Search Results

What Causes Damp?

Damp occurs when there is excess unwanted moisture in the air but can mean serious issues for your home. Damp can be caused by poor maintenance, ill fitting building materials and poor ventilation. Damp areas can be found on walls, doors, floors, around windows and pipe-work in any home. The most common form of damp is condensation, condensation forms when warm moist air touches a cold internal wall or surface.

Damp and mould on internal wall

Damp occurs when there is excess unwanted moisture in the air that has no way of escaping. Excess moisture can be caused by steam when cooking, drying clothes inside the home and perspiration caused through showering and bathing. This excess moisture can also be as a result of damage to a building such as leaking pipes, rain seeping in through windows or ill-fitted washing machines.

Damp can affect any type of home, older homes for example were designed to be naturally 'breathable' and allow damp air to evaporate out of the house. The removal of existing chimneys and energy-saving measures, such as fitting air-tight double glazing, can reduce ventilation in old homes, and create a condensation problem. Whereas in newer homes, often the properties have not been left to dry and water used when builiding is still existent creating excess moisture in the air. 

However not all damp is the same and each damp requires it's own treatment. In this article we explain the different types of damp, the causes of damp and how you can prevent it.

Rising damp on wall

Damp problems tend to be at their worse during the winter however if left unresolved damp can be an issue all year round. You can spot the signs of damp on walls and ceilings, your walls may feel cold and look wet whilst ceilings will look stained and discoloured.  

Damp patches on walls are generally the result of penetrating damp, where water from outside gets into the brickwork through gaps and cracks. If the patches are clustered around windows and doors, then it's likely that rain is getting in through gaps around the frames. 

Basically the affected areas are colder than the rest of the wall creating a dew-point on the walls where the moisture from the ambient air within your property condenses more readily than the higher temperature surroundings. If left untreated damp can have an affect on your health causing things like; runny nose, throat irritation, coughing or wheezing, eye irritation, or, in some cases, skin irritation.

Damp can also be a costly affair, not only could you potentially have to pay a professional to resolve the issue you may find you've wasted money either trying to fix it yourself with countless products or racked up high energy bills trying to keep the damp down.


Rising Damp

Rising damp only happens at ground floor levels as the moisture drawn up the wall comes from the soil in the ground. It is often confused with damp caused by condensation. 

Rising damp signs include; decaying skirting boards, crumbling plaster and tide marks on walls. You may even notice some external damage such as crumbling mortar and white salt stains.

Many often mistake this damp and seek out the wrong treatment which can be costly but of course ineffective. As this type of damp is easy to misdiagnose, it is advisable to get expert advice. The recommended treatment for rising damp is to avoid attempting to resolve yourself. 

Rising damp on wall

Penetrating Damp

Penetrating damp is caused by water entering a property through walls, floors and ceilings, causing external construction damage to guttering, rendering and wall joints.

Common causes of penetrating damp are; leaking walls, air gaps, burst gutters and pipes, porous bricks, cavity wall problems and/or poor cavity insulation. It could be the result of a problem with plumbing such as an incorrectly set up washing machine.

Damage to plastering, decaying timber and watermarks on masonry all indicate a potential problem with penetrating damp. You may even notice penetrating damp on your chimney caused by rain, condensation or even salt contamination.

Penetrating damp can end up being a costly problem to fix so prevention is definitely the best method. Keep an eye out for any leaks and make sure window frames are air tight.

Getting rid of penetrating damp

Condensation Damp

Condensation is arguably the most common form of dampness with 1 in 5 homes in the UK affected. It's caused by an excess of moisture in the air that reacts with a cold surface such as a wall.

Tell tale signs of condensation include streaming windows and walls, deterioration in decoration such as discolouring of window panes and eventually the growth of black mould.

There are ways you can help to reduce condensation in your home such as; wiping down cold surfaces and keeping kitchen and bathroom doors closed. You can find more tips on reducing condensation here. 

EnviroVent have specialised in curing condensation problems in thousands of homes across the UK for the past 30 years.

Condensation causing water droplets on window

Interstitial Condensation

Interstitial condensation creates structural damping that occurs when moist air penetrates inside the hidden space within an enclosed wall, roof or floor cavity structure. When that moisture laden air reaches a layer inside the interstitial structure that is at dew point temperature, it will condense into liquid water.

The moisture laden air can penetrate into hidden interstitial wall cavity from the exterior in warm outdoor temperatures and inside the building during cold outdoor temperatures. 

The resulting structural damage, along with mould and bacteria growth may occur without any visible surface indications until significant damage or extensive mould and bacteria growth has occurred. 


Treating Damp and Mould

There is no one cure for mould due to the variety and level of severity the mould is and some require professional removal. For example if you have a problem with toxic mould, then you need to seek professional treatment in order to ensure that your home is a safe environment for you and your family. If you find a colony of toxic mould, it is very important that you do not disturb it. Touching or moving the mould can cause an enormous amount of harmful spores to be released in the air, to the detriment of you and the people you share your home with.

For other, more common strains of mould, there is a wide variety of mould treatments available that clean the mould, which are easy to use on your own. 
A simple solution for removing non-toxic mould from your home is to clean it using a non-toxic, mould cleaning solution. When the mould has been eradicated, it is important to dry the surface thoroughly, in order to prevent the mould from returning.


Whatever type of damp your home is suffering with you don't want a damp house at all. Once you've resolved any existing damp issues you want to ensure that the damp doesn't reoccur. The best way to keep your home damp free is to keep the moisture levels in the air to a minimum through good ventilation. 

Preventing damp starts with the small stuff like opening windows to allow air to circulate, avoiding drying clothes inside as much as possible and using pan lids when cooking. However prevention also means ensuring your windows are properly sealed and fixing any leaks asap. You can also paint your walls using a damp sealant but first you need to ensure the cavity in the walls is properly insulated.


Additionally an effective extractor fan is paramount for ensuring good ventilation in your home. The Cyclone 7 is a major advancement in extractor fan technology, designed to deliver high performance in controlling humidity levels in kitchens, bathrooms and utility rooms using the lowest energy consumption.

Covered by an unrivalled 7 year warranty as standard, the Cyclone 7 offers the highest quality and the lowest maintenance requirements for utmost peace of mind, saving time, money and hassle.

Other causes of damp

A previous damp treatment has not worked -

If you have previously had an injected damp-proof course in order to rectify a rising damp problem in your property it may have not been fully resolved. If when the solvent was injected into the wall it was still damp, the solvent would have never completely dried out and the chemicals never cure; the process will just saturate the wall with even more water.

Damp plaster

Damp plaster can retain a residue of salts deposited by the water. This damp can often reappear because these salts absorb moisture from the atmosphere of the room.

Cement rendering

Cement rendering is used on exterior walls, if the cement render is very badly cracked it will trap water, but the water cannot escape because the render is impermeable. This then encourages condensation to form as moisture from inside the house and results in clay lump walls collapsing.

Replaced floors

Excess moisture can rise from below and up through the floor and into the properties air which lets it dissipate leaving no build up. If a floor is replaced with a modern solid design that prevents this from happening, moisture is forced to travel under the floor and into the walls to escape. This will increase the moisture in the walls and potentially make those walls damp.

Modern/ excessive use of plaster

In the worst of usage this will also stop moisture from circulating, causing a build up and ultimately damp.

Poorly laid patios

Patios are often laid too high, causing bridging of DPSc or rain 
splashing on hard surfaces saturating the walls, causing a build up of excess moisture which then causing damp and mould to emerge. 

Cement Mortar

Cement based mortar is the worst for excess moisture, it stops moisture escaping into the air but also encourages water into the wall. Cement based mortars also force natural salts to crystallise in brickwork, causing the bricks to break up.

Damp Proofing 

There are many damp proofing options available and it can be difficult to know which is best for your property, if in doubt it is always best to consult a professional. 

Some of the most common damp proofing methods are;

Damp proof membranes - they are made from High Density Polyethylene (HDPE) or Polypropylene and are impervious to moisture and moisture vapour. Damp Proof Membranes can be applied internally with little or no surface preparation. However, it is very important to install the membrane correctly to prevent expensive water ingress in the future. They should be used in conjunction with a Damp Proof Course in outer walls to create a continuous barrier to water.

Damp proof paint - Damp proof paint is a non-toxic product (free from solvents and plasticizer) that can be applied to surfaces to act as a barrier to moisture. Damp proof paint is most frequently used on walls under a render as a waterproof layer when damp proofing walls, to cover up damp stains on painted areas as well as under tiled areas as a secondary protection for wet areas such as bathrooms. 

Cementitious tanking - Tanking is a form of damp proofing that blocks water ingress from entering a structure by creating a barrier. Cementitious tanking is a cement-based coating, consisting of Portland Cements, blended with aggregates and chemical modifiers. It is microporous, meaning that it is fully breathable. It is applied to the internal face of the structure. It can be used on concrete, stonework, brickwork and blockwork. If areas of the property are suffering from more severe water ingress then you should use cementitious tanking as a waterproof barrier rather than damp proof paint. It is also for those situations where the installation of a full damp proof membrane is not necessary.

Renovating Plaster - it is a pre-mixed, lightweight backing plaster designed to control dampness passing through walls of older properties. Renovating plaster contains perlite aggregate, which controls dampness that passes through the walls of old properties. Renovating Plaster can be used for plastering most traditional background surfaces during renovation work. It can also be applied shortly after the installation of a new damp proof course system or used in conjunction with a basement tanking systems. 

Liquid Epoxy Damp Proof Membranes - The solvent-free membrane contains certain chemicals that allow it to cure rapidly, reducing the passage of water vapour and acting as a barrier against residual moisture. A liquid Epoxy Damp Proof Membrane can be used as an above ground damp proof membrane on concrete floors and concrete screeds. It is often used before the installation of a new floor covering. The surface you want to damp proof must be of sufficient quality.

Anti-mould Paint - this works by bringing together modern paint technology with highly effective biocides. The anti-mould biocide is combined throughout the paint film, which has been scientifically engineered for water resistance and durability, imparting toughness and elasticity. Anti-mould paint is ideal for walls and ceilings in homes as well as a wide range of public and commercial buildings. It is fully washable and resistant to the effects of condensation when the coating is fully dried out.

With all of these methods however they will not work unless the underlying damp issues have been identified, treated and resolved. The best way to then ensure no damp arises is with adequate ventilation. 

8 Ways to reduce damp

1) Try to keep the inside temperature reasonably constant.

2) Avoid drying clothes indoors.

3) Do not dry clothes over any radiators.

4) Ensure tumble driers are properly vented or the condensate is regularly emptied.

5) Keep furniture away from walls.

6) Do not turn off or disable extractor fans.

7) Ensure extractor fans are well maintained and offer adequate airflow.

8) Bath your Pets and wash their bedding regularly

Arrange a Survey

We have local experts across the UK who can offer free advice and recommend the right products for your property.

Request a Brochure

Want to find out more about our products and service? Request a free brochure and we'll send one out in the post to you.

Find a Local Expert

We have local ventilation specialists throughout the United Kingdom who are able to help you with your problems.