5 Signs You Need Your Walls Replastered

Plaster doesn’t last forever. Even a quality plaster job will eventually show signs of age, and external factors like damp, movement, and wear can shorten its lifespan. Knowing when to replaster - and when a simple repair will do - can save you money and protect your home from more serious problems.

Here are the five key signs that your walls may need replastering, along with guidance on when to act and what to expect.

Lee on what triggers most customer calls

What brings most customers through the door is visible damp, either a patch on the wall, paint that’s bubbling and peeling, or a musty smell that won’t go away. After that it’s blown plaster, you tap a wall and it sounds hollow, or you can see the surface is starting to bulge. Cracking comes up too but it’s more often cosmetic than serious. Water damage from a burst pipe or a leak is a regular call-out, that’s a sudden problem rather than a slow one. The thing I’d say to anyone unsure: don’t wait until the wall fails. A patch repair caught early is much cheaper than a full replaster after the damage spreads.

1. Cracking

Not all cracks are created equal. Understanding what your cracks are telling you is the first step in deciding whether you need replastering:

Hairline Cracks

Fine hairline cracks in plaster are extremely common, especially in newer properties where the building is still settling. These are usually cosmetic and can be filled and painted over without replastering.

Wider Cracks

Cracks wider than 1-2mm may indicate more significant movement in the wall or a failure of the plaster bond. If you can fit a coin edge into the crack, it’s worth getting a professional assessment.

Pattern Cracking

A network of cracks (sometimes called “map cracking” or “crazing”) across a wall or ceiling suggests the plaster has lost its bond with the substrate or has dried too quickly during application. This usually requires replastering.

Cracks That Return

If you fill a crack and it comes back, there’s an underlying cause that filling won’t fix. This could be structural movement, thermal expansion, or a bond failure in the plaster itself.

Lee on cracks

Hairline cracks in new plaster are usually cosmetic, the result of slight movement or the plaster drying. They can be filled and painted and never come back. What worries me are diagonal cracks, stepped cracks following brickwork, anything that crosses a corner from one wall to another, those can indicate structural movement and I’ll always recommend a structural engineer takes a look before I touch them. The other concerning one is a crack that you’ve filled and it’s come back, that means something’s still moving and just filling it again is a waste of time and money.

2. Bubbling and Flaking

When paint bubbles, flakes, or peels away from plastered walls, it often points to a problem with the plaster beneath:

What Causes Bubbling

Damp - moisture behind the plaster pushes the surface coating away from the wall
Efflorescence - mineral salts carried by moisture crystallise on the surface, pushing paint and plaster apart
Poor preparation - if the wall wasn’t prepared properly before plastering, the plaster may not have bonded correctly
Painting too soon - applying paint before plaster has fully dried traps moisture and causes bubbling

When to Act

Isolated bubbling may be treatable with localised repair, but widespread bubbling across a wall typically indicates a damp problem or a fundamental plaster failure that requires the wall to be stripped and replastered.

3. Damp Patches and Staining

Damp patches on plastered walls are a clear warning sign. They indicate that moisture is getting into the wall from somewhere, and the plaster is suffering as a result.

Types of Damp to Watch For

Rising damp - appears as a tide mark on lower walls, typically up to about one metre from the floor. May be accompanied by salt deposits and a musty smell.

Penetrating damp - appears as patches on walls, often corresponding to external defects (cracked render, missing pointing, leaking gutters). The damp patch may get worse during or after rain.

Condensation - appears as moisture on cold surfaces, often on external walls, behind furniture, or in corners with poor air circulation. Can lead to black mould growth.

The Right Approach

Simply replastering over damp is a waste of money. The source of moisture must be identified and fixed first, and the wall must be allowed to dry before new plaster is applied. In many cases, specialist damp-proof plastering systems are needed after treatment.

Lee on plastering over damp

Plastering over damp without dealing with the cause is one of the biggest mistakes I see. The new plaster might look perfect for a few months, but the moisture is still there, salts will rise through, the bond will fail, and you’re back to square one within a year. Damp is about 50 percent of my workload, so I’ve seen the consequences plenty of times: customers who’ve had a previous plasterer just skim straight over a damp wall, paid good money for it, and then I’m called in to do it properly after it fails. Always treat the cause first. If it’s penetrating damp from outside, that’s the render or pointing. If it’s rising damp, it might need an injection course. If it’s condensation, it might be a ventilation issue. Plastering is the last step, not the first.

4. Hollow or “Blown” Plaster

“Blown” plaster is one of the most reliable indicators that replastering is needed. Here’s how to check for it:

The Tap Test

Gently tap your wall with your knuckles. Sound plaster gives a solid, dull thud. Blown plaster sounds hollow, like tapping on a drum. The hollow sound means the plaster has separated from the wall behind it.

Why Plaster Blows

Age - over decades, the bond between plaster and substrate gradually weakens
Damp - moisture dissolves the bond between plaster and the wall
Movement - even slight structural movement can crack the bond
Vibration - heavy traffic, building works, or even slamming doors can loosen old plaster over time

Can Blown Plaster Be Repaired?

Small areas of blown plaster can sometimes be cut out and patched. However, if a significant portion of a wall or ceiling sounds hollow, replastering is the right course of action. Patching large areas of blown plaster is false economy - the remaining plaster will likely blow in time, and you’ll end up with a wall covered in visible patches.

Lee on blown plaster

The way I judge it is straightforward: tap the wall and listen. If maybe 10 to 20 percent of the surface is hollow and the rest is solid, that’s a patch job and you can save the customer money. Once you’re getting up to 30, 40, 50 percent hollow, I’ll recommend a full replaster, because patching that much wall is false economy. The patches will weather differently to the surrounding plaster, you’ll see them through the paint, and the remaining blown areas will fail in time anyway. Better to hack it all off, sort the wall properly, and have a clean finish that lasts another fifty years.

5. Age and General Deterioration

Sometimes plaster simply reaches the end of its useful life. Victorian and Edwardian properties in Kent often have original plaster that’s over 100 years old. While old plaster can be remarkably durable, it does deteriorate:

Soft or crumbly plaster - plaster that crumbles when you press on it or flakes away when you remove wallpaper
Uneven surfaces - walls that have become bumpy, wavy, or uneven over time
Poor decoration adhesion - paint and wallpaper that won’t adhere properly to the surface
Repeated repair needs - walls that seem to need constant patching and filling

When to Replaster vs Repair

As a general rule:

If less than 25% of a wall is affected by problems, localised repair is usually sensible
If 25-50% is affected, it’s often more cost-effective to replaster the entire wall
If more than 50% is affected, replastering is almost always the right choice

This is a guideline rather than a rule - the specific situation matters. A professional plasterer can assess your walls and give you honest advice on whether repair or replastering is the better option.

Lee on old plaster in Kent properties

I’ve worked on lime plaster that’s been on the wall for over 150 years and still in decent condition, especially on properties where it’s been left alone or properly maintained. Lime plaster is forgiving over time, it moves with the building, it breathes, and it can heal hairline cracks through carbonation. The oldest plaster I’ve come across is on heritage projects like the Ursuline Convent area and listed buildings in Sandwich, where the original lime is still doing its job. The problems usually start when someone’s tried to patch lime with modern cement-based products, which is the wrong material and traps moisture. Right material for the right job, that’s the rule.

What Happens During Replastering

If you’ve identified one or more of these signs, here’s what to expect from a replastering job:

Assessment - your plasterer examines the walls and identifies any underlying issues (damp, structural movement) that need addressing first
Preparation - old plaster is removed back to a sound surface. The wall is cleaned and treated as needed
Replastering - new plaster is applied in one or more coats, depending on the condition of the substrate
Drying - fresh plaster needs two to four weeks to dry fully before painting
Decoration - once dry, the walls can be painted or wallpapered

Don’t Ignore the Signs

Failing plaster is more than a cosmetic issue. Left untreated, it can mask damp problems that damage your home’s structure, create an unhealthy living environment, and ultimately cost more to fix.

If you’ve noticed any of these signs in your Kent home, contact Perfect Plastering for a free assessment. We’ll give you honest advice on whether you need replastering or whether a simpler repair will do the job.