There are many different versions & perceptions about what leaky buildings are, and what they look like. Most people judge a house by its cladding, so if they see a plaster on a house, they automatically become sceptical and assume it leaks. A thermal imaging inspection can tell a different story from the inside out.
Higher risk design elements causing leaky buildings:
With all the media attention, most people are now aware that most of the leaky buildings don’t have a cavity system (not labelled in the image above, but very important). This means the cladding is directly fixed onto the timber framing and water can’t escape, and air can’t circulate in to dry any moisture out. Further to this, the timber in many cases is untreated to it tends to rot relatively quickly, and black mould begins to grow etc etc.
So are their perceptions of leaky buildings justified? (from paragraph 1)
There are plenty of houses out there constructed with plaster systems like monolithic and harditex, but it’s not so much the cladding itself that leaks, it’s the way it’s installed and what flashing systems are in place (if any at all).
Here is an example relating to the previous paragraph: If you point a hose at a blank plaster section of wall for an hour, providing there are no cracks in the cladding, then it won’t leak. Now, if you point that same hose at a junction where the plaster meets aluminium joinery (like at a window or door), then there is a much higher probability of the water penetrating the building envelope. Unfortunately with some homes, the only waterproofing around the window frames is a coat of paint or silicone. The better designs having flashings or scribers which prevent water getting in the side of windows.
Common design features causing leaky building issues
There are several other contributing factors that increase the probability of a house leaking. Some homes are built using ALL the highest risk design elements that have created absolute havic. The most common features are:
- Decks over rooms – if waterproofing membrane fails then it fills the external walls below with water.
- Flat roofs (which means internal gutters in most cases)
- No ground clearance – Water can soak up the cladding and saturate the bottom plate of timber framing
- Hand railings fixed through the top of balustrades – Water will pool ontop of the balustrade and enter the through the fixings. Decks are very vulnerable to expansion and contraction due to their exposure to heat and rain, causing joins and junctions to open up.
- Pergolas fixed directly into window/door lintels – Water gets across the bolts and directly into the framing
- … and the list goes on.
What is the riskiest type of plaster house to buy?
Some home buyers and builders will argue that they are all risky, which could be true to an extent (especially with no cavity and untreated timber), but there are some that present a lower risk.
Let’s look at the lower risk features to look out for when buying:
- Single level,
- pitched roof,
- external guttering,
- good ground clearance.
These are the key features that will dramatically reduce risk of leaking because it’s rare that a home with a pitched roof and eves will let water enter the external building envelope, which primarily means external load bearing structures.