Penetration and lateral damp is a common form of dampness in buildings. It can occur through walls & roofs, or through openings (e.g. window reveals, light fittings, pipes, cables, etc) and through the underground walls of basements and cellars.

Water typically penetrates the outer skin of a building and then appears inside.

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Common Defects Include:

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• Roof defects such as faulty flashing, cracked or missing slates or tiles.

• Faults in the brickwork or masonry such as missing or cracked pointing.

• Porous bricks or stones.

• Missing or defective sealing around windows frames and doors.

• Blocked weather facing or even non- existent weep holes.

• Missing or defective trays in cavity walls.

• Structural cracks corroded spalling and unsealed expansion joints.

• Poor painting and unsealed parapets.

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Penetrating damp is most often associated with single-skin walls, but can also occur through cavity walls such as tracking across wall ties.

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What Causes Penetrating and Lateral Damp?

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• Cracks in render and masonry provide a pathway for damp to penetrate.

• The primary cause of rain penetration through walls is defects in the masonry such as porous masonry (i.e. under-fired bricks, porous stone, or porous mortar).

• Defective pointing.

• Unfilled joints and perpends.

• Defective seals around doors and windows.

• Holes in walls – e.g. where cables or pipes protrude.

• Defective render.

• Broken down flashing and untreated parapets.