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Penetrating Damp

Unlike Rising Damp, Penetrating Damp is generated by water seaping through walls and is generally caused by structural issues such as leaking pipes, damaged guttering or roofing problems. In the case of Penetrating Damp the water moves around a building horizontally rather than vertically as is Rising Damp. Rain penetration through masonry (known as penetrating damp) is a common problem in buildings – particularly in the case of those of solid wall construction. The problem is also increasingly common in buildings of cavity wall construction where cavity wall insulation has been poorly installed or used in walls that are not suitable for cavity wall insulation. Other paths through which rain can cross through a cavity wall include incorrectly positioned wall ties and mortar obstructions in the cavity.

The tell-tale signs of Penetrating Damp

The most common visual symptom of rain penetration is dampness in walls – often causing paint to flake or wallpaper to peel. However damp masonry caused by penetrating damp can also result in a wide range of other symptoms including:

Reduced thermal resistance of damp masonry – causing heat loss and condensation
Moss and mould growth
Frost damage
Rotting of embedded timbers
Disfiguring carbonate deposits
Mossy WallPenetrating Damp StainingRain Penetration DecaySpalled Brick
Traditional Measures for Preventing Penetrating Damp

A wide range of traditional penetrating damp solutions are available to deal with the problem of rain penetration through walls, and offer masonry moisture protection. These include:

Cedar CladdingExternal RenderRender First FloorPainted House
Cladding
External renders
Weatherproof paints and coatings
Tile or slate hanging
Timber boardings


Whilst all these solutions for treating penetrating damp can be effective, they all have the disadvantage of changing the visual appearance of the building to which they are applied. For this reason an alternative approach to waterproof masonry protection is required in situations where the original appearance of brick or stone masonry needs to be maintained.

This is where Stormdry waterproof masonry protection can help.

Stormdry Masonry Protection Cream and a repointing moisture barrier can be used to treat penetrating damp without affecting the visual appearance of brickwork or stonework.


The application of waterproof Masonry Protection Cream from Stormdry prevents the absorption of rainwater into porous building materials such as brick or sandstone whilst still allowing the passage of water vapour – i.e. the wall is still able to ‘breathe’. Because Stormdry Masonry Protection Cream penetrates deeply into common masonry substrates such as brick and stonework, it is able to resist rain penetration through shallow cracks. Nevertheless, all cracks in masonry visible at the time of application should be filled before the application of Stormdry.

Cracks in mortar and small shrinkage cracks at the interface between the mortar and brick/stone can provide a pathway through which rain can penetrate, thus causing damp in walls. For this reason, prior to the application of Stormdry Masonry Protection Cream, any cracked or unsound mortar should be raked out and repointed using a suitable sand:lime or sand:cement mortar incorporating a repointing moisture barrier tooled to a "bucket handle" finish.

Additional Measures

Good building design and maintenance plays an important role in preventing dampness in walls. For example, blocked downpipes and poor detailing can result in large amounts of rainwater coming to bear against a small section of wall. Any such defects should be identified and rectified.


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Next page: Condensation Damp