Replastering after damp means removing plaster that has been spoiled by moisture and salts and replacing it with a system designed for walls that have been wet. It is usually needed after rising damp treatment, and sometimes after penetrating damp or a long-running leak. The cause of the damp has to be fixed first; new plaster on a wall that is still getting wet will fail in the same way as the old.
Why can’t the old plaster just be left to dry?
Sometimes it can. Plaster that was wetted briefly by a leak that has now been fixed may dry out and only need making good and redecorating. But where water has passed through a wall for months or years, it brings dissolved salts with it. As the water evaporates at the surface, the salts are left behind in the plaster.
Some of those salts, especially chlorides and nitrates from the ground, are hygroscopic: they draw moisture from the air. A salty wall can look damp and feel damp on humid days even when no water is reaching it any more. Other salts crystallise as they dry and break the plaster up from inside, which is why you see blown, powdery or bubbling patches. In those cases the plaster has to come off.
Signs your plaster needs replacing
- White, fluffy or crystalline deposits on the surface
- Plaster that sounds hollow when tapped or has come away from the brick
- Crumbling or soft patches, especially low on the wall
- Paint and wallpaper that keep bubbling or lifting after redecoration
- Dark damp-looking patches that come and go with the weather or humidity
- Gypsum plaster that has softened after being soaked
Which plaster system is right for the wall?
There is no single right answer. The choice depends on what caused the damp, the age and construction of the wall, and how the room is used.
| Situation | Typical approach | Why |
|---|---|---|
| After a new DPC on a brick wall | Salt-resistant renovating plaster system | Designed to hold back residual salts and moisture while the wall dries |
| Older solid wall in a period house | Breathable lime-based plaster | Lets moisture move out of the wall rather than trapping it in the brick |
| Wall that cannot be fully dried, such as some below-ground walls | Membrane system with a dry lining or plaster finish | Separates the finish from the damp masonry behind |
| Short-lived leak, plaster still sound | Dry out, make good and redecorate | No need to remove plaster that has recovered |
Ordinary gypsum plaster is not suitable on a wall that has had rising damp or heavy salt contamination; it softens when wet and does not resist salts. Equally, sealing an old solid wall with dense cement render inside can trap moisture in the brick and push damp elsewhere. Getting the material right is as important as the workmanship.
Where the plaster sits below ground level, such as in a cellar, ordinary replastering is not enough and the wall needs waterproofing. Our cellar damp proofing page explains those systems.
How the work is done
- Check the cause is dealt with. We confirm that the leak, bridge or failed DPC has been fixed, or is being fixed as part of the same job, such as a damp proof course injection.
- Protect the room. Floors and furniture are covered, and skirting boards, sockets faceplates and radiators are noted. Any electrical work around sockets is left to a qualified electrician.
- Remove the damaged plaster. The plaster is usually taken off to around a metre on rising damp walls, or beyond the visible salts and damp, so no contaminated plaster is left at the edges.
- Prepare the background. Loose mortar is raked out and the brickwork is cleaned down so the new plaster bonds properly.
- Apply the new system. Undercoats and finish coats are applied in the order the system requires, with proper time between coats.
- Refit and advise. Skirting is refitted or renewed, and we explain how long to leave the wall before decorating and what paint to use.
Textured coatings, old boards and some plasters in homes built or refurbished before 2000 can contain asbestos. We do not hack off or sand anything suspected of containing asbestos until it has been tested by a licensed specialist.
How long before you can decorate?
New plaster has to dry before it is painted or papered. That usually takes several weeks, and can take longer in winter, in rooms that are not heated much, or where the wall behind is still drying after damp treatment. A breathable, water-based emulsion is often recommended for the first decoration on renovating and lime plasters. Vinyl wallpaper, oil-based paints and other non-breathable finishes are best avoided until the wall is fully dry, and some systems advise against them altogether. When you are ready to redecorate, our mould-resistant decorating service can help in rooms that have also had mould.
Replastering in Liverpool’s older houses
Many Liverpool homes still have their original lime plaster on solid brick, often patched over the years with gypsum and cement. In large Victorian houses and conversions in Aigburth and Toxteth, and in the terraces with back extensions found across Wavertree, we often find several materials on one wall. Matching the new plaster to the wall, rather than using whatever is quickest, helps the finished wall stay sound and dry out properly.
Replastering is one part of our damp and mould repairs in Liverpool. We plan it together with the damp treatment so you are not left with an open wall and no clear timescale.
What affects the cost of replastering after damp?
The main factors are the area of plaster to remove and replace, the system used, the height and number of walls, access around kitchens, stairs and fixed units, skirting and timber repairs, and any making good around windows, doors and sockets. Drying time and redecoration also need planning. We give a written quote after the visit.
Plaster spoiled by damp?
Call 07777 659786 or use the form. Tell us which walls are affected and whether the damp has already been treated, and our Merseyside damp specialist will call back to arrange a visit.
Frequently asked questions
Do I need to replaster after a new damp proof course?
In most cases, yes. Years of rising damp leave salts in the plaster that keep drawing moisture from the air, even once the new DPC is working. Removing that plaster and replacing it with a salt-resistant system is normally part of rising damp treatment. Where the plaster is sound and salt-free, it may not be needed.
How high does the plaster need to be removed?
On walls treated for rising damp, plaster is usually removed to around a metre above floor level, or higher if salts or damp extend further. For penetrating damp, it is usually removed beyond the edge of the damaged area. We decide the extent on site so no contaminated plaster is left behind.
Can you use lime plaster on an old Liverpool house?
Often, yes. Lime plaster is breathable and well suited to many older solid brick walls, because it lets moisture move out rather than trapping it. It is not right for every situation, for example where salt contamination is very heavy or the wall cannot dry. We explain the options for your wall.
Why has my new plaster gone damp again?
Usually because the cause of the damp was not fully fixed, or because unsuitable plaster was used. Gypsum plaster on a salty wall, a DPC that is bridged outside, or a leak that is still active can all spoil new plaster. Condensation can also make new plaster look damp in cold rooms. We look for the reason before suggesting any more work.
Can I paint straight onto the new plaster?
Not straight away. New plaster needs to dry, usually for several weeks and sometimes longer, before decorating. A breathable water-based emulsion is often recommended for the first coat on renovating or lime plasters. Check the manufacturer’s guidance for the system used, and avoid vinyl or non-breathable finishes until the wall is fully dry.
Can plasterboard be used instead of wet plaster?
Plasterboard can be used in some situations, such as with a membrane or on a wall that has been properly dried, but it is not a good choice directly on a wall with rising damp or salts. Gypsum boards can soften and grow mould if they get damp. We recommend the approach that suits the wall.