Rising Damp: How To Treat Damp Walls

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Photo showing rising damp on an internal wall in a house.

What Is Rising Damp?

Rising damp is a condition where groundwater moves up through the pores in the walls of a building by capillary action. This often leads to visible dampness on the lower sections of internal walls, sometimes accompanied by salt deposits, which can damage plaster and paint.

Effective prevention or treatment typically requires the installation of a damp-proof course or the use of damp-proofing techniques to block the capillary action and protect the structure.

Rising damp is a prevalent issue that can affect any building, leading to significant structural damage and health problems if not addressed promptly.

Understanding early signs of damp is crucial for any homeowner, as it can manifest in peeling paint, damp patches on walls, and a musty smell—classic early signs of damp that should not be ignored.

In this guide, we will explore effective strategies to diagnose early signs of damp and treat rising damp, ensuring your home remains dry, safe, and structurally sound.

From using sophisticated damp meters to identify the problem areas to choosing the right damp proofing techniques, we’ll cover everything you need to tackle this pervasive issue.

photo of a cottage near the sea with damp problems
Older buildings near water or damp land can suffer from rising damp. Photo © Jennifer Petrie (cc-by-sa/2.0)

The Effects of Rising Damp in Walls

Rising damp can be a serious issue in any building, manifesting itself subtly before causing significant damage. It occurs when moisture from the ground rises up through the porous materials of walls and other structural elements.

it can be a common occurrence in older buildings, such as remote houses and countryside properties.

Understanding the effects of rising damp is crucial for maintaining the health of your property and the well-being of its occupants. This section outlines the primary consequences of unchecked rising damp, highlighting why it is essential to address this problem promptly.

  • Structural Damage: Moisture deteriorates building materials, weakening walls and compromising structural integrity.
  • Health Issues: Damp environments foster mould and mildew growth, which can lead to respiratory problems and other health concerns.
  • Aesthetic Damage: Peeling wallpaper, blistering paint, and unsightly stains degrade the appearance of interiors.
  • Decreased Thermal Comfort: Moisture in walls increases heat transfer, making heating more costly and less effective. This is particularly true in sandstone houses.
  • Reduced Property Value: Ongoing damp issues can significantly lower a property’s market value and appeal.
  • Odours: Persistent musty smells, which are difficult to eliminate, can pervade the home.
Photo of a stone cottage with rising damp issues in the walls.
Older homes such as stone cottages are prone to damp problems. Photo © Ray Bird (cc-by-sa/2.0)

Identifying Rising Damp in Your Home

Detecting rising damp early can save significant time and expense by preventing the extensive damage it can cause.

This section guides you through the use of a damp meter to identify rising damp and outlines the key signs that indicate the need for a damp specialist.

Using a Damp Meter: A Step-by-Step Guide

  • Purchase a Reliable Damp Meter: Choose a damp meter suitable for the materials of your home. Digital meters are generally more accurate and easier to read.
  • Check the External Walls: Start with the external walls closest to the ground, as these are most susceptible to rising damp.
  • Measure at Various Points: Place the damp meter at different points along the wall, both near the base and higher up. Consistently high readings near the base that decrease higher up typically indicate rising damp.
  • Record the Moisture Levels: Keep a log of the moisture levels in different areas to monitor changes over time or after remedial action.
  • Assess the Interior Walls: Repeat the process inside, particularly in areas where external dampness was detected. Pay special attention to corners and areas near plumbing.

Signs That You Need a Damp Specialist

  • Tide Marks and Salt Deposits: Visible marks or a white powdery substance on walls are classic indicators of rising damp.
  • Deteriorating Plaster and Paint: If the wall coverings are flaking off or you notice crumbling plaster, it’s a sign of significant moisture intrusion.
  • Mould Growth: Extensive mould on the lower parts of walls, especially in corners and behind furniture, often requires professional assessment.
  • Musty Smells: Persistent damp odours that do not improve with ventilation are a tell-tale sign of underlying dampness issues.
  • Previous Damp Treatments Not Working: If you’ve tried DIY remedies without success, a specialist can diagnose deeper problems and suggest more effective solutions.

Damp Proof Course Or Damp Proofing Membrane

Image illustrating a damp proof course, sometimes called a damp proof membrane.

Understanding the differences between a damp proof membrane (DPM) and a damp proof course (DPC) is essential for effective moisture control in any building structure.

Both serve critical roles in preventing moisture from rising through the walls, but they do so in distinct ways and are used in different contexts.

What is a Damp Proof Membrane?

A damp proof membrane is a sheet of material, typically made from polyethylene or PVC, that is installed in floors and walls to prevent moisture from passing through into interior spaces. DPMs are particularly useful in modern construction where they are laid under concrete floors or incorporated into walls to block moisture from the ground or adjacent wet areas. Here are key aspects of a damp proof membrane:

  • Installation: DPMs are usually laid horizontally at foundation level or included within walls vertically during construction or renovation.
  • Functionality: They act as a barrier to moisture from the ground and are essential in basements and areas with high ground moisture.

What is a Damp Proof Course?

A damp proof course is a horizontal barrier inserted into the walls of a building at a specific height above ground level to prevent capillary action from drawing moisture up from the ground.

Traditional materials for DPCs include slate, bitumen, and plastic, which are impervious to water and are installed during the building’s construction. Essential features of a damp proof course include:

  • Location: DPCs are embedded near the ground level in the mortar joint between bricks or blocks of a wall.
  • Purpose: The main function of a DPC is to stop ground moisture from rising up through the walls by capillary action.
Illustration of a cottage with a damp proof course around the outside of the walls.
Pouring a concrete damp proof plinth around the base of a stone house can help prevent rising damp.

Damp Proof Paint: Does Damp Proof Paint Work?

Damp proof paint is a popular solution touted for combating moisture problems in buildings, particularly for treating and preventing the appearance of dampness on internal wall surfaces.

Understanding how effective damp proof paint can be is crucial for homeowners looking to protect their properties from moisture-related damage.

What is Damp Proof Paint?

Damp proof paint is a specially formulated coating designed to prevent moisture from penetrating through walls and ceilings. It is typically a thick, waterproof paint that includes a water-repellent resin and is applied to the interior surfaces of a building.

The paint creates a barrier that moisture cannot easily penetrate, helping to keep the underlying structure dry.

How Does Damp Proof Paint Work?

  • Application: Damp proof paint is applied directly to dry, prepared surfaces, often requiring multiple coats to ensure a complete seal.
  • Properties: The paint contains a resin that forms a barrier once dry, which repels water and prevents it from soaking into the wall.
Photo of a worker applying damp proof paint to a wall.
Using damp proof paint can be a good treatment for internal walls, but may not resolve the dampness problem.

Effectiveness of Damp Proof Paint

  • Surface Conditions: Damp proof paint is most effective when applied to surfaces that are free of existing moisture. It is not a cure for walls that are already damp; the source of moisture must be addressed first.
  • Longevity: The effectiveness can vary depending on the quality of the paint and the environment. Regular maintenance may be required to sustain its protective properties.
  • Limitations: While damp proof paint can prevent the ingress of moisture, it does not solve issues of rising damp or penetrating damp where structural or external waterproofing solutions are needed.

When You Should Use Damp Proof Paint

  • Preventative Measure: Ideal for use in damp-prone areas like basements, kitchens, and bathrooms as a preventative measure.
  • After Treatment: Useful after resolving an underlying damp issue, such as fixing leaks or installing a damp proof course, to provide an additional layer of protection.

Damp proof paint, sometimes known as anti-damp paint, can be an effective part of a broader damp proofing strategy, particularly for internal surfaces. However, it should not be seen as a standalone solution for serious damp issues.

Proper assessment and treatment of the source of moisture, combined with the application of damp proof paint, will provide the best protection against damp-related problems in the home.

Photo of mould on a wall caused by rising damp which could be treated with damp proof paint.
Illustration showing mould caused by rising damp. This kind of damage can be restricted by using damp proof paint on the wall, but the root cause of the moisture should still be addressed.

How to Treat Damp Walls Internally

Treating damp walls internally involves a combination of proper diagnosis and targeted intervention strategies.

The first step in any effective treatment is conducting a thorough damp survey. This assessment helps identify the exact cause and extent of the damp issues, ensuring that the correct measures are taken to resolve them.

Steps for Treating Damp Internally:

  • Conduct a Damp Survey: Engage a professional to carry out a damp survey. This detailed inspection will determine the type of damp (whether rising damp, penetrating damp, or condensation) and suggest appropriate remedies.
  • Address the Source: Before any internal treatments are applied, it’s crucial to address the external sources of moisture. This may involve repairing damaged roofing, fixing leaks, or improving external drainage.
  • Prepare the Walls: Remove any damaged plaster, flaking paint, or wallpaper. Ensure walls are clean and dry before proceeding with treatments.
  • Apply Damp-Proofing Treatments: Depending on the survey results, treatments may include injecting a chemical damp-proof course, applying damp-proof membranes, or using specialised plaster that prevents moisture penetration.
  • Replaster and Repaint: Use damp-resistant plaster and paint to finish the walls. These products will help prevent future moisture ingress and protect the integrity of the wall surfaces.

Older homes such as rural cottages, Georgian houses and Edwardian homes are particularly prone to dampness issues.

If you own a property like this you should consider employing a damp specialist.

How Can You Treat Damp Walls Internally?

To treat damp walls internally, begin by conducting a damp survey to identify the moisture source. Next, address any external issues such as leaks or poor drainage. Strip back affected interior finishes, clean the walls, and ensure they are dry. Apply appropriate internal damp-proofing treatments like chemical damp-proof courses or damp-proof membranes. Finally, replaster using damp-resistant plaster and repaint with a damp-proof paint to seal the walls against future moisture ingress. This comprehensive approach ensures effective management of internal dampness.

How Do You Treat Rising Damp in an Old House in the UK?

Treating rising damp in an old house involves several key steps. Firstly, conduct a thorough inspection to confirm the presence of rising damp. This typically requires a professional damp survey. Once confirmed, install or repair the damp-proof course (DPC) to prevent moisture from rising through the walls. This might involve chemical injection or the insertion of a physical barrier. Additionally, remove and replace any salt-contaminated plaster to ensure the wall finishes are not compromised. Finally, ensure adequate ventilation to prevent future damp issues. Properly addressing these elements is crucial for effectively managing rising damp in historic buildings.

What is the Cost of a Damp Proof Course in the UK?

The cost of installing a damp proof course (DPC) in the UK can vary widely, typically ranging from £280 to £2,000. The price depends on the extent of the damp, the method used for damp proofing, and the size of the affected area. Chemical DPCs, involving the injection of a silicone-based liquid into the walls, tend to be at the lower end of the cost spectrum, while more extensive methods like installing a new physical barrier might be more expensive. For accurate pricing, it’s advisable to obtain quotes from several damp proofing specialists after a thorough damp survey.

What Is Damp Seal Paint and How Does It Work?

Damp seal paint is a specialised coating designed to prevent moisture from penetrating and damaging interior walls and ceilings. It acts as a barrier against damp by sealing porous surfaces and covering stains left by moisture damage. Typically, damp seal paint is formulated with a water-resistant base that locks out moisture and prevents it from reaching the wall’s surface. It is particularly effective in areas susceptible to damp but should be applied to dry surfaces for best results. This type of paint is ideal for prepping walls before applying the final decorative layer of paint, ensuring a clean and moisture-free finish.

How Can I Find a Damp Specialist Near Me in the UK?

To locate a damp specialist nearby, start by asking for recommendations from friends, family, or local tradespeople who have previously dealt with similar issues. You can also consult local trade directories or community boards for trusted professionals in your area. Ensure you check for any available customer reviews or testimonials about their service quality. Once you have identified potential specialists, contact them to inquire about their services, experience, and to obtain quotes for the required damp proofing work.

How To Get Rid Of Rising Damp

Addressing rising damp effectively is crucial for maintaining the structural integrity and health of your home.

As we’ve explored in this article, identifying the presence of rising damp early through professional surveys, understanding the different treatments like damp proof courses and membranes, and applying preventive measures such as damp seal paints are integral steps in managing this common issue.

Each method discussed provides a strategic approach to combat the pervasive effects of rising damp within a property.

Remember, the success of treating rising damp not only preserves the aesthetic appearance of your home but also enhances its market value and ensures a healthier living environment.

Should you encounter signs of dampness or rising damp in general, consider consulting with a damp specialist to tailor a solution specific to your property’s needs, thereby ensuring long-term protection and peace of mind.

Additional resources:

Advice for tenants with damp problems
UK Gov’t advice for the effects of damp problems

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