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What Causes Damp?

Damp and mould are caused by excess moisture. Moisture in buildings can be caused by leaking pipes, rising damp in basements or ground floors, or rain seeping in because of damage to the roof or around window frames. The most common form of damp is condensation, condensation forms when warm moist air touches a cold internal wall or surface. Damp can form quickly in bad weather, especially if there is an issue with the exterior of the building.

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What Causes Damp?

Damp develops in the home when there is too much moisture in the air and no way fro it to escape.  Causes of excess moisture include steam from cooking, drying clothes inside the home and water vapour released into the air when showering and bathing. 

In addition to moisture in the air, problems with the building itself such as leaks in the ceiling or around windows, damaged pipework, and damage to your damp proof course can also lead to damp problems.

The most common factors that allow moisture into a property include poor ventilation, leaking roof, failed damp proof course and plumbing problems such as a leaking washing machine or dishwasher.

Often damp problems in walls are only noticeable when internal damp symptoms become apparent. Such symptoms include black mould growth and crumbling plaster.


Damp can affect any type of home, older buildings 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 building is still existent creating excess moisture in the air. 

Damp problems can be a serious concern in any home, whether you are a home-owner or renter, or living in any style of property. At best it can be a nuisance and make a room feel cold, unwelcoming and unhealthy, and at worst it can indicate structural or weatherproofing issues.


Identifying Damp

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.

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.

Prolonged exposure to high levels of indoor dampness can reduce lung function and cause chronic health problems such as asthma. Those who already suffer from asthma and allergies are more likely to have more severe symptoms when exposed.


Assessing Your Damp Issue

The first task you will have to carry out is to assess the affected wall area to establish how damp it actually is:

Back of hand – Although not the most accurate way to measure damp on your walls it will give you a good idea of how bad the damp actually is. Touch the back of your hand against the damp area and gauge the level of dampness. Now touch the back of your hand against a dry area on the wall and compare the two. 

Damp meter – These are handy little gadgets that feature two prongs on the base and a level indicator on the front. Stick the two prongs into your damp wall surface and leave for a while. The level indicator on the front will then display the percentage of damp within the wall’s surface.

Arrange a free home survey - Your local expert will assess any condensation, damp and mould problems that you may be facing in your property and take readings of the relative humidity levels throughout the property. All our ventilation specialists are highly trained in carrying out home surveys to identify any underlying problems and make recommendations.


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 seek professional advice. 


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. 

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.


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. These issues are arguably one of the most common causes of damp on walls. Condensation forms when warm moist air within a room touches a cold internal wall or surface. This condensation then sits on the internal wall's surface and creates damp patches on the wall. 

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. 


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. 


How to remove mould

Protect yourself from mould spores by wearing goggles, long rubber gloves and a mask that covers your nose and mouth. Open the windows but keep doors closed to prevent spores spreading to other areas of the house.

  • Have a plastic bag ready to take away any soft furnishings, clothes and soft toys that are mouldy. Soft furnishings should be shampooed and clothes professionally dry cleaned.
  • Fill a bucket with water and some mild detergent, such as washing-up liquid or a soap used for hand-washing clothes.
  • Use a rag dipped in the soapy water to carefully wipe the mould off the wall. Be careful not to brush it, as this can release mould spores.
  • When you've finished, use a dry rag to remove the moisture from the wall.
  • Afterwards, put the rags in a plastic bag and throw them away.
  • All the surfaces in the room should be thoroughly cleaned by either wet wiping or vacuuming to remove any spores.

Repairing Damage Caused by Damp

Once you have located the source of the damp and ensured the root issue is resolved you'll then be left with the aftermath caused by the issue. We've previously discussed how to remove mould a common consequence of a damp issue but there can be other afflictions that need addressing. 

Once the mould covered area has been cleaned and throughly dried it can be treated with a damp seal and then re-painted. If the mould affected an area in the bathroom it maybe best to remove any grouting in order to ensure all mould has been removed. Once you are sure you have cleaned and again dried the area you can use a sealant gun and simply re-grout. Remember to let the grouting fully dry before using the bathroom again otherwise it will not be protected. 


How to Treat Damp Walls Internally

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.


Need help with condensation, mould or damp problems?

One of our local experts will contact you to learn more about your problems, offer free expert advice and make recommendations for a permanent solution.

During the free survey we will

  • check Assess any condensation, damp or mould problems in your property
  • check Take readings of the relative humidity levels
  • check Identify any underlying problems and make recommendations for a permanent solution

Arrange a FREE Home Survey now