Replace an internal window board — HomeGraft

Take out your old window board, cut a new one to fit, and fix it securely for a neat finish.

WB-01Clear the area and check the old boardMove furniture and curtains away from the window and lay a dust sheet under the sill. Check whether the old board is nailed, screwed, or just bedded on adhesive. Look at the reveal underneath for any signs of damp or rot before you start.

1 each · Dust sheet

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WB-02Find your stopcock and check for cables and pipesWindow boards sit on external walls, where pipework sometimes runs close to the surface. Before drilling or cutting anything, find your stopcock (usually under the kitchen sink) and check it turns freely. Scan the wall with a cable and pipe detector, but still expect something to be there — detectors miss cables that are deep, in metal conduit, or behind metal-backed plasterboard. If you have any doubt, isolate the circuit at the consumer unit before drilling near a socket, and turn the water off at the stopcock before cutting into anything that could carry water.

1 each · Cable and pipe detector

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WB-03Remove the old window boardRemove any visible screws first, then work a pry bar gently along the length of the board rather than levering hard at one end. Pull out any leftover nails or screws in the reveal. Scrape away old adhesive or sealant so the surface is clean and flat.

1 each · Pry bar

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1 each · Filler knife

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WB-04Work out what's behind the revealMost boards fix into solid masonry, but in extensions, dormers or stud partitions the wall under the window may be plasterboard on timber or metal studs. Tap along the wall: solid brick or block sounds dense throughout, while a stud wall sounds hollow between studs and solid every 400-600mm. Look for a line of screw heads showing through paint, or use a stud detector. Drill a small pilot hole in a hidden spot — timber dust means a timber stud, fine grey swarf means a metal stud, and dust with no resistance means you're between studs on plasterboard.

1 each · Stud detector

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WB-05Measure and cut the new boardMeasure the reveal width at both ends, since walls are rarely perfectly square, and decide on the overhang beyond the wall face — typically 20-25mm. Mark the new board and cut it slightly oversize with a hand saw or jigsaw so you can trim for a tight fit. Sand the cut edges smooth.

1 each · MDF window board

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WB-06Fix the new board — method depends on the wallIn solid brick or block, drill 6mm holes 40mm deep, insert wall plugs, and drive 50mm woodscrews through the board into the plugs. In dot-and-dab plasterboard, standard plugs won't reach the masonry behind the dab — use 75-90mm fixings that pass through the plasterboard, the dab void, and into the solid wall behind. Into a timber stud, drive a 50mm wood screw into the centre of the stud. Into a metal stud, never use a plastic plug or wood screw — it strips straight through 0.5mm steel — use a self-drilling metal-stud screw or a toggle-type hollow-wall anchor rated for the load. For lath and plaster, the lath itself is weak; locate the joists behind using the same tapping and pilot-hole method and screw into those, or spread toggle fixings across several laths rather than relying on one. In every case, run a bead of grab adhesive under the board too for a solid, rattle-free finish.

1 pack · Masonry wall plugs (pack of 10)

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1 pack · Woodscrews 50mm (pack of 10)

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1 pack · Long fixings 75-90mm (dot-and-dab)

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1 pack · Metal-stud self-drilling screws

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1 pack · Toggle-type hollow-wall anchors

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1 tube · Grab adhesive

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WB-07Fill the gap between board and wallRun a bead of decorator's caulk or silicone sealant along the joint where the board meets the wall and reveal. Smooth it with a wet finger for a neat, even line. Leave it to cure fully before painting, following the time on the tube.

1 tube · Decorator's caulk

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WB-08Fill screw holes and sandFill any visible screw holes or small gaps with flexible decorators' filler. Once dry, sand smooth with fine sandpaper so the surface is ready for paint.

1 tub · Decorators' filler

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1 pack · Fine sandpaper

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WB-09Prime and paint the boardApply a coat of primer if the board is bare MDF or timber, and let it dry fully. Apply two coats of satinwood or eggshell paint, sanding lightly between coats for a smooth finish.

1 tin · Wood primer

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1 tin · Satinwood paint

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1 each · Paintbrush

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WB-10Clean up and refit fittingsRemove the dust sheet and vacuum up any dust or debris from cutting and drilling. Refit curtains, blinds or any window furniture you removed earlier. Give the board a final check to make sure it's stable and level before you finish.

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