Crafting a DIY cabin from building site waste

Mareet Carley’s cabin, on her rural property near Pōkeno, is fully insulated, stylishly finished – and built entirely from waste materials.

About 50 per cent of the waste that goes to landfill comes from the construction industry. And Carley, who works as a project manager for a building company, has long been struck by this.

She gives the example of bricking a house. “Typically, when you get bricks on site you allow for a certain percentage of breakages or waste from cut bricks,” she says.

It is the same with things like gib, carpet and timber. And it is simply too costly and too much of a logistics exercise to get those small excess quantities returned to suppliers and put back into stock systems.

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So Carley started to rescue usable materials destined for the tip. When she decided to build a cabin for her teenage kids, she was determined to put everything to use.

“I had these bits of joinery pulled out from various places, like two ranch sliders and a window from an old build. So those were my starting point for measurements and the frame,” says Carley. The steel frame was created around the different joinery sizes rather than trying to fit them in afterwards.

With a completed frame, it took Carley and her family 12 weekends to finish the building, which measures 6 metres by 3m. “It’s an embarrassingly long time,” she laughs.

She did a lot of research and occasionally turned to YouTube videos, particularly for grouting the tiles, which was tricky.

Inside there is structural, grooved ply lining the walls and Karndean flooring and tiles. Outside there’s a deck made from treated pallets and leftover timber, a composting toilet, a 35-litre solar shower and a freestanding, claw-foot bath which came from a demolition. When she collected it, the demolition man told her “it is heartbreaking” to see what is thrown away.

The cabin is fully compliant with the building code and has cost about $11,000 to build, fit out and landscape. The lack of running water inside meant council consent was not required, says Carley.

As the costs of new building materials are constantly increasing, and we are all trying to reduce rubbish, building in this way seems a no-brainer. But Carley is clear, it isn’t always easy, and she had an advantage working in the construction industry. Her job meant she regularly spotted materials destined for landfill and had the contacts to be able to find specific things where needed.

Jeremy Gray, marketing manager for online tradie hub Builderscrack.co.nz, echoes this idea of challenges. When Gray and his partner tried to build their own family home with recycled materials several years ago, it was problematic.

“In my experience, the fact that you have to design around those recycled materials is a big hurdle,” says Gray. For example, recycled roofing iron often already has holes where the screws were removed. Roof trusses tend to be engineered for specific buildings so are hard to repurpose. Then, for consent, many councils require spec sheets for materials used – and if the materials are recycled, that’s often tricky.

The relentless issues eventually made the couple abandon their plan. “The environmental impact of the build would have been substantially lower,” says Gray, “but the costs and bureaucracy were just prohibitive.”

Ultimately, says Gray, it comes down to the size and complexity of the build. “Building a larger home from scratch is really difficult this way. But smaller structures or renovations, or converting your garage into a rumpus room, those are all much easier to achieve with recycled stuff.”

The good news is that if you want to use recycled or excess materials, they are out there. As part of her mission to cut building waste to landfill, Carley offers excess materials free of charge on her Facebook page as and when she comes across them. There is also a Facebook group for surplus building/ex-demo materials where people sell everything from leftover galvanised nails to entire kitchens.

Ben O’ Reilly, who manages the yard at Canterbury’s Graceworks Demolition, says while some things such as roofing iron, windows and doors are particularly easy to find, they also get a good variety of materials through – from new tiles and bricks to recycled rimu flooring.

And in the past year or so, he says there have “definitely” been more people coming through the yard. “We’re also trying to grow more relationships with builders, so that we can sell that excess for them and those things they’re replacing, like bathrooms and kitchens.”

Meanwhile, Carley has been so motivated by her cabin building and the reaction to it that she is now working on a tiny-house experiment. The idea is to collaborate with suppliers to build a series of tiny homes using excess building materials.

And ultimately her advice is encouraging: “Go for it,” she says. “If you have a little bit of building knowledge and know what you want, then just go for it.”