Floors, Ceilings and Staircases

Filed Under: Do it yourself, Home repair, Remodeling    by: ITC

Solid concrete floors in modern houses are usually made up of a layer of gravel, topped by a layer of concrete (the subfloor), on top of which there is a waterproof membrane linked to the flashing in the base of the surrounding walls and finally a screed of mortar, which provides a smooth, level surface for your floorcovering. This type of construction is very tough, but even so, defects can occur; cracks, uneven surfaces and damp patches due to faulty waterproof membrane are all common problems.

Rotten wooden floors can be replaced with solid concrete ones relatively cheaply and they have the added advantage of providing a much more stable surface for laying something like quarry tiles or wood blocks. In this instance, however, you must incorporate pipe work air ducts to link any ventilation holes or grilles in the external walls with the suspended wooden floors in adjacent rooms.

If the surface of the floor is uneven you can smooth it with a self-leveling floor screed. Supplied in powder form for mixing with water or latex (depending on which it is based) the screed provides a smooth ‘Ain layer on which you can lay floorcoverings.

Pour small amounts of screed onto the floor at a time and trowel roughly level. There is no need to work out trowel marks, since they gradually settle out. Before you apply the screed you must remove the baseboards and make sure there are no major cracks or depressions in the floor — fill these as previously described.

Nail a batten temporarily across the threshold of any interconnecting doorway to provide a positive edge to the screed. When it has set, remove the batten and trowel a narrow sloping fillet of mortar along the edge to blend it into the adjoining floor.

Water-proof membranes may be thick plastic sheet, PVC, butyl rubber or painted-on bitumen emulsion, and to be effective they must provide a continuous layer across the floor and be joined to the wall flashing.

If the waterproof membrane becomes punctured, damp patches will appear on the floor- covering. Small areas of damp can be treated by breaking through the surface screed and coating the damaged area of waterproof membrane with bitumen emulsion, then rescreeding with mortar.

If the problem is widespread, or if the floor has no waterproof membrane at all, the real solution is to dig it all up and lay a new floor.

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