Rising damp can present homeowners with a multitude of problems, from salty tidemarks to peeling wallpaper, wet plaster and heat loss. There’s also a number of health problems that can be made worse by mould – you're more likely to have respiratory problems, respiratory infections, allergies or asthma, according to the NHS .
Dealing with damp
- Make sure your damp course provider is approved by the Property Care Association (PWA)
- Choose a supplier that offers a 25- or 30- year guarantee for the work
- Make sure your home is well ventilated before calling in a damp proof specialist
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.
What is 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. 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 also encourages mould and mites to grow.
How to tell if you have rising damp
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.
It’s fairly easy to spot the signs of rising damp:
- Curling or discoloured wallpaper
- Wet or rotting skirting board or timber
- Damp stained walls
- Wet plasterwork or brickwork
- Discolouration or staining of exterior brick or stonework
Beware of misdiagnosis
Rising damp is frequently misdiagnosed or sold in as an essential by unscrupulous damp proofing companies. The real problem could be:
- Condensation, the most common form of dampness
- Faulty plumbing
- Leaking guttering
- Blocked air bricks
- Defective ground and surface drainage
Check all of the above thoroughly or get a second opinion before starting any remedial work.
How rising damp is treated
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.
How much time/expense is needed to treat damp?
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 3-bedroom house, the average cost of damp proofing is between £3-4,000.
Damp proof treatments can usually be completed fairly quickly, usually within 1-3 days, however it’s the drying time that can be lengthy. It takes 1 month per inch of wall thickness to dry. You can speed up the process by using a dehumidifier.
Can you DIY?
The short answer is no, we don’t recommend it. This is because when you come to sell your property your buyers will want to see a 25 year guarantee for survey or mortgage purposes.
How to prevent rising damp
To help keep your walls damp free:
- Check moisture levels with an electronic moisture meter (available from DIY shops for between £5-£50) twice a year
- Any soil resting directly against your house should be dug away to leave a gap
- Complete a thorough check of likely misdiagnoses above