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Flat roof design has developed as building materials and construction methods have changed. The latest edition of BS 6229, published in 2025, brings updated guidance on drainage, insulation and fire performance. These changes affect how roofing systems are planned, specified and installed.
For property owners, the practical point is that a flat roof needs to work as a complete system. The deck, insulation, waterproof covering and drainage details all have a part to play. A well considered design can help reduce the risk of standing water, heat loss and avoidable faults.
Contact us TodayBS 6229 is a code of practice for designing, constructing and maintaining roofs with continuously supported flexible waterproof coverings. It applies to flat or curved roofs with a pitch of up to 10 degrees. The supporting deck may be concrete, metal or timber based.
This can include roofs finished with single ply membranes, provided the roof meets the standard’s scope. The standard is intended to guide roofing professionals and clients through the design and construction process. It provides recommendations rather than setting out building law.webstore.ansi.org
The 2025 edition supersedes BS 6229:2018, which is now withdrawn. The new edition came into effect on 31 December 2025. It updates design guidance, particularly in three areas: roof falls and drainage, the thermal performance of inverted warm roofs, and the fire performance of roof systems.
Get a Fast Flat Roof Leak RepairThe updated standard gives specific attention to the thermal performance of inverted warm roofs. In this type of roof, insulation sits above the waterproof layer. The design needs to account for how rainwater can affect heat loss through the insulation.
For property owners, this shows why insulation should not be selected in isolation. Its performance depends on how it works with the waterproofing, deck and other roof layers. Good detailing also matters around edges, outlets and roof openings, where gaps or poorly joined materials can affect the finished roof.
Building Regulations have separate requirements for energy performance. In England, Approved Document L provides statutory guidance on meeting the energy efficiency requirements of the Building Regulations. BS 6229 can inform good roofing practice, but it does not replace those requirements.
Request Emergency Leak InspectionThe 2025 edition also updates guidance on fire performance, including the fire classification of a roof system. This draws attention to the complete roof build up, rather than the waterproof covering alone.
When a roof is specified, the designer should check that the chosen materials are suitable for the building and the intended use. This is especially important for commercial properties or roofs with other uses or equipment. Property owners should ask their roofing contractor how the proposed materials and construction have been selected for the project.
Request Your Free Flat Roof QuoteBS 6229 is a code of practice, not a law in itself. Its recommendations help guide good design and construction, while Building Regulations set separate legal requirements. The BSI also makes clear that following a British Standard does not provide immunity from legal obligations.webstore.ansi.org
The right approach is to consider the standard alongside the relevant regulations, the building’s needs and the roofing manufacturer’s instructions. A qualified contractor can help explain which requirements apply to a particular project.
Schedule a Commercial Roof SurveyBS 6229:2025 is the current edition. It superseded the 2018 edition and came into effect on 31 December 2025.
It can apply to roofs with continuously supported flexible waterproof coverings. Whether it applies to a specific roof depends on its construction and whether it falls within the standard’s scope.
The main updates concern designing roof falls to achieve drainage, the thermal performance of inverted warm roofs, and the fire performance of roof systems.
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