 |
This characteristic black staining is found on the ground floors of many properties built in the 1920s. It occurs at the locations of ferrous nail fixings, where timber floors have been laid directly onto a clinker ash substrate coated with pitch tar acting as a damp-proof membrane. Over a considerable period of time ground moisture has gradually been introduced into the timber boards from each corroding nail fixing. The risk of wet rot in the timbers increases considerably when floors have been overlaid with linoleum or foam-backed carpet. |
