Feather-fill an uneven wall before painting

Fill dips and cracks so they blend invisibly into the wall before you paint, working slightly differently depending on what's under the surface.

FF-01Clear and protect the roomMove furniture away from the wall and lay dust sheets on the floor. Mask the top of skirting boards, coving and any sockets near the work area with low-tack tape. Open a window for ventilation, especially if you'll be sanding old paint.

2 each · Dust sheet

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1 roll · Low-tack masking tape

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FF-02Work out what's behind the surfaceKnock gently along the wall with your knuckles. A solid brick or block wall sounds dull and firm everywhere. Plasterboard on timber or metal studs sounds hollow between fixings and firmer roughly every 400-600mm where a stud sits behind. Dot-and-dab plasterboard sounds hollow almost everywhere with occasional firm patches at the adhesive dabs. Lath and plaster (common in homes built before the 1930s) feels slightly springy and uneven, and cracks often form a network rather than a single line.

FF-03Strip back loose or flaking paintScrape off any blistering, cracked or flaking paint with a hand scraper, then feather the edges of sound paint with abrasive so filler doesn't sit on a ridge. If the house was built or decorated before the 1960s, don't dry-sand old paint layers. Dampen the surface first, use a hand scraper rather than a power sander, and wear a mask, since old paint can contain lead.

1 each · Hand scraper

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1 pack · Dust mask (FFP2)

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FF-04Clean and key the surfaceWash the wall with a sugar soap solution to remove dust, grease and loose debris, then rinse with clean water. Leave to dry fully, ideally overnight. If the surface is gloss-painted or very smooth, lightly scuff it with fine abrasive paper so the filler has something to grip.

1 bottle · Sugar soap

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1 pack · Fine abrasive paper (240 grit)

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FF-05Choose and mix your fillerFor wide, shallow dips, use a ready-mixed lightweight filler, which is easier to spread thinly. For any crack wider than about 5mm, use a flexible or fibrous filler so it doesn't crack again when the wall moves slightly. If using powder filler, mix small batches to the manufacturer's instructions so it doesn't go off before you've used it.

1 1kg tub · Ready-mixed multi-purpose filler

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1 330ml tube · Flexible filler for cracks

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FF-06Apply the first feathered coatLoad a wide filling knife and spread from the middle of the dip outward, pressing a little harder as you near the edges so the filler thins to nothing over 200-300mm rather than stopping in a hard line. On plasterboard or dot-and-dab, use light, even pressure only, digging the corner of the knife in can tear the paper face or dent the board. On lath and plaster, work in short, light passes since the surface can flex slightly under pressure.

1 each · Filling knife 150mm

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1 each · Filling knife 250mm

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FF-07Let it dry and check the surfaceLeave the filler to dry fully, this can take a few hours depending on thickness and the product used. Once dry, shine a torch sideways across the wall (a raking light) or run a straight edge over it to spot any remaining dips, ridges or high spots.

1 each · Straight edge or spirit level

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FF-08Apply a second thin coat if neededIf any dips remain, repeat the feathering technique over just those areas, blending the edges even wider than the first coat so the join disappears. Let this coat dry fully before moving on.

FF-09Sand smoothOnce completely dry, sand the filled areas with fine abrasive paper (120-180 grit) on a sanding block, using light circular strokes so you don't gouge a new dip. Wipe away dust with a damp cloth or tack cloth before painting.

1 each · Sanding block

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1 pack · Fine abrasive paper (120-180 grit)

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FF-10Seal, then tidy upApply a mist coat or proprietary filler primer over the patched areas so they don't 'flash' through the final paint as a different sheen. Let it dry fully before painting. Fold dust sheets inward to trap the dust, rinse tools in water while any filler on them is still wet, and vacuum the floor.

1 2.5L tin · Mist coat / filler primer

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