Project Description

WHAT IS RISING DAMP?

Rising damp occurs when moisture from the ground travels up through a brick wall by capillary action. Meaning that water below the ground is sucked up a wall through the tiny spaces within bricks. The water also carries with it salts and minerals from the ground.

Other porous building materials, such as plaster and timber absorb the groundwater which further affects the wall that is suffering rising damp. Rising damp that affects timber can cause further structural damage and will require specialist treatment to avoid worsening conditions or costly renovations.

This type of damp has specific symptoms that can be seen on affected internal and external walls. Loose plaster and wallpaper, a stain with a definitive tide mark and salts blooming on the surface can be common signs. However, rising damp is often misdiagnosed as visual evidence and moisture meter readings are interpreted incorrectly. Indeed, some believe rising damp to be a complete hoax.

Is rising damp a myth?

Unfortunately it is the case that there are unethical damp control companies that intentionally misdiagnose rising damp in order to sell expensive damp treatments. However, this doesn’t mean that rising damp is a myth and should be ignored as an underlying condition of a building’s damp problem.

You will most likely find authors condemning the term rising damp by saying it simply doesn’t exist. One of the main commentators of this view is Stephen Boniface, former chairman of the construction arm of the Royal Institution of Chartered Surveyors (RICS). The argument for and against the existence of rising damp is a long-standing one and still continues.

The fundamental reasoning behind this debate is the common misdiagnosis of sign damp, often delivered by unqualified and inexperienced surveyors. This leads to the wrong damp control treatment. There is, however, scientific and academic research proving its existence as well as case studies in which rising damp treatment has helped alleviate a damp problem. and APP has over 30 years of damp control diagnosis, and we’d always suggest you contact a specialist you can trust and who can get to the core of your damp issue.

How to stop rising damp

Tide marks on internal walls are usually the first signs of rising damp in your home. A tide mark is a water stain on the wall that has a clear line that stops where the rising water reaches in your wall. These tide marks are mostly about a metre above the skirting board, but can be seen higher in some cases.

Brickwork and masonry containing a high ratio of fine pores will lead to a higher rise of water than denser brickwork. Pore structure of your brickwork and rate of evaporation determine the height the tide marks on your internal walls could reach. 

You may also see paint bubble and a powdery white deposit on the surface of the walls. This is caused because the water often brings with it salts from the ground that are left once the water evaporates. Sulphates form crusty white stains, whereas hygroscopic salts (nitrates and chlorides) continue to suck moisture. Rising damp with evidence of hygroscopic salt should be treated as soon as possible.

The cause of rising damp

There is usually some form of barrier in place in the majority of buildings that prevent water from rising up through the brickwork. This barrier is called a damp proof course (DPC) and they can be made out of non-absorbent, water-resistant materials. The material that the damp proof course is made from is dependent on the period of the property and can range from slate, bitumen and plastic. In older houses, these DPCs may not even be installed at all.

DPC, such as the above, can sometimes fail over time and this can lead to water making its way up your wall. The DPC could still be undamaged, but could still be bridged. This is where a construction fault allows water to bypass the damp proofing and continue up the wall.

Treating rising damp on internal walls

The capillary action of the brickwork, as discussed above, is responsible for rising damp in internal walls. This will occur as a result of damaged or non-existent DPC in the wall itself. So, before any work to treat rising damp can begin the skirting board needs to be removed. Damaged plaster will also need to be removed especially if it has been affected by salt.

A remedial DPC can now be injected into the exposed brickwork, meaning we can target the problem area. Holes will need to be drilled into the the mortar course that is 150mm above the exterior ground level. After the holes have been prepared the damp proof course injections can be administered.

Rising damp treatments

Damp walls will damage plaster, wall paper, paints and skirting boards. The core of the damp problem needs to be rectified before cosmetic repairs are undertaken. The most economical way to treat rising damp and the best way to reduce damp proofing costs is with a damp proofing injection cream. 

The cream is injected into the affected walls and once it enters the wall it turns into a liquid. The liquid then penetrates the brickwork pores, cures and hardens. This chemical DPC creates a strong, water-repellent barrier, stopping water from rising up the wall.

A less cost effective rising damp treatment is to install a new damp proof course membrane. This involves removing the bricks around the affected area and replacing the DPC with a new physical membrane. 

If you have a bridged damp proof course then you will need to remove or fix the issue that is causing the bridge. For example, if the external ground level is too high then you will need to dig a trench at least 6 inches below the current DPC. But make sure to not let the new trench collect water as this may cause further damp issues.

Carrying out quick-fixes, like painting over damaged decor, or re-pointing brickwork will only lead to bigger damp control problems in the future. You will need to continually re-paint and the damp walls will continue to degrade further.

We always recommend seeking the advice of trusted damp control specialists like APP Protect for an honest evaluation of your damp problems.

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