Dealing With Rising Damp

Waltons Heating and Air - Home Improvement Blog

Rising damp can present homeowners with a multitude of problems, from salty tidemarks to peeling wallpaper, wet plaster and heat loss. There’s also the health problems brought on by mould, a particular issue if you suffer from a bad chest.

Tips for dealing with damp

Of late there has been some debate around whether rising damp actually exists. This is largely because of the activities of unscrupulous ‘specialists’ offering a quick fix DPC (damp proof course) when the real problem lies with condensation or inadequate ventilation.

This article looks at symptoms, treatments and prevention of rising damp.

Rising damp occurs where a DPC is faulty or damaged (or in some cases missing) or where the ground level around the house has been elevated, perhaps by a new path, flowerbed, patio or driveway.

Water from the ground permeates brick, stone and mortar – all naturally porous materials - and travels up the walls, rather like oil travelling up the wick of a lamp. The ground water contains soluble salts which are deposited on the surfaces of the wall as they dry out, attracting more moisture which makes the walls feel permanently damp. Rising damp usually affects the lower one metre of the wall but left unchecked it can seep as high as five metres.

As well as looking unsightly, causing heat loss and timber decay, it’s also potentially unhealthy as it encourages mould and mites to grow.

Rising damp can occur in modern properties but it’s more prevalent in older houses. Since 1875 all new houses have been built with a DPC, however the English House Condition Survey conducted in 1996 shows that 13% of pre-1850 and 11% of properties built between 1900-1918 are affected by rising damp. 1% of homes built after 1956 are affected but if the damp protection is “bridged”, ie the exterior ground level raises above the interior level, problems are more likely. The first step is a survey to determine the extent of the damage. Treatment typically involves the installation of a chemical or osmotic DPC which is injected into holes in the masonry to repel water.

Alternatively a new damp membrane can be fitted to act as a physical barrier to moisture. Plaster usually needs to be replaced with new salt-retardant plaster and a new skirting board fitted. Obviously this depends on the square meterage of affected wall, but as a general guideline expect to pay between £70-100 per linear metre for the damp proofing. The cost of plastering and reinstating skirting boards and electricity sockets will be extra. For a typical three bedroom house the average cost of damp proofing is between £3-4,000.