Damp proofing a house

Damp Walls

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How to Treat Damp Walls

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

Our guide to dampness in the home will help you to identify the cause of your damp walls by explaining the causes and 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 book a survey or call us on 0800 0121 437 to discuss your damp issues with a specialist.

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What Causes Damp?

Dampness and specifically damp stains on walls are most commonly caused by leaks inside the home, rising damp or condensation problems.

Many properties built pre the 1940s were built without protective treatments such as damp proof course (DPC) or damp proof membrane (DPM) making them especially prone to dampness.

Unfortunately, a damp proof course can also be damaged and cracked by building subsidence meaning damp can also affect newer buildings. Other causes such as condensation and leaking or blocked downpipes and gutters will also cause damp patches on the wall of the property.

Damp on walls

Rising Damp on Walls

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.

The most common cause of rising damp in walls is the failure of the existing damp proof course (DPC).

Signs 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

What Are The Symptoms of Penetrating Damp

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 Penetrating Damp on Walls

  • 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

Treating Condensation Symptoms on walls

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. More noticeable in the colder winter months, 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.

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

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

How to Repair Damp Walls

The first step to treating a damp problem is understanding exactly what you are dealing with. Damp problems are often misdiagnosed by people with insufficient training and this will inevitably result in incorrect treatment being applied.

Rentokil Property Care would always recommend getting the opinion of a CSRT qualified surveyor from a rated and approved company before spending your hard-earned money on any form of DPC treatment.

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.

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.

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.

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.

External Damp Walls

The most promintent 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 masonary 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.

Damp Cavity Wall Insulation

Cavity wall insulation is not a cause of damp on its own, which is good news for the millions of homes in the UK that have it installed. However, cracks in brickwork, plasterwork and other building materials and subsequent water ingress can result in the insulation becoming wet and contributing towards penetrating damp problems.

If you have cavity wall insulation and have noticed damp walls on the inside of your property, then it is worthwhile having the exterior of your property surveyed.

Why Damp Patches on Walls Are a Problem

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

Damp Treatment and Wall Repair Specialists

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 on 0800 0121 437 or click the button below to book a damp survey today.

Book a Survey Online for a £25 Discount