The UK’s rich history means many homes are quite old, and stone walls are a common feature. A question that often comes up is, ‘Can stone walls be made damp-proof?’ It’s a valid concern, especially if your home is listed or if you’re cautious about using modern damp-proofing methods in an older property.
A stone wall can become damp due to a process called rising damp. This happens when moisture moves up from the ground into the walls through capillary action. Capillary action allows moisture in once the damp proof course (DPC) fails.
The DPC’s main job is to prevent rising damp from moving upward and causing damage to the walls. It’s a thin layer of chemicals injected into the wall that blocks moisture. Rising damp is often localised in one spot because the DPC has failed there, allowing dampness to seep through.
Identifying rising damp is relatively straightforward. Typically, the dampness is limited to about one meter above the ground, affecting floorboards, skirting, or joists and possibly warping the floor or other timber in your property.
This article aims to provide you with ideas on effectively preventing damp in homes with stone walls.
If you ignore and don’t treat rising damp in stone walls, it can spread and cause serious problems. As mentioned earlier, be vigilant for signs like warped wood if damp is present. But that’s just the beginning – untreated damp can lead to dry rot, where a nasty orange fungus rapidly grows on your timber.
Are stone houses prone to damp?
Old stone and cob buildings are especially vulnerable to rising damp because they lack effective damp proof courses. Often, these structures have wet walls because of the use of unsuitable finishes like cement and masonry paint, instead of lime and mineral silica paints.
How do you damp proof stone walls?
Stone walls, much like brick or other materials, can effectively combat rising damp through the installation of a damp proof course. This method ensures certainty that no additional moisture will seep into the stone walls of your property.
Can you waterproof stone walls?
The best technology for waterproofing stone walls is a highly breathable masonry protection cream. These creams establish an invisible barrier on exterior walls, repelling water while maintaining excellent breathability.
What stone is suitable for damp proofing?
For damp-proofing, suitable stone materials typically include asphalt, cement, and slate. Occasionally, other stones like sheet lead and vitrified brick may also be used for this purpose.
Why is water coming through my stone wall when it rains?
Stone walls can also face water ingress, primarily due to building Faults, damaged or deteriorating mortar that can result in water ingress through the render. Cracks in the brickwork or substrate can also allow water to seep in.
Should you seal stone walls?
Most experts recommend sealing all stone while others emphatically state that not all natural stone needs to be sealed. To get a general idea of how absorbent the stone is, place several drops of water on the surface of the stone and time how long it takes for the water to completely disappear.
Some suggest sealing all stone walls, while others assert that not every natural stone requires sealing. To gauge absorbency, place a few drops of water on the stone’s surface and note how long it takes for the water to vanish.
How do you insulate the inside of a stone wall?
For thinner materials like calcium silicate-based insulation board and aerogel-based blanket, it’s best to apply them directly to the masonry. Thicker materials such as fibreboard and hemp board are more effectively secured with framing. When insulating a wall, it’s essential to minimise thermal or cold bridges as much as possible.
What is the disadvantage of a stone wall?
Drawbacks of stone walls include their thickness and weight, which reduce floor space. They possess high self-weight, coupled with low flexural strength, tensile strength, and seismic resistance. Stone masonry is time-consuming and demands skilled workers due to its difficulty in being easily altered, repaired, or relocated.
Can you waterproof natural stone?
Sealing the surface of natural stone, such as with a paint finish, can strip it of its valuable and attractive properties. Waterproofing natural stone offers a successful compromise, enhancing resistance, making maintenance easier, and preserving its natural beauty at the same time.
Using perimeter drainage to control damp
Even with proper lime finishing, it’s important to control the amount of water at the base of the wall. A common source of excess water is downpipes that aren’t directed into drains or away from the building. Pay attention to the runoff direction from the surrounding ground, especially if it slopes toward the property.
Maintaining Gutters and Downpipes to Control Damp
Gutters play a crucial role in protecting your building from weather damage. Unfortunately, they are often overlooked. Faulty gutters can lead to significant re-rendering and even structural repairs over time.
When gutters and downpipes are not functioning properly, they collect and concentrate rainwater. If they overflow, they can unleash a large volume of water directly onto the walls. This frequently initiates or worsens the cycle of cracking in cement render.
To prevent damp issues in cob and stone buildings, maintaining rainwater systems is vital. Regularly clear gutters of debris, ensure downpipes are securely connected, and direct discharged water away from the property. Observing them during rain can help identify faults, but dark staining and algal growth are also telltale signs of potential issues.
Maintaining Chimneys to Control Damp
Leaky chimneys are a major culprit for water damage in old cob and stone buildings. Many chimneys in older properties lack proper flashing and are approaching the end of their lifespan. Addressing a leaky chimney is crucial as it can accelerate the need for re-pointing and re-rendering works.
When a chimney starts leaking, water runs down the flues, which are typically integral to the walls in old cottages. Stone walls are often mortared with clay, which washes away when exposed to water. This damages the stone lining of the flue, making it loose. The water from a leaky chimney is impure and deposits impurities on the stonework, causing damage, especially to softer stone.
Dealing with leaky chimneys may require rebuilding using a sturdy hydraulic lime mortar. However, if addressed promptly, a robust lime render might be sufficient. Due to their exposure to the weather, it’s recommended to use a very strong hydraulic lime like NHL 5.
Old buildings naturally absorb moisture, and if they can’t release it through their pointing or render, they may face issues like unpleasant living conditions and damage to the building’s structure.
Lime should be used along with the other methods discussed here. At Damp and Mould Solutions, we are skilled lime masons. We can guide you on the significance of each element and assist in prioritising where to invest money in maintaining your old building.
Using Air Flow to Control Damp
A well-ventilated building is less prone to internal dampness. Dampness inside a building typically occurs through daily activities like washing and cooking by occupants and the evaporation of moisture from walls and floors into the living space.
In older stone and cob buildings without effective damp proof courses, improper finishes like cement and masonry paint can contribute to wet stone walls. As the internal temperature is usually higher than outside, excess moisture in walls or floors is drawn inward, increasing internal humidity.
Maintaining a constant, low airflow through a building allows damp air to escape. This can be achieved through trickle vents, a positive pressure ventilation system, or simply by keeping windows slightly open.
While airflow is a cost-effective way to manage damp, addressing other factors is necessary for proper building drying.
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