Update to British Standard on Flood Resilient Construction, 27 March 2025
Today, the British Standards Institute (BSI) Group published an updated version of Standard BS 85500: Flood Resilient Construction – Improving the Flood Performance of Buildings - Guide.
The new standard provides detailed and useful guidance on how to construct and retrofit buildings to make them more resilient to flooding, including the steps to take to improve the ability of buildings to recover their thermal performance after a flood event. Choosing appropriate insulation materials for the walls, for instance, will help avoid the insulation slumping or becoming dislodged during a flood, and can aid the building’s ability to dry out afterwards.
Supporting building recoverability after a flood is of paramount importance to flood resilience, particularly as efforts to keep water out of a property could fail in all but the most minor of floods. The Standard describes, for instance, how mineral wool insulation does not impede the drying out of masonry cavity walls. The ‘vapour open’ nature of this material allows water vapour to diffuse and the masonry to dry via the cavity even when it is fully filled.
Coupled with water repellent additives and inherent vapour open properties, certain mineral wool insulation products also have mechanical and strength characteristics sufficient to withstand the forces associated with flooding without slumping.
MIMA responded to the BSI’s consultation on the draft Standard last year, emphasising the need for it to include clauses to make clear that designers and specifiers should contact manufacturers directly to confirm the flood resilience of a given insulation product, for use in specific applications in buildings in flood prone areas. Gaining written confirmation of the expected performance is recommended. It should not be assumed that any particular insulation type or product is automatically ‘safe’ to use in a flood zone.
Find out more about Standard BS 85500 here.
Also see research by Glasgow Caledonian University on the flood performance of mineral wool insulation in masonry cavity walls here.
27th March 2025