How do I replace a damaged floorboard?
Cutting out a damaged board over the right bearing, supporting the new one properly, and dealing with the tongue so the replacement drops in without wrecking its neighbours.
- Difficulty
- intermediate
- Time
- 1 hr
- Read
- 4 min
- Safety
- warning
Short answer
Cut the damaged board out over the centre of a joist at each end, or beside a joist with a support batten screwed to the joist face. Cut the tongue off the replacement so it can drop in, bed it on the same bearings, and screw rather than nail it so the repair can be lifted again.
Do this first
The mistake that makes this job fail is cutting in the wrong place. A new board with no bearing at its ends drops under load and squeaks from the first day, and no amount of screwing into thin air fixes it. Everything else about the job is straightforward.
Safety
Cables and pipes run in the void directly beneath floorboards as a matter of course, often notched into the tops of joists where a saw blade will reach them. Set the blade depth to the board thickness only, scan before every cut and every fixing, and if the floor is above a kitchen or bathroom assume there are pipes until you have looked. Cutting a live cable in a floor void is a real and common injury.
What you'll need
- a cable and pipe detector
- a circular saw or multi-tool with adjustable depth, or a hand saw
- a bolster and a pry bar
- timber for support battens (optional)
- replacement board of the right thickness and width
- screws and a drill/driver
Step by step
- Find the joists.The lines of nail or screw heads across the boards mark them, typically at 400mm centres. Confirm with a detector, and mark each joist centreline on the boards with a pencil.
- Scan the whole work area for services.Cables and pipes are usually run along or across joists in notches or holes. Scan the board you are removing and both neighbours, and mark anything found.
- Decide where to cut.Either directly over the centre of a joist, so old and new boards share the bearing, or clear of the joist with a batten added to carry the new end. Never cut in the middle of a bay with nothing beneath.
- Set the saw depth to the board thickness.Measure the board, set the depth, test on the offcut. A blade set deeper than the board is the mechanism by which cables get cut.
- Free the tongue on one side.On tongued and grooved boards, run a multi-tool or a circular saw along the joint to cut the tongue, or work a bolster into the joint. Trying to lever a T&G board straight up snaps the tongues off the neighbouring boards.
- Lift the board from the cut, not from the neighbour.Get a bolster into the cut end and lever upwards against a wide packing piece resting on a joist, so the pressure is not applied to the adjacent board.
- Add support battens where needed.Screw a length of timber to the side of the joist so its top face is flush with the top of the joist, giving the new board end a solid landing. Two screws minimum per batten.
- Prepare the new board.Cut it to length. Cut the tongue off the long edge with a saw or a plane so it will drop straight in between two fixed boards. Check the thickness matches — old boards are often thicker than modern stock and you may need to pack or plane.
- Fit and screw it down.Drop it in, check it sits flush with its neighbours, and screw it — pilot, countersink, screw into each joist and each batten. Screws let you lift the board again in future without damage; nails do not.
- Finish to match.If the floor is exposed, fill the countersinks with a matched wax or filler, and take the new board's colour towards the old with stain before finishing. New timber next to old is always lighter; expect several attempts on a sample offcut.
Tips
- Take a short offcut of the old board to the timber merchant. Old boards vary in thickness and width, and matching by eye from a photograph rarely works.
- Reclaimed boards of similar age match far better than new timber and are widely available. Check them for old nails before they touch a saw blade.
- If more than one board in an area is damaged, stagger the end cuts over different joists rather than cutting them all on the same line, so you do not create a weak seam across the floor.
- Number the boards as you lift them if you plan to put them back — floorboards are rarely the same width as each other and they only fit in one order.
Common mistakes
- Cutting the board out in mid-bay — The new ends have nothing to bear on. The board drops each time it is stood on, and the repair squeaks from day one.
- Leaving the tongue on the replacement board — A full tongue cannot enter the groove of a fixed board from above. The board sits proud, and forcing it splits something.
- Nailing the repair down — Nails loosen and the repair starts creaking. They also make the next lift destructive, and a board that has been repaired once usually needs lifting again for services.