If you've noticed your plaster beginning to crack, bulge or sound hollow when tapped, it's often referred to as blown plaster.
Whilst it can be tempting to simply repair the damaged area and redecorate, blown plaster is often a sign that something else is happening beneath the surface.
In many cases, moisture is the underlying cause.
At Weather Wise Solutions, we regularly inspect properties where damaged plaster has been caused by condensation, penetrating damp, rising damp or long-term moisture exposure.
The key is understanding why the plaster has failed before deciding how to repair it.
Quick Answer
Blown plaster occurs when the bond between the plaster and the wall breaks down. This can be caused by damp, salt contamination, age, movement within the building, poor workmanship or prolonged moisture exposure.
1. Damp
Moisture is one of the leading causes of plaster failure.
Persistent damp can weaken the bond between the wall and the plaster over time.
2. Salt Contamination
Ground salts and hygroscopic salts left behind by moisture can continue attracting water long after the wall appears dry.
This often causes plaster to deteriorate.
3. Penetrating Damp
Water entering through defective brickwork, pointing or render may damage internal plaster finishes.
4. Condensation
Long-term condensation can contribute to plaster deterioration, particularly where mould has been present for prolonged periods.
5. Building Movement
Natural settlement or structural movement may cause plaster to crack or separate.
6. Poor Previous Repairs
Incompatible materials or poor preparation can reduce adhesion.
7. Age
Older plaster eventually reaches the end of its service life.
8. Water Leaks
Leaks from plumbing or roofing can rapidly damage plaster.
What We See During Surveys
One of the most common mistakes homeowners make is replacing damaged plaster before identifying the source of moisture.
Unless the cause is resolved, the new plaster may also fail.
How Is Blown Plaster Repaired?
The correct repair depends entirely on the cause.
This may involve:
- Resolving moisture ingress
- Removing contaminated plaster
- Allowing the wall to dry
- Installing an appropriate renovating plaster system
- Replastering once the wall is suitable
About The Author
Written by Peter Potts
Peter Potts is an ABBE Level 3 Award in Dampness in Buildings holder and FODCS Certified Surveyor who enjoys helping homeowners understand the causes of damp-related defects.
Technical Review
Reviewed by Neil Hudson
Neil Hudson is Director of Weather Wise Solutions, CSTDB-qualified surveyor, ABBE Level 3 Award in Dampness in Buildings holder and FODCS Certified Surveyor.
Contributor
Aaron Worrall
Aaron Worrall is Director of Weather Wise Solutions and a Tech.DEW qualified specialist with Advanced City & Guilds Mould Remediation qualifications.
Frequently Asked Questions
Can damp cause plaster to blow?
Yes. Long-term moisture exposure is one of the most common causes.
Is blown plaster dangerous?
It can become loose and may continue deteriorating if left untreated.
Can I just replaster over blown plaster?
No. The underlying cause should be addressed first.
Does hollow plaster always mean damp?
Not always. Age and movement can also contribute.
How do I know if damp is causing my plaster to fail?
A professional survey can determine whether moisture is responsible.
References & Further Reading
- Historic England – https://historicengland.org.uk
- British Gypsum – https://www.british-gypsum.com
Book Your FREE Survey
If you've noticed cracking, hollow or blown plaster, our qualified surveyors can identify the cause and recommend the most appropriate remedial solution.