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Suspended
wooden flooring removed to allow drying and examination of floor joists (photo
courtesy of WA Fairhurst & Partners, Dundee)
The floor surface, whether boarding or concrete, should be exposed as far as possible. Carpets, sheet vinyl finishes, tiles and similar should be removed and the floor area sufficiently ventilated.
In the case of suspended wooden floors, some boards should be lifted away and any water present in the cavity should be removed. This can be achieved by draining through air-bricks, cutting holes in the perimeter walls or using a pump however do get advice (from expert builders or damp-proof experts) before cutting holes in walls.
Spaces beneath suspended concrete floors should naturally drain and dry out through existing air bricks or drain holes, though forced ventilation may be needed.
Wet mineral wool insulation and pipe insulation should be removed and replaced and aluminium/metal foil around the insulation should be punctured to drain off any water.
Floor joists showing signs of rot should be replaced and the surrounding area treated to prevent any spread. Distortion or twisting of joists can be prevented by stiffening the joists with struts or battens. Electrical connections and junction boxes must be checked by an electrician.
Floodwater will seriously damage most chipboard and there is the added problem that contaminants can get into the wood. Chipboard should be replaced if you think that the floodwaters have made contact with it or it appears swollen, distorted or damp. Where you cannot replace it (e.g. under partitions) provide extra support with struts.
Heaved floors are those that have not returned to their original level or have cracked badly. The floor may have to be removed and a new floor constructed. If a floor is badly cracked, but has returned to its original level, a new floor may be placed over the old one. A vapour barrier should be added between the two floors and the new floor should be at least 2 inches thick.
The best way to tell when the flooring is dry by using a humidity meter, which will give a percentage humidity reading. This reading should generally be under 24% between October and May, and 22% between June and September.
Generally it is best to get advice before undertaking these kinds of repairs, either from surveyors or expert builders (see Who to contact).
When you are replacing floorings, consider using materials that are less vulnerable to damage from flooding or that are more easily moved following a flood warning (e.g. rugs rather than fitted carpets).
20 November 2002