Can You Damp Proof Stone Walls?

Stone walls are common in older UK homes, but can you damp-proof them effectively? Understanding how moisture behaves in stone-built properties is essential before choosing the right treatment. In this blog, we cover what issues you may encounter in a stone-built property, and the best solutions for repairing damp in listed buildings.

Why do Stone Walls get Damp?

Stone walls can get damp for similar reasons to modern cavity wall brick constructions. Some of these reasons include:

• Rising Damp, where moisture from the ground rises through capillaries in stone or plaster/render, bypassing an existing damp proof course. This moisture often creates visible tide marks or causes paint and wallpaper to peel on internal walls.
• Penetrating Damp, where moisture ingresses through an external defect in the wall, such as failed pointing or leaking gutters/roof tiles. This moisture then creates damp patches on the adjacent internal walls and ceiling.
• Condensation, where warm internal moisture turns to water droplets on cooler surfaces, especially in bathrooms or kitchens. This moisture often encourages the growth of black mould on the surface of the wall.

Can You Damp-Proof Stone Walls?

The short answer is yes; it is possible to damp-proof stone walls. However, it is important to understand the root cause of your damp issue prior to starting any treatment. Applying the wrong treatment method to your wall could lead to additional damage if moisture inadvertently becomes trapped within the wall. This is especially true if your property has breathable stonework, which controls moisture by allowing water to ventilate naturally through passive ventilation.

What Treatment Options can I use to Damp-Proof Stone Walls?

The treatment options for your property will vary depending on the issue you’re experiencing. It will also depend on how invasive a treatment you’re willing to allow to resolve a damp problem. If you book a survey with Timberwise, our surveyors will discuss these options and other methods to find the perfect solution for your situation prior to beginning work.

Here are some recommended solutions for each damp problem.

Rising Damp Solutions:

Rising damp is a potential problem in any home, no matter what age it is. When considering rising damp as a contributing factor of moisture in your property, you should discuss the following solutions with your surveyor:

• Installing a Damp-Proof Course (DPC) will prevent damp from being able to rise up a wall by creating a moisture-resistant barrier within the wall. This is created by injecting a gel into the mortar joints just above floor level. It is also appropriate to remove any plaster or render that is in contact with the ground, as this can allow moisture to bridge over a DPC and ingress into the wall above, even if one is installed. You should also consider replastering the internal walls with a salt-retardant plaster specification, which will remove any historic salts that may have built up in the existing plaster and prevent the attraction of moisture back into the wall.
• Installing an Electro-Osmotic System prevents dampness using a titanium wire connected to nodes installed on the surface of the wall. As a small electrical current is then run through the wire, it depresses the rise of moisture within the attached wall. Unlike a chemical DPC, this method is reversible and suitable for use on period or listed properties where preservation is the key factor in treating a damp problem.
• Installing a Damp-Proof Membrane prevents damp by installing a water-impermeable barrier on the surface of the wall, which prevents moisture ingress. This moisture runs down the membrane and is collected in a gulley at the base of the wall, which is then drained into an existing drain or pumped off-site into a wastewater system. This method is most often used in basements or areas where persistent flooding is a risk to the property. This method is also considered reversible as the membrane can later be removed from the wall surface if desired.
• Check external ground levels to ensure they aren’t too high in relation to the internal floor. High ground levels can allow damp to penetrate laterally into the wall, which can provide a source for moisture to then spread up a wall or into floorboards. Ensure any drainage system is clear of debris to allow wastewater to drain away from walls.

Penetrating Damp Solutions:

Stone walls are often found in listed properties or those of a considerable age. Over time, weathering can damage the stonework or mortar, causing defects to form within the wall. To prevent penetrating damp issues, you should consider the following:

• Fixing external defects is often the first course of action when treating a penetrating damp solution. Potential problem areas include rainwater goods, roof linings and installations to the wall (such as waste pipes or hanging planters). Each of these should be checked periodically for moisture ingress within the property and dampness or algae growth around any fixtures. Any identified defects should be treated appropriately to reduce the likelihood of moisture ingress.
• Repointing with lime mortar will restore breathability to a wall where the mortar has failed and chipped away. This will also prevent moisture from being able to ingress easily through the facing stonework.
• Breathable water-repellent coatings repel rainwater from external walls while still allowing moisture to escape. This can be a suitable replacement for external render on exterior walls if applied correctly.

Condensation solutions:

Stone walls are often constructed with a single layer, rather than multi-layer cavity walls. This makes their surfaces colder and more prone to condensation concerns. You can fix condensation issues in your stone-built property by;

• Improving ventilation through passive and mechanical methods will allow moist air out of the property more readily. Installing hydrostatic fans can help reduce condensation in moisture-rich environments like bathrooms or kitchens. Installing wall vents and window trickle vents will allow moisture to disperse naturally out of your property.
• Adjusting your living habits, especially around moisture-generating activities, will help prevent moisture from building within a property. Taking shorter or cooler showers, drying clothes outside and opening windows while cooking can all reduce the amount of humidity within a property.
• Using ThermalTek Anti-Condensation paint, which can prevent mould growth by reflecting thermal energy away from the walls. This prevents condensation from forming. This product can simply be painted onto an existing interior wall.
• Investing in a dehumidifier, which can remove excess moisture in the rooms it is used in. These machines can be moved between any problem areas within your property. However, these machines only treat the symptoms of condensation rather than the cause, and so should not be considered a permanent method of removing moisture from a property.

Conclusion

It is possible to install damp proofing solutions on stone walls, and there are several treatments you can use to remediate an issue, depending on the problems you’re experiencing within your property.

You should always confirm the root cause of damp before starting any treatment. Not all signs of damp can be attributed to one specific cause of moisture, and unless diagnosed correctly, you could still have problems later down the line.

You should discuss your concerns with a PCA-accredited surveyor to find the solution that’s right for you and your property. Using too invasive a solution may cause problems in graded or listed buildings, and using the incorrect solution for your issue may inadvertently allow moisture to remain trapped within a property.

FAQs

Can Stone Walls be Damp Proofed Without Harming Breathability?

Yes, stone walls can be damp-proofed without harming breathability. Breathable coatings can be applied to exterior walls, which not only repel rainwater but also allow moisture within a wall to escape. Using a sealed film can also repel rainwater, but it can also prevent moisture from escaping from within a wall. Use of sealed film should only be considered after discussion with a PCA-approved surveyor.

Is Damp Proofing Different for Old Stone Walls Vs Modern Masonry?

Yes, you should consider the materials your property is constructed from prior to conducting any remedial work. Older properties often use different materials in their construction, such as lime mortar, and so similar materials should be considered when repairing any defects. Using alternative materials may cause heritage concerns in listed buildings, and could reduce the breathability of a wall and inadvertently trap moisture within the property if the correct materials aren’t used when fixing any defects.

How Long Does Damp Proofing a Stone Wall Last?

Timberwise provides long-term guarantees for all its work, provided it is not tampered with after installation. Damp-Proof Coursing carries a 20-year guarantee, while waterproofing, such as installing a Damp Proof Membrane, carries a 10-year guarantee upon installation.

Can I Damp-Proof Stone Walls Myself?

It is possible to damp-proof stone walls yourself if you have the correct knowledge and experience prior to beginning work. You should always request a survey from a PCA-qualified surveyor to identify the root cause of your damp issue. DIY also carries the risk of error, either through incorrect diagnosis, incorrect installation, or accidentally trapping damp by using an incompatible method.

How Much Does Stone Wall Damp Proofing Cost?

Our range of damp proofing solutions varies widely in cost depending on the recommended solution for your unique property and situation. Our surveyors provide a quote for any recommended remedial work with a completed survey, and will discuss alternative solutions with you regarding alternative methods or partial remediation to suit your budget and timescale.