Are hairline cracks in new plaster normal?

Some are. Fresh plaster shrinks as it dries, and fine cracks at corners, beads and joints are common, particularly in a new build or extension losing construction moisture. Widespread crazing across a whole wall is not normal and points at how it was dried.

Should I fill them or get the plasterer back?

Fill an isolated, settled hairline crack. Get the plasterer back for crazing over a large area, for cracks along bead or joint lines, or for a crack that has already been filled once and returned, because those are finish faults rather than decorating ones.

How long should new plaster dry before painting?

Until the colour is uniformly pale rather than patchy dark, which depends on the thickness, the background and the ventilation rather than a fixed number of days. Then a thinned mist coat goes on, so the plaster is not sealed while it is still releasing water.

Can I speed the drying up with a heater?

That is usually what caused the cracking. Direct heat and strong draughts dry the surface before the plaster behind it has shrunk, which is exactly the condition that crazes it. Gentle background warmth and ordinary ventilation are what it wants.

Low risk

Updated 30 August 2026

Hairline Cracks In Newly Plastered Walls

Fine cracks have appeared in a wall or ceiling within days or weeks of it being plastered.

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What's happening?

Fresh plaster shrinks as it dries, and cracking is what happens when it shrinks faster than it gains strength. That is why the timing and the pattern matter more than the crack itself. Fine crazing spread over a whole wall, appearing within a day or two, is drying shrinkage — usually the room was too warm, too draughty or in direct sun. Short cracks radiating from corners, sockets and beads are stress concentrations where the plaster is thin or restrained. Cracks that turn up weeks later along a specific line are normally the background moving, not the finish failing, which puts the cause in the structure. On a new build or a new extension, some shrinkage cracking is expected as construction moisture leaves the fabric, and NHBC standards treat it as part of drying out.

What usually causes it?

Dried too fast — heating turned up, a dehumidifier running, a hot day or a draught through the room
Skim applied too thick in one pass, so the surface set while the plaster behind it was still shrinking
Strong background suction pulling water out of the plaster unevenly, often where dubbing out was skipped
Weak or unprepared background, or PVA used as a substitute for the right bonding coat
No scrim or bead at a joint, corner or change of material, leaving the plaster to span a moving junction unaided
Construction moisture leaving a new build or extension, with timber and blockwork shrinking behind the finish
Decorated too early, so a vinyl emulsion sealed the surface while the wall was still losing water

Is it dangerous?

No. Hairline cracking in a new finish is a quality and appearance issue, not a safety one, and it does not indicate that the wall or ceiling is failing. The judgement to make is whether the crack has stopped. Shrinkage cracks appear early, then stay the same width for good; a crack that keeps widening, or that steps and tapers, is movement in the structure and belongs with a builder rather than a plasterer. The only genuine hazard here is second-hand: cracking that lets moisture into a new bathroom or utility finish, or cracking that is hiding a wet background that will blow the plaster later.

Can I fix it myself?

Often, yes. Settled hairline cracks are filled with a fine surface filler, sanded flush and spot-primed before painting, and crazing under a coat of good-quality paint frequently disappears. What helps more is not creating them: let a newly plastered room dry with gentle background warmth and ordinary ventilation rather than a fan heater aimed at the wall, and put a thinned mist coat on before any full-strength emulsion. What does not work is filling a crack that is still moving, or sealing the surface with a heavy paint while the wall is still dark and damp.

When should you call a plasterer?

Call the plasterer back if the cracking is widespread crazing, if cracks follow bead lines or joints, or if the same crack has been filled and reopened. That is a finish that needs re-skimming rather than decorating around. Call a builder instead if a crack is stepping through the wall, widening month on month, or opening at the junction with an extension, because the plaster is only reporting movement behind it.

What will the plasterer actually do?

Separate drying shrinkage from background movement by the pattern, the timing and whether the crack is still opening
Cut out and reinforce cracks at joints, beads and material changes with scrim or mesh rather than filling them
Correct the background — dubbing out, controlling suction, applying the right bonding coat — before re-skimming
Re-skim the affected wall or ceiling in full where crazing would show through any patch repair
Set out drying conditions for the room, so the new finish is not forced dry the way the last one was
Advise when the surface is ready to decorate, and what mist coat the plaster needs first

Frequently asked questions

We’re happy to answer all your questions.

Sources & References

New Plaster Will Not Dry OutCaution Wavy Or Uneven Plastered WallsLow risk Cracks Across A CeilingCaution Cracks In A New Build HomeLow risk

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