Substructure issues

Even in a listed building a concrete floor may have been laid to replace older flooring, on the assumption that concrete is the superior material. However, the detailing must take into account practical workmanship issues. A line drawn on a plan to represent a damp-proof membrane is probably one of the most difficult details to achieve practically on site in an older property.

To completely link a damp-proof membrane to some form of damp-proof course is complex, very time consuming and consequently very expensive. This type of work requires close and direct supervision, to be successful. What is usually laid is a concrete floor on a DPM that is turned up at the edges. A solid structure such as a concrete floor tends to push water to the perimeter walls, and if these are not linked to the DPM, they will wick the water up into the building fabric. Once a concrete floor is laid and moisture appears up a wall, there are very few options other than complete removal or dry lining. Further damp-proofing is unlikely to produce a satisfactory solution.

Vented suspended floors are more likely to provide a better long-term solution.