The short answer
Cracks above doors and windows in a new-build are usually shrinkage and settlement cracks. A new house contains a great deal of construction water, and as it dries the plaster, timber and blockwork all move slightly. Openings are the weak points in a wall, so the movement shows up at their corners first.
Why openings crack first
A wall with a doorway or window in it is not a continuous surface. Loads travel around the opening and concentrate at the corners, and there is a junction between the lintel, the wall above and the plaster finish. Any movement in the structure resolves itself at those corners, which is why cracks radiate diagonally from them.
Add drying shrinkage: plaster and skim lose water for months after they go on, timber studwork and joists dry to their in-service moisture content, and the whole house settles onto its foundations. All of it is small, but plaster is brittle and shows movement of a fraction of a millimetre.
The usual causes
- Drying shrinkage in plaster and skim, typically appearing in the first 12–24 months.
- Timber shrinkage in studs, joists and lintel bearings as construction moisture leaves.
- Settlement as the building takes up its load — normal and expected in the early years.
- Thermal movement, worse on sunny elevations and around large glazed openings.
- Scrim tape failure at plasterboard joints, which produces a suspiciously straight crack following the board edge.
- Missing or poorly detailed movement joints in longer wall runs.
Which cracks are worth worrying about
As a rough guide, hairline cracks you can barely fit a fingernail into, that are stable and mostly cosmetic, are typical of normal settlement. Cracks that are wider than about 5mm, that are visibly wider at one end than the other, that continue through into brickwork outside, or that appear alongside doors that suddenly stick and floors that slope, are the ones that warrant a structural assessment rather than decoration.
Timing matters too. A crack that appeared in year one and has not changed since is a different animal from one that has been getting steadily longer over the past three months.
Why filling it usually fails
Most cracks that come back have been filled rather than repaired. Standard filler in a live crack simply cracks again along the same line, often within a decorating cycle, because nothing has been done about the joint underneath, the failed scrim or the movement itself.
A repair that lasts depends on establishing whether the crack is still moving, opening it out properly, choosing the right material for that substrate, and reinforcing the joint before any skim goes on. That assessment is the part that decides whether you see the crack again next winter.
If your home is still under NHBC warranty
New homes typically carry a two-year builder's defects period. Shrinkage cracking within defined tolerances is often excluded, but genuine defects are not, and it is worth logging cracks with photographs and dates while the cover is live. We are happy to look at what you have and tell you honestly whether it reads as shrinkage or something to escalate.
How we put it right
Plaster patch repairs, from £75
We assess whether the crack is live, repair the joint properly and make good ready for decoration.
Serving Leamington Spa, Warwick, Kenilworth, Whitnash, Cubbington, Southam and surrounding Warwickshire.
Common questions
How long do new-build shrinkage cracks keep appearing?
Most drying movement happens in the first one to two years, with the bulk of it in the first heating season. Cracks appearing for the first time several years in have a different cause and should be looked at.
Should I decorate before or after getting cracks repaired?
After. Repairing cracks means opening them out, so any fresh paint over them is wasted. It is also worth waiting until the main drying movement has settled before a full redecoration.
Are cracks along ceiling and wall joints the same problem?
Related but distinct — those are usually joist deflection and the ceiling moving independently of the wall. They need a flexible detail rather than a rigid filled repair.