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Cracks In A New Build Home
Fine cracks have appeared in a house that is only a year or two old, usually at ceiling and wall junctions.
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What's happening?
A new house is full of water — in the mortar, in the plaster, in the screed and in the timber — and it spends its first heating season getting rid of it. As the materials dry they shrink, and the shrinkage concentrates at the weak lines: the junction of ceiling and wall, the corners of window and door openings, along plasterboard joints, and where different materials meet. These are the classic shrinkage cracks, they are fine and roughly even in width, and they are expected rather than defective. Separately, the building itself settles onto its new foundations in its early years. Both are normal. Neither should be diagonal, tapering, growing, or visible through the brickwork outside.
What usually causes it?
- Drying shrinkage in plaster and plasterboard during the first heating season
- Timber frame, joists and studs losing moisture and shrinking, opening the junctions they are fixed to
- Screed and mortar curing and shrinking as they lose water
- Plasterboard joints and taped angles moving as the boards and framing shrink at different rates
- Early settlement of the new structure onto its foundations
- Central heating run too hot too soon, drying the house faster than the materials can cope with
- Thermal movement in long walls and at junctions between different materials
Is it dangerous?
Fine, even-width shrinkage cracks are cosmetic. What is not cosmetic in a new build: cracks that are diagonal and taper, cracks visible in the external brickwork as well as internally, cracks that keep widening after the second year, and cracks over about 3mm at ceiling or wall junctions. Those go beyond drying and should be raised as a defect rather than redecorated over. Approved Document A is the structural standard the house was built to, and NHBC Standards set the workmanship benchmark most warranty providers assess against.
Can I fix it myself?
Waiting is the right first move, and it costs nothing. Warm the house gently and evenly rather than blasting the heating, and ventilate it so the moisture has somewhere to go. Photograph and date the cracks so you can show what has changed. Most builders will not redecorate until the end of the first or second year precisely because filling too early means filling twice. When the time comes, a flexible filler at a wall-to-ceiling junction outlasts a rigid one, because that joint will always move a little.
When should you call a builder?
Report every crack to the developer within the defects period, in writing, with photographs — that is what the period is for and the record matters. Escalate to your warranty provider if the developer will not engage. Call an independent builder or a structural engineer if cracks are diagonal, tapering, growing, or showing through the outside brickwork, because those are not drying shrinkage and you want your own assessment rather than the developer's.
What will the builder actually do?
- Distinguish drying shrinkage from structural movement by the shape, the direction and whether it shows externally
- Check whether cracking follows plasterboard joints and framing, which points at shrinkage rather than the structure
- Monitor and record any crack that is still moving, over a full seasonal cycle
- Cut out, tape and refill shrinkage cracks properly rather than skimming filler over them
- Use flexible sealant at wall-to-ceiling and material-change junctions that will always move
- Refer genuine structural cracking to the developer, warranty provider or a structural engineer with the evidence attached
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