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Guest Post: How to Identify, Repair and Treat Damp at Home

Are you struggling with damp, and looking for ways to fix the problem?

Damp is inevitable, especially in old houses where damp proof measures may have failed or if routine building maintenance has not been kept up. It can cause serious damage to the fabric of a building if left untreated. Although the most common form of dampness in homes generally occurs during the winter months, due to high levels of humidity causing condensation.

This can be easily treated and prevented if you remain vigilant and look out for the early signs of dampness regardless of the time of year. There are more serious forms of damp, which we will also cover in this article albeit thankfully less common.

Once you spot signs of damp in the house, ensure you identify the root cause before taking any treatment or prevention measures.

Understanding the kind of damp affecting your home will help you avoid unnecessary costs incurred in eradicating the problem as different types involve different treatment methods.

Let’s take a look at the most common types of damp for residential properties…


The most common form of damp in domestic homes is condensation. It forms when warm moist air is prevented from escaping through poor ventilation and touches a cold internal wall or surface, ultimately leading to dampness. It mainly affects kitchens and bathrooms as they tend to generate a lot of air moisture.

That said, it can also be triggered in other rooms around the home, especially if good ventilation measures are not practiced or built in air flow mechanisms are not used. The simple practise of routinely opening windows can significantly prevent any build-up of air moisture.

Image illustrates a build-up of condensation within an ‘at risk’ room which has poor ventilation and therefore created an ideal condition for mould to grow and take hold.

Signs Of Condensation

The signs to look out for are:

  • Formation of dark mould on windows frames and surrounds.

  • Bad mouldy smell.

  • Water droplets on windows or walls.

  • Peeling and stained wallpaper.

Managing Condensation In The Home

When condensation is left untreated it can cause additional damage to paintwork, decoration and even wall plaster. It will also eventually cause decay to wooden window frames. The good news is there are five simple and cheap solutions to avoid these issues which include:

Ventilate your home. Open a window, install window vents, roof ventilation tiles and air vents especially in the ‘at risk’ rooms to help curb condensation.

Wipe away condensation. Always ensure all surfaces are thoroughly wiped down with a dry cloth to prevent water droplets collecting and damaging the surface.

Control humidity levels. Consider installing extractor fans in “high risk” or affected rooms ensuring doors are closed when the fans are on to enhance efficiency.

Non-effective control methods. Try to avoid the temptation of applying non-porous paints and wall coverings as they hinder the free circulation of air.

Consider buying a dehumidifier. Dehumidifiers can help by drawing moisture out of the air. You can also purchase window vacuum cleaners as they help in keeping your windows dry all the times.

Central heating. Set your heating at a constant but slightly lower temperature than normal. Try to avoid turning your heating right up at once as this can contribute to the problem and encourage damp issues in those rooms at risk.

Rising Damp

Rising damp occurs when an impermeable layer fails and moisture from the ground travels up through the walls by capillary action. This means that ground water is effectively sucked up through tiny tubes in the bricks, like a series of straws. This water contains salts that also travel up through the wall which can start to affect the timber floor joists and plasterwork. However, rising damp is not as common as you may think as most houses will have a Damp Proof Course (DPC) fitted when it was built.

The age of a house will determine what was used to form the DPC. Older buildings may have used non-porous materials such as slate, whereas modern builders will use waterproof materials like bitumen and plastic. The DPC prevents travel of ground moisture, however, if it falls off the DPC is bridged and raising damp can occur.

What is meant by the term bridging the DPC? This is when standing water from the ground is able to travel up past the DPC because of a construction fault. Examples of this include:

  • Debris in the wall cavity or subfloor void.

  • Internal or external renders/plasters overlapping the DPC.

  • External ground levels being raised above the DPC.

  • Inappropriate insulation material in the cavity.

  • Solid floors.

  • Intersecting masonry structures/abutting garden walls.

Signs Of Rising Damp

Rising damp is a relatively rare form of damp and the correct treatment will only work if diagnosed correctly in the first place. It is vital you employ a professional to carry out a rising damp survey of your home including analysis of the salts before embarking on any course of action to treat the issue. It can be hard to distinguish rising damp from other forms of damp like condensation or penetrating damp.

To help make an initial assessment of the type of damp you are dealing will these are the more common signs of rising damp to be on the look out for:

  • Tide marks of salts.

  • Dark patches on walls that can be damp to touch up to a height of approximately 1.5m.

  • Staining of wall coverings, peeling wallpaper and blistering paint.

  • Damp and musty smell.

  • Discolouration of plaster.

  • Rotting timber, e.g. skirting boards, floorboards, floor joists.

How To Treat Rising Damp

Once you have a confirmed diagnosis of rising damp, the easiest and best course of action is to employ a qualified professional company to treat the issue. They will either recommend using a chemical injection treatment after stripping back the décor and plasterwork or replacing the Damp Proof Membrane. Be aware, the installation of a new DPC can be costly and time consuming as it requires the stripping back of internal plasterwork, replacement of all damaged brickwork and installation of a new DPC membrane.

However, the first course of action should always be to confirm the DPC has not been bridged by a construction error as this must be resolved first before moving onto chemical treat or replacement of the DPC and in most cases will resolve the overall damp issue on its own.

Employing The Professionals

Ensure the professional company you instruct to carry out the treatment process is experienced, reliable and offer a guarantee for their work. This will normally be a clause in most insurance policies and will protect you if the issue is not resolved and you have to carry out the work again. It will also give you the necessary documentation you will require if and when you sell your property in the future.

Penetrating Damp

Penetrating damp is the ingress of rainwater through masonry walls. It tends to happen where there are structural problem, such as faulty guttering, roofing or cracks in the external wall. It is a common problem in buildings constructed from a solid wall construction and increasingly common in buildings with a cavity wall construction, where cavity wall insulation has been poorly installed or used in walls that are not suitable for cavity wall insulation.

Other routes through which rainwater can ingress include incorrectly positioned wall ties, mortar obstructions in the cavity and air gaps between windows and doors.

Signs Of Penetrating Damp

The most common signs of this problem include:

  • Wet rot: Rotting skirting boards or timber floor joists.

  • Plaster damage: Plaster and paint decoloration, blistering, staining and signs of salt.

  • Localised dampness: Blotchy patches on internal walls.

  • Mould: Mouldy smell or signs of growth on external walls.

  • Brick damage: Moisture entering the brickwork causing surface damage also known as spalling.

How To Treat Penetrating Damp
Air Gaps

Gaps between windows or doors frames can quickly lead to penetrating damp, therefore timely repairs should be made to prevent these being a source of the problem.

Burst Gutters And Pipes

You might find that your penetrating damp is being caused by water leaking from gutters and downpipes on the outside of your property, creating a constant flow of rainwater onto an area of brickwork. This will, if left, deteriorate the masonry and eventually allow water ingress.

So a thorough examination should be carried out of external guttering and downpipes in and around the area where signs of penetrating damp are found within the home.

Resolving these issues will normally eradicate the damp problem but you should allow the wall to dry out before making any repairs to the masonry work itself.

Porous Brickwork

Depending on the age of your home you may find that the bricks themselves have become porous and are allowing water to ingress into your home. You may, therefore, need to replace the damaged bricks to resolve the issue. Alternately, you could try painting the bricks with an exterior silicone water-repellent fluid, which will seal your walls again while still allowing them to breathe.

Damp-proof exterior paint can also be a good option. It is always worth getting a professional opinion first who can advise you on the best course of action depending on the age and construction of your home.

Cavity Wall Issues

Modern homes (from the 1920s onwards) are usually constructed using two walls forming a cavity between them. This allows any moisture that penetrates through the external wall to evaporate before coming in contact with the inner wall. Where the external wall is purposely broken – such as window openings, it is standard practice to install a cavity tray to drain rainwater away.

If the cavity tray is faulty, or not in place at all, there is a danger you could experience penetrating damp on the inner wall. A further common problem found with cavity walls is when masonry debris builds up within the cavity forming a bridge between the walls. This allows water to come in contact with the inner wall again resulting in penetrating damp.

Can Damp And Mold Affect My Health?

The simple answer is yes, if you have a damp and mould issue within your home, you are more likely to experience respiratory problems. It can also affect your immune system.

Who Are Most Vulnerable?
  • The elderly.

  • Babies, infants and young children.

  • Individuals with an existing skin problem such as eczema.

  • Individuals with an existing respiratory condition such as asthma.

  • Individuals who have a weakened immune system, such as those undergoing treatment for cancer.

How Does It Affect An Individual’s Health?

Mold produces allergens which can cause an allergic reaction. Coming into contact with by inhaling or touching mould spores may cause an allergic reaction, such as a runny nose, sneezing, red eyes and even a skin rash. There have also been cases of mould bring on asthma attacks after prolonged periods of exposure.


There are three main types of damp you are likely to come across within the home, which are:

  • Condensation

  • Rising

  • Penetrating

The most common form of damp you are likely to experience is condensation, which is easily identified and treated. Less likely is rising damp, as the DPC would have to have failed or been bridged. The final type of is penetrating damp caused by the ingress of rainwater through the external wall into the internal wall via a structural defect or failing. This is relatively straightforward to identify but can be costly and time consuming to remedy.

Remember, when you think you are dealing with either rising or penetrating damp it is prudent to call in professionals and seek their advice on the best course of action to take. It is also advisable in most cases to employ a professional company to carry out any treatment and remedial work as in doing so will provide you with some peace of mind and a guarantee of the work conducted.

Finally, we considered what the health effects were on the occupants of a home who live with a damp and or mould issue. The effects are real and can be extremely incapacitating. Meaning owners and landlords alike should not only be concerned with the integrity of the fabric of their building, but be encouraged to take action and address the problem at the earliest opportunity in order to prevent health issues to loved ones or tenants.

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