Penetrating damp signs on exterior wall of house

What is Penetrating Damp and How To Treat It?

What is Penetrating Damp?

Penetrating damp is the process of moisture being built up horizontally through the external walls of the building into the property.

Often misdiagnosed as rising damp, penetrating damp can lead to further, more serious issues such as wood rot, increased heat loss, frost damage into masonry and unsightly water damage on both the outside and inside of a property.

Penetrating damp can affect any type of property however, old properties that have had no or little property maintenance are more prone to water penetration. Modern properties can also suffer from penetrating dampness if the design and workmanship of the property have defected then these can suffer from having damp in walls.

What are the Causes of Penetrating Damp?

Penetrating damp is essentially water that has found its way through the fabric of a structure, usually because of an external defect. Defects come in various guises such as damaged rainwater goods (for example blocked gutters) defective pointing, porous masonry, faulty roof fabric or cracked and broken render.

When it rains, rainwater usually evaporates out of the brick / stone work. However, in certain circumstances, such as periods of heavy rainfall or when the property suffers from an external defect (as mentioned above), the moisture fails to evaporate and is allowed to pass through to the inner surface.

For further information check out the causes of penetrating damp page.

Did You Know?

“One of the main causes of penetrating damp is the failure of a cast iron soil and rainwater pipes. This is often due to the rusting around the back of the pipe, due to the back being inaccessible it often proves difficult to paint and maintain the pipework.

This is can be a nightmare for properties as cast iron needs to be painted thoroughly to prevent rust from forming. Once rust occurs, a penetrating damp problem is not far behind.”

Penetrating damp on walls outside a home

How To Identify Penetrating Damp?

Fortunately, there are several indicators which make identifying penetrating damp relatively easily. In particular you should look out for:

  • A presence of a damp musty smell
  • Damage to internal walls (skirting boards) or external (roofing)
  • Patchy black mould appearing internally on walls
  • Watermarks that may appear on the masonry
  • Damaged timber as a result of the wood being saturated by damp (which could possibly have the potential of providing the ideal conditions for a wood rot fungus to germinate)

Is Cavity Wall Insulation a Cause of Penetrating damp?

Cavity wall insulation is a popular method of improving the heat retention in your property however, there is a risk that it can also cause penetrating damp. The chances of cavity wall insulation causing penetrating damp are quite small but, it is something you should be aware of. Damp can penetrate the property due to the following factors:

• Home is not in a sheltered position e.g. not covered by buildings or trees
• The external walls are poorly constructed or have been poorly maintained e.g. cracks in the brickwork
• The property is exposed to high intensity winds e.g. properties located on the west coast of the UK.

If the cavity is fully insulated, then there is an increased chance of penetrating damp. This is due to moisture bridging the cavity from the insulation installed which will then penetrate through the inner walls of the house.

Can Penetrating Damp Cause Health Risks?

If the penetrating damp problem is sorted in an efficient amount of time, then you should not worry about the health effects of penetrating damp. As described earlier the main signs of penetrating damp are a musty smell and stains on the walls which, although they look unpleasant, are not a health risk.

Living with damp conditions is not ideal and damp problems should be sorted out as soon as possible. If you are suffering from severe penetrating damp problems then this can also lead to condensation issues occurring, with black mould being one of the symptoms.

Is Penetrating Damp Covered By Home Insurance?

In a majority of cases, insurance companies will not cover penetrating damp. If the property defect has been caused by property maintenance then this is generally not covered by home insurance. This is due to the fact it is the responsibility of the property owner to keep the building maintained. If the roof has become damaged from wear and tear over time, then maintenance will need to be paid by the property owner. A definable event (which is classed as storm or fire) would allow the homeowner to make a claim to the insurance company.

Surveyor inspecting outside wall of property

How To Treat Penetrating Damp?

The most important step in penetrating damp treatment is establishing and rectifying the source of moisture/ water ingress. It is more than likely that the cause of penetrating damp is down to property issues. There are on average five potential points of water ingress that can affect a property - even in new build properties.

  • Defective pointing
  • Porous brickwork
  • Cracks in render
  • Defective rainwater disposal goods

All of these areas must be kept in tip-top condition and any issues identified and problems rectified to prevent the masonry from becoming saturated.

Damp Proofing with a Karsten Tube

Identifying if Masonry is Porous

When dealing with an issue such as penetrating damp it is best to leave it in the hands of the specialists. Firstly, your Timberwise surveyor will need to identify if your property is susceptible to dampness. Our trained surveyors can then perform a water-absorbancy test on the outside of your property. This simple test will give a clear indication of how porous the brickwork/stonework is. Our surveyors will then share their findings with you.

Weathertek Masonry Protection


Once evidence of penetrating damp has been identified, a masonry protection treatment can be applied to prevent further moisture from seeping into the property. WeatherTek is a highly advanced masonry protection treatment which penetrates deeply into the masonry before curing to form a breathable, colourless, water¬ repellent barrier.

Weathertek is designed as a protective and preventative maintenance product that is designed both for homeowners and commercial property owners to protect property from penetrating damp.

WeatherTek can be applied on various building materials such as brick, stone, and concrete. Not only can WeatherTek help protect your property against penetrating damp but it also has insulating qualities improving the thermal performance of your walls by up to 29%, therefore, helping you reduce your energy bills. To find out more about WeatherTek and how it can help your home, click the button below.

Find Out More

DIY Tips for Treating Penetrating Damp

There are ways of sorting the problem by yourself and there are some DIY tips that can help stop penetrating damp from causing damage to your property. The key to getting rid of the penetrating damp issue is to identify the source of the problem.

As previously explained, penetrating damp is caused by damage to the external areas of the building. Below are the most common external defects and how using DIY can resolve the problem:

  • Roof Damage- If you have the knowledge and expertise then the cracked or missing tiles will need to be replaced
  • Damaged guttering and pipes- This is the most common cause of penetrating damp problems. It is a simple fix that can be carried out by yourself. Simply unblock the gutters and pipes or if there is any damage then it will need to be repaired or replaced.
  • Cracks in the Render- When the render has become damaged then this will allow water to pass through. These cracks will need to be patched using a sealant or a new render.
  • Damaged Windows- If the windows have become damaged over time then these will need to be replaced.
  • Porous bricks- It is normal for bricks to become damaged over a long period of time and prolonged exposure to the elements. It is important that when the bricks become porous that they are replaced as these will allow moisture to penetrate through the walls. Using a penetrating damp solution called WeatherTek will help damp proof and protect the brickwork.

A common mistake from property owners is that they try to provide self-diagnosis and treatment for the damp problem. This can often lead to misdiagnosis and the wrong treatment being carried out which not only does it cost a lot of money to fix the problem but will also cause further damage to the building. It is possible that the property may be being affected by more than one damp issue so the appropriate treatment will be needed to get rid of all of the damp problems.

Having a fully qualified damp surveyor to inspect the property will be able to diagnose and treat the problem, from a range of solutions we offer, to suit the needs of your particular property care problem.

How is a Penetrating Damp Survey Carried Out?

It is important to have a specialist to provide a damp survey on your property for any penetrating damp issues you may have. Timberwise has surveyors who are fully qualified by the Property Care Association. Our surveyors are CRST(Certified Surveyor in Remedial Treatment) qualified meaning they are highly trained in providing solutions to all forms of damp issues that could be affecting your property.

Once the damp inspection has been carried out by the surveyor they will provide a report on all the damp problems that were found during the survey. This will detail the causes of the issue and the treatments that are needed to rectify the penetrating damp problem.

Contact our Penetrating Damp Specialists

It is important that penetrating damp is identified as soon as possible to ensure that the property structurally isn’t severally damaged, call our penetrating damp specialists today on 0800 288 8660 to receive the right penetrating damp solutions or click the link below to arrange a survey online.

Alternatively, you can visit our damp proofing page for more information on what types of treatments can be used to get rid of dampness. Timberwise has over 5 decades of experience in identifying and providing treatments to damp using techniques.