Fill gaps between floorboards using flexible filler, rope, or timber fillets, matched to the size of the gap.
FGF-01Clear the room and check the boardsMove furniture out and lift any rugs. Vacuum along every gap to remove grit and old fluff. Press on each board as you go - if any feel springy, loose or squeak underfoot, fix those first. This job only works on boards that are sound and don't move.
1 each · Vacuum cleaner (with crevice tool) FGF-02Measure the gaps and pick a methodCheck gap widths in a few spots along each run - they're rarely the same all the way. Use flexible filler for gaps up to 3mm, rope bedded in glue for 3-10mm, and thin timber fillets for anything over 10mm. It's fine to use more than one method in the same room.
FGF-03Fill hairline gaps with flexible fillerLoad a flexible decorator's caulk or a flexible wood filler into a sealant gun. Run a thin, even bead along the gap and smooth it with a wet finger or a filling knife straight away, before it skins over. Wipe off any excess immediately with a damp cloth.
1 tube · Flexible decorator's caulk (wood colour) FGF-04Bed rope into medium gapsFor gaps between 3mm and 10mm, brush a thin line of wood glue into the gap. Push a length of soft jute or cotton rope in on top of the glue using a filling knife or an old screwdriver, pressing it just below the surface. Leave it overnight to dry before you touch it again.
FGF-05Glue in timber fillets for wide gapsFor gaps over 10mm, cut thin fillets of matching timber a fraction wider than the gap, tapering one edge slightly so it wedges in tight. Run wood glue down both sides of the fillet and tap it into the gap with a hammer and a scrap block, leaving it very slightly higher than the floor. Leave for at least 2 hours to cure fully.
3 m · Timber fillet strips (matching floor timber) 1 each · Hand saw or multi-tool FGF-06Trim and sand everything flushOnce all glue is fully cured, plane or sand the fillets and rope down flush with the floorboards using a sharp block plane or a fine sanding block. Go over the whole filled area with 120-grit paper to blend old and new surfaces together. Vacuum up all the dust before moving on.
3 sheet · Sandpaper, 120 grit FGF-07Match the finishIf the floor is varnished, oiled or stained, touch in the filled sections with the same finish so they don't stand out against the rest of the boards. Apply thinly with a small brush and let it dry fully according to the tin before walking on it.
1 tin · Floor varnish or oil (matching existing finish) 1 each · Small paintbrush FGF-08Tidy up and check ventilationClear away offcuts, dust sheets and empty tubes, then vacuum the whole room one last time. Don't seal a suspended timber floor completely gap-free - a few small unfilled gaps help air move through the void below and stop damp building up. Once everything is dry, put the furniture back.
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