Improving BCA understanding - how can we help?
There are building inspectors (both registered and unqualified) operating in Western Australia without experience in matters of identifying defective building work. As a result The BCA is often misquoted and often misunderstood within inspection reports (and in turn by construction supervisors and managers) and this can generate unnecessary costs for unnecessary rectification work.
Flashings – an example
A single storey full brick house has several windows along an elevation which is not adequately protected by an eave. The building inspector has noticed that there are no sill or head flashings to the windows and has written this as a defect in his report. He has stated that the windows do not meet the BCA requirements. The owners of the house are now demanding the windows are removed and the flashings installed because their building inspector has identified the omission as a defect.
Was the inspector right? What does the building code say?
Volume 2 of the Building Code of Australia outlines the structural performance requirements of building work in Australia. Since 2011 the BCA has shied away from explaining how building work must be undertaken, and instead allowed for alternative solutions, providing that the performance requirements are met. In the past requirements for the construction of eaves, window heights and flashing requirements to prevent water entry were stated in the BCA - but not anymore. Currently and into the foreseeable future, the BCA performance requirements state the minimum requirements for acceptable building work as far as the The BCA is concerned.
In regards to weatherproofing of wall openings performance requirement BCA 2.2.2 Weatherproofing states:
“P2.2.2 Weatherproofing
A roof and external wall (including openings around windows and doors) must prevent the penetration of water that could cause—
(a) unhealthy or dangerous conditions, or loss of amenity for occupants; and
(b) undue dampness or deterioration of building elements.”
What this means is that unless water has entered around the openings (a) or caused unhealthy conditions or dampness (b) there is no defect implied in accordance with the BCA requirements.
What else does the BCA say about weatherproofing?
“Part 3.3.1.0
Performance Requirement P2.1.1* is satisfied for unreinforced masonry (including masonry-veneer) if it is designed and constructed in accordance with one of the following:
(a) AS 3700.
(b) AS 4773 Parts 1 and 2.”
*(Performance Requirement P2.1.1 lists the requirements of building Stability and resistance to actions and includes - among other things- resistance to rainwater action.)
AS 3700 Masonry Structures 4.7.3 Damp Proof Courses and Flashings states:
“4.7.3 Damp-proof courses (DPCs) and flashings
DPCs or flashings shall be incorporated into masonry construction where it is necessary—
(a) to provide a barrier to the upward or downward passage of moisture through masonry;
(b) to prevent moisture from entering into the interior of a building from the exterior;
(c) to prevent moisture passing across a cavity to the inner leaf; or
(d) to shed moisture through masonry to the outer face.”
It is considered that most regular window installations will automatically satisfy Australian Standard 3700 (and therefore the performance provisions of the BCA) because:
Part (a) is satisfied providing that the gutters above have overflow provision and adequate drainage. (No water can tip into the cavity from above).
Part (b) is satisfied if the sills have fall away from the window, there is adequate sealing around the window / frames and the provision of weepholes to the window frame.
Part (c) is satisfied if the window has fins.
Part (d) is satisfied if there are weepholes at the base of the wall.
Summary:
If the windows are not leaking and the windows satisy AS 3700 part 4.7.3 - there cannot be a breach of the BCA performance requirements therefore there can be no defect with reference to the BCA.
No rectification work (with reference to the BCA) needs to be undertaken.
