Appropriate Open link in same pagePerformance Requirements
Where an alternative roof cladding is proposed as a Open link in same pagePerformance Solution to that described in Open link in same pagePart 3.5.1, that proposal must comply with—
Roofing tiles: AS 2049 and AS 2050.
Metal roofing: AS 1562.1.
Plastic sheet roofing: AS/NZS 4256 Parts 1, 2, 3 and 5; and AS/NZS 1562.3.
Corrugated fibre-reinforced cement sheet roofing: AS/NZS 1562.2.
Asphalt shingles: ASTM D3018-90.
Pliable membrane and underlay: AS/NZS 4200 Parts 1 and 2.
Compliance with this acceptable construction practice satisfies Open link in same pagePerformance Requirements
the building is located in an area with a Open link in same pagedesign wind speed of not more than N3; and
roof tiles are installed in accordance with Open link in same page3.5.1.2; and
metal sheet roofing is installed in accordance with Open link in same page3.5.1.3.
Roof tiles, complying with AS 2049, must be installed, fixed and flashed in accordance with the relevant provisions of this Part.
Roof tiles on roofs with a pitch of not less than 15 degrees and not more than 35 degrees must be fixed in accordance with Open link in same pageFigure 3.5.1.1.
Fixings for roof battens and batten sizes must comply with Open link in same pagePart 3.4.3.
All tiled roof Open link in same pageflashings, ridge and hip tiles must be installed in accordance with Open link in same pageFigure 3.5.1.2.
Lead Open link in same pageflashings must not be used on any roof that is part of a potable water catchment area.
Sarking must be installed under tiled roofs in accordance with Open link in same pageTable 3.5.1.1b.
Where sarking is installed, an anti-ponding device/board must—
be provided—
on roofs with pitches of less than 20°; and
on all roof pitches where there are no eaves overhang; and
be fixed along the eaves line from the top of the fascia back up the rafter with a clearance of approximately 50 mm below the first batten.
All water discharged from a gutter/valley or downpipe onto a tiled roof must be prevented from inundating or penetrating the tiling by the provision of—
a spreader pipe; or
a flashing; or
sarking installed with a minimum width of 1800 mm either side from the point of discharge and extended down to the eaves gutter.
Figure 3.5.1.1 MINIMUM MECHANICAL FASTENING FOR TILES AND ANCILLARIES |
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Wind classification | Tile installation | Ancillary installation | |
Edge of roof | Field of roof | Ridge, hip and barge tiles | |
less than N2 | Mechanically fasten each full tile in second course and then every second tile in every course, or every tile in each alternative course. | Mechanically fasten each tile | |
N2—N3 | Mechanically fasten each full tile in second course | Mechanically fasten each second full tile in every course | |
Notes:
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Figure 3.5.1.2 TILED ROOF FLASHING AND OTHER DETAILS |
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Diagram a. | Mechanical fastening-ridge clip (Also see Open link in same pageFigure 3.5.1.1) | ||
Diagram b. | Dry valley | Diagram c. | Bedded and pointed valley |
Diagram d. | Fastening of hip tiles | ||
The design and installation of metal sheet roofing must comply with the relevant provisions of this Part.
Metal sheet roofing must be protected from corrosion in accordance with Open link in same pageTable 3.5.1.1a.
Table 3.5.1.1a ACCEPTABLE CORROSION PROTECTION FOR SHEET ROOFING
ENVIRONMENT | LOCATION | MINIMUM METAL COATING IN ACCORDANCE WITH AS 1397 | |
---|---|---|---|
Metallic coated steel | Metallic and organic coated steel | ||
Low (Mild steel corrosion rate 1.3 to 25 µm/y) |
Typically remote inland areas. |
Z450 galvanised or AZ150 aluminium/zinc or AM125 aluminium/zinc/ magnesium |
Z275 galvanised or AZ150 aluminium/zinc or AM100 aluminium/zinc/ magnesium |
Typically more than 1 km from sheltered bays. | |||
Medium (Mild steel corrosion rate 25 to 50 µm/y) |
Typically more than 1 km from Open link in same pagebreaking surf or aggressive industrial areas. |
Z450 galvanised or AZ150 aluminium/zinc or AM125 aluminium/zinc/ magnesium |
Z275 galvanised or AZ150 aluminium/zinc or AM100 aluminium/zinc/ magnesium |
Typically more than 50 m from sheltered bays. | |||
High (Mild steel corrosion rate 50 to 80 µm/y) |
Typically more than 200 m from Open link in same pagebreaking surf or aggressive industrial areas. |
AZ150 aluminium/zinc or AM125 aluminium/zinc/ magnesium |
AZ150 aluminium/zinc or AM100 aluminium/zinc/ magnesium |
Typically within 50 m from sheltered bays. | |||
Very High (Mild steel corrosion rate 80 to 200 µm/y) |
Typically extends from 100 m inland from Open link in same pagebreaking surf to 200 m inland from Open link in same pagebreaking surf, or within 200 m of aggressive industrial areas. | Not suitable |
AZ200 aluminium/zinc or AM150 aluminium/zinc/ magnesium |
Typically within 100 m of Open link in same pagebreaking surf | Not suitable | Not suitable | |
Notes:
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Table 3.5.1.1b SARKING REQUIREMENTS FOR TILED ROOFS
Roof—degrees of pitch | Maximum rafter length without sarking (mm) |
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≥ 18 < 20 | 4500 |
≥ 20 < 22 | 5500 |
≥ 22 | 6000 |
Note: The maximum rafter length is measured from the topmost point of the rafter downwards. Where the maximum rafter length is exceeded, sarking must be installed over the remainder of the rafter length. |
Where different metals are used in a roofing system, including cladding, Open link in same pageflashings, fasteners, downpipes etc, they must be compatible with each other (to prevent corrosion due to an adverse chemical reaction) as described in Open link in same pageTable 3.5.1.2 and—
no lead materials can be used upstream from zinc-aluminium coated materials; and
no copper materials can be used upstream from galvanised coated materials.
Metal sheet roofing must—
be fixed at spacings in accordance with Open link in same pageFigure 3.5.1.5; and
use fastening devices made of a compatible metal to the roofing in accordance with Open link in same page3.5.1.3(c); and
when using both clipped and pierced fastening systems—
employ an anti-capillary feature in the side lap of the sheet, to prevent capillary action drawing moisture into the lap and allowing the lap to drain (achieved by not over tightening the sheet fixings, see Open link in same pageFigure 3.5.1.3); and
wherever possible have the sheets laid so that the side lap is facing away from prevailing weather.
Table 3.5.1.2 ACCEPTABILITY OF CONTACT BETWEEN DIFFERENT ROOFING MATERIALS
CLADDING MATERIAL | ACCESSORY OR FASTENER MATERIAL | |||||||
---|---|---|---|---|---|---|---|---|
Stainless steel | Zinc–coated steel and Zinc | Zinc/Aluminium coated steel or aluminium/zinc (AZ) and aluminium/zinc/magnesium (AM) coated steel | Lead | |||||
Atmosphere Classification (L = Low, M – VH = Medium to Very High as per Table 3.5.1.1a) | ||||||||
M–VH | L | M–VH | L | M–VH | L | M–VH | L | |
Copper and copper alloys | No | Yes | No | No | No | No | No | Yes |
Stainless steel (300 series) | Yes | Yes | No | No | No | No | No | Yes |
Zinc-coated steel and zinc | No | Yes | Yes | Yes | Yes | Yes | No | Yes |
Zinc/aluminium coated steel | No | Yes | Yes | Yes | Yes | Yes | No | No |
Aluminium/zinc (AZ) and aluminium/zinc/magnesium (AM) coated steel | No | Yes | Yes | Yes | Yes | Yes | No | No |
Lead | Yes | Yes | No | Yes | No | No | Yes | Yes |
Notes:
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Figure 3.5.1.3 SIDE LAPPING FASTENING DETAIL |
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Sheets must be—
laid wherever possible using complete lengths from ridge to eaves; or
where a complete length cannot be laid—
each run should be laid in specific sequence (see Open link in same pageFigure 3.5.1.4) from bottom to top before moving on to the next run; and
the distance for end lapping where sheets meet is—
for roof slopes between 5–15 degrees (1:12–1:4) — a lap of 200 mm; and
for roof slopes above 15 degrees (1:4) — a lap of 150 mm; and
stop ended (i.e. each valley turned up 60 degrees) at the ridge line of each length.
Figure 3.5.1.4 SHEET LAYING SEQUENCE |
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Metal sheet roofing must comply with the pitch and span limitations between roofing supports as shown in Open link in same pageFigure 3.5.1.5.
Figure 3.5.1.5 MAXIMUM SPAN AND FIXING FOR METAL SHEET ROOFING |
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---|---|---|---|---|---|
Diagram a. | Typical profiles — Pitch is appropriate for a sheet run up to 25 m in length | ||||
Note: The end span of some trapezoidal roofing systems may need to be reduced to 1.5 m (see proprietary information). | |||||
Diagram b. | End and internal roof spans | ||||
PROFILE | BASE METAL THICKNESS | END SPAN | INTERNAL SPAN | FIXING (crest fastening) | |
(mm) | (mm) | (mm) | END SPAN | INTERNAL SPANS | |
Corrugated | 0.42 | 950 | 1200 | Every second rib | Every third rib |
Close pitched trapezoidal | 0.42 | 1900 | 2400 | Every rib | Every second rib |
Trapezoidal | 0.42 | 1350 | 1700 | Every rib | |
Concealed fasteners | 0.48 | 1800 | 2100 | Every rib |
Sheet metal roof Open link in same pageflashings and cappings must comply with the following:
Roof Open link in same pageflashings and cappings must be purpose made, machine-folded sheet metal sections of materials compatible with all up and downstream metal roof covering materials in accordance with Open link in same page3.5.1.3(c).
The type of fasteners for Open link in same pageflashings and cappings must comply with Open link in same page3.5.1.3(d).
The fastener fixing frequency for transverse Open link in same pageflashings and cappings must comply with Open link in same pageTable 3.5.1.3.
Table 3.5.1.3 FASTENER FREQUENCY FOR TRANSVERSE FLASHINGS AND CAPPINGS
ROOF TYPE | FIXING FREQUENCY | FASTENER TYPE |
---|---|---|
Concealed fastened roofs | Every rib | Rivets and self drilling screws |
Pierced fastened roofs | Every 2nd rib | Self drilling screws or rivets |
Corrugated roofs | Every 4th rib | Self drilling screws or rivets |
Joints in Open link in same pageflashing and cappings must be not less than 25 mm, fastened at intervals not more than 40 mm and lapped in the direction of the fall of the roof.
Wall and step Open link in same pageflashings must be fastened into masonry walls with galvanised or zinc/aluminium sheet metal wedges at each end of each length and at intermittent intervals of not more than 500 mm and must overlap by not less than 75 mm in the direction of flow.
Lead Open link in same pageflashings must not be used with prepainted steel or zinc/aluminium steel or on any roof if the roof is part of a potable (drinking) water catchment area.
Anti capillary breaks must be installed in accordance with Open link in same pageFigure 3.5.1.6 and be—
for flat surfaces — 10 mm/30 degree fold; and
all other surfaces — 10 mm/90 degree or 135 degree fold.
Figure 3.5.1.6 ANTI CAPILLARY BREAKS |
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Acceptable Open link in same pageflashing configurations are shown in Open link in same pageFigure 3.5.1.7.
Figure 3.5.1.7 ACCEPTABLE FLASHING DETAILS |
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Diagram a. | Parapet flashing |
Diagram b. | Parapet and end wall flashing |
Collar Open link in same pageflashings must permit the total drainage of the area above the penetration.
On the completion of installation, the roof structure must be restored to its original strength by installing roof trimmers and soaker supports as necessary.
The type of fasteners for Open link in same pageflashings and cappings must comply with Open link in same page3.5.1.3(d).
Lead Open link in same pageflashings must not be used with prepainted steel or zinc/aluminium steel or on any roof if the roof is part of a potable water catchment area.
Acceptable Open link in same pageflashings for penetrations are shown in Open link in same pageFigure 3.5.1.8.
Clearance for heating appliance roof support members must be in accordance with Open link in same pagePart 3.7.3.
Figure 3.5.1.8 TYPICAL ROOF PENETRATION FLASHING DETAILS |
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Diagram a. | PVC aprons | Diagram b. | Collar flashings |
Diagram c. | Large penetrations — using apron | ||