Understanding Waterproofing
Waterproofing is the formation of an impervious barrier over surfaces of foundations, roofs, walls, and other structural members. The function of the impermeable barrier is to prevent water penetrations. The building surfaces are made water-resistant and sometimes waterproof.
A waterproofing membrane is a layer of material installed around building foundations to repel water. There are two primary types of membrane: a liquid, such as water-based, solvent-based, cement-based and bituminous-based; or a sheet, which includes torch-on bitumen, PVC, Butynol or Peel and Stick. Membranes are designed with specific properties that make them suitable for particular environments. Polyurethane liquid membranes, for instance, are good for flat roofs or exposed areas and recommend using sheet systems for balconies and basement waterproofing, and bituminous coatings can be a good choice for concrete foundations. A quality membrane will be durable, possess excellent waterproofing properties and be able to withstand natural building movement. The other factors will depend on your particular usage.
Defining Membrane Class Types
Waterproofing membranes are sold based on the merits of the elongation properties and their ability to bridge cracks. The current Australian Standards classify membranes into Class I, II and III according to % Elongation:
-
Class I: 0-59%
-
Class II: 60-299%
-
Class III: 300% and above
Note: The % E is measured without any re-enforcing mat – which when added, will reduce the elongation.
Real World Performance
The membrane can have restricted or non-restricted movement depending on its bonding to the substrate. The way the membrane is bonded also affects the extent of the flexibility and elasticity of the product. If you use a bond breaker over a crack, it is much better if the crack were to open up later on. This is shown in Figure 1 (bond breaker) in comparison with Figure 2 (no bond breaker).
Benefits of Liquid Membranes
-
Seamless – so no joins or seams as areas of potential weakness.
-
Flexible – membrane contracts & expands with roof surface.
-
Conforms to Shape – around roof services, rails, stairs etc.
-
OH&S Compliant & Eco-Friendly – no heat, fumes or torches.
-
High Performance - Long Live & Robust Adherence.
-
Encapsulation – preserving whatever is underneath & protection from weathering.
-
Cost Effectiveness – liquid roofing provides a cost-effective method of making a new or existing roof waterproof.
Benefits of Sheet Membranes
-
Uniform Thickness : Since the sheet membranes are packaged in rolls that are applied onto the surface, you can be assured that the thickness of the membranes is uniform and even throughout.
-
Exact Coverage : The amount of coverage for each sheet membrane is already determined per roll. Given its consistent size/thickness, it is not subject to over or underuse like liquid membrane can be.
-
Can be applied in a wide range of weather conditions, and over green concrete.
