Damp issues in homes are not only horrible to look at but, in the long run, can also lead to structural damage and health concerns if left unaddressed.
Two of the main types of damp are rising damp and penetrating damp. While they may appear similar, understanding their differences is important for effective treatment and prevention.
What is rising damp?
Rising damp is a phenomenon where moisture from the ground travels upward through the porous materials of a building’s walls, such as bricks and mortar. This upward movement, known as capillary action, occurs when there is no effective damp-proof course (DPC) or when the existing DPC has failed. The moisture carries salts from the ground, which can accumulate on the walls, leading to visible damage and deterioration.
Mould and mildew growth
These can harm air quality and trigger health issues, especially respiratory problems.
Damage to walls and plaster
Damp can lead to bubbling paint, peeling wallpaper, and deterioration of wall materials.
Structural weakening
Persistent moisture can weaken a building’s structure, which may lead to costly repairs in the long run.
Rising damp signs
Identifying rising damp early can help stop extensive damage. Common signs include tide marks or staining on walls, usually up to a meter above the skirting board. You may notice peeling paint or wallpaper, a musty smell in affected areas, and salt deposits on the wall surface. These indicators suggest that moisture is being drawn up from the ground, affecting the internal finishes of your home.
How to treat rising damp
Dealing with rising damp involves several steps. Firstly, identify and fix the source of moisture, which may involve improving drainage or lowering external ground levels. Secondly, install a new damp-proof course. Chemical DPCs are commonly used, where a damp-proofing cream is injected into the wall to form a barrier against moisture. Finally, repair internal finishes. Once the moisture source is addressed, affected plaster and decorations should be removed and replaced to restore the appearance and integrity of the walls.
What is penetrating damp?
Penetrating damp, also known as lateral damp, occurs when water infiltrates a building through external defects. Unlike rising damp, which moves upward from the ground, penetrating damp travels horizontally through walls, ceilings, or roofs. Common entry points include damaged brickwork, faulty guttering, and leaking roofs. This type of damp can affect any level of a building and is often worsened by wind-driven rain.
Penetrating damp symptoms
Signs of penetrating damp include damp patches on walls or ceilings, often accompanied by a musty smell. You may observe discolouration, peeling paint or wallpaper, and in severe cases, mould growth. Externally, you might notice damaged brickwork or mortar, and water stains on walls. These symptoms typically worsen during periods of heavy rain and are localised to specific areas where water ingress occurs.