The ground floor – removing cement and replacing it with limecrete
The cement floor was the biggest single problem. It had to be removed to make the building habitable, because headroom on the ground floor was well under 6 feet. The plan was to drop the floor 8 inches. The architects advised, and indeed the conservation officer insisted, on a limecrete floor, using expanded glass balls from power station waste as a lightweight filler instead of gravel. Underneath was a thick layer of a similar expanded glass, for insulation, and also to allow water to drain away quickly from beneath the building. The winter water table, as measured by the well outside, is less than half a metre below the floor.
Limecrete, bought from Ty-Mawr, is a modern variant on the old materials, and its use has been a resounding success. The building feels dry even in the dampest of weather. But a simple experiment shows that this is because the limecrete and the unglazed clay tiles laid on top are expelling the damp into the air continuously, but slowly enough for it to be ventilated out of the house. The experiment which shows this breathability is to leave a large piece of plastic on the floor for a few weeks (accidentally, as it happened). Underneath, it became quite damp. But the house still felt dry. With the old concrete floor, water was forced up round the edges into the walls because that was the only way it could escape.