Cavity Wall Damp Problems
Cavity walls are designed to help protect a property from moisture, but problems can still occur if the cavity becomes bridged, blocked, poorly insulated or affected by external defects. When moisture is able to pass from the outer wall to the inner wall, it can lead to damp patches, damaged plaster, mould growth and recurring internal staining.
If you are seeing damp on internal walls and are unsure whether the wall construction is part of the problem, read our guide to cavity wall damp, signs and causes. It explains the common warning signs, why cavity wall damp is often mistaken for other damp problems, and when to arrange a specialist damp survey.
How it works
Cavity wall construction is a method commonly used in building structures, especially in regions with varying weather conditions. It consists of two separate walls, an outer leaf and an inner leaf, which are built with a gap or cavity between them. Here’s a detailed description of the components and process involved:
1. Outer Leaf: This is the exterior-facing wall, typically made of brick or blockwork. It serves as the primary barrier against external elements such as rain, wind, and temperature variations.
2. Cavity: The gap between the outer and inner leaves is known as the cavity. It acts as a buffer zone, providing insulation and preventing moisture from penetrating the inner wall.
3. Insulation: Insulation material is often placed within the cavity to enhance thermal efficiency, helping to regulate indoor temperatures and reduce energy consumption.
4. Inner Leaf: The inner leaf forms the interior-facing wall of the structure. It is usually constructed using materials like brick, blockwork, or concrete blocks.
5. Ties: Wall ties are metal fasteners that connect the outer and inner leaves, ensuring structural stability and preventing them from separating. These ties are typically made of stainless steel to resist corrosion.
6. Damp Proof Course (DPC): A DPC is installed at the base of the wall to prevent moisture from rising up through the structure via capillary action. This is essential for preventing dampness and protecting the integrity of the walls.
7. Weep Holes: Weep holes are small openings incorporated into the lower courses of the outer leaf. They allow any water that may have entered the cavity to drain out, preventing moisture buildup and potential damage.
8. Lintels and Openings: Lintels are horizontal supports installed above doors, windows, and other openings to bear the load from the structure above. They are typically made of steel, concrete, or reinforced brickwork.
The construction process of a cavity wall typically involves laying the outer leaf first, followed by the installation of insulation and wall ties. The inner leaf is then constructed, ensuring that proper spacing and alignment with the outer leaf are maintained. Finally, lintels are installed over openings, and any necessary finishing touches, such as rendering or cladding, are applied to the exterior surface.
Cavity wall construction offers several benefits, including improved thermal performance, better moisture control, and enhanced structural strength. It is a widely adopted method in modern construction due to its effectiveness in providing a comfortable and durable living environment.