Egg-shaped school waterproofed by 1.2mm thick membrane

A rubber membrane just 1.2mm thick has waterproofed an egg-shaped primary school in Birmingham.

AAC Waterproofing roofed the 1,600sq m, timber-bearing Four Dwellings Primary School, a new build project forming part of the Birmingham BSF (Building Schools for the Future) programme, using its Prelasti prefabricated EPDM material.

AAC Waterproofing accurately measured and prefabricated the challenging, curved roof off-site at its North Wales factory. The company used a Datum line and bonded individual sheets in stepped lengths.

The new Four Dwellings Primary School, on the site of the secondary school with the same name, has been designed “from the inside out” by project architects dRMM. Classrooms surround a central hall and provide a link between internal communal areas and external landscaping.

AAC discussed with dRMM its Prelasti EPDM “synthetic rubber” alternative to asphalt and felt materials, and the two worked together on a basic specification for a solution using EPDM material.

At the tender stage BSF lead contractor Birmingham Lend Lease Partnership chose AAC’s Prelasti solution for its durability, cost, environmental (BREEAM A+) and lightweight qualities that particularly suit timber-bearing structures such as Four Dwellings.

AAC supplied a prefabricated single-ply EPDM solution consisting of a vapour control sheet, 150mm flat board insulation and Prelasti cover. The stepped-length EPDM sheets were bonded off-site using vulcanising technology, making the roof more durable than adhered strips.

AAC’s Project Manager Mike Grant said: “We are finding that timber-frame structures are being used more widely as an alternative to steel because of their environmental properties.

“EPDM is the ideal waterproofing membrane for timber structures such as Four Dwellings, as it is lightweight, environmentally sound, and involves no hot works or fires, as asphalt does.”

Typical AAC projects include commercial and residential roofing, including school refurbishments, new builds, and Government building projects across England and Wales.

AAC installed Prelasti at TV adventurer Bear Grylls’ lighthouse off the North Wales coast, and roofed Snowdon’s rebuilt mountain summit café.

The company has also supplied and installed Prelasti as a complete external “skin” for an artist-designed house in Dungeness, and an environment-friendly row of terrace houses at Scotland’s first housing expo.