Waterproofing is essential to many concrete structures to prevent water penetration which not only causes problem of mold and damage inside the structure but may degrade the integrity of the structure. In other cases many structures such as pits and tanks may be designed to hold water and over time cracks and erosion may reduce the water holding integrity of the structure.

Naturally concrete is a porous material and may require special admixtures such as Xypex added to the wet cement mixture. Xypex forms a crystaline structure deep in the pores of concrete preventing water ingress into the concrete, this is a highly effective waterproofing solution.

For repair and remedial waterproofing of existing concrete structures or where a waterproofing additive has not been specified in the concrete formulation typically a waterproofing membrane is the most used waterproofing solution. A waterproofing membrane is a thin layer of material which forms a continuous layer over a structure and does not allow water to pass through. A typical example is a waterproofing membrane that laid above a structural slab and below the finish tiles in wet areas of a house.

A waterproofing membrane needs to be strong, flexible, tear-resistant and elastic enough it will stretch to cover cracks and the contours of the building. In case the membrane will be subjected to the sun, it needs to be UV stable. The membrane should be flexible enough to take any shape it's laid over, and be capable of turning up and around other construction features and walls.

There are two types of membranes, sheet and liquid applied.

Sheet membranes are generally sold in large rolls and composed of plastic, polymer, rubber or bituminous synthetic backed material. In the case of PVC and rubber backed sheeting they are simply laid across the area to be waterproofed. PVC sheeting has the advantage that the seams can be welded to form a seal. Rubber-sheeting is used in higher traffic areas or areas subject to inundation.

Torch on membranes are often used in construction situations which involves melting and then fusing a rubber, bitumen, or elastomer layer onto the surface to be waterproofed. It is imperative that there is not large temperature fluctuations during the curing process as this may affect the seal with the surface. This type of waterproofing is permanent, durable and if laid correctly a very effective waterproofing solution for large areas.

Liquid or spray applied membranes are the other main type of waterproofing used. Liquid membranes such as polyurethane elastomers, bitumen and other epoxy-modified sprays are most common. They are popular for horizontal waterproofing application such as floors as they can be applied to large areas rapidly. Polyurea coatings are another type of waterproofing applied to floors and is more durable and flexible than epoxy. These types of coatings are often used as a protective surface coating and need to be reapplied periodically.

Another type of liquid applied membrane are cement-based waterproofing renders. These are a mixture of Portland cement and polymers which stops water penetrating the concrete. Typically used in remedial waterproofing applications and concrete patching. They provide an impermeable top coat and have the added advantage of filling cracks and resurfacing the concrete.

Some of the most common concrete waterproofing membranes are:

• Emer-clad a flexible UV stabilised acrylic membrane suitable for external applications such as facades and balconies.

• Hydron Elastoseal a synthetic rubber sheeting suitable for high traffic structural applications.

• Xypex waterproofing additives and chemical treatments which impart a crystaline structure to the concrete preventing water ingress.

• Parchem Vandex waterproofing render a cement-based barrier applied coating

• Torch On Membranes such as Fidia and Testudo synthetic polyester-based membranes