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In this article, we will be looking at how you can damp proof solid stone walls. Including the different methods that can be used, for various types of damp.
These days, most modern homes, tend to be built using cavity wall construction. This will be fitted with insulation and a modern plastic DPC. As a result, the walls are well protected from most potential forms of damp, due to the following reasons.
- DPC stops rising damp
- The cavity gap improves the risk of penetrating damp
- And the cavity insulation reduces dew points on internal walls stopping condensation
However, many older period properties were not built with a cavity wall. Instead, they are often solid stone. If they were build pre-1870s, they are also unlikely to have a DPC installed. Those built after, are likely to have one made from a no porous building material such as slate.
Generally, this type of construction is designed to be breathable. It will use lime mortars and renders. As well as internal lime plaster.
This is in direct contrast with modern properties, that tend to use less porous materials, such as cements. These are designed to keep moisture out.
You can damp proof a solid stone wall. However, you will need to approach it differently to a modern cavity wall construction. You will also need to determine what is causing the damp in the first place. The main issues are:
- Condensation due to poor airflow and ventilation?
- Penetrating damp due to defects on the outside of the property
- Rising damp coming up from the ground below your property
How to stop condensation on solid stone walls
Condensation is one of the biggest issues in most UK homes. This is particularly true in older stone-built properties, as they lack insulation. This means that the internal side of external walls can be particularly cold. As a result, condensation can be a big problem.
If the property is poorly ventilated and there is not good airflow, warm moist air will condense on the cold surfaces.
Whether the walls are finished with a traditional lime plaster, or have been refurbished with more modern materials, the issue here will be the same, water will condense on the wall and cause damp and eventually mould.
It is arguable, that lime plaster will suffer slightly less, as it is able to breathe better. But this does not remove the issue of condensation occurring, and the subsequent mould that will follow if it is not treated.
The best way to reduce condensation is to remove the moisture in the air. This can be done in several ways, including:
- Regularly opening windows and doors to allow fresh air to circulate.
- Try to create less moisture. For example, avoid long hot showers, open windows when cooking and try to avoid drying clothes indoors.
- Install extractor fans in areas that suffer with high levels of moisture.
- Try to maintain a consistent temperature with your central heating.
- Consider buying a dehumidifier – You can read more about how a dehumidifier can help here
Can you insulate a stone wall to stop condensation?
If you have a solid stone wall, there is no way to add insulation inside the wall, as there is no cavity. The only way to achieve this, is adding insulation internally.
This will usually be done in two ways:
- Dot and dab insulation boards onto the stone wall
- Use timber battens to fix insulation boards
You could also build an internal stud wall and insulate and board. However, this method will take up more space internally.
The advantage of these methods, is the insulation board, and the original wall, will have a small cavity between them. This will allow the wall to breathe. You could also add small air grates to improve airflow.
Once your wall is insulated it should no longer suffer with condensation. However, you should still make sure you are trying to remove moisture in the air, this will avoid problems in other areas of your home.
How to stop penetrating damp on solid stone walls
In many ways this is the same as any other property. Penetrating damp will be the result of an external defect. This could include any of the following:
- Damaged old pointing
- Cracked or broken stonework
- Issues with external render
- Damaged guttering and down pipes
- Issues with the roof and chimney
As with any other property, the goal here should be to repair the defect and as a result the damp issues should stop.
One thing that may be different with a traditional stone building, is the materials you will need to use. Ideally you should replace like for like.
For example, any mortar used for pointing, or any render on the property is likely to be lime based. If this is the case, you should avoid using cement-based products to make repairs.
Lime mortars are much more porous and breathable, whereas cement dries much harder and is less porous. The latter is not good for softer natural stone, as the pointing is stronger and more rigid, which can damage the stone when it expands and contracts.
Also, because cement is less porous than the stone, water will wick out of the masonry rather than the pointing. This can lead to damage to the stone, which can expose them to even more penetrating damp.
Finally, if you do decide to use any type of covering, or sealant on the external of your property, you will also need to ensure it is breathable. Water should be allowed to escape from the stone walls, and you should not apply any products that seal and trap moisture inside.
Some external masonry paints and creams may be suitable, but you should always make sure they are breathable.
How to stop rising damp on solid stone walls
The final issue with damp comes from rising damp. This is by far the least common type of damp.
You should completely rule out all other types of damp before you come to this conclusion. Rising damp is often misdiagnosed, especially if you don’t know what you are looking for.
However, if this is the problem, it is also less simple to fix solid stone-built properties. Solid stone walls tend to have a minimum thickness of 35cm and can be significantly thicker.
As a result, something like a DIY damp proofing kit will usually not do the trick.
If you are considering a chemical damp proof course, you will need to hire a professional damp proofing company. Ideally you should talk with several companies to find the most affordable solution.
Other potential options could involve internal tanking with a slurry or membrane. Rising damp is only able to rise approximately 1m above ground level. This means a tanking solution could stop rising damp from penetrating inside.
Also, if the outside of your property is maintained with traditional breathable materials, the moisture should evaporate through the external wall.
Unfortunately, there isn’t a one size fits all solution for rising damp in a solid stone wall. You will need to speak to experts in this case.
We recommend hiring via local comparison sites. This is by far the best option for this type of work, as the companies are all verified. Plus, they all have reviews from previous customers, so you know you are hiring a legit expert and not a cowboy.
Also, they tend to guarantee the best price, because more than one company is quoting for the work. This usually results in some nice discounts.
Damp proofing solid stone walls can cause some unique problems. However, using a mixture of modern techniques and traditional methods, most problems can be solved.
One of the biggest causes of damp in older stone-built properties, is the overuse of modern nonporous materials.
Whatever the problem is, you should always make sure the solution allows the original structure to breathe. If you trap moisture, it is highly likely you will suffer with more problems in the future.