Penetrating dampness is dampness that penetrates through the external envelope of a building, causing dampness to internal surfaces. This dampness can cause rot/decay to nearby internal timbers and damage internal plasterwork. Typical examples are dampness caused by leaking roofs or defects to external walls, including defective external wall rendering, defective brickwork pointing, leaking rainwater fittings and rot affected external timbers (fascia/soffit boards, window and doors). Flat roofs are particularly prone to leaks. Older buildings (typically pre 1950) were mostly constructed using solid external walls, as opposed to modern buildings which are usually constructed using cavity walls. As solid walls do not have a central cavity to protect against water crossing from the outside face of the wall to the inside face of the wall, they are very susceptible to penetrating dampness. Accordingly external maintenance of solid walls including associated fittings and wall openings is essential. Remedial works will involve external repairs to prevent further penetrating dampness followed by internal repair/redecoration works. Where internal timbers have been (or are suspected of being) in contact with damp affected walls/ceilings/chimney breasts, a precautionary inspection of the affected timbers will be important. The reason for this is that the dampness combined with the heat from habitable areas, may have allowed rot/fungal decay to develop in untreated timbers (especially in unvented parts). This inspection may require exposure works.