The material factors that influence durability are complex and related to the chemical composition of the liquid constituents, the thickness of the system as well as the type and density of the reinforcement. Central to the long-term success of liquid-applied waterproofing systems is preparation of the substrate and achieving the required membrane thickness.
Typically, manufacturers only guarantee their products when applied by approved and trained installers. This is not surprising as standards of application by squeegee, roller, brush or spray are very demanding; layers are measured to tenths of a millimetre and avoidance of air holes is essential. The weather conditions in which the liquid is laid are critical as are the times between application of coats.
Other key durability issues include:
- Ensuring the substrate construction and condition is free from material which may impair the bond, create thin spots or penetrations in the coating.
- Provision for moisture removal of damp substrates.
- Ensuring there are no point loads on the roof.
- Specifying a system suited to the expected traffic load.
- Appropriate detailing at edges, verges, upstands, outlets, movement joints and day joints.
Liquid-applied coating that forms the waterproofing layer of an inverted roof should not require replacement during the life of the building, provided it is fully protected from ultra-violet radiation and extreme temperature variations by a loading layer above it.
By increasing the longevity of roof materials by using liquid roof coatings, organizations can avoid a substantial amount of roofing waste. There are an estimated 11 million tons of asphalt roofing waste going into landfills every year. Using liquid roof coatings can greatly increase the life of existing roof materials (particularly roof coatings) and reduce the amount of torn-off roofing waste going into landfills. The roofing waste that remains can be recycled into road mixes using existing processes already operating.