Insulation -Solid Floors

Solid floors are difficult to insulate if you want to retain the finish and height of the existing floor. If you have beautiful flagstones, these can be carefully lifted, the subfloor dug out, a damp-proof membrane or new concrete slab laid, insulation and a screed installed, and the flagstones put back. However this is a difficult and expensive job.

The alternative is to build a new floor on top of the existing floor. This will also preserve the existing floor finish, which may be important in a listed building, but of course you will no longer be able to see it. The usual approach is to lay rigid boards of insulation on top of a damp-proof membrane with plywood or chipboard on top. However this can add well over 100mm to your floor height and require adjustments not only to doors but skirting boards, kitchen units, radiators, bathroom fittings and sockets. You may be able to avoid some of these problems by using a thinner layer of high performance insulation such as 40mm of phenolic board or 30mm of aerogel.

It is necessary to take a comprehensive approach to avoid trip hazards where the floor level changes.