Why Is My Plaster Cracking?

You’ve decorated a room, everything looks great, and then you notice it – a crack running across your plaster.

Cracks in plaster walls and ceilings are extremely common, particularly in older properties, but they can appear in newer homes too. Some cracks are nothing more than cosmetic movement, while others can be a warning that something else is happening behind the plaster.

At Thanet Plastering & Damp Solutions, we’ve been plastering and repairing properties across Kent for over 40 years. One of the questions we're regularly asked is:

“Why is my plaster cracking?”

The answer depends on the type of crack, where it appears and what is causing it.

Your Property Is Naturally Moving

All buildings move slightly.

Changes in temperature, moisture levels and even the seasons can cause building materials to expand and contract. Newer properties can also experience some settlement as the building adjusts over time.

This movement can create small hairline cracks in plaster, particularly around:

• Doors and windows

• Corners of rooms

• Where walls meet ceilings

• Plasterboard joints

• Extensions and alterations

• Areas where different building materials meet

A small hairline crack isn't necessarily something to worry about. However, if the crack keeps returning, becomes wider or appears suddenly, it is worth having it investigated.

The Plaster Has Dried Too Quickly

Plaster needs to dry correctly.

If freshly applied plaster dries too quickly, it can shrink and develop fine cracks across the surface.

This can sometimes happen when a room is heated aggressively immediately after plastering or when plaster is applied in particularly hot or dry conditions.

Good preparation, correct application and allowing plaster to dry naturally all help reduce the risk of cracking.

There Could Be a Problem With the Original Plaster

Older plaster can eventually lose its bond with the wall behind it.

You might notice cracks appearing alongside areas that sound hollow when gently tapped. In more severe cases, sections of plaster may begin to bulge or come away from the wall.

Simply filling the visible crack won't necessarily solve the problem.

The damaged or loose plaster may need to be removed before the area is properly prepared and replastered.

Cracks Can Appear Along Plasterboard Joints

If your walls or ceilings have been constructed using plasterboard, cracks can sometimes appear where two boards meet.

This can be caused by movement in the boards, problems with the jointing tape or insufficient support behind the plasterboard.

These cracks are often very straight, which can help distinguish them from other types of plaster cracking.

Repairing the crack correctly means dealing with the joint itself rather than repeatedly filling the surface.

Damp Can Damage Plaster

This is one we see regularly in properties across Kent.

If moisture is getting into a wall, the plaster can deteriorate. You may notice cracking alongside other symptoms such as:

• Bubbling or flaking paint

• Discoloured patches

• A musty smell

• Crumbling plaster

• Salt deposits on the wall

• Black mould

• Plaster becoming loose or blown

In these situations, replastering alone isn't the answer.

You need to establish where the moisture is coming from first.

It could be rising damp, penetrating damp, a leaking pipe, damaged external render, defective guttering or another source of water entering the property.

If the underlying damp problem isn't fixed, there's a good chance the new plaster will eventually become damaged too.

Cracks Around Windows and Doors

Cracking around the corners of windows and doors is particularly common because these are natural weak points within a wall.

Small cracks can result from everyday movement, but larger diagonal cracks should be investigated.

If you've noticed a crack getting progressively wider, don't just cover it with filler and paint over it. It is better to understand what's causing the movement first.

Cracks Where an Extension Meets the Original House

If you've had an extension built, you may notice cracks developing where the new part of the property joins the original building.

Different parts of the building can move at slightly different rates.

Minor cracking can sometimes be dealt with relatively easily, but recurring or significant cracks may require further investigation before any plaster repairs are carried out.

Should I Be Worried About Cracks in My Plaster?

Not necessarily.

Fine hairline cracks are extremely common and are often cosmetic. What you should pay attention to is whether the crack is changing.

We would recommend getting professional advice if:

• The crack is becoming wider

• It keeps returning after being repaired

• Several new cracks have appeared

• The plaster is bulging or coming away from the wall

• The crack runs diagonally from a door or window

• You can see signs of damp around the crack

• The wall or ceiling has recently suffered water damage

• You're simply unsure what's causing it

If there are indications of significant structural movement, you may also need advice from an appropriately qualified building professional or structural engineer.

Can I Just Fill Cracks in Plaster?

For a very small, stable hairline crack, filling and redecorating may be perfectly adequate.

But there's an important difference between repairing a crack and hiding a crack.

If the plaster underneath is loose, the plasterboard joint is moving or moisture is entering the wall, putting filler over the surface is unlikely to provide a permanent solution.

The crack may simply reappear.

That's why identifying the cause should always come before deciding how to repair it.

Cracked Plaster in an Older Property?

Kent has thousands of beautiful older and period properties, and they often require a different approach to modern buildings.

Older walls may have been constructed using traditional materials designed to breathe. Applying inappropriate modern materials can sometimes create additional problems, particularly where moisture is involved.

At Thanet Plastering & Damp Solutions, we have extensive experience working with older properties and can advise on suitable plastering, lime plastering, rendering and damp solutions depending on the construction of your home.

How Do You Repair Cracked Plaster?

There isn't one repair method that works for every crack.

Depending on the cause and condition of the wall, the solution could involve removing loose material, repairing plasterboard joints, preparing and replastering damaged areas, skimming walls or ceilings, dealing with water ingress or carrying out damp-proofing work before the wall is restored.

The important part is getting the diagnosis right first.

Need Someone to Look at Cracking Plaster?

If you're concerned about cracks in your walls or ceilings, send us a photograph or arrange for us to take a look.

Thanet Plastering & Damp Solutions is a local family-run business with over 40 years' experience in plastering, damp proofing, dry lining and rendering.

We work across Thanet and Kent, including Margate, Broadstairs, Ramsgate, Canterbury, Whitstable, Faversham, Sandwich, Deal, Dover, Folkestone, Ashford, Maidstone and surrounding areas.

Whether it's a small plaster repair or cracking connected to a more significant damp problem, we'll help identify what is happening and recommend the appropriate solution.

Don't keep filling a crack that keeps coming back – find out what's causing it.

Contact Thanet Plastering & Damp Solutions

Call 07852 701 996 or send us photographs of the affected wall or ceiling via WhatsApp.

Alternatively, contact us through our website to arrange a no-obligation survey or quotation.