Carpentry Guides Flooring

Repairing and Replacing Floorboards

repairing and replacing floorboards

Most older homes will have floors constructed using individual floorboards nailed to the floor joists, either on both floors or just the first floor. Newer homes may have floorboards, solid concrete floors or floors constructed using large sheets of chipboard. If you are planning to expose the floorboards in your home, or are planning to lay a new floor covering over them, it is important that they are in good condition and firmly attached to the joists. Carpet will do a good job of hiding faults in the floorboard beneath, but laminate flooring will show any major defects in the boards below it.

Lifting Floorboards

In older houses the floorboards will be straight edged and lifting them is no problem. Simply insert a wide-bladed chisel or bolster into the gap at one end of the floorboard and prise the board gently up until you can insert a claw hammer into the gap. Gradually work along the board prising it up as you go.

Removing a tongue and grooved floorboard is slightly more difficult as you will need to saw through the tongue on the least one side. It is best to use a convex blade flooring saw for this, but a pad saw or circular saw can also be used. Cut along the full length of one tongue to allow the board to be gently levered up. Be careful not to cut into any joists as this will weaken them and could mean that they will need to be replaced.

If you just want to access a particular section of pipework below a floorboard, it is not always necessary to lift the whole thing. Use the method above to lift the board over the section you wish to access. When it has lifted above the next floor joist (but is still attached further along the board), use a floorboard saw to cut through it and remove a section. Make sure that the cut is directly above the joist so that the cut end is not hanging without support when the section of floorboard is replaced.

If your floor is constructed of sheets of chipboard, these can simply be unscrewed and lifted out of the way. As with floorboards, chipboard may be tongue and grooved. If this is the case, you will need to cut through the tongue on at least one of the sides. If possible, try to cut through the tongue on an edge that is just above or just past a joist.

Joist Problems

Well insulated, treated and ventilated floor joists should last for many years with no problems. If there are problems with your floor joists, it is most often due to damp, which is most often due to lack of ventilation (a blocked airbrick for example). Discovering that floor joists are damaged or rotten is difficult without lifting the floorboards. There can often be very little sign that anything is wrong until a huge amount of damage has been done. If you think that an airbrick has been blocked for any length of time, or if there is movement in the floor, it is worth checking the joists.

To check for damaged or rotten joists, lift several floorboards (in a couple of different areas if possible) and inspect the joists with a torch. Use a bradawl or screwdriver tip to check how firm suspect areas of the board feel. If you think that a joist has started to rot, you don’t always need to replace it. Instead, you can bolt a new joist or new section of joist to the existing one, making sure that it is fixed to a section of the joist not effected. Evidence of woodworm should be treated accordingly. You can read more about woodworm, including ways to treat it in our guide to Locating and Treating Woodworm.

If, however, you discover dry rot (usually white strands of mould on the wood), you should seek professional advice. Dry rot can spread quickly and turn the wood to dust in a short time. Wood that is showing signs of dry rot should be removed by professionals as the spores released into the air can be harmful if inhaled.

Loose Floorboards

floorboardsLoose floorboards are easily fixed by replacing the nails holding them in place with screws. You can either remove the nails and use the existing holes for the screws, or knock the heads of the nails below the surface and drive a screw in next to them. If you want a better finish, countersink the screw holes using an 8mm drillbit and then make a wooden plug using a short length of dowel. Glue the dowel into the hole, wait for the glue to fully dry and then trim off the excess and sand it flush.

If a floorboard is loose because it is warped (pulling the nail out of the joist), you should replace the whole section with either new or reclaimed boards. If you plan to sand the whole floor afterwards, matching the boards is not so important (although you should obviously make sure it is the same wood). On the subject of sanding a wooden floor, always carefully make sure that nail heads are punched below the surface before you start. This should also always be done if you plan to lay carpet over old floorboards.

Damaged Floorboards

Split or cracked floorboards can often be repaired by inserting strong wood glue into the crack and then forcing the edges together using wedges driven into the gaps between the boards. This is not always an option if the crack of split is severe, or the edges have been damaged. Some common faults in floorboards can simply be sanded out (cupping, for example, where the ends of the board have curved up above the surface of the floor), or perhaps even hidden by lifting the board and turning it over.

Severely damaged floorboards can either be completely replaced or you can simply cut out the damaged section and replace only that part. If you are cutting a floorboard, make sure that the cut is over a joist so that the end can be firmly fixed (as well as the end of the new section when it is slotted in). If you can’t find a replacement floorboard that fits exactly, buy one slightly wider and plane down the edge until it is the correct size. If the existing boards are thinner or thicker than your replacement board, you can either chisel out a slot in the joist or add some thin strips of packing material underneath it.