Prep, sand, fill and paint window frames inside for a smooth, durable, professional-looking finish that lasts years.
PW-01Prepare the roomMove furniture away from the window and lay dust sheets over the floor and sill. Open the window fully for ventilation, as paint fumes build up fast in a closed room. Take curtains or blinds down if they're in the way.
PW-02Check for old paint and remove hardwareIf your home was built or decorated before 1960, the existing paint may contain lead. Don't dry-sand it — wet-sand with a damp cloth or use a chemical stripper, and wear a dust mask throughout. Unscrew handles, catches and hinges where you can, or mask them off with tape if they're stuck fast.
1 each · Dust mask (fine particle) PW-03Wash the frame downMix sugar soap with warm water and wash the whole frame to lift grease, nicotine staining and grime. Rinse with a clean, damp cloth and let it dry fully before you touch it again. Paint won't stick properly over dirt or grease.
PW-04Sand the surfaceSand the whole frame with fine-grit sandpaper (120-180 grit) to key the surface and knock back any flaking or glossy patches. Sand with the grain on wood, and in one direction on UPVC to avoid scratches. Wipe away all dust with a dry cloth before moving on.
1 pack · Fine-grit sandpaper PW-05Fill any cracks or holesPress flexible wood filler into any cracks, gaps or old screw holes with a filling knife. Leave it to cure fully — check the tin for timing, usually a few hours. Sand it flush once hard.
1 tube · Flexible wood filler PW-06Mask the glass and wall edgesRun masking tape carefully along the edge of the glass and where the frame meets the wall or plaster. Press it down firmly so paint can't creep underneath. Cover the sill and any surrounding surfaces with extra dust sheet if needed.
PW-07Prime any bare woodIf sanding or filling has exposed bare wood, brush on a coat of wood primer over those areas only. This stops the wood absorbing the paint unevenly and helps everything else stick properly. Let it dry fully before the next step.
1 tin (750ml) · Wood primer PW-08Apply an undercoatBrush a thin, even coat of undercoat over the whole frame, working with the wood grain or along the profile of the UPVC. Don't overload the brush — thin coats dry evenly and avoid drips. Leave to dry for the time stated on the tin, usually 2-4 hours.
1 tin (750ml) · Undercoat 1 each · Angled sash brush PW-09Apply the first topcoatUse a satinwood, eggshell or gloss finish depending on your preference — satinwood is the most forgiving for beginners. Brush in thin, even strokes, working top to bottom and finishing each section before the edge dries. Check the tin for recoat time.
1 tin (750ml) · Satinwood or gloss topcoat PW-10Apply a second topcoatOnce the first coat is fully dry, lightly key it with a very fine sandpaper (240 grit) if the tin recommends it, then wipe away the dust. Apply a second, even coat for full colour and a hard-wearing finish. This second coat is what gives lasting durability.
1 pack · Fine-grit sandpaper (240 grit) PW-11Remove the masking tapePeel off the masking tape while the paint is still slightly tacky, pulling it away at a shallow angle for a crisp line. If you wait until it's fully hard, the tape can pull flakes of paint away with it. Clean brushes straight away with water or brush cleaner, depending on the paint type.
PW-12Leave to cure and refit hardwareAvoid opening or closing the window for at least 24 hours to let the paint harden fully, even though it may feel dry to the touch sooner. Refit handles, catches and hinges once the paint has cured. Fold and store dust sheets, and give the room a final tidy.
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