How to fill cracks in walls
Updated: 23 October 2026
A crack has opened above the skirting, or screw holes remain where a shelf came down, and you want to paint this weekend. How to fill cracks in walls, for a static dry gap, is a short job: open the line, keep it dry, stay inside the depth on the tub, and do not paint a skin that is still soft. Which tub to open sits on the [filler comparison](/hub/fillers-adhesives-and-sprays/filler). Depth figures below are examples from this set on 19 October 2026. This is not a lab test. A qualifying purchase through our amazon.co.uk links can earn us a commission at no extra cost to you.
A crack has opened above the skirting, or screw holes remain where a shelf came down, and you want to paint this weekend.
A crack has opened above the skirting, or screw holes remain where a shelf came down, and you want to paint this weekend. How to fill cracks in walls, for a static dry gap, is a short job: open the line, keep it dry, stay inside the depth on the tub, and do not paint a skin that is still soft. Which tub to open sits on the filler comparison. Depth figures below are examples from this set on 19 October 2026. This is not a lab test. A qualifying purchase through our amazon.co.uk links can earn us a commission at no extra cost to you.
Our top picks
| Badge | Product | Stated depth | Pack | Listing note | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  Palace Palace fine surface filler, 600 g | 3 mm per layer | 600 g | Interior hairline | 7.0 | about £1.25 | View offer |
| Best value |  Sika Sika SikaWall all-purpose filler, 600 g | 9 mm × 25 mm | 600 g | Shape before it cures | 8.9 | about £4.49 | View offer |
 Sinto Sinto hole and crack filler, 5 kg | 1 cm | 5 kg | 12 hour full cure | 6.8 | about £16.33 | View offer |
On this page
Check the crack before you buy another tub
A filler only holds a gap that is already still. If the line opens when a frame moves, that gap wants a sealant. If the plaster sounds hollow, Ronseal’s hole guide says to call a specialist. Polycell’s how-to says the crack should be dry. Some powder guides say dampen. Do not copy that onto these pastes. Palace asks for layers of no more than 3 mm. SikaWall states 9 mm by 25 mm. The Decex kit states holes up to 10 mm. Sinto’s bullet says up to 1 cm. If a cable or a pipe may be behind the hole, look before the knife goes in. Choosing the tub is the wall filler buying guide.
Fill a static crack or a screw hole
Rake a hairline into a shallow V. Wickes says to vacuum the hole so dust is not mixed into the paste. Knock off loose flakes. If a nail head is still proud, Polycell’s how-to suggests an oil-based touch-in on the metal. Press the paste across the crack and then along it. A wet knife helps it lie flatter. That is not wetting the wall. Leave the fill slightly proud. A 3 mm Palace layer is a hairline. A 9 mm SikaWall fill is a modest hole, and the sheet talks about another layer after about an hour. Polycell’s how-to says to build in layers above 10 mm. That figure is the brand how-to, not a depth on the 330 g amazon tube. Past the line on your tub, stop and let the layer go off.
Dry, sand and paint
The Decex kit says surface-dry in 1 to 2 hours. Sinto’s bullet says a full cure of 12 hours. One Strike reviews describe a dry crust over a soft middle. If a fingernail dents an unseen edge, leave it. Sand only the proud edge. Wickes says to wear a dust mask and to ventilate. HSE guidance on FFP3 and extraction is for people sanding plasterboard joints all day, not one screw hole. Open a window and vacuum before paint. Put the lid back on at once. Reviews of Polycell, Palace and Ronseal describe paste that goes solid once air gets in.
When the repair fails
Shrink usually means the layer was too deep, or paint went on while the core was still moving. Sinto’s listing says zero shrinkage, and United Kingdom reviews still report shrink. Shape a thick coat of SikaWall, Ronseal or Palace while it is workable. If the middle stays soft, leave it. Call a plasterer when the plaster is hollow, damp, or still opening. If you might stain the timber, use wood filler or wall filler.
Common questions
How do I fill a hairline crack?
Rake the line into a shallow V, vacuum the dust, and press in a fine-surface filler slightly proud. Palace states layers of no more than 3 mm, which matches a hairline better than a deep-hole tub. Let it go hard, sand the proud edge, and paint. A smear over a closed line falls out as a ribbon.
Should the crack be damp or dry?
Dry, for the ready-mixed pastes in this set. Polycell’s how-to says the surface and the crack should be dry. Some powder instructions say to dampen, and that advice belongs to powder. If the wall is moist, sagging or bulging, stop and get the cause checked before you fill.
How long do I wait before paint?
Use the time on the tub, then check the core. The Decex kit says surface-dry in 1 to 2 hours. Sinto’s bullet says a full cure of 12 hours, and deep holes in the reviews take longer. A dry skin over a soft middle, which One Strike reviewers describe, is not ready. If a fingernail dents the edge, wait.
Why is the filler too hard to sand?
A thick coat of SikaWall, Ronseal or Palace can cure harder than a hand block will cut. Shape the paste before it sets, and stay inside the depth on the label, so you are only knocking back a proud edge. Sanding a lump flat is a different job from feathering a screw hole.
Why did it shrink or crack?
The usual causes are a layer deeper than the tub allows, a moving joint, or paint on a soft core. A will-not-shrink bullet is a listing claim. Sinto’s file includes that claim and United Kingdom reviews that report shrink. Let the first layer go hard, then fill the sink, or change product.
Do I need a dust mask?
For a few screw holes, open a window, sand as little as you can, and a dust mask is a sensible extra, which is what Wickes suggests. HSE guidance on FFP3 and extraction is for high dust from commercial plasterboard jointing, not one hole in a flat. Do not sand a cloud of filler with the door shut.
When is this no longer a tub job?
Stop when the plaster is hollow, the crack keeps opening, the wall is damp, or a cable or pipe may be behind the hole. Also stop when the hole is deeper than every coat you will layer, and when a soft core will not go hard. That is a plasterer, or a change to powder, not another scoop from the same tub.
Related pages
Sources
Public UK sources used for this comparison. amazon.co.uk prices, stars and review counts were taken from the listings on 19 October 2026.
- Everbuild One Strike filler data sheet (retrieved 19 October 2026)
- Everbuild all purpose powder filler data sheet (retrieved 19 October 2026)
- HSE CIS36, gypsum dust (retrieved 19 October 2026)
- HSE, sanding taped plasterboard joints (retrieved 19 October 2026)
- HSE, GB CLP (retrieved 19 October 2026)
- General Product Safety Regulations 2005 (retrieved 19 October 2026)
- Ronseal multi purpose wood filler (retrieved 19 October 2026)
- amazon.co.uk listings for the nine ASINs in this set (retrieved 19 October 2026)