The traditional ‘pour and roll’ felts consists of a 3-layer system consisting of thin bitumen felts glued together with a hot liquid bitumen between each layer. There is minimum internal reinforcing of natural hessian fibres, which is prone to rotting, drying out and cracking with age or UV sun damage. A life expectancy of up to 10 years.
While low cost and used for all types of roofs of any size, the system requires a blow torch to heat and melt the rear of the felt into the roof structure below. The roof construction may not be able to take the weight without movement or cracking occurring. Any moisture rising from underneath can cause surface bubbles. More recent modified bitumen technology contains polymers, which offer better resistance to UV damage and cracking.
Self-adheres with no laps or joints
UV stable for up to 15 years
Can be used as roofing, deck or podium membrane for Green roof applications, and Warm roofs
Compliant with the requirements for the resistance of water penetration and susceptibility to leakage
Product warranty of 5/20 years, depending on type of application and workmanship
The self-adhesive version consists of asphalt, polymers and filler but has a low shelf life as bonding properties of the membrane reduce with time.
Generally unsuitable for exposure to sunlight, bituminous coating will dry out and become very brittle, allowing moisture to enter. Unless modified with more flexible material such as polyurethane or acrylic based polymers.
Self-levelling membrane ideal for standing seam metal, aged SPF, wood and concrete
Can also be sprayed, brushed, or roll applied up to 80 millimetres thick on a vertical surface
Can be fully reinforced with fabric
EPDM (ethylene propylene diene monomer) – known as a “rubber” roof – is usually made of black vulcanized rubber and can often be installed in one complete layer.
While lightweight, flexible, hard wearing and no torch heat required, the surface may shrink by as much as 6 per cent per year. Edges of the building can be pulled out causing seams to be pulled apart and vent pipes displaced, among other issues. The seams of EPDM are sealed with water-soluble glue which can also lead to seam failure over time.
Most ‘rubber’ roofs are glued down to a new wooden roof substrate, although they can be laid on top and mechanically fixed by screws at intervals depending on wind uplift ratings, or held down with ballast, which can weigh 8-12 pounds per square foot.
In time, temperature fluctuations can make the sheet brittle and cause cracking, while wind damage can unfasten the sheet from the substrate.
Can be elongated to 360% of finished size and full recovery
Can withstand extreme uplift pressure
Meets the requirements for cyclic movement over joints over time
Polyurethane (popularly known as PU) coating is highly flexible with excellent heat resistance and highly sensitive to moisture content, which makes it suitable for use as a waterproof coating. However, the moisture content in a concrete slab has to be carefully evaluated to prevent peeling or de-bonding of membranes, which can occur in time.
Polyurethane is made up of two components, which combine in a specific ratio to create a liquid coating for waterproofing applications, most often for a flat roof area exposed to weathering.
Available as a single component and relatively low cost, the membrane can be easily applied with brush or roller, and is a popular waterproofing choice. However, water-filled blisters can appear under the membranes resulting in interior leakage when the blisters expand to a crack or joint in the concrete slab. Their size can be so large that replacement of the entire membrane will be required.
Highly strict quality control criteria includes moisture content reading before, during and after application
Product durability in ALL weather conditions
Waterproofing and Damp proofing of wet areas in buildings
Membrane will exceed a twenty-year life expectancy
Usually a rigid or semi-flexible type waterproofing often used in the internal wet areas such as toilets, where it is not exposed to sunlight and weathering. Cementitious products have minimal flexibility and will tolerate almost no joint or crack movement.
Metal Coating Systems
Metal roofs, and their washers or screws, will wear out over time due to the expansion and contraction of the
metal, which can lead to water in the building. The mastic along the seams will eventually harden and crack. Skylights and seals are also a common cause of failures.
The true cost of using cheap quality coatings is that the waterproofing is usually short-lived. Some coatings become brittle with age, turn chalky, or harden and crack over time. Cutting corners to save costs by not using fabric for seam reinforcement will prove expensive in the long run. A system that is unable to withstand the amount of elasticity required, will soon result in cracks appearing on the seams and an entire roof system failure.