While the upper floors of a house will always be constructed of wood, the ground floor may be made of wood or it may be of solid concrete.
All wood floors are based on the same method of construction with minor differences. They all have a supporting framework of wooden beams called joists onto which are nailed wooden boards or plywood panels and may have a plain or decorative finish.
The joists of wooden ground floors are supported at their end — and sometimes at one or two points in between — or additional wood beams known as “wall plates”. These, in turn rest on the tops of low brick “sleeper” walls.
These are not solid, but are laid in honeycomb fashion with spaces between the bricks to allow the air to circulate below the floor to prevent condensation and rot forming. For the same reason, vents are usually fitted at the base of the external walls and must always be kept clear. Slates or strips of flexible flashing material are laid between the wall plates and sleeper walls to prevent damp attacking the wood.
Sometimes the joists are laid on top of individual bricks set on the ground. Upstairs, the joists are also supported by wall plates but these are held by metal brackets called joist hangers, which are cemented into the walls. Sometimes the joist ends may be set in sockets between the bricks, with a metal plate below to spread the load through the wall.
Most modern houses have solid ground floors. These comprise of a layer of compacted gravel on top of which is a 4in layer of concrete called the subfloor. A damp-proof membrane bitumen or thick plastic is laid next and is carried up and down the wall to link with the flashing around the base of the house.
A thin layer of mortar can be laid on top of the membrane which will provide a level surface for most types of flooring.
Over the years a wooden floor can suffer considerably from wear and tear. The joists may warp or sag, boards may shrink to open up gaps through which draughts whistle, or they may become loose or damaged. The whole structure may be further weakened by woodworm or rot. Fortunately, many of the minor problems can be cured easily, although serious rot or insect attack may mean complete replacement and should be dealt with by a specialist.
Probably the most common fault with a wooden floor is creaking floorboards due to the fixings working loose. The cure is simple: either drive the nails back in or replace them with longer nails or screws. Punch nail heads below the surface and countersink the screw heads.
Gaps of less than 1/tin can be filled with papier-mdché, which you can make yourself. Half fill a bucket with small pieces of torn, soft white paper, gradually adding boiling water while you pound the paper into a thick paste. Allow it to cool and stir in enough cellulose wallpaper paste to make a thick mixture. Add wood stain to match the color of the boards.
When the papier-mâché is quite cold, force it between the boards with a filling knife, leaving it slightly proud of the surface. Leave it for at least 48 hours then sand smooth.
Fill wider gaps with softwood fillets: cut the fillets fractionally wider than the gaps they are to fill, using a backsaw. The fillets should be fractionally deeper than the floorboards: that is, about lin. Plane the fillets so that they taper slightly at the bottom then tap them into the gaps with a hammer and block of wood. Use a plane to shave the top edges of the fillets flush with the tops of the floorboards. Make sure the ends of fillets meet on a joist: secure them to the joists with brads.
Damaged boards
Damaged sections of boards should be cut out and replaced, or a new board fitted if the damage is substantial. First check that there are no pipes or cables running below the damaged section, otherwise you will have to remove the entire board in case you cut into them by accident.
To cut out a section of board, first find the edges of the joists at each end. Do this by sliding a knife blade along the gap between the boards. If the boards are tongued-and-grooved, you will have to cut through the tongues by drilling a starting hole and using a keyhole saw or with a circular saw set to the depth of the board.
Drill a starting hole for the saw just in from the edge of each joist and cut through the board at each end in line with the joist edges.
Lift out the damaged section; if it is nailed to intermediate joists, lever it free using a masonry chisel and a stout length of wood. Lever the board upwards at the fixings with a chisel until you have lifted the end enough to be able to slide the wood below it, while resting it on the tops of the boards on each side. Pushing down on the end of the board will spring the fixings from the joist. Continue in this fashion until you have freed the board. A complete floorboard can be removed in the same way.
Screw or nail lengths of 2in sq batten to the sides of the joists flush with the undersides of the old boards. Then nail a new section of floorboard to the tops of the battens.
Sagging joists
On wide, unsupported spans, the joists may sag in the centre of the floor, giving it a slightly “dished” surface. To overcome this, add packing pieces to the tops of the affected joists.
Lift the floorboards and place a straightedge across the joists at several points. Measure any gap between the tops of the joints and the straightedge and use the measurements to mark out lengths of softwood batten. These must be the same width as the joists. Plane the battens to size and nail them to the tops of the affected joists. Finally, re-lay the floorboards.
