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When the question raised by “what is the best flat roof covering?”, there are a lot of factors that have to be considered, what is the roof build up, what is the surface being used for (i.e. a leisure deck), balcony, roof garden, water containment, highly trafficked deck, zero falls in the roof warm deck, cold deck. As you can see that within the realms of flat roof covering most liquids cover nearly all these questions. GRP can be applied to OSB board or overlay systems but on larger scale projects over 60m² an expansion trim joint will need to be used. Modern GRP systems can meet the requirements listed as these areas seamless and can be applied to zero falls. GRP can be applied to insulation, but this process is time consuming.
Liquid PU systems are another great system but nearly all are not self-terminating as this can cause problems on larger areas of overlaying roof types, without the terminus edge water can track back under the adjoining system after a period of time. But with the ease of application straight from the tin and no catalyst added, this means working time is greatly reduced with larger scaled areas being applied in a single day. Pu or Polyurethane liquids are a lot more flexible then resin based grp but are not as robust and need a carrier membrane (on timber/ uneven deck).
PMMA Poly (Methyl Methacrylate) is a fast curing acrylic resin. The system is also seamless, crack bridging and joint-bridging waterproofing system that can withstand mechanical stresses and for challenging vegetated roof systems. Bitumen (hot) coated systems can be applied with a reinforced felt or fleece imbedded layers, and are great for standing water areas, they are extremely flexible and with rubber being added to the bitumen this makes it extremely flexible making it a contractor’s choice. The material is sensitive to UV light and all upstands/ details where the membrane becomes exposed a protective membrane such as torch-on cap sheet should be applied to stop UV degradation.
Polyurea systems are a fast-applied system, mainly applied in a single pass and reinforcement is generally not added, these have a good long-term resistance to UV light. Unsaturated polyester resins with fleece reinforcement can be sprayed or hand applied and with this embedment makes them extremely flexible and cancels out ‘crack bridging’. Bitumen emulsion type systems are water based systems are cheap alternative but have to be applied and allowed to cure before fully sealing the building, they are designed to be sprayed or roller applied, with a primer added, this system comes with added strengthens, and under the right condition is a great material. As we can see with the liquid roofing systems some have strong advantages but also come with limitations and with worldwide sales in liquid products being on the rise all these systems ‘hold their own’.