NCC 2019 Volume Two Amendment 1
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Part 3.10.6 Attachment of decks and balconies to external walls of buildings
Explanatory information:
Appropriate Performance Requirements
Where an alternative method for attaching a deck or balcony to an external wall is proposed as a Performance Solution to that described in Part 3.10.6, that proposal must comply with—
- Performance RequirementP2.1.1; and
- the relevant Performance Requirements determined in accordance with A2.2(3) and A2.4(3) as applicable.
Acceptable Construction Practice
3.10.6.1 Application
Compliance with this acceptable construction practice satisfies Performance Requirement P2.1.1 for the attachment of a deck or balcony to an external wall provided—
(a)
the deck or balcony is not located in an alpine area; and
(b)
the height of the deck or balcony is not more than 3 m measured from the uppermost finished floor surface of the deck or balcony at any point to the top of any supporting footing; and
(c)
the waling plate does not support—
(i)
more than one floor; or
(ii)
loadbearing or non-loadbearing walls; or
(iii)
roof loads; and
(d)
the deck or balcony does not cantilever off the external wall; and
(e)
the total imposed load on the deck or balcony does not exceed 2 kPa; and
Explanatory information:
Explanatory information:
A 2 kPa imposed load is commensurate with domestic and residential activities associated with Class 1 buildings (e.g. dwellings with limited occupancy and restricted public access) and is not appropriate for applications where the deck or balcony supports heavy equipment, spa/bathing pools or circumstances where the deck or balcony is intended for community access (e.g. applications with a mid-high occupancy and possibility of public access).
If the design live load of the deck or balcony is more than 2 kPa, the framing members of the deck or balcony must be designed by a professional engineer or other appropriately qualified person in accordance with the relevant structural design manuals in Part 3.0.
(f)
the deck or balcony framing including member sizes, spans and spacing, bracing for racking and shear forces, fixings and structural supports complies with Part 3.0; and
(g)
the deck or balcony framing is constructed of—
(i)
steel framing in accordance with Part 3.4.2; or
(ii)
timber framing in accordance with Part 3.4.3; and
(h)
the external wall supporting the deck or balcony is constructed of—
(i)
190 mm thick fully core-filled concrete masonry, reinforced with vertical N12 bars at not more than 600 mm centres; or
(ii)
steel framing complying with Part 3.4.2; or
(iii)
timber framing complying with Part 3.4.3; and
(i)
the external wall referred to in (h) must be continuous from the upper most surface of the deck or balcony to the supporting footing and contain no openings or lintels below the deck or balcony; and
(j)
the waling plate is fixed to the external wall in accordance with 3.10.6.2 and attached by—
(i)
fixing the waling plate through wall cladding complying with Part 3.5.4 or Part 3.5.5, provided the cladding is directly fixed to the external wall; or
(ii)
removing parts of the wall cladding so that the waling plate is directly fixed to the external wall, with—
(A)
the junction of the waling plate and the external wall flashed in accordance with 3.10.6.3; and
(B)
the cladding restored to its original strength by installing blocking supports as necessary on completion of installation; and
Explanatory information:
Explanatory information:
3.10.6.1(j)(ii) requires consideration to be given to restoring cladding, weatherproofing and structural properties. Other considerations include restoring the appropriate sound and thermal insulation, and the capacity to maintain an FRL where required.
(k)
the deck or balcony is braced to prevent longitudinal movement in accordance with 3.10.6.4.
Explanatory information:
Explanatory information:
3.10.6.1 describes the circumstances under which the methods of attachment described in this Part are deemed appropriate.
Where a deck or balcony is constructed outside the conditions listed in 3.10.6.1, e.g. attachment to a masonry veneer wall, the method of attachment to the building or structure must be designed by a professional engineer or other appropriately qualified person in accordance with the relevant structural design manuals in Part 3.0. Such a design will need to consider the suitability of the wall to withstand the loads imposed by the deck or balcony, and the capacity of the connections.
Examples of external wall construction that are outside the application of Part 3.10.6 include a masonry external wall that is not fully core-filled, cavity brick and masonry veneer construction where fasteners may be subject to withdrawal.
An alternative to attaching a deck or balcony directly to an external wall includes providing supporting piers, posts or columns or the like parallel to the wall line or at right angles to the wall.
3.10.6.2 Fixing decks and balconies to external walls
Where a deck or balcony relies on the external wall of a building or structure for support, the method of attachment, including any fixings, to the external wall must comply with the following:
(a)
The deck or balcony's joist framing members must be supported at the wall by a waling plate.
(b)
The joist span nearest the external wall must not be more than 3 m (single or continuous span).
(c)
The size of a waling plate required by (a) must be not less than—
(i)
for a timber waling plate — 190 x 45 mm with a minimum stress grade of F5 or MGP10; or
(ii)
for a steel waling plate — C15015 (minimum Grade G550) with the web located against the external wall.
(d)
A waling plate must be attached so that—
(i)
for core-filled reinforced concrete masonry external walls, fixings are staggered along the waling plate at not more than 300 mm centres measured along the waling plate; and
(ii)
for timber external walls, two fixings are provided into a solid joist or bearer framing member that is not less than 190 x 100 mm with a minimum stress grade of F5 or MGP10, at not more than 300 mm centres measured along the waling plate; and
(iii)
for steel framed external walls, two fixings are provided into a joist or bearer framing member not less than C20015 (Grade G550) at not more than 300 mm centres measured along the waling plate; and
(iv)
fixings are—
(A)
installed within 300 mm of each end of the waling plate; and
(B)
for a timber waling plate — not located within 120 mm from the ends or within 60 mm from the top and bottom edges; and
(C)
for a steel waling plate — not located within 50 mm from the ends or within 30 mm from the top and bottom edges.
Explanatory Information:
Explanatory Information:
Consideration needs to be given to offsetting the waling plate fastener spacing to avoid interference with joist attachment. To ensure fasteners are positively anchored to the building or structure they need to be located so that they are not fixed into mortar beds between masonry units or fixed into blocking or the end grains of timbers.
An I-beam is not considered a solid joist or bearer framing member under 3.10.6.2(d)(ii) and is therefore not permitted as an appropriate method of support for attachment of a deck or balcony to an external wall.
(e)
Fixings for attaching a waling plate to an external wall must be—
(i)
for timber external wall frames with a minimum stress grade of F5 or MGP 10—
(A)
M12 coach screws with not less than 3 mm thick 55 mm diameter washers fixed so that the coach screw is embedded not less than 96 mm into the joist or bearer framing member (see Figure 3.10.6.1b); or
(B)
4.6/S M12 bolts with not less than 3 mm thick 55 mm diameter washers placed on the waling plate under the bolt head; and
(ii)
for steel external wall frames, 8.8/S M12 bolts with not less than 3 mm thick 55 mm diameter washers; and
(iii)
for a core-filled masonry external wall, 4.6/S M12 chemical or expanding/mechanical anchors with—
(A)
a minimum 2 kN working load capacity in shear and 1.5 kN in tension; and
(B)
not less than 3 mm thick 55 mm diameter washers placed on the waling plate under the anchor head (see Figure 3.10.6.1a).
(f)
Fixings used for attaching waling plates to external wallsmust be—
(i)
stainless steel where the building is located within 200 m of breaking surf; or
(ii)
hot-dipped galvanised, stainless steel or monel metal for all other areas.
Explanatory information:
Explanatory information:
The working load capacity of an anchor required by 3.10.6.2(e)(iii)(A) may be available in technical data provided by the manufacturer of the anchor.
The bolt category 4.6/S refers to a commercial bolt of a strength grade of 4.6 using a snug tight method of tensioning. AS 4100 contains information on tensioning techniques and the methods of determining the strength of an anchor.
Where the waling plate is fixed to the external wall through wall cladding, fixing length must be increased to compensate for the additional width of the cladding to ensure the connection to the external wall is structurally adequate.
All coach screwed joints should be pre-drilled with a pilot hole whose diameter is not greater than that of the threaded portion of the screw.
3.10.6.3 Flashings to the junction of the waling plate and the external wall
Where the wall cladding is removed to attach a waling plate, 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 the sides of the junction of the waling plate and the external wall, and must be installed so that the flashing—
(i)
extends not less than 150 mm beyond each side of the waling plate where practicable; and
(ii)
is attached to the waling plate and wall framing; and
(iii)
at the top and bottom of the waling plate, 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.
(d)
Flashings must be securely fixed at least 25 mm under the cladding at ends and edges of the framing of the opening.
Explanatory Information:
Explanatory Information:
Consideration needs to be given to the method of fixing the waling plate to the external wall so that deterioration of the external wall as a result of water entry will not occur. Such cases would include where the wall cladding is removed to attach a waling plate.
This may be achieved by installing flashing between the external wall and the waling plate.
3.10.6.4 Bracing
Where a deck or balcony is more than 1 m off the ground when measured from the upper most surface of the deck or balcony at any point to the top of any supporting footing, bracing must be installed as follows:
(a)
Two diagonally opposed 30 x 0.8 mm galvanized steel straps must be installed across the top or underside of the joists and be attached using one fixing at—
(i)
each joist or equivalent framing member; and
(ii)
the waling plate.
(b)
A secondary set of 30 x 0.8 mm steel straps must be installed using one fixing at each joist or equivalent framing member in accordance with Figure 3.10.6.2 where the deck or balcony extends more than 4 m from the external wall.
(c)
The steel straps must—
(i)
be continuous and extend diagonally at an angle between 30° to 60°; and
(ii)
span not more than 4 m when measured along a line at a right angle from the external wall.
(d)
Fixings for the steel straps must be—
(i)
for timber framing, 50 x 3.15 hot-dipped galvanized flat head ring shank or flat head deformed nail; or
(ii)
for steel framing, 8-18 self embedding head or wafer head screws.
(e)
Where the deck or balcony is located within a severe corrosion environment the bracing and fixings must comply with Table 3.4.4.7.
Figure 3.10.6.1a Methods of attachment - 4.6/S M12 chemical or masonry anchors into a core-filled reinforced masonry external wall
Figure 3.10.6.1b Methods of attachment - M12 coach screws into a timber framed external wall
Figure 3.10.6.2 Bracing of decks and balconies
