Building Membrane Changes in the new edition of the NCC

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On the 1st of May 2019, the National Construction Code will introduce a new section titled ‘Condensation Management’, which includes important changes to the selection of wall wraps.

The change will affect all Building Permits approved after the 1st of May 2019. Building Permits approved using NCC 2016 will not be affected by this change and may still use the wall wrap included in the original specification.

New Condensation Management section:

F6.2 Pliable building membrane

(a) Where a pliable building membrane is installed in an external wall, it must –

(i) comply with AS/NZS 4200.1; and

(ii) be installed in accordance with AS 4200.2; and

(iii) be a vapour permeable membrane for climate zones 6, 7 and 8; and

(iv) be located on the exterior side of the primary insulation layer of wall assemblies that form the external envelope of a building.

(b) Except for single skin masonry and single skin concrete, where a pliable building membrane is not installed in an external wall, the primary water control layer must be separated from water sensitive materials by a drained cavity.

Under part (a) of the new section, the NCC 2019 change states that if a pliable building membrane is installed onto an external wall frame in BCA Climate Zone 6, 7 & 8 (a large section of Victoria), it is required to be vapour permeable and a water barrier. This change will be mandatory for lightweight clad construction (unless the cladding battens are fixed vertically).

Under part (b), Brick Veneer does not require pliable building membrane to be installed as it includes a drained cavity which separates water sensitive materials from the primary water control layer.

Furthermore, Part (b) of the clause may be interpreted to mean non-water barrier or ‘perforated breather foil’ may still be installed as a reflective insulation onto the external wall frame. However, as Breather products do not provide water hold-out or air control, Dahlsens still recommends the use of vapour permeable, water barrier membranes such as Bradford’s Enviroseal RW wrap.

The new Condensation Management sections can be located in Volume 1 Part F6.2 and Volume 2 Part of the NCC Preview available on the NCC website.

The solution

Bradford Enviroseal™ ProctorWrap™ Wall Wrap

Made from a special light-weight fabric, Enviroseal™ RW provides a tough barrier that blocks out wind and water while also allowing internal condensation build-up to escape through the external walls.

Speak to your local Dahlsens store for more information on the Bradford Enviroseal™ ProctorWrap™ wall wrap or if you are unclear about how the NCC changes affect your building material selection.