Part 3.5.4 Timber and composite wall cladding

NCC 2019 Volume Two

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Part 3.5.4 Timber and composite wall cladding

Appropriate Performance Requirements

Appropriate Performance Requirements

Where an alternative wall cladding is proposed as a Performance Solution to that described in Part 3.5.4, that proposal must comply with—

Performance RequirementP2.1.1; and
Performance RequirementP2.2.2; and
the relevant Performance Requirements determined in accordance with A2.2(3) and A2.4(3) as applicable.

Explanatory information:

Masonry wall cladding

Masonry used as wall cladding, including masonry veneer, is not covered by Part 3.5.4 but is covered by Part 3.3.

Alternative wall cladding materials and systems

The Provisions of this Part and those of Part 3.3 (Masonry) do not cover all of the wall cladding materials that may be used for a Class 1 or Class 10 building.

Wall cladding materials and systems not covered by the Deemed-to-Satisfy Provisions may be considered under a Performance Solution that complies with the relevant Performance Requirements.

One of the Assessment Methods that may be used to demonstrate compliance with the Performance Requirements is the use of documentary evidence in accordance with Part A5.

Acceptable Construction Manuals

3.5.4.0 Application

Performance RequirementsP2.1.1 and P2.2.2 are satisfied for autoclaved aerated concrete wall cladding if it is designed and constructed in accordance with AS 5146.1.

3.5.4.1 Application

Compliance with this acceptable construction practice satisfies Performance Requirements P2.1.1 and P2.2.2 for wall cladding provided—

(a)

It is installed in accordance with—

(i)

3.5.4.2 for timber cladding, including weatherboards and profiled boards; and

(ii)

3.5.4.3 for fibre-cement and hardboard wall cladding boards; and

(iii)

3.5.4.4 for fibre-cement, hardboard and plywood sheet wall cladding; and

(b)

fibre-cement sheet eaves where provided, are installed in accordance with 3.5.4.5; and

(c)

openings and penetrations in cladding are flashed in accordance with 3.5.4.6; and

(d)

the bottom surface of the cladding terminates in accordance with 3.5.4.7; and

(e)

parapets, where provided, are flashed in accordance with 3.5.4.8.

3.5.4.2 Timber wall cladding

Timber wall cladding must be installed as follows:

(a)

Splayed timber weatherboards must be fixed in accordance with Figure 3.5.4.1 and with a lap not less than—

(i)

30 mm for hardwood, Cypress and treated pine; and

(ii)

20 mm for Western Red Cedar; and

(iii)

25 mm for Baltic Pine.

(b)

Profiled timber boards must be—

(i)

fixed in a horizontal, vertical or diagonal direction with the overlap and groove closely fitted, where provided; and

(ii)

with tongue and groove profile, fixed with tongue edge up, where they are fixed in a horizontal or diagonal direction; and

(iii)

where fixed in a vertical or diagonal direction, provided with a vapour permeable sarking complying with AS/NZS 4200.1 (see Figure 3.5.4.2) installed behind boards with—

(A)

each adjoining sheet or roll being—

(aa)

overlapped not less than 150 mm; or

(bb)

taped together; and

(B)

sarking fixed to supporting members at not more than 300 mm centres.

(c)

Splayed and profiled timber weatherboards must be fixed in accordance with Table 3.5.4.1, with—

(i)

one fixing at each stud or equivalent framing member for splayed timber weatherboards; and

(ii)

one fixing provided at each stud or equivalent framing member for profiled timber boards not more than 130 mm wide; and

(iii)

two fixings provided at each stud or equivalent framing member for profiled timber board more than 130 mm wide; and

(iv)

fixings located so that the fixing does not penetrate the tip or thinner edge of the board beneath.

Explanatory information:

3.5.4.2(c)(iv) ensures the fixing of the wall cladding does not split the wall cladding board below. For example, for a 30 mm lap, fix 35 mm from the butt or 5 mm above the corresponding overlapping board (see Figure 3.5.4.1).

Table 3.5.4.1 Fixing requirements—Splayed and profiled timber weatherboards

Design wind speed

Maximum stud spacing (mm)

Minimum nominal stud fixings

N1 — N3

600

Timber: 2.8 G or (8-18) S

Steel: (8-18) S

Notes to :

G = galvanised plain shank, threaded or equivalent nails.
S = self embedding head or wafer head screw.
Fasteners must penetrate not less than 30 mm into timber frames and not less than two full screw threads through steel frames.
Wall cladding may be fixed through timber or metal battens attached to the wall frame in accordance with AS 1684.2, AS 1684.3, AS 1684.4 or NASH standard as appropriate (see fixing requirements for roof battens) so long as the minimum penetration into the wall frame is achieved.
Steel framing members must have a base metal thickness (BMT) not less than 1.2 mm.

(d)

Fixings used for timber cladding must comply with the following:

(i)

Where fixings are punched or countersunk and filled prior to painting, fixings must be standard steel flat head nails or standard steel self embedding head screws.

(ii)

Uncoated copper or steel fixings must not be used for Western Red Cedar (silicon bronze, monel metal, stainless steel or hot-dipped galvanised are suitable).

(iii)

Where the building is located within 200 m of breaking surf, fixings must be—

(A)

stainless steel when fixed into timber framing members; or

(B)

hot-dipped galvanized (min 600 g/m²) when fixed into steel framing members.

(iv)

In all other cases, fixings must be hot-dipped galvanised (min. 600 g/m²) flat head nails or hot dipped galvanised (min 600 g/m²) self embedding head or wafer head screws.

Explanatory information:

Timber cladding profiles

3.5.4.2 covers the following types of timber cladding profiles:

Horizontal bevel-back
Horizontal rebated bevel-back
Horizontal rusticated
Vertical and horizontal shiplap
Tongue and groove

Machine and hand driven nails

Table 3.5.4.1 applies to both machine and hand driven nails.

3.5.4.3 Wall cladding boards

Wall cladding boards must—

(a)

for 7.5 mm (minimum) thick fibre-cement — comply with AS/NZS 2908.2 or ISO 8336; and

(b)

for 9.5 mm (minimum) thick hardboard — comply with AS/NZS 1859.4 for exterior grade; and

(c)

be fixed in accordance with Tables 3.5.4.2a and b with—

(i)

one fixing provided at each stud or equivalent framing member for wall cladding boards not more than 130 mm wide; and

(ii)

two fixings provided at each stud or equivalent framing member for wall cladding boards greater than 130 mm wide; and

(iii)

fixings located along the studs at not more than 100 mm centres; and

(iv)

fixings located so that they do not penetrate the tip or thinner edge of the board beneath; and

(d)

have a lap not less than—

(i)

for 7.5 mm (minimum) thick fibre-cement—25mm; or

(ii)

for 9.5 mm (minimum) thick hardboard—20 mm.

Explanatory information:

Where the wall cladding boards contain a shiplap join as opposed to a lapped join, 3.5.4.3(d) does not apply, and the joins between the boards are required to have the overlap and groove closely fitted.

Table 3.5.4.2a Fixing requirements—Minimum 7.5 mm thick fibre-cement wall cladding boards

Design wind speed

Maximum stud spacing (mm)

Minimum nominal stud fixings

N1 — N3

600

Timber: 2.8 GC

Steel: (8-18) S

Notes to :

GC = galvanised fibre-cement nail.
S = self embedding or wafer head screw.
Fasteners must penetrate not less than 30 mm into timber frames and not less than two full screw threads through steel frames.
Steel framing members must have a base metal thickness (BMT) not less than 1.2 mm.
Wall cladding may be fixed through timber or metal battens attached to the wall frame in accordance with AS 1684.2, AS 1684.3, AS 1684.4 or NASH standard as appropriate (see fixing requirements for roof battens) so long as the minimum penetration into the wall frame is achieved.

Table 3.5.4.2b Fixing requirements—Minimum 9.5 mm thick hardboard wall cladding boards

Design wind speed

Maximum stud spacing (mm)

Minimum nominal stud fixings

N1 — N3

600

Timber: 2.8 GC

Steel: (8-18) S

Notes to :

GC = galvanised fibre-cement nail.
S = self embedding or wafer head screw.
Fasteners must penetrate not less than 30 mm into timber frames and not less than two full screw threads through steel frames.
Steel framing members must have a base metal thickness (BMT) not less than 1.2 mm.
Wall cladding may be fixed through timber or metal battens attached to the wall frame in accordance with AS 1684.2, AS 1684.3, AS 1684.4 or NASH standard as appropriate (see fixing requirements for roof battens) so long as the minimum penetration into the wall frame is achieved.

Figure 3.5.4.1 Fixing of wall cladding

Diagram a Timber cladding

Figure 3.5.4.1 Fixing of wall cladding

Diagram b Wall Cladding Boards

Figure 3.5.4.2 Fixing of vertical wall cladding

Note to Figure 3.5.4.2: For fixing of diagonal wall cladding, equivalent fixing details apply.

3.5.4.4 Sheet wall cladding

(a)

Fibre-cement sheet wall cladding must—

(i)

comply with AS/NZS 2908.2 or ISO 8336; and

(ii)

be fixed in accordance with Table 3.5.4.3.

Explanatory information:

Where sheet bracing is also acting as structural bracing, fixing requirements are listed in AS 1684 and NASH Standard – Residential and Low-Rise Steel Framing, Part 2.

Table 3.5.4.3 - Stud and fixing spacings for 6 mm fibre-cement sheet wall cladding

Design wind speed

Maximum stud spacing (mm)

Maximum nail spacing within 1.2 m of the external corners of the building (mm) ^{Note 1}

Maximum nail spacing elsewhere (mm) ^{Note 1}

≤ 1.2 m of external building corners: 600

Elsewhere: 600

Body: 300

Edges: 200

Body: 300

Edges: 200

≤ 1.2 m of external building corners: 600

Elsewhere: 600

Body: 200

Edges: 200

Body: 300

Edges: 200

≤ 1.2 m of external building corners: 450

Elsewhere: 600

Body: 200

Edges: 200

Body: 200

Edges: 200

Notes to Table 3.5.4.3 :

Maximum nail spacing using 2.8 mm fibre-cement nails.
Fixings must be located not less than 50 mm from the edge of all corners.
Fasteners must penetrate not less than 30 mm into a timber frame.
Wall cladding may be fixed through timber or metal battens attached to the wall frame in accordance with AS 1684.2, AS 1684.3, AS 1684.4 or NASH standard as appropriate (see fixing requirements for roof battens) so long as the minimum penetration into the wall frame is achieved.

(b)

Hardboard sheet wall cladding must—

(i)

comply with AS/NZS 1859.4 for exterior grade; and

(ii)

be fixed in accordance with Table 3.5.4.4.

Table 3.5.4.4 Stud and fixing spacings for 9.5 mm thick hardboard sheet wall cladding

*Design wind speed*	Maximum stud spacing (mm)	Maximum nail spacing within 1.2 m of the external corners of the building (mm) ^{Note 1}	Maximum nail spacing elsewhere (mm) ^{Note 1}
N1	600	Body: 300 Edges: 150	Body: 300 Edges: 150
N2	600	Body: 300 Edges: 150	Body: 300 Edges: 150
N3	600	Body: 300 Edges: 150	Body: 300 Edges: 150

Notes to Table 3.5.4.4 :

Maximum nail spacing using 2.8 mm galvanised clouts or flat head nails.
Fixings must be positioned a minimum of 12 mm from the edge of the sheet and not less than 50 mm from the edge of all corners.
Fasteners must penetrate not less than 30 mm into the timber frame.
Wall cladding may be fixed through timber or metal battens attached to the wall frame in accordance with AS 1684.2, AS 1684.3, AS 1684.4 or NASH standard as appropriate (see fixing requirements for roof battens) so long as the minimum penetration into the wall frame is achieved.

(c)

Structural plywood wall cladding must—

(i)

comply with AS/NZS 2269.0; and

(ii)

be fixed in accordance with Table 3.5.4.5.

Table 3.5.4.5 Stud and fixing spacings for plywood wall cladding equal to or greater than 6.5 mm thick

*Design wind speed*	Maximum stud spacing (mm)	Maximum nail spacing within 1.2 m of the external corners of the building (mm) ^{Note 1}	Maximum nail spacing elsewhere (mm) ^{Note 1}
N1	600	Body: 200 Edges: 100	Body: 200 Edges: 150
N2	600	Body: 200 Edges: 100	Body: 200 Edges: 150
N3	600	Body: 150 Edges: 100	Body: 200 Edges: 150

Notes to Table 3.5.4.5 :

Maximum nail spacing using 2.8 or 3.5 mm galvanised clouts or flat head nails.
Fixings must be positioned a minimum of 12 mm from the edge of the sheet and not less than 50 mm from the edge of all corners.
Fasteners must penetrate not less than 30 mm into the timber frame.
Wall cladding may be fixed through timber or metal battens attached to the wall frame in accordance with AS 1684.2, AS 1684.3, AS 1684.4 or NASH standard as appropriate (see fixing requirements for roof battens) so long as the minimum penetration into the wall frame is achieved.

3.5.4.5 Eaves and soffit linings

Where provided, external fibre-cement sheets and linings used as eaves and soffit linings must—

(a)

comply with AS/NZS 2908.2 or ISO 8336; and

(b)

be fixed in accordance with Table 3.5.4.6 and Figure 3.5.4.4 using—

(i)

2.8 × 30 mm fibre-cement nails; or

(ii)

No. 8 wafer head screws (for 4.5 mm and 6 mm sheets only); or

(iii)

No. 8 self embedding head screws (for 6 mm sheets only).

Table 3.5.4.6 Trimmer and fastener spacings for 4.5 and 6 mm fibre-cement eaves and soffit linings

Maximum eaves width

Design wind speed

Maximum trimmer spacings (mm)

Maximum fastener spacings (mm)

Within 1200 mm of the external corners of the building

Elsewhere

Within 1200 mm of the external corners of the building

Elsewhere

600

600

900

200

300

600

800

200

300

500

700

200

300

1200

600

750

200

300

600

700

200

300

500

650

200

300

Figure 3.5.4.4 Eaves trimmer detail

3.5.4.6 Flashings to wall openings

Openings in external wall cladding exposed to the weather must be flashed with materials complying with AS/NZS 2904 and in accordance with the following:

(a)

Flashings must be provided to bottom, tops and sides of openings, except as permitted by (d), and must be installed so that the flashing—

(i)

extends not less than 110 mm beyond the reveals on each side of the opening where practicable; and

(ii)

is attached to the window and wall framing; and

(iii)

at the top and bottom of the opening, drains to the outside face of the wall or cladding.

(b)

Joins in the flashing must—

(i)

overlap by not less than 75 mm in the direction of flow; and

(ii)

be securely fastened at intervals of not more than 40 mm; and

(iii)

have sealant installed between laps.

(c)

The method of flashing must be suitable for the framing and cladding used and any reveal for the window or door system or any architrave or finishing trims that may be installed.

(d)

The top of an opening need not be flashed where it is adequately protected by an eave of a width more than 3 times the height of the cladding above the opening (See Figure 3.5.4.5).

(e)

Flashings must be securely fixed at least 25 mm under the cladding and extend over the ends and edges of the framing of the opening.

Explanatory information:

3.5.4.6(a)(i) applies 'where practicable' because it is often impractical to extend the flashing 110 mm beyond the reveal; for example, where openings are positioned adjacent to a corner or where two windows are within 110 mm of each other. In such cases consideration should be given to ensure the flashing prevents the penetration of water into the external wall.

Figure 3.5.4.5 Weather protection of openings

3.5.4.7 Clearance between cladding and ground

(a)

The minimum clearance from the bottom of the wall cladding to the adjoining finished ground level must be—

(i)

100 mm in low rainfall intensity areas or sandy, well-drained areas; or

(ii)

50 mm above impermeable (paved or concreted) areas that slope away from the building in accordance with 3.1.3.3(a); or

(iii)

150 mm in any other case.

(b)

Wall cladding must extend a minimum of 50 mm below the bearer or lowest horizontal part of the suspended floor framing.

Explanatory information:

The 3.5.4.7 clearances may also be subject to other requirements for drainage in Part 3.1.3, clearances for inspection zones for termite management in Part 3.1.4 and screening and sealing of gap requirements for construction in bushfire prone areas in Part 3.10.5, where appropriate.

3.5.4.8 Parapet cappings

Where a wall cladding is used to form a parapet wall, the cladding must be attached to a supporting frame and have a capping installed that complies with the following:

(a)

Cappings must—

(i)

be purpose made, machine-folded sheet metal or equivalent sections of a material compatible with all up and downstream metal roof covering materials in accordance with 3.5.1.2(b); and

(ii)

extend not less than 50 mm down the sides of the parapet; and

(iii)

be separated from the supporting framing by a vapour permeable sarking installed in accordance with (f); and

(iv)

be fixed with either self drilling screws or rivets with rubber washers at intervals of not more than 500 mm that do not penetrate the top of cappings, except at joints and corners.

(b)

The top of the capping must slope a minimum of 5 degrees.

(c)

Joints in cappings must—

(i)

overlap by not less than 50 mm in the direction of flow; and

(ii)

be securely fastened at intervals of not more than 40 mm; and

(iii)

have sealant installed between laps.

(d)

Fixing for cappings must be compatible with the capping material.

(e)

Lead cappings 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.

(f)

Sarking must comply with AS/NZS 4200.1 and be installed behind all wall cladding where parapets are installed, with—

(i)

each adjoining sheet or roll being—

(A)

overlapped not less than 150 mm; or

(B)

taped together; and

(ii)

sarking fixed to supporting members at not more than 300 mm centres.

Explanatory information:

For the purposes of 3.5.4.8(f), sarking is required to be installed to the whole external wall which contains the parapet, and extend to the top and back of the parapet. A gap should be provided between the sarking and the parapet capping to help control condensation.

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Part 3.5.4 Timber and composite wall cladding

Appropriate Performance Requirements

Explanatory information:

Acceptable Construction Manuals

3.5.4.0 Application

3.5.4.1 Application

3.5.4.2 Timber wall cladding

Explanatory information:

Explanatory information:

3.5.4.3 Wall cladding boards

Explanatory information:

3.5.4.4 Sheet wall cladding

Explanatory information:

3.5.4.5 Eaves and soffit linings

3.5.4.6 Flashings to wall openings

Explanatory information:

3.5.4.7 Clearance between cladding and ground

Explanatory information:

3.5.4.8 Parapet cappings

Explanatory information: