Guidance for the Use of Building Boards with A1 or A2 Reaction to Fire Classifications in Flat Roofing

Within the flat roofing industry, there is a growing demand for products with A1 or A2 reaction to fire classifications (formerly referred to as non-combustible and of limited combustibility, respectively) to be used as alternatives to OSB3 and plywood. This is due to the apparent drive of Approved Document B towards the increased use of less combustible flat roof decks and the fluctuation in prices and supply of building materials. It has resulted in an increasing number of enquiries to SPRA, LRWA, NFRC, and their members about the use of such products in flat roofing applications. Some of the materials being considered, however, do not have relevant third-party approvals.

With the input of relevant manufacturers and suppliers, the document offers guidance for the use of Calcium Silicate, Cement-Bonded Particleboard, Fibre Cement, Gypsum (mat-reinforced), and Magnesium Oxide building boards as structural flat roof decks; structural abutment wall upstands (including parapets); acoustic mass layers; thermal barriers; cover boards; and/or recovery boards in flat roof overlays.