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Repairing Hairline Cracks In Plaster Ceiling

If you’re looking to paint your plaster ceiling but have noticed hairline cracks running along the surface, it’s important that you repair them first.

Whilst painting straight over hairline cracks in your ceiling with an opaque flat matt such as Tikkurila’s Anti-Reflex 2 might make the cracks look virtually invisible, you leave yourself open to damp or mould issues, especially if the hairline cracks are in rooms where there is excess moisture such as in kitchens or bathrooms.

Furthermore, as plaster is a very porous substrate, any absorption of moisture could result in your ceiling warping.

With that in mind, here’s our guide to repairing hairline cracks in plaster ceilings.

How To Repair Hairline Cracks In Plaster Ceilings

Step 1: Rake out all of the loose plaster around the crack with the edge of a filling knife or screwdriver. This will give the new filling something to adhere to.

Step 2: Wet in the area where the defect has occurred. You can either use clean water or diluted PVA. This will provide even more adhesion for the new filling.

Step 3: Allow the area to thoroughly dry then apply your plaster filling. Gyproc Easi-fill is the go-to for most decorators. Simply follow the instruction on the packet.

Step 4: Once the filler has dried (usually around an hour) use a fine abrasive to sand down the area to a smooth finish.

Step 5: Paint over with your chosen ceiling paint.

Why Do Hairline Cracks Appear In Plaster Ceilings?

Hairline cracks can appear in old plaster ceilings but are more commonly found in buildings that have been newly constructed.

They will also appear in plaster that has completely dried out as in this instance the plaster will shrink in size and ultimately crack. This typically happens when the weather is unusually hot.

Furthermore, poor craftsmanship can also result in cracked plaster ceilings. This is commonly the case if gypsum plasterboard hasn’t been screwed to the studwork properly.