Ben’s self-build story: what is a concrete strip foundation?
After more than six years of research and planning, Ben Adam-Smith’s vision for a 226sqm Passivhaus is built on solid foundations. With a rollercoaster few years behind him, it’s a huge relief to be finally pouring the real thing.
Like most first-time self builders, House Planning Help founder Ben Adam-Smith and his wife Kay have overcome stumbles and setbacks to get their ambitious plans for a Passivhaus off the ground. From a long and arduous plot search to being stunned by the sky-high bids from contractors, it’s not been the easiest ride.
The good news is that their determination has paid off. After securing a beautiful rural half-acre plot in Hertfordshire back in 2016, they’re now putting their architect’s plans in the hands of their chosen contractor. Their dream home is about to get real.
Plans for Ben’s Passivhaus were drawn up by Norfolk-based architecture firm Parsons and Whittley. An interesting element of their plans is that they don’t rely on rarefied building skills or unconventional and expensive materials.
Instead, the house will be a traditional cavity wall masonry build, which is a common choice in the UK. The key difference will be the attention to detail that’s required by Ben’s building contractors.
“We wanted to build a Passivhaus because it would be cheap to run and would offer a really comfortable and healthy place to live,” says Ben. “When we first saw the return quotes from the contractors, we were surprised. We already had an efficient form and a cost-effective build method, but ultimately we had to make some compromises to bring the cost down. as well as pay more than our initial budget.”
With contractors appointed and the site secured, the team has been busy getting the first few key stages of construction completed.
First up was the precision job of pinpointing precisely where the house will sit on the plot. While this sounds a simple job in principle, it needs to be extremely precise – deviating by as little as 5mm from the approved plans.
With that job done, and things getting off on a solid footing, it was time to build a genuinely solid footing in the form of foundations. Ben's architecture firm specified a concrete strip foundation. But what exactly is that?
What is a strip foundation?
According to Chris Parsons from architects Parsons + Whittley, “strip foundations are how most houses have been built for the past 40 years. It’s a simple, traditional and cost-effective way of doing things.”
The process involves digging out trenches around the perimeter of the house and along the line of all load-bearing walls. Concrete is then poured in until it reaches just below ground level.
The site’s good sandy ground also made strip foundations a practical solution. Good ground conditions are important in strip foundations, because the sides of the trench play a big part in supporting the load.
Rain, rain go away
Heavy rain did slow the job down a little bit. Flooded trenches had to be pumped out before concrete could be poured, but overall this stage of construction passed without any nasty surprises.
With the concrete foundations fully set and the rest of the earth levelled, it’s now deliveries rather than rain that are flooding the site. Ben’s team is ready to move on to the next stage of the build – laying a beam and block ground floor – and you can read all about what happened in our next post.
About The Author
Ian Winterton is a freelance writer based in the Tarn in South-West France. In his spare time, he renovates the old stone house he lives in with his wife and two children in the medieval village of Boissezon.