How to Treat Rising Damp in houses

Rising damp is one of most talked about topic because it is found in every house .This How To guide takes you through identifying rising damp, the causes and how to effectively deal with it. A large part of this guide is given over to correctly identifying rising damp in your home, telling it apart from much more common damp issues. We also bust some myths around rising damp and its treatment.      

What is Rising Damp?

Rising damp is a relatively rare form of damp that affects the walls of buildings. It occurs when moisture from the ground travels up through the walls by capillary action. This means that ground water is effectively sucked up through tiny tubes in the bricks, like a series of straws. This water contains salts that also travel up through the wall.

Around the affected wall, you get other porous building materials such as plaste rwork and the timber found in the floor boards, joists and skirtings. These materials will also absorb the ground water easily and you may find evidence of wet rot in the timber. 

Generally rising damp is first noticed by the damage it causes to the internal walls of a building. Plaster and paint can deteriorate and any wallpaper tends to loosen. A visible stain often appears on the wall in the form of a tide mark at the point where the ground water has reached. You may also see salts blooming on the internal surface. This is something often associated with rising damp and will lead to the debonding of paints and even plaster work. Externally, mortar may crumble and white salt stains may appear on the walls. We will go into the common signs of rising damp in more detail later in the guide.

Causes of Rising Damp

Rising damp is a relatively rare form of damp that affects the walls of buildings. It occurs when moisture from the ground travels up through the walls by capillary action. This means that ground water is effectively sucked up through tiny tubes in the bricks, like a series of straws. This water contains salts that also travel up through the wall.

Around the affected wall, you get other porous building materials such as plaster work and the timber found in the floor boards, joists and skirting. These materials will also absorb the ground water easily and you may find evidence of wet rot in the timber.

Sometime the DPC can remain intact, but the DPC can be bridged. This is where the damp from the ground is able to travel up past the DPC because of a construction fault.

Examples of this include:

• Debris in the wall cavity or sub floor void.
• Internal or external renders / plasters overlapping the DPC
• External ground levels being raised above the DPC. 
• Inappropriate insulation material in the cavity.
• Solid floors
• Intersecting masonry structures / abutting garden walls.

Rising Damp – Internal Walls

Most people first notice an issue with rising damp on internal walls. Rising damp often results in tide marks on your internal walls up to the height where the water has reached. In most cases, these tide mark stains appear up to a metre above the skirting board. In some very rare cases, water can travel beyond this point.

The height the water reaches depends on several key factors. These include the pore structure of the bricks and mortar and the rate of evaporation. Masonry containing a high proportion of fine pores will allow the water to rise higher than one with less pores. Rising damp can occur up to 1.5 metres and even higher in some very rare instances.

The water from the ground often contains salts that are then deposited on the wall when the water evaporates. These salts can cause the paint to bubble and a white fluffy deposit to be left on the surface. There are two main types of salt – sulphates which result in crusty white patches and invisible hygroscopic salts known as nitrates and chlorides. The hygroscopic salts continue to draw moisture and therefore must be treated.  

What causes rising damp in internal walls?

Rising damp in internal walls is caused by the same movement of ground water up through the brickwork by capillary action. It is the result of a failed or non-existant DPC or when the DPC has been bridged. 

Rising Damp External Walls

Rising damp can affect both internal and external walls. When looking for evidence of rising damp on external walls, again you should keep an eye out for tide marks. You may also see some of the mortar crumbling between the bricks or stonework and salt deposits too.

Signs of Rising Damp

Rising damp is a relatively rare form of damp and treatment will only work if it is correctly diagnosed. It is therefore vitally important to get a professional diagnosis from a qualified surveyor – this will involve a rising damp survey of your home including analysis of the salts.

It can be hard to distinguish rising damp from other forms of damp like condensation or penetrating damp.

Having said that, the following are some of the more common signs of rising damp that you can look out for:

• Tide marks of salts
• Dark patches on walls that can be damp to touch – for a better indication of rising damp you want to determine that the brickwork / masonry is actually wet and not just the plaster or wallpaper. 
• Staining of wall coverings, peeling wallpaper & blistering paint.
• Damp and musty smell.
• Discolouration & fragmenting plaster.
• Decaying timber e.g. skirting boards, floor boards, floor joist

Rising Damp Treatment

The most effective and economical way to treat rising damp is with a damp proofing injection cream. You can choose between complete kits or individual cartridges of cream from leading brands such as Kiesol C and Aida. 

The cream is injected or hand-pumped into specially-positioned holes in the mortar course. Once inserted, the damp proofing cream reverts to a liquid. This allows it to penetrate the bricks and achieve complete absorption. As it cures, it creates a powerful water-repellent barrier and a new chemical DPC that stops water from rising up the wall. For full instructions on how to treat rising damp with damp proofing cream read our guide to injecting damp proof courses.        

Alternatively, you can install a new damp proof membrane to act as a damp proof course. This is a much bigger and more complicated process that involves taking out each brick along the failed mortar course and installing a new physical damp proof membrane. 

How to treat rising damp on internal walls

When you see evidence of rising damp on internal walls, you need to remove any wallpaper and plaster back to the bricks or substrate. You will also need to do this on the external wall of the property. 

Check that the DPC has not been bridged in any way before proceeding with the injection of a new DPC. Treating rising damp on internal walls is all about carrying out the injection process as outlined above and then getting in a position to make good and redecorate internally. 

The quickest way to do this is with a damp proof membrane.