Plastering advice
Cracks in Plaster Walls – What They Mean and How to Fix Them
Short answer
Fine hairline cracks in new plaster are often caused by shrinkage as it dries. Straight ceiling cracks may follow board joints or joists, while diagonal cracks around windows and doors can indicate movement. The pattern alone cannot diagnose the cause: widening, recurring or displaced cracks need assessment before they are covered up.
Hairline cracks in new plaster: shrinkage
Fresh plaster can develop fine surface cracks as moisture leaves it, particularly if it dries too quickly. Gentle ventilation and normal background warmth are better than directing a heater at the wall.
Once the plaster is fully dry and the crack is stable, a suitable fine filler and decorating may be enough. A crack that keeps opening, or plaster that sounds hollow or feels loose, needs its cause checked rather than another coat of paint.
Ceiling cracks along joists: screw up, scrim and skim
Straight cracks can follow plasterboard joints or joist lines where boards move against one another. Filling the visible line alone will not secure a loose board.
Where the boards and joists are sound, we can screw the boards securely to the joists, apply scrim tape across joints and skim for an even finish. We check for concealed pipes and wiring before fixing. Sagging, water-softened boards or failing lath and plaster may need replacement or another repair rather than a cosmetic skim.
Old textured coatings applied before 2000 may contain asbestos. Do not scrape, sand or drill an untested coating; arrange appropriate testing and assessment before work.
Diagonal cracks at windows and doors: when to call a surveyor
Diagonal cracks near openings can come from movement around a lintel or in the building itself. Some are historic and stable, but a photograph cannot establish whether the structure is sound.
Ask a qualified building surveyor or structural engineer to assess cracks that are new, widening or repeatedly returning, especially if doors or windows start sticking, masonry is cracked outside, or the two sides of a crack are displaced. Sudden substantial cracking or signs of instability need urgent professional assessment. Resolve active movement before plaster repairs.
How we repair cracks in plaster
We first check whether the plaster is sound and whether damp, loose boards or movement has caused the crack. Anything outside plastering needs putting right first.
Loose or blown plaster is cut back to a sound edge and rebuilt using materials suited to the existing wall. Stable cracks and board joints are reinforced where appropriate, then patched or skimmed. Where several repairs would leave an uneven finish, we explain the option of skimming the whole surface. Reinforcement cannot stop ongoing structural movement.
Cracks in Sutton? Send us a photo
Send SJF Plastering a clear close-up and a wider photograph of the wall or ceiling on WhatsApp, with a note about when the crack appeared and whether it is changing. We can advise on the next step and arrange a free quotation for plaster repairs. Call 07967 302162 or use the WhatsApp button below.
Frequently asked questions
Are hairline cracks in new plaster normal?
Fine shrinkage cracks can occur as plaster dries, especially if it dries too quickly. Let it dry fully before repairing stable surface cracks. Widening or recurring cracks need assessment.
Can you repair a cracked ceiling without replacing it?
Often, if the boards and supporting structure are sound. Securing loose boards, scrimming joints and skimming can work; sagging or damaged material may need replacement.
When should I call a surveyor about a plaster crack?
Seek assessment for new, widening or recurring diagonal cracks, displacement, sticking doors or windows, or matching cracks in external masonry. Active movement should be resolved before plastering.
Need this doing?
SJF Plastering covers Sutton, Surrey and South West London. Call 07967 302162 or message us on WhatsApp for a free quotation.
What customers say
Good communication, job arranged quickly
Steve was in touch straight away, gave a very reasonable quote and was good at communicating what was needed and when he would be able to do the work. Steve arrived on time on the day, did a good job and carried out the work in very good time. I would use Steve again for any similar work.
Replacing ceiling due to leak
Steve and his team did an amazing job on our ceiling. We had to get it replaced due to a leak from the flat above and Steve was super communicative, friendly and helpful throughout.
Excellent job!
Had a large hole in the wall which Steve fixed for me, told me the price and gave other options as well all before starting the work. He did an excellent job, got the work done without any fuss!