How to Prevent Damp - A Damp Proofing Guide

Damp problems affect thousands of properties across the United Kingdom every year, leading to unpleasant living conditions and can cause damage to the fabric of the property. Because there are several types of damp that can affect properties differently, the remedial damp proofing required may differ, or in some cases may not be necessary.

If the wrong treatment is carried out because the source of damp has been incorrectly diagnosed, this will not stop the root cause of your issues. This is why it is important to accurately diagnose the type of damp affecting your property, and this can sometimes be done by identifying telltale signs that indicate the source of the problem.

We have put together a guide to help provide information on damp proofing, helping you understand if the problem affecting your property requires remedial treatments. If you require specialist advice from a qualified professional, Rentokil Property Care is here to help. Sometimes it can be complex to understand where the damp problem is coming from, so you may need a professional surveyor who can carry out a damp and timber survey.

Rentokil Property Care have a number of CSRT and CSTDB qualified surveyors who are experts in identifying different types of damp, and will provide you with detailed recommendations for damp proofing, if required.

We are Property Care Association Members and have a number of branches across the United Kingdom, meaning we have qualified and experienced surveyors and technicians local to you. 

Damp proofing is the generic term used to describe the preventative measures taken to stop moisture and protect a building or property from water ingress. There are different types of damp proofing depending on the source of damp, but typically it involves preventing moisture affecting walls, floors and ceilings.

If damp proofing is not carried out, excess damp can lead to structural issues such as the deterioration of plasterwork, mortar and masonry, timber problems associated with fungal decay and woodworm, and even health issues associated with mould growth.

The damp proofing method depends on the type of damp, with treatments differing depending on if it is condensation, rising damp or penetrating damp. The application of below ground waterproofing is also a form of damp proofing. Because the damp proofing required will differ depending on the type of damp, a qualified surveyor should carry out a damp and timber survey in order to determine the source of moisture, and provide recommendations. They will provide you with recommendations on how to prevent the problem, and if required details on remedial damp proofing treatments.

If you are unsure if your property requires damp proofing, a damp and timber survey can provide you with answers from a qualified professional, and provide recommendations for damp proofing - but only if treatments are necessary.

Damp walls are usually caused by penetrating damp, where external moisture is able to penetrate into the wall, rising damp, where moisture is able to rise upwards through capillary action, or through condensation where warm moisture laden air inside the property turns to water droplets on cold surfaces. It is also possible that damp patches can be caused by salt damp, internal plumbing leaks, or faulty appliances.

Penetrating damp is often caused by driving rain or defects to a building, typically missing roof tiles, damaged gutters, defective external renders or cracks in masonry and missing mortar. If damp patches on walls are visible in the same place as a defect externally, this could be causing the problem.

For rising damp most properties are built with a waterproof barrier that prevents moisture rising upwards, known as a damp proof course, or DPC. These are usually pre-installed during the building process. They are usually just above ground level, and if these become damaged or defective, can lead to rising damp. Damp proof courses can be bridged by external cladding, flowerbeds pushed up against the brickwork or through heightened ground levels.

Condensation is the most common cause of damp walls, especially during winter. Condensation will form when there is an excessive amount of moisture in the air which then condenses on cold surfaces. Increased ventilation helps remove this excess moisture, and there are ways to improve the thermal temperature of a wall to prevent them from becoming damp from condensation. These measures will also help prevent mould from forming.

If a damp problem is left untreated it can cause further damage to surfaces, causing plasterwork to degrade and fall away from the wall. Wallpaper will become wet and peel away, while paint can crack and blister. When walls are cold and wet to the touch they lose their thermal efficiency, meaning your property is harder to heat, increasing energy bills.

The biggest cause for concern for damp problems is the structural damage it can cause, whether it's by fungal decay or woodworm. Fungal decay can lead to weakened structural timbers, rotting skirting boards and weak floorboards. Wet rot may be isolated at the source of moisture, while dry rot is able to spread, often causing severe damage to timber across a property.

This is why it is important to deal with a damp problem as soon as you spot the signs, while a damp and timber survey can provide you with a detailed understanding of the source of the problem, and the extent of any damage to timber. Sometimes people are tempted to use specialist paints that are ‘damp proof’ - but if the root cause of the problem is not identified, the problem will return and could cause more costly damage in the future.

Rising damp will only occur when an existing damp proof course (DPC) has been bridged or damaged in some way, or if a building does not have a damp proof course. Without a waterproof barrier to prevent moisture rising upwards through tiny pores inside masonry, rainwater in the ground seeps into the building through a process known as capillary action.

It is important to note that rising damp will only ever affect the ground floor of a building, while symptoms on internal walls include:

• Damp walls that form with a ‘tide mark’ above the skirting board
• Musty smells
• Evidence of salt deposits left on the surface of the wall
• Damaged or rotting skirting boards
• Plaster flaking away and wallpaper peeling off

Penetrating damp is often caused by a combination of building defects, a lack of regular maintenance and periods of bad weather, particularly wind driven rain. If gutters fail, or drains become blocked then water will pool and penetrate into the property, causing damp problems and even fungal decay. External renders can also fail, trapping moisture which can then penetrate into walls. Sometimes penetrating damp is caused by high ground levels, common in rural areas or in properties built on slopes.

Penetrating damp can occur anywhere across a property, meaning damp patches on walls, around windows and ceilings. In order to find the source of damp, you may need to inspect the same spot outside as the problem inside. This can give an indication of what could be causing it.

Condensation problems are the most common damp issues that homes in the United Kingdom face, with as many as one in five properties affected every year.

It is more common in solid wall properties and will often be more noticeable on north facing walls, as these tend to be the coldest points in a property. Condensation will affect properties during winter as ventilation is reduced to keep the heat in, while the moisture produced inside the home is no longer able to escape. Condensation will often form on cold surfaces and in areas of a room where there is a lack of air circulation, typically behind furniture, long curtains, in cupboards or bay windows. 

The first sign is often steamed up windows running with beads of water in the morning, with mould beginning to form around window frames. In severe cases walls will run with water beads, especially cold north facing bedrooms, while mould may begin to form behind headboards of beds, in or behind wardrobes and cupboards.