What is Rising Damp?
Rising Damp is a result of a capillary action i.e., the flow of water from the ground against gravity. This is usually due to a lack of a physical damp-proof course (DPC). Where this occurs a damp zone usually extends to the whole length of the wall to a height of 500mm or more above skirting-board level. Where the DPC does exist and if this DPC is broken or bridged then patches of damp may occur.
What are the signs of Rising Damp?
Damp signs can differ depending on the type. If you notice any of the signs below, it is likely that you have rising damp:
- Skirting boards or plaster within the property may damaged or rotting.
- Wet patches may become visible which can often lead to paint and wallpaper peeling off.
- You may notice floor coverings lifting or damp patches.
- A white powder-like substance can be left when soluble salts dissolve from the ground.
- A tide line of yellowish or brownish staining or brown plaster in the lower area of your wall. This will be above your skirting board.
Treating Rising Damp
To solve the issue of rising damp in your property you may require the installation of a damp proof course.
Injection of a Dryzone Damp-Proofing Cream this is a patented high-strength silicone-based cream that is injected into holes drilled at regular intervals along a mortar course. Once injected, the cream diffuses along the mortar course before curing to form a breathable water-repellent resin – preventing dampness from rising up the wall.
Any existing plaster to the affected areas will almost certainly be contaminated with hygroscopic salts. This would need to be hacked off to approximately 300mm above the damp stains but usually not less than one metre. These walls can then be replastered using renovating plaster.
It is important to use the appropriate plaster when renovating walls that have been affected by damp issues. Especially in cases of rising damp where hydroscopic salts are still likely to be present after treatments.
Standard gypsum plaster soaks up residual moisture left in the wall and salts in the wall migrate to the surface and can break down the plaster structure requiring further repairs.
Renovation plasters have been developed specifically for replastering internal walls that have been treated for rising damp or penetrating damp problems.
Low Profile Membrane
Low profile membrane is a plaster membrane which is a studded polypropylene waterproofing sheet with a special mesh moulded to one side. It is fixed to damp contaminated walls using plaster plugs with the studs facing the wall. This creates an air gap which allows the wall to breathe whilst blocking the passage of moisture to the finished surface. On the reverse side of the membrane the mesh can be plastered on to. This allows a dry plaster finish to be achieved without the risk of contamination from any damp or salts in the wall. Plasterboard can also be applied directly to the membrane, by applying dabs of bonding compound to the head of the plugs that are used to attach the membrane to the wall and skim to finish.