How to Repair and Replace Floorboards
The majority of floors in older homes will have individual floorboards nailed to floor joists. In modern homes, sheets of flooring-grade chipboard (particle board) will be nailed or screwed to the joists. If a new floor covering is to be laid, it is essential that floors are in good condition. If floorboards are to be exposed, they need to be in even better condition, as any defects will be visible.
Lifting floorboards
To inspect the underfloor space or fit new floorboards, you will need to lift existing floorboards. You may find some that have been cut and lifted in the past to provide access to pipes or cables. These should be easy to lever up with the flat blade of a bolster (stonecutter’s) chisel – do not use a screwdriver as you will damage the floorboard.
To lift boards that have not been cut, check first that they are not tongued-and-grooved – a tongue along one edge of each board fitting into a groove along the adjacent edge of its neighbour. If they are, use a floorboard saw or a circular saw with its cutting depth set to 20mm to cut through the tongue.
Lever up the floorboard with your bolster chisel, and use a floorboard saw to make a right-angled cut across it. Make the cut exactly over a joist so that the two parts of the board will be supported when they are replaced. Chipboard sheets are easy to unscrew, but you may need to cut through tongues in the same way as for traditional floorboards.
Joist problems
Most of the problems associated with floor joists are due to dampness, which may occur if airbricks (vents) have become blocked or if there are not enough airbricks to ensure adequate ventilation of the underfloor space.
Lift a few floorboards and inspect the joists with a torch and a mirror, prodding any suspect areas with a bradawl (awl). If sections of joist are damaged, you should be able to cut and lift floorboards or chipboard sheets over the damage and bolt on a new section of joist of the same size, making sure that it is fixed to solid wood. Do not bother to remove the old joist unless it is actually rotten. If you do find signs of dry rot (typically white strands), all damaged wood must be removed by a firm of professionals. If you find signs of woodworm attack, treat the affected areas with a recommended woodworm eradicator or call in a professional firm.
Loose floorboards
If floorboards are loose, the best answer is to replace the nails holding them down with screws. Do not put a screw in the middle of a board – there could be a pipe underneath. If nail heads are protruding, use a hammer and nail punch to set them below the surface of the floorboards. This is essential before attempting to use a sanding machine or laying carpet or sheet vinyl.
How to Replace a Wooden Floorboard