How to repair wood and chipboard with filler so it does not show

What you need

• Flexible filling knives, 3 cm and 8 cm (Bellota or similar)
• Sanding block with 120, 180 and 240 grit paper (Norton, 3M or Bosch)
• Craft knife or a fine-pointed knife
• Small brush and a lint-free cotton cloth
• Heat gun or hairdryer (only to speed up drying of water-based filler)
• Water-based wood filler in a similar shade (Ceys, Pattex or Bostik, at Leroy Merlin and Bricodepot)
• Two-part epoxy wood filler for holes over 5 mm (Ceys, Pattex or Loctite)
• White carpenter's glue (Titebond or Pattex Cola Blanca) to firm up edges
• Touch-up wax or filler crayon for melamine, in several shades
• Water-based stain or varnish in the original shade (Xylazel, Bruguer or Bondex)
• Isopropyl alcohol or a mild solvent for degreasing

Step by step

1. 1

   Assess the damage

   Run a fingernail over it and press with a flat screwdriver. If the wood gives like a sponge or the chipboard crumbles to dust, there is damp and the filler will not hold: the area has to be cut out or the piece replaced. If the material is hard, carry on.

2. 2

   Protect and clean

   Put masking tape 2 mm from the damaged area so you do not mark the rest. Degrease with a cloth and isopropyl alcohol and leave it to dry for 5 minutes. Filler will not stick to wax, kitchen grease or dust.

3. 3

   Remove anything loose

   Use the craft knife to cut away splinters and loose fibres and ease the edges back at a gentle angle. In a screw or knob hole, scrape the inside so the filler has something to grip. Brush the dust out with a small brush and vacuum it up.

4. 4

   Firm up soft edges

   If the chipboard edge is spongy but dry, brush on a thin coat of white glue diluted 50 % with water, leave it for 30 minutes and check that it no longer crumbles. For holes that will take a screw, always fill with epoxy, not water-based filler.

5. 5

   Mix and check the colour

   With two-part filler, mix equal parts until the colour is uniform (1-2 minutes). Try a pinch on the back of the piece: water-based filler lightens as it dries and epoxy usually darkens slightly. If there is no exact shade, mix two fillers or buy a lighter one and stain it afterwards.

6. 6

   Fill in thin layers

   With the 3 cm knife, press the filler into the hole to push the air out and smooth it in a single stroke. Do not go over 3-5 mm per layer: any thicker and it cracks as it dries. Leave about 1 mm proud of the wood, because filler shrinks.

7. 7

   Let it cure for as long as the tin says

   Water-based filler can be sanded after 1-2 hours per thin layer; epoxy usually needs 3-12 hours depending on the product. In summer on the coast, with 28-30 degrees indoors, the time drops, but do not sand until the filler is hard and has lost its damp sheen.

8. 8

   Sand flush

   With the 120 grit block and light pressure, take down the excess until you cannot feel a step with your fingertip. Finish with 180 and 240 grit, following the grain. Peel off the masking tape and wipe with a dry cloth to see the result.

9. 9

   Match the colour

   On solid wood or veneer, apply water-based stain with a fine brush in light coats until the shade matches the grain around it. On melamine use touch-up wax that you melt in with a warm spatula, or a crayon in the closest colour. If the piece is to be painted, prime the filler before applying the topcoat.

10. 10

    Seal and protect

    Once the stain is dry (1-2 hours), apply a coat of water-based varnish or hard wax in the same finish: matt, satin or gloss. Avoid cleaning the area with water for 48 hours so the seal finishes curing.

Which wood filler to choose for each material

There is no all-purpose filler. Water-based wood filler is the most convenient for dents and small holes in doors, skirting boards and furniture that will later be painted or stained: it sands easily, cleans up with water and hardly smells. It shrinks as it dries, so you need to leave it slightly proud. Two-part epoxy filler, on the other hand, does not shrink, holds screws and is good for rebuilding corners, hinge recesses and areas that take knocks. It costs more and is harder to sand.

On chipboard and melamine (kitchen units, IKEA wardrobes, shelves) water-based filler cracks easily on the edges. For chipped corners, epoxy filler or touch-up wax in a matching shade works better, and for lifted edges an iron-on edging strip applied with an iron. If you are wondering how to repair melamine kitchen units with small dents, a filler crayon in the right shade and a little wax are enough.

When filler is not the answer

Filler repairs lost material, not degraded boards. If the chipboard has swollen from a leak or condensation, the fibres never recover their shape and, even if you fill it, the area bulges again within a few weeks. In that case you need to cut out the damaged part and fit a new piece, or replace the door front. The same goes for rotten wood: if it crumbles when you push a screwdriver in, filler only hides the problem.

Nor does it replace a proper fixing. A hinge screw that has lost its grip is fixed with wooden dowels and glue or with epoxy, and then you wait a full day before screwing it back in. If the door or unit has to carry weight (a shelf, a kitchen cupboard hinge), let the filler cure the full 24 hours before loading it.

Common mistakes with wood filler

• Filling without cleaning or degreasing. Wax, dust and kitchen grease stop the filler gripping and it comes away when you sand.
• Putting on one thick layer. It sinks and cracks. Two layers of 3 mm are better than one of 6.
• Not leaving it proud. If the filler is flush when you apply it, it will be sunken once dry and you will have to repeat the job.
• Sanding too soon. Soft filler drags, leaves little balls and marks the surface.
• Choosing a shade from the tin. The colour changes as it dries; always test on a hidden spot.
• Using wall filler (plaster or polyfilla) on wood. It does not bond and does not stand up to knocks. For walls, see how to fill holes in a wall.

When to call a professional

A small repair is an afternoon's job, but some cases are worth handing over: hardwood or veneered doors with an open-pore finish that has to be matched to the shade, broken corners on kitchen units you see every day, hinge recesses that no longer hold, or several faults scattered around the home. At Manitas Costa adjusting a door costs €40-70 and replacing hinges (3) €50-90; repairs to wooden furniture and filler work are quoted by the hour: first hour €35-45, following hours €28-35, with a fixed price before we start.

The usual route is to send us a photo on WhatsApp of the area close up and another of the whole piece. From that we tell you whether filler will do or the piece has to be replaced, and we come the same day in Valencia, Alicante, Torrevieja and Benidorm. See our carpenter service, carpenter prices and, if you have a battered door, how to repair a wooden door. For repainting afterwards, see how to paint melamine furniture and how to paint wooden furniture.

Damp, salt air and residents' associations

On the Alicante and Valencia coast ambient humidity is above 70 % for much of the year, and in seafront flats the chipboard in furniture soaks up water through the edges and the base. That is why you should always seal filler on a low area (legs, skirting boards, the base of kitchen units) with varnish or wax, and avoid water-based fillers in bathrooms and kitchens exposed to steam unless there is a coat of sealer on top.

If you rent or live in a building with rules set by the comunidad de vecinos (residents' association), tell them before sanding in shared areas (entrance hall, landing, storage room door): sanding dust and epoxy smells carry in closed stairwells. In a rented home, keep before and after photos to make clear that the damage was already there or that you repaired it yourself.