PENETRATING DAMP

Penetrating damp, which soaks through the perimeter walls of a dwelling, is perhaps the most common form of dampness in buildings.  In most instances wall penetrating dampness occurs in isolated areas as a result of one or more defects in the structure of the building.
Common causes that can result in the transfer of moisture from the external facade of a structure into its living accommodation are leaky rainwater goods, dilapidated masonry, and faulty joints between windows and walls.
Fortunately once the defect is correctly identified, and the source of water ingress eliminated, the likelihood of further penetrating damp is minimised.

Cavity wall structures are designed for the function of preventing the transfer of water from the outer leaf to the inner.  However defects in cavity wall construction and in maintenance work can often lead dampness via blockages in wall cavities.  Typically blockages can occur at construction stage where mortar droppings an fall onto cavity trays and wall ties to provide a bridge by which water can migrate across the divide.
Blockages can also be the result of building repair activity where rubble is allowed to fall into the cavity and accumulate at window heads or where heavy hammer drilling machines have caused the cavity face of the masonry to burst, leaving large lumps of brick lodged in the cavity.  The problem is made worse where such brick debris forms a drain-like channel in insulating materials that are located between the walls.
Where porous masonry contributes to penetrating damp, a silicone / siloxane pore-lining emulsion can be painted or sprayed onto the external surface of the masonry to provide a water repellent surface that reduces the capillary absorbsion of the building facade without clogging of capillary pores and without impairment to vapour permeability (ability of the wall to breathe and allow evaporation).