Most masonry building materials are permeable. Such permeable structures allow water vapor to be transmitted, but also allow liquid water to penetrate. Liquid water or moisture can penetrate permeable masonry building materials due to natural capillary absorption. Water is the main cause of deterioration of masonry building materials. Problems such as rising damp, moisture penetration, dampness through shower or bathroom walls, efflorescence on external walls, stains, fungi or algae growth, concrete corrosion, and loss of thermal insulation are all due to water penetration.

Surface coating or membranes can stop water penetration by forming a continuous film to block the open capillaries of the masonry materials. However, surface coatings or membranes are not an ideal method to protect masonry from penetrating damp. This is because surface coatings may stop water vapor transmission resulting in wet walls due to condensation of water vapor within the capillaries. Water may still penetrate into the masonry through hairline cracks in the coating film. Surface coatings cannot stop rising damp. Surface coatings have a limited lifetime due to natural deterioration of the coating film. Surface coatings will change the surface appearance of masonry building materials.

The ideal method to stop water penetration into masonry while still allowing water vapour transfer, is to treat the wall with a water repellent impregnant. Water repellent impregnants can penetrate the masonry capillaries forming a few millimetres water repellent barrier near the surface of the masonry to stop water penetration without blocking the capillaries. It does not change the surface appearance. The water repellent permanently bonds to the masonry via chemical bonding resulting in a durable water repellent barrier within the masonry. Durability of a water repellent treatment is much longer than a surface coating.

Tech-Dry has an extensive range of water repellent products specially formulated for different masonry building materials. For more information click Products. For general information on how to identify the source of damp in a building, please click here.