 56 Matching barge and gutter
©TAFE NSW Construction and Transport Division
CARPENTRY - HOUSING
‘Colorbond®’ patent verge finishes
In recent years the method of finishing the verge for gable roofs has changed. New metal fascia
and barge profiles provide an alternative to using primed fascia boards. They are attached
directly to the ends of the rafters or outriggers, using special brackets, and the gutter or barge
soaker is attached to them.
The benefits of using these Colorbond® products is that they do not require painting, they are
not susceptible to decay caused by leaking gutter joints, they do not cup or twist, they are
available in a full range of popular colours and they are relatively simple to fit.
The Colorbond® metal barge is attached using barge rafter brackets and then the Colorbond®
metal barge soaker is placed over the top. The benefit of using the barge soaker removes the
need to bed and point the verge, which eventually cracks and becomes loose over time.
The following details were supplied courtesy of ACE GUTTERS PTY LTD.
Barge Soaker
mm
26
180mm
Steel Fascia
10mm
70mm
28mm
97mm
16mm
95mm
36
Barge Rafter Bracket
Straight Joiner
Barge Apex
Cover
mm
Barge Mould L.H. & R.H.
Fig. 57 Barge, soaker, and accessories
©TAFE NSW Construction and Transport Division
45
BASIC ROOF and CEILING FRAMING
CALCULATING ‘DROP-OFF’
The finished height of the brickwork is determined by the height of the timber frame and the
drop-off needed to give the eaves width required. In turn the pitch of the roof and the head
height of the windows influence the eaves width and drop-off.
Where eaves soffit finishes above the head of the windows, the space may be infilled with
brickwork or with timber framing and cladding material.
The drop-off measurement is taken vertically from the top of the wall plate to finished height of
the brickwork. The purpose of the drop-off measurement is to provide the bricklayer with a
finished height, in relation to the height of the wall frame, to allow an even gauge to be set out
on the storey rod.
Note: In a brick veneer cottage with a suspended timber floor, the brickwork is normally
completed to the underside of the bearer and then the brick gauge is calculated to drop-off
level.
Same Roof Pitch
30°
Same Roof Pitch
30°
Drop-off
Drop-off
Smaller eaves width
Larger eaves width
SMALLER DROP-OFF
(HIGHER WALL)
Larger Roof Pitch
LARGER DROP-OFF
(LOWER WALL)
Smaller Roof Pitch
30°
22½°
Smaller eaves width
Larger eaves width
SAME WALL HEIGHT
SAME WALL HEIGHT
Fig. 58 Details showing how drop-off affects the width of the eaves
46
©TAFE NSW Construction and Transport Division