Norbord OSB raises the roof at new “Forest school” building
Norbord’s 18 mm Sterling OSB has been used to provide structural rigidity to the roof of a new school building in the West Midlands.
Designed by local practice, APEC Architects, the new 100 sqm single-storey building provides a “forest classroom” for pupils at St John and St Monica Catholic School in Moseley, near Birmingham.
The single-storey structure is a timber frame supplied by Frame Wise of Presteigne, working closely with principal contractor Beam Construction, which incorporates Sterling OSB in the walls and roof.
As originally specified, the timber frame came in over budget so Frame Wise value-engineered its system to reduce costs. Instead of bespoke sections, a standard wall section with factory-installed insulation was supplied. To further reduce costs, the thickness of the external sheath was reduced to 9 mm Sterling OSB with no loss of performance. Standardisation is the key to keeping costs down.
However, the biggest innovation was the use of Sterling OSB sheathing to simplify the roof design. “The original design required larger timbers and a certain amount of steel bracing to support the roof” says designer Naomi Fisher. “Sarking the roof eliminated the need for all this bracing” she explains.
Instead of using steel cross-bracing to stiffen the roof structure, Frame Wise built the roof in the form of cassettes which could be manufactured off-site and craned into position. To provide the necessary rigidity, Norbord’s 18 mm tongue-and-grooved Sterling OSB was used as a sarking board which allowed the roof to work as a diaphragm and give the structural integrity the building needed.
This solution not only saved time and money; it also brought several other benefits. It simplified all the connections and layout and, by removing the steelwork, reduced cold-bridging. Even the architecture was improved by providing a completely clear-vaulted ceiling with no beams or tie-bars spanning the roof space.
Eileen Walker, head teacher of St John and St Monica Catholic School comments; “We are thrilled with our Forest School Building – both how it looks and how the project was completed within budget.”