A new class system

Architects working on school building projects are increasingly turning to I-joists for large-span roof sections where environmental performance and speed of construction are key factors in the design and build programme.

Recently James Jones & Sons' Timber Systems Division has worked with distributor North Yorkshire Timber (NYT) on two schools in Wales to provide the roof structures for a primary and a special needs school, both of which used over 4,000m² of roof cassettes constructed using JJI-Joists.

Sandfields Primary School in Port Talbot is one of the largest projects of its kind to have a roof built using roof cassettes. Timber Systems Division undertook the fabrication drawings for the project and supplied its UK manufactured, FSC-registered JJI-Joists to NYT in 220mm, 350mm and 450mm sizes. NYT in turn produced 4,000m² of roof cassettes in varying lengths up to 12m.

The £7m project for Neath Port Talbot County Borough Council had a 61-week contract period and was all delivered to programme, reaching completion in good time for the start of the school year last autumn.

The building fabric is SIPs (structural insulated panel systems), which is acknowledged as one of the most energy efficient and sustainable forms of building. The school will house over 300 primary school pupils, and incorporates photovoltaic cells, underfloor heating and a rainwater harvesting system, and is expected to achieve a BREEAM rating of "Excellent".

In Anglesey, in North Wales, The Ysgol Y Bont Special Needs School also incorporates one of the UK's largest school roofs to be built using cassettes. 4,000m² of roof cassettes, in varying lengths up to 12m long, were fabricated by NYT using 10,000m of 300/400mm James Jones JJI-Joists. James Jones also supplied 1,600m of glulam in varying dimensions.

This project has adopted several approaches to achieve an Excellent score from BREEAM including photovoltaic panels; biomass heating; solar hot water; low water demand sanitary installations and a sedum green roof.

The new two-storey school will provide modern learning facilities for students from three to 19 years, including classrooms, a multi-purpose hall, a hydrotherapy pool and sensory rooms.

The completed project, on behalf of Anglesey County Council, cost a total of £8.5m and was delivered to programme.

Design and performance
In both of these projects, using JJI-Joists to create roof cassettes allowed the design and build teams to have large, clear-span roof systems that met stringent targets for insulation and minimal heat loss.

"I-joists incorporated into roof cassettes are increasingly popular where a large span roof section is needed that can meet tough environmental performance standards and still allow for fast build and easy onsite handling," said Mark Tilston, business development manager for James Jones' Timber Systems Division.

"More and more customers are looking for the certainty that comes with off-site manufactured roof cassettes - dimensional accuracy; the ability to achieve thermal values relating to current sustainable code; significantly reduced health and safety risk; cost certainty and, above all, speed of installation," added Rob Timmens, sales director for North Yorkshire Timber.

Add to this the fact that, uniquely, James Jones can supply carbon negative data for JJI-Joists, allowing architects and specifiers the opportunity to quantify the beneficial impact of using them as part of a building's overall carbon footprint, means that more and more schools will use this method of construction in the future.