Damp proofing a house

Damp Walls

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Damp Walls in the House

Symptoms of damp appearing on walls are usually a sign that there is a fault or crack somewhere in the internal or external wall of your home. Alternatively, you may have a problem with high levels of humidity inside the home.

Our guide to identifying and treating damp walls in the home will help you to understand the causes of damp walls and explain how to treat signs of rising damp, penetrating damp and condensation. If you feel your property is suffering from wet walls we are here to help. Get in touch with our damp proofing team today by clicking the button below to discuss your damp issues with a specialist.

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Damp on walls

What Causes Damp Walls in Houses

  • Leaks inside the home or cracks allowing water ingress from the outside
  • A broken damp proof course causing rising damp problems
  • Excessive condensation leading to humidity settling on walls and turning mouldy
  • DPC or damp proof membrane (DPM) damaged and cracked by building subsidence

What Causes Rising Damp on Walls?

The most common cause of rising damp in walls is the failure of the existing damp proof course (DPC). A damp proof course is a barrier installed at the lower level of the wall to prevent water ingress from below ground level. If a damp proof course is not in place, there is nothing to prevent moisture from the ground travelling up through the walls through capillary action.

What Causes Penetrating Damp on Walls

Penetrating damp can be caused by a number of factors but it tends to occur in properties with maintenance issues after periods of heavy rainfall. Maintenance issues can include defects such as overflowing or damaged gutters and pipes. Other common causes of penetrating damp are defective masonry, render and pointing. This allows water to seep through gaps and cracks in the external wall, and potentially leaving moisture patches and damaged wallpaper on the internal wall.

What Causes Condensation on Walls

Condensation on walls is caused when hot humid air cannot escape effectively through traditional ventilation and settles as moisture on cold surfaces like windows and walls. Signs of condensation tend to appear in the form of black mould spots on paintwork, wallpaper and near window frames. Condensation is prevalent in kitchens and bathrooms where excess moisture is created and tends to occur in autumn and winter when people stop opening their windows.

Symptoms of Rising Damp on Walls

  • Tide marks that appear halfway up the wall
  • Rotting or decaying timber along the affected wall e.g skirting or floorboards
  • White salt residue on the wall

Moisture rising from below the ground level of a property and into the masonry walls can be identified by a distinctive tide mark stain. As moisture absorbed from the ground penetrates the internal brickwork, wallpaper and plaster can become damaged and white hygroscopic salt deposits can appear. The skirting board can also start to decay.

Damp Penetrating Through External Wall

  • Damage to internal decoration
  • Damp staining that appears to grow in size when coming into contact with moisture
  • Localised damp patches
  • Damaged plaster and brickwork

Penetrating Damp occurs when a continuous source of moisture penetrates the wall of the property, either externally e.g from rain penetration through the render or pebbledash or from within e.g a burst pipe or leak.

Signs of penetrating damp will vary from case to case as they can manifest in different ways depending on the source of the moisture. Penetrating damp from soaked wall insulation will look different from ingress caused by broken guttering for example, and this makes it difficult to diagnose the correct treatment programme.

To treat effectively, the moisture source must be located and fixed or the excess moisture will continue to damage the walls.

Signs of Condensation on the Walls

  • Cold walls that are wet to the touch
  • Black mould appearing on window sills and walls
  • Peeling wallpaper or cracked paint from excessive moisture

Condensation is often dismissed as a less serious form of dampness, but it can eventually lead to damaged walls and mould growth in seriously affected areas.

Condensation is common in new builds where more effort has been made to trap heat that easily escaped in old buildings.

repairing a damp wall

How to Fix Damp Walls

The next section of our guide will outline how to fix damp problems in the house on both internal and external walls.  We will break this down into three sections that explain how to solve each of the main causes of damp walls.

We recommend getting the opinion of a CSRT qualified surveyor before spending your hard-earned money on any form of DPC treatment.

Damp Treatment on Internal Walls

If a new damp course has to be installed due to hygroscopic salts, or if the damp patches on your internal wall are severe enough, then you will likely need to replaster the affected areas before you can redecorate the wall.

Our experts recommend using salt retardant plaster so that you can paint or wallpaper the wall with peace of mind knowing that the active additive will resist any residual salts while enabling the wall to breathe and allow the passage of water vapour.

Treating Rising damp problems - Installing a remedial damp proof course using water-repellent damp proofing cream, sometimes called a chemical DPC, is the most common and cost-effective way to prevent water from rising into your ground floor walls. Our damp proof cream injection solutions are guaranteed for 20 years, and after replastering the injection sites are completely invisible.

Repairing Penetrating damp - Once you have identified the building fault that is allowing the water ingress and repaired it, then you may have to deal with related issues like wet or dry rot before they have the chance to take hold.

Removing Condensation and mould on walls - If you have tried to ventilate affected rooms without success then you may require a mechanical ventilation unit to clear out rooms with high humidity levels, mould and persistent, stubborn condensation problems.

External Damp Walls

The most prominent damp problem on external walls is penetrating damp. This type of damp wall is usually caused by heavy rain and faulty guttering or downpipes. Penetrating damp will show as stains on the brickwork and masonry and moss or other plants growing on the exterior of the building.

Rising damp will often show on exterior damp walls too. Rising damp will create tidemarks on the external damp wall in a similar manner to the staining it will cause on the inside. You may also be able to see salts that have been present either in groundwater and moss growth on exterior walls suffering from rising damp.

How to Identify Damp on Walls

Damp walls need to be fixed or treated at the earliest opportunity otherwise you risk turning your home into a damp and unpleasant environment suffering from problems like:

  • An unpleasant musty smell and odour
  • Discoloured “brown” patches on walls and ceilings
  • Peeling wallpaper, blistering paint and flaking plaster
  • Condensation on windows and walls
  • Black mould
  • Walls that feel cold or damp to touch
  • Rising damp patches that start at the base of the ground floor wall
  • White salt marks on walls
  • Rotting timber skirting and window frames

How to Stop Walls Getting Damp

Prevention is always better than the cure, so before any treatment is required you can take our help and advice offered in our damp guide on how to prevent damp appearing in your home in the first place. Essentially the main things to consider in order to avoid damp patches and stains appearing on the walls of your house are:

  • Ensure there is adequate ventilation in all rooms
  • Check downpipes and gutters
  • Dry clothes outside or use dehumidifier - not indoors on radiators if possible
  • Ensure insulation fitted properly
  • Cast an eye over potential building faults, cracks or blocked air vents

Damp Wall Specialists Near You

The damp proofing professionals at Rentokil Property Care have the qualifications, training and experience to correctly diagnose your damp problem and develop an effective solution for damp proofing your walls.

You can contact our expert team at Rentokil Property Care today by clicking the button below to book a damp survey today.

Book a Survey Online for a £25 Discount