RISING DAMP & How To Treat Damp Walls

What is Rising Damp & How to Treat Damp Walls - Rising Damp is a common form of dampness found in buildings.  When dealing with rising damp, positive identification and appropriate remedial action is essential. 

Rising damp can be defined as the vertical flow of water up through permeable (absorbent) wall structures, the water being sucked up from the ground.  The water rises through the pores (capillaries) in the masonry, acting like a wick, the mortar forms the only continuous pathway for water to rise up the wall, it's the easiest path for water to take. Even if a wall is built from impervious bricks the water can still rise through the mortar. But if an impervious mortar is used then no water will rise, so it is essential to treat the mortar.

Ground water contains soluble salts including chlorides, nitrates and sulphates which are carried in the water solution up the wall. These are left behind when the water evaporates during drying and over a period of time these salts accumulate and leave a ‘salt band’ towards the maximum height of the rising damp.

In general the greater amount of salts the greater the absorption of moisture especially under humid conditions, therefore even if the rising dampness has been controlled by the insertion of a damp proof course these salts alone can cause the wall and any contaminated decorations to remain damp.

How to identify Rising Damp 

Mis-diagnosis of Rising Damp is common place so make sure that the problem is not due to leaking rainwater goods, faulty plumbing, high ground levels, plaster bridging an existing damp course or condensation.

• Rising Damp leaves damp patches / stains usually up to 1 metre above floor level
• Plaster and brickwork can be salted (which is white in colour)
• Wallpaper will lift and plaster will soften
• Skirting boards may show signs of rot
• Black mould usually indicates condensation problems, but can also indicate rising damp

Always employ a professional damp-proofing surveyor to identify and treat the problem.

Rising Damp Treatment 

Remove old contaminated plasterwork, decoration and skirting to expose the brick/stone up to approximately one metre.

Insert a chemical damp proof course into the wall. The quickest and easiest method is by injecting a silicone based cream such as Focus cream or Dryzone into the mortar joint. The chemical will seep into the mortar to form a damp proof course which will block water from rising through the capillaries of the mortar. 

Complete the damp proof course by re-plastering with Renderpel (waterproof and salt inhibitor additive) in a sand and cement mix (Gypsum is not suitable to use following a damp proof course injection).

Further instructions can be found on the product pages of Focus Injection Cream and Dryzone. 

For further advice on how to treat damp walls, please call our technical advice line: 01509 216 323.