How To Fix a Dent in the Wall

How do you fix a dent in the wall?

A dent in a plasterboard wall — from a chair back, a pet, a dropped box — is a fifteen-minute job with a half-hour wait attached. Clean the area, knock off any sharp edges, press Selleys Spakfilla Rapid firmly into the dent with the scraper supplied, wait at least 30 minutes, sand lightly, and paint.

The thing worth knowing before you start is that you do not need to overfill. Spakfilla Rapid is virtually non-shrinking, so the surface you leave with the scraper is very close to the surface you will sand. That is what keeps the repair small and the sanding minimal — and less sanding means less chance of cutting through the surrounding paint and turning a dent into a patch.

Technical specification

Technology	Water based
Colour	White
Sand / paint time — less than 2 mm	30 minutes
Sand / paint time — more than 2 mm	24 hours
Shrinkage	Virtually non-shrinking, non-cracking
Applications needed	One
Use	Interior and exterior

Indicative data only, not intended for the preparation of specifications.

What the 30-minute figure really covers

This is where a lot of otherwise good repairs go wrong. The 30 minutes applies to thin applications — less than 2 mm deep. A shallow scuff or a light dent qualifies. A deep gouge where the plasterboard has actually been compressed does not: for more than 2 mm, the technical data sheet gives 24 hours. Cold or humid weather stretches both figures.

The practical reading is simple. If you can still see the filler sitting proud and glossy, it is not dry. If you are filling a deep dent, either accept that it is an overnight job, or build it up in thin passes so each one falls inside the 30-minute window. Sanding a fill that is still soft underneath drags material out and leaves a hollow you then have to fill again.

What you need

• Selleys Spakfilla Rapid — the scraper comes with it
• 240 grit sandpaper
• A clean cloth
• A water-based primer, and your topcoat

How to fix the dent

1. Prepare the surface. Make sure the surface to be filled is clean, dry and free of loose or powdery material.
2. Knock off the sharp edges. Sand the surface lightly if needed to remove any sharp edges. A dent usually has a raised lip of crushed paper or paint around it, and filler laid over that lip will never sit flat.
3. Press the filler in. Use the scraper provided to press the Spakfilla firmly into the hole. There is no need to overfill, because there is virtually no shrinkage as it dries.
4. Wait. Allow at least 30 minutes drying time. Allow longer for deeper dents and holes, and longer again in colder weather — over 2 mm deep, that means 24 hours.
5. Sand lightly. Lightly sand with 240 grit if needed. Minimal sanding should be required.
6. Wipe the dust off. Wipe the surface with a clean cloth to remove sanding dust. Selleys also recommends cleaning dust and loose filler particles off with Sugar Soap or Super Kleen before painting.
7. Prime, then paint. Prime with a suitable water-based primer before applying topcoats. You can paint over with water-based paints after 30 minutes, but wait at least 24 hours for oil-based paints.

Limitations — where Spakfilla Rapid should not be used

• Not on plastic, metal, or exterior timber likely to swell or shrink on absorption of water.
• Not below 5°C or in wet conditions.
• Do not nail it.
• Not where load or compression occurs, as the product may be crushed. The example the data sheet gives is the wall behind a door where the knob touches — which is, awkwardly, one of the most common places a dent appears. Filling it will work cosmetically, but the same knob will crush it out again. A door stop is the actual fix.
• Where movement occurs, use Selleys No More Gaps.

If you are using the product outside, protect it from rain until it is dry and painted over with two coats of a quality exterior paint.

Clean up and storage

Uncured filler comes off with water; application tools can be cleaned with water. Once cured, it has to be scraped or sanded off. Keep the container closed between uses. If the filler stiffens, stir it and add a teaspoon of water if needed; discard it if it has hardened.

Safety: a fifteen-minute job is still a classified product

Spakfilla Rapid carries Warning — H317, may cause an allergic skin reaction, and H319, causes serious eye irritation. Sugar Soap carries Danger — H318, causes serious eye damage; Super Kleen carries Warning — H315 skin irritation and H319 serious eye irritation.

The risk on a job this short is not that something dramatic happens. It is that nobody bothers, because it is one dent and it takes fifteen minutes.

H317 is the classification that makes that a bad bet. Skin sensitisation is not irritation that washes off — it is the immune system learning the material, it is generally permanent once acquired, and it is built out of small repeated contacts rather than one big one. One dent is nothing. A tub of Spakfilla worked in with a fingertip across every knock in a rented house, and again at the next place, is the exposure pattern the classification describes. The scraper comes in the pack; there is no reason to use a finger, and a scraper gives a flatter fill anyway.

The eye classifications sort themselves out by dilution. The H318 on Sugar Soap belongs to the concentrate. For wiping sanding dust off one patched dent, a weak mix on a damp cloth is entirely proportionate, and Super Kleen — classified as eye irritation rather than eye damage — is the lower-hazard of the two options this page offers for that. Keep the neat product and the goggles for what it is actually for: pouring the concentrate, and scrubbing in-ground marks with a sponge.

The one place this job genuinely calls for eye protection is a dent up near a cornice. Wiping down above head height with a wet cloth is the geometry that delivers cleaner straight into an upturned eye, and an H318 splash needs fifteen minutes of irrigation with the eyelids held open and urgent medical attention rather than a blink and a rinse.

Poisons Information Centre — 131 126 in Australia, 0800 764 766 in New Zealand.

Common questions about fixing a dent in the wall

How long do I have to wait before painting?

30 minutes for a thin fill with water-based paint. At least 24 hours if you are using oil-based paint, or if the fill is deeper than 2 mm.

Do I need to overfill the dent?

No. There is virtually no shrinkage as Spakfilla dries, so fill flush and scrape the excess off.

What grit sandpaper?

240 grit, used lightly. Minimal sanding is needed for a smooth finish.

Do I have to prime?

Prime with a suitable water-based primer before applying topcoats. It evens out the absorbency difference between the filler and the surrounding paint, which is what stops the repair showing through.

Can I use this on a metal or plastic surface?

No. Spakfilla Rapid is not recommended for plastic, metal, or exterior timber likely to swell or shrink as it absorbs water.

The dent is behind a door handle. Will the repair last?

Not on its own. Selleys specifically warns against using the filler where load or compression occurs, giving a door knob hitting the wall as the example. Fit a door stop as well as filling the dent.

What if the dent is deep?

Allow longer drying — 24 hours for more than 2 mm — or build it up in thinner passes. For a substantial hole rather than a dent, see how to repair a large hole in a wall.

Can I use it outdoors?

Yes, it is rated for interior and exterior use, but protect it from rain until it is dry and painted with two coats of quality exterior paint.

It is cold in the room. Does that matter?

Yes. Avoid using the product below 5°C, and expect longer drying times in cold or humid conditions.

Can I hang something on the filled spot?

No. Do not nail the product, and do not use it where load or compression occurs.

Do I need to clean the wall before painting?

Yes — wipe the sanding dust off with a clean cloth, and clean dust and loose filler particles away with Sugar Soap or Super Kleen before you paint.