New BS 8217 Standards for Built-Up Roofing Take Effect

The revised BS 8217:2026 standard for reinforced bitumen membranes has now come into force, introducing significant changes to the way built-up roofing systems are specified, installed and warranted across the UK.

What Has Changed

The most notable update is the tightening of thermal performance requirements. Minimum U-values for flat roofing assemblies have been reduced from 0.18 W/m2K to 0.15 W/m2K for new builds, bringing flat roof specifications in line with the targets set out in the Future Homes Standard. For refurbishment projects, the threshold moves from 0.18 to 0.16 W/m2K.

This means thicker insulation layers will be needed on most projects. For a typical 150mm PIR insulation build-up, contractors will now need to specify 180mm or more to achieve compliance. This has knock-on effects for upstand heights, threshold details and drainage falls.

Who Is Affected

The changes apply to all new build and major refurbishment projects in England and Wales where planning permission is sought after 1 April 2026. Scotland and Northern Ireland are expected to adopt equivalent standards by mid-2027.

Roofing contractors, architects and building control bodies all need to update their standard specifications. Manufacturers have already begun updating their system declarations and BBA certificates to reflect the new requirements.

What Contractors Need to Do

There are several practical steps contractors should take now:

Review your standard specifications. Any template specifications referencing BS 8217:2020 need updating. Check insulation thicknesses, vapour control layer requirements and detailing standards against the new document.

Check manufacturer guidance. Most major membrane manufacturers including IKO, Bauder and Alumasc have published updated technical bulletins. These detail exactly which product build-ups achieve compliance under the new standard.

Update your quoting process. The additional insulation thickness will increase material costs on most projects. Make sure your estimating templates reflect the thicker build-ups required.

Training and CPD. The NFRC and several manufacturers are running training sessions on the new requirements throughout Q2 2026. These are worth attending, particularly for companies working on design and build contracts.

Looking Ahead

The revised standard is part of a broader shift toward improved building performance. The roofing industry should expect further tightening in 2028 when the full Future Homes Standard takes effect. Contractors who adapt early will be better positioned to win specification-led work.

For detailed guidance on the new requirements, the NFRC has published a free technical guide available to all members on their website.