Waterproofing and foundations

Drainage and Waterproofing

A wet foundation will bring uprising damp as well as peeling renders and paints. Capillary suction is a natural property of all masonry and renders. Proper drainage and protection of the foundation will reduce rising damp.

Capillary processes in masonry

All materials with a continuous porous system will create capillary suction. The finer the pore structure the higher the rise. In brick masonry with lime-based bedding mortars, up to 150 cm capillaries have been recorded. It is therefore of utmost importance to avoid water reaching the construction. Both clogged and old drainage can be a cause of wet foundations as they prevent water from flowing away from the foundation. A badly planned transition zone between the façade and ground is also a frequently encountered issue, both in old and new buildings. The use of asphalt close to the foundations may trap water and lead to poor drainage. We also see renders that experience capillary suction and are used down into wet soil which allows capillary rise both in the render and in the masonry itself.

Drainage and waterproofing on the outside of the foundation

A good rule is to stop the water on the outside of the wall. Stopping the damp on the inside is often a short-term solution. A prerequisite for dry foundations is a well designed and applied drainage system. Well planned drainage consists of a system for leading the water flow away from the foundation, including surface fall, a drainage system, drainage materials (e.g. Leca®) and suitable waterproofing of the base. Waterproofing can consist of both sheet materials and bitumen-based materials. Injection systems to stop rising damp are also available; in those cases, a full drainage programme is not possible. But as a good rule, all waterproofing systems should be used in combination with good drainage. When water is not present, no rising damp should occur and therefore reduce the risk of damage due to moisture and frost. Please contact your local organisation to get a description for both systems and materials that can be used in your region.