Week one of our extension project

It's week one of the build and the footings have been poured. It's been raining ever since and I've spent most evenings bailing out. Finally the weather clears and the builder returns. We're not building in blockwork, but polystyrene from a company called Beco Wallform. Sorting your levels out when your first layer of bricks is floating in two inches of water in the footings isn't easy. But somehow the builder manages and we're off. The bricks -- which slot together like Meccano to leave a cavity which is to be filled with concrete -- go up quickly. Our builder, who's never constructed with this product before, is soon off and flying. At last we can relax a little. We're out of the ground.

A couple of weeks ago, £8,000-worth of polystyrene was delivered on the day a force 8 storm was predicted. We had visions of our building materials flying off down the valley. But weighed down with tarpaulin and anything heavy we had to hand, the polystyrene was still there the following morning. Big relief.

We're confident the polystyrene will deliver superb insulation (five times what can be acheived with a traditional build, we're told). Although we've seen the product twice on Grand Designs, it does feel a little 'experimental' in the flesh. And, being polystyrene, it snaps easily. It's hard to imagine it adding up to anything substantial. But once a few courses have gone up, the walls lock solid. And then, when the equivalent layer of concrete has been poured, it starts to feel substantial and permanent.

The outline of our extension is taking shape. We're turning a bungalow into a house, slotting an extra gable on the side which will give us a large kitchen/breakfast room and, above, two bedrooms and a family bathroom. In the loft of the existing bungalow, we'll have space for our bedroom and an en suite. The builder has predicted a six-month build. But I'm doubtful.