Some cracking is normal and nothing to worry about. Some of it means the job was done badly. Here is how to tell which you have got, from a plasterer, not a forum.
Fine hairline cracks in new plaster are common and usually harmless. Plaster shrinks slightly as it dries, and a few hairline cracks, particularly along plasterboard joints, are a normal part of that.
Wide cracks, hollow-sounding areas, or cracks that keep growing are not normal. Those point at a problem with the preparation or the application, and you are entitled to have that looked at.
We are going to be honest with you here, even though some of this reflects badly on our own trade. If you have just had work done and you are worried, this page should tell you where you stand before you pick up the phone.
Annoying, but not a sign you have been let down.
Barely visible, thin as a hair. Plaster shrinks as it dries and this is the result. Fill with a fine filler before painting and you will never see them again.
Plasterboard expands and contracts with temperature and humidity. Even with scrim tape correctly applied, a hairline crack can still appear along a joint. It is not a guarantee of bad work.
If the heating has been cranked up or it has been baking hot, the plaster dries too fast at the surface and can craze. Not ideal, but often the house, not the plasterer.
Older properties move. Skimming over old walls always carries a risk of cracking, and a good plasterer should have warned you of that before starting.
If you see any of these, get them back.
Anything wider than a hairline, half a millimetre or more, is not shrinkage. Something has gone wrong.
Tap around the crack. If it sounds hollow and drummy rather than solid, the plaster has not bonded to the wall. It has blown, and it will come off. That is a preparation failure.
Long, running cracks across a wall are not drying shrinkage. They suggest movement, or a coat applied too thin.
A network of fine cracks like a cracked mirror across the whole wall usually means suction was not controlled, the wall was not sealed, so it sucked the moisture straight out of the plaster.
Shrinkage cracks appear and then stop. Cracks that are still growing weeks later mean something is still moving.
You filled them, painted, and they reappeared. That is not a filling problem, the underlying issue is still there.
Tap the wall with your knuckle, all around the cracked area and then across the rest of the wall. Sound plaster gives a solid, dull knock. Blown plaster sounds hollow and drummy, like tapping a cardboard box.
If it sounds solid, you are almost certainly looking at shrinkage cracks. Fill them and paint. Irritating, not serious.
If it sounds hollow, the plaster has not bonded. That is a proper problem, it will get worse, and it needs hacking off and doing again. See why plaster blows for what causes it.
Start reasonably. Most plasterers are decent and would rather come back and sort it than have an argument. Say something like: "I have got some cracking on the new plaster. Some of it sounds hollow when I tap it. Can you come and have a look?"
That is fair, it is specific, and it gives them the chance to put it right, which any tradesman worth hiring will want to do.
If it turns out to be hairline shrinkage on sound plaster, honestly, that is on the house rather than on them. If it is hollow, blown or crazed across the whole wall, that is workmanship, and they should be making it good at no cost to you.
One thing worth knowing: a good plasterer will have warned you before starting that skimming over old walls carries a risk of cracking. If yours did, they were being straight with you. If they did not, that is a mark against them.
We are not going to slag off another tradesman's work sight unseen. That is not fair and it is not useful. But if you are in or around Exeter and you genuinely do not know where you stand, send us a photo on WhatsApp and we will tell you what we think. If the answer is "that is normal, fill it and paint it", that is what we will say.
The ones we get asked most.
Fine hairline cracks in new plaster are common and usually harmless, plaster shrinks slightly as it dries, and hairline cracks along plasterboard joints are a normal part of that. Wide cracks, hollow-sounding areas, crazing across the whole surface, or cracks that keep growing are not normal and indicate a problem with preparation or application.
Tap the wall with your knuckle around the cracked area. Sound plaster gives a solid, dull knock. If it sounds hollow and drummy, the plaster has not bonded to the wall and has blown. That is a preparation failure and needs hacking off and redoing. If it sounds solid, you are almost certainly looking at harmless shrinkage cracks that can simply be filled before painting.
If the cracks are hollow-sounding, wider than a hairline, or crazed across the whole wall, that is a workmanship issue and the plasterer should make it good at no cost. If they are fine hairline shrinkage cracks on sound plaster, that is generally normal and can be filled before decorating. A good plasterer will have warned you in advance that skimming over old walls carries a risk of cracking.
A network of fine cracks across the whole surface, like a cracked mirror, usually means suction was not controlled. The wall was not properly sealed before plastering, so it drew the moisture out of the plaster too quickly. It can also be caused by the plaster drying too fast in high heat.
Yes, but it is straightforward. Fill hairline cracks with a fine filler such as a joint cement, let it dry, sand lightly, then apply a mist coat before decorating. They will not show once painted.
Send a photo on WhatsApp. We'll tell you straight, even if the answer is that there's nothing wrong.