If your pressed for time, here's the gist of it -
- New Zealand and Canada have experienced an epidemic of leaky buildings.
- It's cost NZ $23 billion dollars and counting and cost Canada over $4 billion dollars and counting
- The average remediation cost in Canada per apartment was about $23K
- About 80,000 NZ homes have been affected
- The culprit -
[li]Unwanted water penetration from poor weatherproofing of the building envelope
- Inadequate flashings
- Heavy reliance on sealants instead of flashing
- Condensation forming in the interstitial spaces of the building fabric
- Zero step down balconies
- All the above Compounded by poor workmanship
- It appears Victoria, NSW and the ACT are seeing a rise in this unfortunate phenomenon, no mention of Queensland though, but is this more a when than an if?
My take as a building certifier
I use to provide the technical analysis and recommendation for remedial works when a home warranty insurance claim came through, this was during my time when I was working in the NT as the building regulator. The claims came through like clockwork, after a big storm, there was a lag of about a month before the claims from home owners and body corporates would come through for… you guess it… leaky roofs. The culprit… box gutters. Look, there's nothing wrong with box gutters, but unless it has been designed by an engineer I think the chances are high that it's a ticking time bomb. I've seen the calculations required to design a box gutter and it's no simple arithmetic. Even when you've got the calculations right the engineer still has to draw the thing on paper. A properly designed and documented box gutter cannot be captured by a simple detail on the corner of the page. When it's done properly the engineer's details usually take the whole page or multiple pages and then it needs to be coordinated with the Architect. There was a time in the NT when box gutters were all the rage (might still be the case), it had that streamlined look that homeowners wanted so the Architects obliged. How often do you think I would see fully documented and properly designed box gutters in the building approval plans emanating from a claim?… Never. For these unfortunate homes, the typical detail I saw was basically an arrow pointing to the roof that read "Box Gutter To Comply with AS3500.3" Apparently this was all that was needed to ensure the builder and plumber knew what they were doing… right…
I learnt a few things during my time there –
- There's nothing wrong with simple hip/gable roof designs
- Wide eaves are your best friend
- Windows in single skin masonry walls are just asking for trouble
- When the wind blows hard enough, water will run uphill
- Removing unwanted condensation in the interstitial spaces of your building fabric is a real science.
- House should be designed for the climate they are in.
- The Building Code of Australia is not a perfect document.