IN Brief:
- Version 2.2 of the LRWA Hot Melt Code of Practice replaces the April 2025 edition and reflects BS 6229:2025.
- Guidance has been strengthened around falls, drainage, zero falls, inverted warm roofs, blue roofs, and substrate preparation.
- Electronic Integrity Testing is identified as the recognised on-site verification method in place of traditional flood testing.
The Liquid Roofing and Waterproofing Association has published version 2.2 of its Hot Melt Code of Practice, updating technical guidance for flat-roof waterproofing to reflect BS 6229:2025 and replacing version 2.1 issued in April 2025.
The August 2026 revision strengthens guidance across specification, design, installation, testing, quality control, maintenance, and repair. It places renewed emphasis on achieving correct falls at both design and construction stages, while updating the treatment of zero falls, absolute zero falls, inverted warm roofs, and blue-roof systems.
Electronic Integrity Testing is identified as the recognised on-site verification method in place of traditional flood testing. The code also expands its treatment of substrate preparation, including curing periods, moisture checks, peel-bond testing, and the treatment of curing compounds before the waterproofing system is applied.
The revisions follow the publication of BS 6229:2025, which became effective on 31 December 2025. The British Standard covers flat roofs with continuously supported flexible waterproof coverings and introduced changes around terminology, drainage, responsibility for back falls, deck quality and surface regularity, blue roofs, inverted warm roofs, thermal performance, and the design of roof falls.
Hot melt waterproofing has been used in the UK for more than four decades, particularly where a robust, fully bonded waterproof layer is required. The systems can be used across conventional flat-roof build-ups as well as inverted roofs, biodiverse roofs, and blue roofs, so revisions to the underlying flat-roof standard affect a broad range of specifications.
Falls and drainage carry much of the technical weight in the new edition. Standing water can increase loads, place additional stress on roof components, and affect thermal performance, while inadequate falls may only become obvious once the roof is complete. By pushing responsibility for falls further into design coordination and deck construction, the guidance places greater emphasis on tolerances before the waterproofing contractor begins work.
Mike Bradbury, Technical Guidance Manager at LRWA, said: “This update ensures the LRWA Hot Melt Code of Practice reflects the requirements of BS 6229:2025 and continues to give the industry a definitive, authoritative reference for Hot Melt waterproofing systems. Falls and drainage remain critical to the long-term performance of a roof, and this edition reinforces that guidance throughout.”
Substrate preparation is equally dependent on site discipline. A waterproofing specification can be correct on paper and still perform poorly if concrete has not cured sufficiently, the surface is contaminated, moisture remains trapped, or bond strength is inadequate. More explicit guidance around surface preparation and peel-bond testing gives specifiers, main contractors, and roofing specialists a clearer basis for deciding whether the deck is ready to receive the system.
The move towards Electronic Integrity Testing also changes how completed work is checked. Electronic methods are used to identify breaches in the waterproofing layer without relying on a roof being temporarily flooded. That can avoid the practical difficulties of introducing large volumes of test water to a completed roof, although test value still depends on suitable preparation, compatible system configuration, competent testing, and action where defects are found.
Blue roofs make drainage design more complicated because they are intentionally designed to attenuate rainwater before controlled discharge. The waterproofing layer therefore has to perform while water is being managed as part of the roof build-up rather than simply moved away as quickly as possible. Clear distinctions between intended attenuation and unintended ponding are essential if designers are to avoid treating two different conditions as though they were the same.
The code also covers health and safety duties under CDM 2015 and COSHH, melter requirements, detailing at junctions and penetrations, site quality control, maintenance schedules, repairs, and operative training. That breadth reflects where failures often occur: around outlets, upstands, penetrations, changes in level, and transitions between trades rather than across uninterrupted areas of membrane.
The technical content was developed with input from manufacturers, contractors, and specifiers, including representatives from Alumasc Roofing, Axter, Bauder, BMI Group UK, Briggs Amasco, IKO, Moy Materials, Proteus Waterproofing, Radmat, and Sika. LRWA is making the document freely available, giving project teams a common reference from early specification through construction and later maintenance.
Version 2.2 does not replace the need to work from the British Standard itself, project-specific design information, or manufacturer requirements. It does, however, translate the revised standard into practical hot melt guidance at the point where design tolerances become site workmanship. On a flat roof, a few millimetres in the wrong direction can become a persistent defect, which is why the revised code spends so much of its attention on falls, drainage, and the condition of the deck before waterproofing begins.
