Damp can have many causes and many negative effects. In addition to the physical structural damage to your property, damp can also cause bad odours, mould, and rot.


Our modern lifestyles and building methods can raise the relative humidity inside our homes. Measures such as double glazing reduce ventilation, and bathing, cooking, and washing all generate water vapour. This vapour condenses on various surfaces, resulting in damp. Condensation damp can be diagnosed from water droplets and mould growth on internal surfaces.

Penetrating damp is caused by rainfall seeping into houses due to poor roof maintenance and repair, gutter blockages and overflows, and various other points where water can enter. This water seeps into the structure of the building and the timbers and can cause significant damage. This type of damp shows as large patches or stains on walls, ceilings and floors, particularly after heavy rains.

Internal spillage occurs when a bath or sink overflows or an appliance such as a dishwasher or washing machine leaks. Damaged and burst pipes and geysers also result in internal spillage.

Below ground damp causes what is sometimes called rising damp. Moisture in the ground evaporates but is impeded by the impervious coatings used in building, causing the water to drain towards the perimeter walls, where it soaks up through the brickwork by capillary action. This can also be affected by fluctuations in the water table beneath your property. The rising damp caused by below ground moisture can leave a tidemark on the walls indicating salt deposits, although there is seldom mould growth.

What Causes Damp?

Well, the causes of damp and the causes of rising damp are varied and numerous. They include high humidity or excessive condensation levels in the home, combined with poor ventilation and/or faulty drainage facilities. The appearance of damp often indicates a multitude of problems rather than a single source, but there are still several causes of damp you can look out for to help reduce the risk of it taking over your home:

  • Closed doors and windows trap heat and regularly result in the build-up of excessive moisture and consequently mould and damp. To prevent this from occurring, remember to keep the home well aired; even in the cooler winter months doors or windows should be opened for at least an hour a day.
  • Excessive amounts of baths and showers can also result in a build-up of humidity, which – if lacking an escape route – also ends up manifesting as damp or mould in the property.  If you have a large family and a small home, remember to keep bathroom windows open for as long as possible and try to stagger showers throughout the day if you can.
  • Over-using electrical appliances, such as the oven, washing machine or dishwasher can result in large amounts of heat being produced in a relatively short amount of time, especially if they are all used at the same time.  To keep heat levels down stagger appliance usage and remember to turn everything off after use.
  • Drying clothes indoors, such as on radiators or ‘clothes-horses’ can increase the moisture levels in the home too, especially if the heating is on. Try to hang washing outdoors whenever you can, as even cold winds will dry things quicker and more effectively while also reducing the humidity in the home.
  • Make sure your damp proof course (DPC) is in good condition. A DPC is a thin layer of waterproof material which is inserted horizontally near the bottom of a building’s structure to prevent damp rising up through building materials. Liquid DPCs can also be injected into the walls of your home by a damp treatment specialist. A defective damp proof course is a major cause of rising damp, so make sure yours are in good condition.
  • Finally, check for broken gutters or downpipes outside to see if they are causing leaks that could be letting water into your home. Increased internal moisture often causes damp which, once it takes hold, can be extremely difficult to deal with.

What Does Damp Proofing Entail?

Most often damp proofing is effected by installing damp proof courses or DPCs, a barrier designed to prevent moisture from penetrating your walls and floors. Other methods include application of a paint-on preparation that seals the surfaces. There are also instances of porous ceramic tubes, 50mm in diameter, being inserted into a wall. The theory is that these tubes will collect the damp and allow it to evaporate, but they can be unsightly and there are often problems in application.

Some of the damp proofing methods employed are extreme and require structural alteration to your house.

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How is the DPC Inserted into the Wall?

There are different methods for installing DPCs. In some cases, the DPC is inserted by cutting into the wall or during rebuilding. This can be effective, but it can also result in structural problems and damage to internal finishes, especially where these are custom or antique.

There are chemical damp proofing course solutions available which are injected into holes drilled into the wall. This method is quite widely used today, but it cannot always be applied in older buildings. The cost of chemical DPCs is around £195/m, which includes the cost of re-plastering the holes through which the mixture is applied.

Damp Proofing Costs

This table details damp proofing costs for dealing with common damp situations. These costs are obtained from survey we conducted across our network of tradesmen.  The costs include everything necessary to carry out the work including labour, material and VAT.

Problem: Ground level is above the existing damp-proof course (DPC)
Solution: It is necessary to excavate the soil to make sure that the ground levels is at at least 15cm bellow DPC.
Work neededTerraced houseSemi-detached houseDetached house
Soil excavation of one wall£200£290£450
Whole house soil excavation£330£540£1,300
Soil excavation and laying new gravel path (one wall)£270£395£585
Soil excavation and laying new gravel path (whole house)£350£820£2,000
Soil excavation and laying concrete paving slabs (one wall)£400£690£1,400
Soil excavation and laying concrete paving slabs (whole house)£760£1,890£4,190
Soil excavation and laying 10cm thick concrete path  (one wall)£430£750£1,190
Soil excavation and laying 10cm thick concrete path  (whole house)£850£2,110£4,040


Problem: Non-existent or damaged DPC
Solution: Create a damp barrier with silicone or insert new DPC
Work neededTerraced houseSemi-detached houseDetached house
Damp proof silicone Injection (one wall)£490£760£2,000
Damp proof silicone injection (whole house)£900£2,100£4,700
Insert new DPC (one wall)£290£425£610
Insert new DPC (whole house)£395£920£2,060

How to Save Money on Damp Proofing

  • Ideally, damp prevention measures should be put in place during the building stages, but this is obviously not an option in existing homes, especially in older and period houses.
  • If you do discover a damp problem in your property, the first step towards ensuring that you are treating the problem correctly would be to determine the actual cause of the damp. Oftentimes an expensive and intrusive solution is recommended when a simple, cheap one would be as effective.
  • If the damp is caused by condensation, it could be a simple matter of improving the ventilation in your home. Opening windows and doors to allow air flow could help significantly. Installation of extractor fans in high moisture areas such as kitchens and bathrooms can also make a big difference. Proper insulation can also go a long way towards preventing condensation in your home.
  • Penetration damp can have many external causes as mentioned above, and simply repairing the root cause can solve the problem and allow the moisture to evaporate. Gutter maintenance and repair should be carried out at least twice a year to ensure that there are no blockages or leaks that can cause overflow into the structure of your house.
  • Roof junctions are often areas where leaks can occur, and resealing these areas can prevent leaks. Replace missing or broken roof tiles before leaks can cause damage to roof timbers. Re-point any mortar that needs it to prevent cracks and holes forming where water can get in.
  • The same principle applies to damp caused by internal spillage. Often removing and repairing the source of the water will solve the damp problem without the need for drastic and expensive measures.
  • Future damp problems can also be prevented by using lime plaster instead of the anti-sulphate or renovating plaster that is normally use. Lime-based plaster allows greater breathability, which aids evaporation and decreases the chances of damp build up.
  • Proper drainage in the ground surrounding the house can also prevent below ground damp, especially in basements and cellars. French drains can be effective for this purpose, but need to be set up properly to avoid compounding the problem.
  • Rising damp is often the most difficult and expensive to fix, as the damp has permeated the walls and floors deeply and can be difficult to fully remove. However, investigations have shown that this damp is actually far less common than popularly believed. Often what is diagnosed as rising damp is only condensation, and can be solved as described above.
  • Make sure that you know exactly what type of damp you are experiencing before embarking on an expensive damp proofing solution.


Who Should Do the Damp Proofing?

If you have investigated your damp problem thoroughly and have found that it is not a simple matter to solve, it is time to call in a damp proofing professional. It is always a good idea to approach more than one company, though.

Investigate and research damp solution companies, and wherever possible obtain references and recommendations from previous customers. Try to get at least three quotes from three different firms. Some companies will make unnecessary recommendations for treatments and solutions that are very pricey. If you find that they all make different recommendations and give very diverse prices, it is a good idea to contact a damp proofing specialists.

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