Last week I worked on the foundations for the new straw bale building at Preivale Woods. This building is for the Selbourne Society who manage the woods as a nature reserve. It was on an educational course run by Strawworks.
‘Using car tyres for a foundation? Sounds a bit crazy!’ said my mate down the pub. Well, not really.
Consider the use of gabions as a building material.
These steel baskets filled with rock are load bearing. And are becoming increasingly popular to build with. I noticed that they were used extensively in the construction of the Olympic village in East London.
Well, now think that the weak point in the gabion, the steel that can corrode, is also present in a car tyre. But in the car tyre it’s encased in waterproof rubber. Add to that, the life expectancy of a car tyre is 30,000 years (provided you keep them out of UV light). That makes a long lasting foundation! If that wasn’t enough, they cost garages money to dispose of, which means we can have them delivered to us for free.
Using a car tyre, filled with gravel also eliminates the need to use a plastic damp proof course on top of your foundation. Neither gravel, nor rubber absorb water. The damp proof course is a hangover from concrete foundations – concrete foundations will absorb water, and transfer it to your building. Design your foundation using materials that don’t wick water means no DPC needed!
You may have seen earthships being built from car tyres.
This doesn’t appeal to me, my focus as a builder is to create homes that are healthy to live in, as well as healthy to the earth. I don’t believe that having car tyres in your house will benefit the air quality. They are made from pretty nasty chemicals. But, using them outside the envelope of your home, in the foundations, seems to me like a reasonable option.
So, how do we make car tyre foundations?
Here is Jan showing us how it’s done.
Going on top of the foundation is a wooden box beam. if there are any discrepancies on the heights of the foundations, we will be using slate to raise the box beam to level.
The foundations are great fun to make. As with most natural building, it is more labour intensive than modern construction. The trade-off is that it’s something you can do yourself, for very little money.