Repairing Wooden Flooring

These walls, which rest on a concrete slab in the ground, have alternate bricks missing to allow air to circulate freely and prevent the build-up of dampness under the floor. Solid floors in houses built after 1939 rest directly on the ground. They consist of a layer of hardcore covered with concrete, a damp-proof membrane and another layer of concrete, called screed. The floor covering, tiles or floorboards for example are laid on the concrete screed. Upper floors have boards carried on timber joists, which are built into or supported by the walls. The way in which they are fixed depends on the design of the house.

When floor joists are badly damaged for example, by woodworms or by dry rot they must be removed and replaced as soon as possible. It is dangerous to continue using a damaged floor. Although mot joists are built into the brickwork of the house when it is erected, replacement joists can be fitted using metal hangers. Hangers are made of galvanised pressed steel and sometimes are coated with black bitumen. When the joists to be replaced are on the top floor, it may be impossible to make the repair without damaging the ceiling underneath. In most cases, it will be necessary to resurface the ceiling with plasterboard after the new joists have been fitted. If the floorboards in a room cannot be made to lie flat, the joists beneath them may be bowed or twisted. This fault is most often found in upstairs rooms where the ceiling of the room below has crazed or cracked. The reason for the twisting is usually that the joist timber was unseasoned. Remove the flooring and straighten the joists by nailing struts between them. Fix the struts at the centre of the span of the joists.

If the floor has to be lifted, firstly find out whether they are square-edged or tongued and grooved. Try to push a knife between two boards at several points along the length. If it can be inserted, the boards are square-edged; if the knife cannot be pushed in, they are tongued. Square-edged floorboards can be removed without sawing, provided that both ends are free. Use a tool called a bolster, which resembles a very wide cold chisel. Tongued flooring must be cut free along one side of the board. When the first tongue has been cut, the rest of the floorboards can be removed with a hammer and bolster.

The gaps created by shrinking floorboards cause uneven wear to carpets and linoleum. The most effective repair is to re-lay the board tightly together. Fill the final gap with a length of wood the same thickness as the floorboards. When lifting the floorboards, start close to the skirting at one side, but leave the first board in place under the skirting. If the wood is tongued, plane off the tongue on the edge of the first floorboard when it is removed. To make sure that floorboards butt tightly, cut at least four softwood wedges from wood slightly thicker than the floorboards. They should be at least 18 in. (455mm) long and 2 in. (50mm) deep at their thick end. If the floorboards extend for more than 6 ft (1,8m), cut enough wedges to fit every 3 ft (915mm).

If the gaps between floorboards are wide, say about ¼ in. (6mm) it is possible to fill them with long off-cuts of softwood. With smaller gaps, less than ¼ in. (6mm) a wood pulp made from a mixture of wood shaving and cold glue can be used to fill in the gaps. Bind the shavings to a thick paste and apply to the gaps in the floor using a filler knife.