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Part 3.5.1 Roof Cladding

Acceptable construction manuals

3.5.1.0

Performance Requirements Open link in same pageP2.1.1 and Open link in same pageP2.2.2 are satisfied for roof cladding if it complies with one of the following:

(a)

Roofing tiles: AS 2049 and AS 2050.

(b)

Metal roofing: AS 1562.1.

(c)

Plastic sheet roofing: AS/NZS 4256 Parts 1, 2, 3 and 5; and AS/NZS 1562.3.

(d)

Corrugated fibre-reinforced cement sheet roofing: AS/NZS 1562.2.

(e)

Asphalt shingles: ASTM D3018-90.

(f)

Pliable membrane and underlay: AS/NZS 4200 Parts 1 and 2.

Acceptable construction practice

3.5.1.1 Application

Compliance with this acceptable construction practice satisfies Open link in same pagePerformance Requirements Open link in same pageP2.1.1 and Open link in same pageP2.2.2 for roof cladding, provided—

(a)

the building is located in an area with a Open link in same pagedesign wind speed of not more than N3; and

Explanatory information:
  1. Information on design wind speeds for particular areas may be available from the appropriate authority.
  2. A map indicating cyclonic regions of Australia is contained in Part 3.10.1.
(b)

roof tiles are installed in accordance with Open link in same page3.5.1.2; and

(c)

metal sheet roofing is installed in accordance with Open link in same page3.5.1.3.

3.5.1.2 Roof tiling

(a)

Roof tiles, complying with AS 2049, must be installed, fixed and flashed in accordance with the relevant provisions of this Part.

(b)

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.

(c)

Fixings for roof battens and batten sizes must comply with Open link in same pagePart 3.4.3.

(d)

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.

(e)

Lead Open link in same pageflashings must not be used on any roof that is part of a potable water catchment area.

(f)

Sarking must be installed under tiled roofs in accordance with Open link in same pageTable 3.5.1.1b.

(g)

Where sarking is installed, an anti-ponding device/board must—

(i)

be provided—

(A)

on roofs with pitches of less than 20°; and

(B)

on all roof pitches where there are no eaves overhang; and

(ii)

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.

(h)

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—

(i)

a spreader pipe; or

(ii)

a flashing; or

(iii)

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

Show Full Sized ImageFigure 3.5.1.1 MINIMUM MECHANICAL FASTENING FOR TILES AND ANCILLARIES
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:

  1. Mechanical fastening can be achieved with either nails, screws, clips or flexible pointing materials complying with AS 2050.
  2. For the purposes of this Figure, "edge of roof" is a 1.2 m wide band bounded by the eaves, ridge, hips and barge measured towards the "field of roof".

 

Figure 3.5.1.2

TILED ROOF FLASHING AND OTHER DETAILS

Diagram a. Mechanical fastening-ridge clip (Also see Open link in same pageFigure 3.5.1.1)
Show Full Sized ImageFigure 3.5.1.2a TILED ROOF FLASHING AND OTHER DETAILS
Diagram b. Dry valley Diagram c. Bedded and pointed valley
Show Full Sized ImageFigure 3.5.1.2b TILED ROOF FLASHING AND OTHER DETAILS Show Full Sized ImageFigure 3.5.1.2c TILED ROOF FLASHING AND OTHER DETAILS
Diagram d. Fastening of hip tiles
Show Full Sized ImageFigure 3.5.1.2d TILED ROOF FLASHING AND OTHER DETAILS

3.5.1.3 Metal sheet roofing

(a)

The design and installation of metal sheet roofing must comply with the relevant provisions of this Part.

(b)

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:

  1. Low — remote inland includes dry rural areas remote from the coast or sources of pollution. Many areas of Australia beyond at least 50 km from the sea are in this category, including most cities and towns such as Canberra, Ballarat, Toowoomba, Alice Springs and some suburbs of cities on sheltered bays such as Melbourne, Hobart, Brisbane and Adelaide that are more than 1 km from the sea. However each of these have many exceptions which are in more corrosive categories.
  2. Medium — urban inland, coastal or industrial typically coastal areas with low salinity around sheltered bays, such as Port Phillip Bay. This extends from about 50 m from the shoreline to a distance of about 1 km inland but seasonally or in semi-sheltered bays extends 3 to 6 km inland. Along ocean front areas with Open link in same pagebreaking surf and significant salt spray, it extends from 1 km inland to about 10 to 50 km depending on wind direction and topography. Much of the metropolitan areas of Wollongong, Sydney, Newcastle, Perth and the Gold Coast are in this category. This can extend to 30 to 70 km inland in South Australia while on some evidence, other southern Australian coastal zones are in this, or a more severe category. This also includes urban and industrial areas with low pollution and for several kilometres around large industries such as steel works and smelters.
  3. High typically occurs on the coast around sheltered bays. Category high extends up to 50 m inland from the shoreline. In areas of rough seas and surf it extends from several hundred metres to about 1 km inland. As with other categories the extent depends on wind, wave action and topography. The category will also be found inside industrial plants and can influence a distance of 1.5 km down wind of the plant.
  4. Very high is typical of offshore conditions and is found on the beachfront in regions of rough seas and surf beaches. It can extend inland for several hundred metres. It is also found in aggressive industrial areas with a pH of less than 5.
  5. All locations described in the table contain variations of greater corrosion severity. If significant, this must be addressed by designing for the most severe environment.
  6. In locations where metallic coatings are not a suitable form of corrosion protection, the roof sheeting must be of a type which has been designed and manufactured for such environments.


Table 3.5.1.1b SARKING REQUIREMENTS FOR TILED ROOFS

Roof—degrees of pitch Maximum rafter length without sarking (mm)
≥ 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.
(c)

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—

(i)

no lead materials can be used upstream from zinc-aluminium coated materials; and

(ii)

no copper materials can be used upstream from galvanised coated materials.

(d)

Metal sheet roofing must—

(i)

be fixed at spacings in accordance with Open link in same pageFigure 3.5.1.5; and

(ii)

use fastening devices made of a compatible metal to the roofing in accordance with Open link in same page3.5.1.3(c); and

(iii)

when using both clipped and pierced fastening systems—

(A)

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

(B)

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:
  1. No — means the metal cannot be used in association with the other metal.
  2. Yes — means the metal can be used in association with the other metal.

 

Figure 3.5.1.3

SIDE LAPPING FASTENING DETAIL

Show Full Sized ImageFigure 3.5.1.3 SIDE LAPPING FASTENING DETAIL
(e)

Sheets must be—

(i)

laid wherever possible using complete lengths from ridge to eaves; or

(ii)

where a complete length cannot be laid—

(A)

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

(B)

the distance for end lapping where sheets meet is—

(aa)

for roof slopes between 5–15 degrees (1:12–1:4) — a lap of 200 mm; and

(bb)

for roof slopes above 15 degrees (1:4) — a lap of 150 mm; and

(iii)

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

Show Full Sized ImageFigure 3.5.1.4 SHEET LAYING SEQUENCE
(f)

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

Diagram a. Typical profiles — Pitch is appropriate for a sheet run up to 25 m in length
Show Full Sized ImageFigure 3.5.1.5a MAXIMUM SPAN AND FIXING FOR METAL SHEET ROOFING
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
Show Full Sized ImageFigure 3.5.1.5b MAXIMUM SPAN AND FIXING FOR METAL SHEET ROOFING
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
(g)

Sheet metal roof Open link in same pageflashings and cappings must comply with the following:

(i)

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).

(ii)

The type of fasteners for Open link in same pageflashings and cappings must comply with Open link in same page3.5.1.3(d).

(iii)

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
(iv)

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.

(v)

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.

(vi)

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.

(vii)

Anti capillary breaks must be installed in accordance with Open link in same pageFigure 3.5.1.6 and be—

(A)

for flat surfaces — 10 mm/30 degree fold; and

(B)

all other surfaces — 10 mm/90 degree or 135 degree fold.

 

Figure 3.5.1.6

ANTI CAPILLARY BREAKS

Show Full Sized ImageFigure 3.5.1.6 ANTI CAPILLARY BREAKS
(viii)

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

Diagram a. Parapet flashing
Show Full Sized ImageFigure 3.5.1.7a ACCEPTABLE FLASHING DETAILS
Diagram b. Parapet and end wall flashing
Show Full Sized ImageFigure 3.5.1.7b ACCEPTABLE FLASHING DETAILS
(h)

Open link in same pageFlashing of penetrations must comply with the following:

(i)

Collar Open link in same pageflashings must permit the total drainage of the area above the penetration.

(ii)

On the completion of installation, the roof structure must be restored to its original strength by installing roof trimmers and soaker supports as necessary.

(iii)

The type of fasteners for Open link in same pageflashings and cappings must comply with Open link in same page3.5.1.3(d).

(iv)

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.

(v)

Acceptable Open link in same pageflashings for penetrations are shown in Open link in same pageFigure 3.5.1.8.

(vi)

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

Diagram a. PVC aprons Diagram b. Collar flashings
Show Full Sized ImageFigure 3.5.1.8a TYPICAL ROOF PENETRATION FLASHING DETAILS Show Full Sized ImageFigure 3.5.1.8b TYPICAL ROOF PENETRATION FLASHING DETAILS
Diagram c. Large penetrations — using apron
Show Full Sized ImageFigure 3.5.1.8c TYPICAL ROOF PENETRATION FLASHING DETAILS