With the house beginning to take shape, there was one thought that kept me up at night — how are we going to backfill?

We’d cut out the land, built the concrete retaining wall, insulated it with 300mm of polystyrene and waterproofed it— but then we had to backfill the space to allow us a solid surface on which to build our dry stone wall.

We initially had a geo-textile solution which would involve creating layers of soil and gravel to build up the ground so that the wall could be built on top. But this solution was expensive, and incredibly labour and material intensive.

So instead, we decided to use 1.2 x 2.4m blocks of polystyrene (610mm deep) to backfill — providing a cheap, quick and strong solution which was arguably more sustainable than transporting tonnes of soil and gravel to and around the site.

Building on made up ground is not normally recommended as the ground moves and is compressed over time making it unstable. While the polystyrene might settle a millimetre or two, it’s not really going to move over time, making it a suitable material on which to build our stone wall.

So instead of spending nearly £3,000 plus labour on the geo-textile solution, we’ve spent around £1,400 on the polystyrene solution that will also add extra insulation and waterproofing qualities.

Probably the smartest thing I’ve done on this whole build!

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