There are a number of challenges involved when it comes to building new or renovating an existing home. Whether it’s a steep or rocky site, difficulty with block access or rectifying past mistakes on existing structures, a number of challenges are to be expected.
In our new blog series Ozzbuild Explains, we’ll be tackling some of the more common challenges in building and shedding some light on the importance of having technical aspects of your build completed right. Our first topic? Waterproofing and weatherproofing. This is something that’s often done wrong and can cost you hundreds of thousands to repair down the track.
Keep reading to learn more about this common building mistake and discover the importance of engaging an experienced and educated builder to complete your waterproofing.
What is waterproofing and what areas of a home require it?
Waterproofing is as simple as it sounds – it’s about ensuring unwanted water and moisture can’t enter your home and lead to mould growth, rot and decay. Balconies, internal wet areas like bathrooms, ensuites and laundries, retaining walls and roofs all require waterproofing.
What’s the difference between waterproofing and weatherproofing?
The two are interlinked. Weatherproofing is extremely important when it comes to windows and external walls – any home with a steel or timber frame should be protected with a vapour permeable wall wrap and have a seal around all windows and doors with a waterproof flashing tape.
A home should be air-tight, which in turn makes it water-tight – this stops any moisture penetrating the home. Cladded homes should have a cavity batten between the wall frame and back of the cladding to create an air gap. This gap acts as a buffer between the external materials and the inside of the home. More often than not we see other builders cladding buildings without this gap, which leads to severe water issues.
What does the process of correctly waterproofing involve?
The waterproofing process changes depending on what you are waterproofing and the size of the area, but we’ll use a bathroom example here. The first step is always to clean the substrate (concrete slab or flooring sheets). Next, we’ll install the metal profiles and angles, lay the sheeting and weld it together. We will then flood test it, install the cement tile bedding and use a liquid membrane on top to seal it and stop efflorescence (white-looking calcium build-up that can come through the tiles). This process takes 1.5 – 2 weeks, as cement bedding needs time to cure before the second layer of liquid membrane can be applied.
Many builders will only do one waterproofing layer in a bathroom and be ready to tile within 3 days. We never do this at Ozzbuild as we won’t sacrifice quality for time.
What can happen when waterproofing is done wrong?
If the waterproofing fails in any area of a building the results can be catastrophic. Imagine a bathroom on the first floor leaking down into the lounge room below – water can cause damage to the plaster ceiling, electrical services inside the ceiling, furniture on the ground floor and floor coverings. But the most expensive part of the repair is the bathroom itself as it will need to be ripped apart and restarted from scratch. This can cost many tens of thousands and if it’s been more than 6 years since the build was completed, your builder is no longer liable – you will have to pay.
What should builders take note of when waterproofing?
You should always ensure you’re using the right waterproofing product for the application. We use a range of sheet, liquid, torch-on and cementitious membranes. Each area and material will require a different type of membrane to be used and there is no one-size-fits-all product.
It’s important to make sure the area you’re treating is absolutely spotless before beginning your work to ensure materials bond to the surface you’re working with.
What are some common waterproofing mistakes you’ve seen?
Generally, it is people using the wrong kind of waterproofing – many builders in the industry opt for a typical paint-on liquid membrane for all purposes. We have seen this fail on balconies and behind retaining walls, even in first floor bathrooms where a timber frame system has been used.
We only ever use sheet waterproofing on the first floor of a building (this is guaranteed to never fail), liquid on a concrete substrate and a cementitious membrane behind retaining walls.
Ozzbuild are currently working on a remedial project in North Bondi, which features a number of waterproofing issues. What have you had to rectify here?
This project had no wall wrap or battens and there was no parapet capping around the perimeter of the building, protecting the exposed walls from the elements above. The damage to this 8-year-old home was so bad we’ve had to rebuild 80% of the wall structure.
This has involved removing existing cladding and replacing all of the rotten timber framing. We’ve also had to remove all windows and doors and re-install these with correct flashings, wrap the home and seal all openings to the wrap. The next stage was to install a cavity batten and the new cladding. This exercise is going to take us around 2 months to complete and will cost the homeowner around $300,000. It’s an extremely costly job now when it could have been done for around $10,000 – $15,000 when the home was built.
What’s the takeaway?
Most builders aren’t doing incorrect work on purpose – it’s just that they’re uneducated with what happens to some homes after a build. You should always endeavour to work with an experienced builder who understands the more technical parts of a building, including waterproofing.
Homeowners should always consider paying more for extremely high-quality waterproofing products and builders who insist on using them. We believe sheet membranes should be mandatory on the first floor of all buildings and legislation should be in place to enforce it.
Failed waterproofing and weatherproofing costs the Home Owners Warranty scheme millions and millions of dollars every year. Education is key in changing this.
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If you want to learn more about the importance of waterproofing or are ready to engage a technical builder with experience on challenging sites, get in touch with the team at Ozzbuild today!