Interview with a designer: cladding in the sub-tropics
Rain and heat mean different cladding and finishing choices in the sub-tropics, says Stephanie Skyring, an architect based in Brisbane. But a focus on sustainable materials is key, no matter the climate. To go with our buyers guide on cladding, we asked Stephanie to tell us about her approach to cladding selection.
Q. Are there particular considerations for cladding in the sub-tropics?
In sub-tropical south-east Queensland, a climate-responsive approach is to use lightweight cladding material, so it doesn’t hold the heat and it cools off fast at night, similar to what works in the tropics. This means lightweight boards or sheet materials fixed to a timber frame (with appropriate sarking and bulk insulation in the wall, of course).
Rain is an important consideration. Effective overlapping of joints is important so the rain can’t get between them. Where possible, using roof overhangs to minimise the rain that gets onto the walls is also important, to stop rain tracking down the wall and into the top of window and door heads. Brisbane has some 1980s house designs that used diagonal timber wall boards; the water tracks diagonally down the cladding and causes all sorts of leaking disasters as it runs into the sides of windows and door frames and wall corners.
Wall colour is also important. Dark materials absorb heat and so expand and contract over the day. This amount of movement in timber causes boards to separate, showing gaps between paint and ultimately leaking—and causing the timber to break down more quickly. Builders have told me that they regularly return to fix and replace house cladding that uses black or dark painted wall boards. If you want to use dark colours, use them on the south or other areas where they don’t get much sun; definitely don’t use them on the west.
Also be careful when using Colorbond. The beautiful colour you choose today will likely be very tired and faded in 10 years. You can repaint Colorbond, but it’s not a great solution. If you choose steel for longevity, you are better to choose Zincalume that will just lose its shine over time and improve with age.
Q. When using timber for cladding, one way to source it sustainably is to use recycled timber. Do you do that?
We don’t often use recycled timber cladding, unfortunately, because it is too difficult to find builders who are prepared to work with it. We specify new Araucaria cladding (hoop pine) from sustainable plantation suppliers like Finlayson. We only tend to use recycled timber for interiors, for hardwood flooring, walling and cabinetry. This timber ideally comes from demolition yards so it’s not remilled, or it comes from places like The Big Red Shed or Kennedys—they obtain large pieces of old hardwood from jetties and bridges and remill it to order into required sizes.
In one project, Gaythorne, we used timber from the demolition of parts of the house. This was easy logistically as the timber was on site and, by reusing it, we prevented the beautiful hardwood going to landfill.
There are a few issues reusing boards from your existing house, unfortunately. The first and major hurdle is finding a builder who is happy to do it. Most of them won’t, as it’s labour intensive; you have to pull the nails out and the boards are all random sizes rather than long lengths.
The boards also often have lead paint on them. In the case of Gaythorne, the boards were in very good condition, so the painter was able to paint over them with an undercoat to make the new water-based top coat adhere. This is standard practice for lead paint that’s in good condition. The weatherboards were hardwood. Hardwood is harder to work (it’s very hard!) and can be bowed. However, because the boards were very old, they were very dry so there were no issues from shrinkage after they were installed.
Usually the only people who reuse boards are those doing the work themselves. I find that when you start talking about reusing boards, most builders will say they are not interested or put a premium on it.
When you demolish parts of a house all the great old hardwood (wall cladding, studs and flooring) typically goes in the skip. However, there are a few furniture-makers in Brisbane that I know of who have connected with builders. They get the hardwood after a demolition and remake it into beautiful pieces of custom furniture. The ways to prevent building materials going to landfill is a good story in itself!
Q. With another property, Spring Hill, you used plantation pine. Do you look for certifications/which ones?
New weatherboards used in construction are typically softwood—preferably Araucaria (hoop pine) because it’s a native Australian plantation species or radiata pine if you get the cheap option (still grown in plantation locally, but not a native species; for Brisbane people, all those forests on the way to the Sunshine Coast are radiata). Softwood is typically straighter, easier to work and doesn’t shrink after installation. New hardwood boards tend to shrink after installation, causing gaps where the boards overlap that have to be repainted.
The Spring Hill boards were Araucaria from a small local supplier. I do look for sustainable certification, but I prefer native trees grown locally in plantation over an imported species grown overseas with certification.
Choosing sustainable materials is very hard; there are so many considerations. So with timber I try to keep it simple: reduce the distance it has travelled, use a plantation local Australian native species so it has provided habitat and a food source to local animals during its life and select plantation over managed forests (chopping down old hardwood trees removes too much wildlife habitat and nesting holes).
Q. The random shiplap boards look great on the Spring Hill project. What made you choose that (and what is shiplap)?
Shiplap, weatherboard and chamferboard are all timber boards that overlap each other for weather protection; they just have different profiles. Shiplap boards have a tongue and groove as well as overlap. I chose the random pattern for something new; I like interesting texture. The supplier had three different sizes, so I just used all of them!
We used a random pattern with the recycled weatherboards on Gaythorne, too—we split some in half to get a narrower board and placed them facing one way and the other. To get proper weatherproofing, the recycled weatherboards are a cladding detail over a fibre-cement sheet as there is a 10 mm gap between boards.
Q. What about painting boards in the sub-tropics?
I always paint external cladding in Brisbane rather than clear finishing it like architects do in the southern states; our sub-tropical weather is just too harsh. With good quality paint in a light colour to avoid too much expansion and contraction, properly applied and kept clean with a regular house wash every five years, your external paint can last 20 years without a recoat.
This case study accompanied our cladding buyers guide in Renew 149. To read the guide, you can buy a copy of the issue online, find it on newsstands, or become a subscriber.
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