Crystalline Waterproofing for Retaining Walls

Basics

• Crystalline waterproofing works by penetrating into the microscopic pores of concrete. Crystalline waterproofing is generally a compound that consists of Portland cement, fine silica sand or quartz, and chemicals. A chemical reaction occurs between the agent, moisture and the chemical by-products of cement hydration to form a nonsoluble structure. When prepared and applied correctly, the crystalline waterproofing will protect the wall from water and a range of aggressive chemicals.

Application

• Crystalline waterproofing is typically sold as a powder and mixed with water shortly before application to form the slurry that is applied to the wall. This type of coating is typically applied as a spray but also can be troweled or brushed on. If applying crystalline waterproofing to a brick or block wall, it may be desirable to apply the coating to only the mortar or grout joints. In this case, either tape over individual bricks or use burlap or another material to clean brick faces following application. Follow manufacturer instructions when preparing and applying crystalline waterproofing.

Considerations

• If the retaining wall is rendered waterproof through the use of crystalline waterproofing or another sealant, there must be some way for moisture that builds up behind the wall to drain or serious structural damage could result. One common drainage method involves the installation of a perforated pipe in a gravel-filled trench at the base of the wall.

  Because crystalline waterproofing forms an integral structure through chemical reactions, it can sometimes take up to a month for a product to reach its full waterproofing abilities.

Additional Sealant Options

• There are handful of other material types that can be applied to a concrete or masonry retaining wall to block penetrating water. Some masonry sealers consist of polymers such as polyester rather than Portland cement. These sealers also fill voids in the concrete but do not react chemically or become an integral part of the structure. Water repellents and clear repellents, though they cannot always make a wall completely waterproof, are treatment options that can greatly slow water absorption.