Penetrating Damp FAQ

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What is penetrating damp?

Penetrating damp, otherwise known as lateral damp, is the development of moisture through the walls and roof or below ground area of a building. Like most cases of damp, if left untreated it can cause problems for the structure and significant damage to the fabric of your home.

If a penetrating damp problem is left untreated it can cause deterioration to the fabric of your property including damage to walls, floors, ceilings and can even cause rot to timbers. Unlike rising damp penetrating damp, can happen at any level of your property. Penetrating damp can affect any age of property. Older properties which have had a lack of maintenance are more at risk of penetrating damp problems causing deterioration to the building fabric. This is not to say that modern buildings do not suffer from penetrating damp. In some cases, due to defective workmanship or design, modern buildings can also suffer from penetrating damp.

The damp can form in isolated patches or can affect full wall areas. The damp can get worse after heavy periods of rain. Living in the UK, your home is at risk of rainwater penetration, however penetrating damp most often affects areas that are exposed to severe weather conditions or there is a defect in the property like missing roof tiles or defective render, gutters and downpipes.

The first sign of penetrating damp that you may see could be a watermark that appears on your decoration. With penetrating damp, damp patches will grow as the water continues to enter. Mould could begin to grow on the damp wall as condensation could occur on the existing cold damp surfaces.

How to Identify Penetrating Damp?

Penetrating damp is unsightly and can ultimately end up in costly structural timber rot repairs. To this end, you need to know the signs of penetrating damp, so you can deal with it as quickly as possible. Some of the signs of penetrating damp are:

  • Damaged/misshapen plaster. Plaster will blister, show signs of disintegration, or signs of “salting”. Salting is water bringing natural salts found in the wall to the surface and will result in a fluff-like residue being found on the surface of the plaster or decoration.
  • Localised dampness. There may be localised patches of damp in seemingly random locations that won’t dry out, no matter what technique you use.
  • Mould growth. If there is visible mould growth or the accompanying musty smell, this may be an indicator of the presence of penetrating damp in conjunction with condensation and mould growth.
  • Damaged internal decoration. Damp, discoloured patches on internal decorations and walls or discoloured tidemarks in line with external ground level or external envelope defects.
  • Rotting floor timbers or skirting boards. If these show signs of wet or dry rot decay, penetrating damp is a very real possibility.

What are the common causes of penetrating damp?

Penetrating damp usually occurs if you own or live in a property that has building defects e.g. Defective roof coverings, a leaking rainwater pipe or faulty pointing to doors and windows. Some of the most common cases of penetrating damp come from defective masonry, render and pointing. Brickwork, pointing and render can deteriorate with age, frost or physical damage. This is one of the main reasons why older buildings are affected by penetrated damp as their building materials may be deteriorating over time or have been affected by storm damage and therefore not able to do the job they were designed to do.

If the structure of a building is failing, then your property may be allowing moisture to soak completely through the wall. This is a sign that your property waterproofing system is failing.
You can also find penetrating damp where the external ground levels are higher than the internal floors or damp-proof membranes to concrete ground floors or solums below your ground floor are defective. You may also find damp in areas below ground level like the basement or cellars of your home.

Proper and accurate diagnosis of the damp problem is important so that the appropriate remedial repair is specified. Each of our customers receives a detailed report once the survey has been completed by our surveyor.

What areas can get affected by penetrating damp?

Some common places to check for potential penetrating damp include:

  • The roof. Missing tiles, the pointing, roof ridge tiles (the shaped tiles at the very top of the roof), and flashing (the point at which a roof meets the wall or a chimney) are all key areas to inspect for causes of penetrating damp on a roof. If any of these are missing or loose, they’ll need maintenance to stop or prevent penetrating damp.
  • Window frames. These must be checked to see if there are any gaps or cracks around the frame. If there are, these should be filled with a flexible frame sealant. Also, make sure to check that there is a “drip groove” – a groove intended to stop water running onto the wall – under the window sill. If one does exist, make sure it hasn’t been filled in, and if it doesn’t, a good solution is to add a hardwood strip around 35mm from the front edge.
  • Door frames. Any cracks that exist around door frames will need repairing. In addition to this, if your external door doesn’t have a weather bar – a board that sits at the bottom of the door and protects from excessive rain – it may be time to think about fitting one.
  • External walls. Cracks in external masonry or missing pieces of mortar (the filling – cement or otherwise – between bricks) can cause penetrating damp. If this happens to be the case, make sure these are repaired with an appropriate filling material. The masonry or external render can become porous or crack with the render breaking away from the masonry allowing rainwater to get in. Get in touch with our team to find out more about what would be best for your home.
  • External rainwater gutters, downpipes and drains. Check the status of your external rainwater goods. If they are leaking, they could cause penetrating damp to your property. Drains should be checked to ensure that they are not blocked and causing water to back up into the building.

It may also be that old bricks or chimney heads have become damaged and porous, allowing water access to your home. These must either be repaired or painted with an exterior silicone water-repellent or lime wash that will still allow your walls to breathe. This also doubles as a good preventative measure; better to nip the problem in the bud now at a cheaper cost than deal with a far more expensive fix further down the line.

How to dry penetrating damp?

At Richardson and Starling, we have an experienced team that can help you eradicate the damp problem in your property. When our surveyors visit your property, firstly they will carry out a survey to determine the cause of the problem.

We use traditional building techniques and new products and repair systems which will keep your property dry. We can apply a physical membrane or chemical water repellent to stop the problem from returning if this is appropriate.

In some severe penetrating damp problems where the stonework and mortar has become so porous that the damp has soaked through all the external walls into the living space of the property we have used a specialist cavity membrane fitted to the outside of the external walls with a traditional render applied. This membrane system waterproofs the outside of the property and lets the original stone breath.

Once the damp problem has been identified and resolved it will take some time for the fabric to dry out and consideration will be given to using specialised drying equipment if this is appropriate to the property.

Can cavity wall insulation cause dampness?

Cavity wall insulation is extremely popular nowadays as it improves the heat retention of the home.

In the UK, most houses built after 1920 were built with a cavity wall construction to their external walls. The cavity wall is made up of an inner wall built to surround the inside of the building and an outer wall that could be covered with render, paint or pebbledash. A gap or cavity is left between the two walls to protect the inside walls from penetrating damp.
In recent years, dampness has been triggered in homes that have had cavity wall insulation installed. When penetrating damp has got through the outside wall the damp has then been transmitted through the cavity wall insulation and affects the internal wall of the property.

Cavity wall insulation has failed many homeowners and if this is a problem then the insulation may require to be removed.

Can penetrating damp cause health issues?

In most cases, if treated quickly enough, you shouldn’t be too concerned about the effects of damp. The recognisable smell and look of damp may be unpleasant, however, the health risks are minimal if dealt with quickly. It is not good for people to live in damp conditions for an extended time and the problem needs to be resolved.

If you are living or working in a property that has extreme damp issues, this may lead to an outbreak of black mould as condensation could form on the cold damp wall areas within your property.

If you are concerned about the growth of black mould or damp within your property contact us today for more information.

Does penetrating damp cause mould? What is damp mould?

Penetrating damp usually occurs on external walls. As mentioned, penetrating damp mainly appears because of a fault outside the home and could be more noticeable after a period of rainfall. If you are looking to identify a patch of penetrated damp, the affected area could look and feel damp to the touch or you could see running water.

Mould growth occurs on condensation and as the penetrating damp walls become cold then condensation could form on this surface and this could cause mould growth.

Would you recommend any DIY penetrating damp solutions?

At Richardson and Starling, we have over 80 years’ experience working in property care, therefore we know the importance of accurate diagnosis. The mistake that many homeowners make is self-diagnosing and self-treatment of the area of damp affecting their property. If treatment is done on a wrong diagnosis of the damp problem this will not only cost more money and time, but the damage could get worse.

Self-treatment may not be successful as it is easy to misdiagnose the form of damp affecting your property which will not solve your problem and continue to affect your property investment. You may have one or more damp issues affecting the property that will require the appropriate treatment to eliminate all the damp issues. Our property care surveyors will be able to diagnose and treat the problem by using our many different repair systems to suit your property problem.

At Richardson and Starling, we have qualified and experienced surveyors that can visit your property to carry out a professional assessment of the damp conditions. After the survey, our surveyor will advise you on how to proceed to effectively treat the damp within your home.

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