Liquid applied waterproofing is becoming an increasingly popular flat-roofing solution for building owners, designers and contractors offering, as it does, a wide choice of high-performance system solutions for a host of requirements and applications. Suitable for roofing refurbishment, repair, new build, complex and inverted roofs; new formulations have enhanced its appeal over alternative bonded or torch-on systems.

In refurbishment, liquid applied waterproofing could be considered to deliver ‘renewability’ benefits, with its capacity to be applied over existing roofs – whether cement, metal or single-ply. This ability to overlay also makes it ideal for repairs. In both situations, the fact that it fully bonds to a variety of substrates makes it a versatile, reliable problem solver, particularly when restricted threshold heights, programme time and building occupancy are key considerations in the system specification process

For new build or where the roof features a large element of detailing – outfalls, penetrations, upstands and the like – liquid applied waterproofing delivers the flexibility to  provide fast, accurate and secure finishes. Where access is an issue, it can easily be laid without power, where lifting to the roof is difficult or where storage of bulk materials would be challenging. Finally, it is ideal for inverted roofs – such as green or blue roofs –where waterproofing reliability is a concern as failures would be particularly challenging to remedy.

Solvent-free BMI Sealoflex Waterproofing applied to international airport pier (2)

Such a superior protective, waterproofing characteristic is a function of seamless fabric reinforcement, combined with high performance polymers – either polyurethane (PUR), Modified Polyurethane or Polymethyl Methacrylate (PMMA). The result is a durable, joint-free, monolithic membrane system that maintains its integrity in the face of temperature-driven expansion and contraction. It’s this seamlessness that also makes it ideal for complex detailing, providing a homogenous seal around edges, rainwater outlets, terminations and HVAC units.

Anti-skid surface being applied to BMI Sealoflex Endura

Chief among  recent innovations is the introduction of new, proprietary solvent and VOC-free materials. Being low odour and 100% hazard-free, these products – such as BMI UK & Ireland’s Sealoflex Ultima – are a superb choice in refurbishment applications where there may be environmental sensitivities – such as concerns around the impact of odour and vapour on contractors, building occupants or the public at large.

Another health and safety feature of liquid applied waterproofing is that it is cold-applied: this eliminates the hazards of hot works, cutting, grinding and welding – and associated risks of fire. Convenience for contractors and building occupants is represented by liquid roofing’s quick cure times which, depending on environmental conditions, can be 45 minutes to ‘rainproof’ and two hours to overcoating; meaning works can be completed  quickly – important when tenant disruption must be avoided.

BMI Sealfolex Endura applied to residential terrace

Two-part catalysed coatings also offer low-temperature curing which means they are ideal for year-round application, and installation in the less climatically hospitable areas of the UK. This is supported by the availability of winter grade coatings for use in exposed and aggressive environments, such as coastal, elevated or northerly situations.

Similarly, for high-traffic areas where membranes need to be hard-wearing, such as balconies, walkways, roof terraces and podium decks; superior grade reinforcing fabrics can be specified, creating exceptional membrane durability. UV-resistant ‘wear coats’  or anti-skid quartz granules can also be applied as finishes.

Fast application and rapid curing times also means that disruption to building users is minimised too, as walkways and terraces need only be closed for the shortest times possible.


Where extra resistance to wear and traffic is required, polymethyl methacrylate (PMMA) systems offer many possibilities for wearing courses and trafficable finishes.

BMI UK & Ireland’s dedicated field service has a network of technical advisers available to provide liquid applied waterproofing specifications that qualify for insurance-backed guarantees of up to 25 years depending on the system. The company’s advisory service for specifiers is free of charge and consultants are available to answer queries on cold-applied liquid waterproofing design and installation. 

For more details on BMI UK & Ireland’s Sealoflex range, visit