The project had to balance multiple design considerations, starting with BS 6229: ‘Flat roofs with continuously supported flexible waterproof coverings’, and compliance with specific education sector building regulations. While BB93 specified acceptable levels of rain noise transfer into various spaces, BB100 outlined fire protection considerations.

Simultaneously addressing these requirements was compounded by mechanical and electrical plant being housed on the flat roof, which demanded non-combustible zones to provide safe access for maintenance. Internal fire rated walls in the building below also required the flat roof to contribute to effective compartmentation.

As non-combustible stone wool insulation, specifying ROCKWOOL HARDROCK® Multi-Fix Dual Density across the entirety of the flat roof streamlined the installation process. Where the roof deck interfaced with the heads of internal compartment walls, ROCKWOOL Trapezoidal Fire Stops were also installed. To minimise acoustic reverberation and achieve BB93 compliance in the dining room and auditorium, ROCKWOOL Acoustic Infills were friction fitted into the perforated metal deck troughs.

Andy Towns, Designer at Southern Industrial Roofing, explained: “We didn’t have to worry about coordinating zones with different materials – it was ROCKWOOL across the board which simultaneously delivered the acoustic, fire and thermal performance we needed.”

Find out more about how ROCKWOOL supported the flat roof construction at Cobham Free School