Flat roofs can present a range of technical challenges, therefore, choosing the right waterproofing system early in the design or refurbishment process helps reduce risk, improve longevity, and ensure practical delivery on site. Whilst you may have numerous questions related to flat roofing specification, below we explore three of the key considerations that can help guide the right decision – especially when dealing with liquids as a system choice. Should you have a question about an upcoming project that we have not answered below, please get in touch with our team who will be happy to assist you further.
1. Is there complex detailing present?
Complexity is common in flat roof design – with penetrations, upstands, abutments, plant, and perimeter trims often requiring particular attention. Getting these details right is key to long-term performance.
Liquid-applied membranes, particularly polyester-based systems, are well-suited for complex or irregular roof shapes. Applied wet and curing to form a single, joint-free membrane, they mould around difficult shapes and transitions without laps or welds. This reduces the reliance on mechanical fixings or additional detailing steps – which can sometimes create failure points in other systems.
Where roof complexity is high, liquids offer an efficient route to durable waterproofing, helping reduce site time and the need for specialist tooling.
2. What is the existing roof’s composition?
Refurbishment projects often involve overcoating existing roof coverings. But not all waterproofing systems are compatible with all substrates. For example, applying single-ply membranes over bitumen may require a separation layer or full strip-out.
Liquid systems are generally compatible with a wide range of existing materials, including felt, asphalt, GRP, concrete, and PVC. Provided the substrate is stable and dry, liquids can often be directly applied, avoiding disruption to the structure and minimising waste.
This flexibility makes them a good choice for overlays, where retaining the existing build-up helps save time, cost, and environmental impact.
3. What are the long-term expectations for the roof’s performance and upkeep?
Maintenance matters. Roofs need regular checks, but the amount of upkeep varies between systems.
Seamed systems like felt or single ply can require more frequent inspection, as laps and welded joints may be vulnerable over time. Liquids, on the other hand, form a single continuous surface with no seams, reducing areas of potential failure.
Periodic inspection, typically once a year or after severe weather, is usually enough to keep a liquid roof in good condition. This means less disruption for clients and greater peace of mind across the roof’s lifespan.
Expert Support From Start to Finish
At Polyroof, we’ve worked with architects, surveyors, and contractors for decades to ensure the right solution is specified, from new builds to overlays. Whether you need a full roof survey, U-value calculation, or assistance with detailing, we’re here to help.
Are you ready to discuss your next specification? Get in touch with our technical team today.
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