June 2006
Purlin Division
METSEC ADDS VALUE WITH DESIGN SERVICE

Added value through its in-house design service is one reason why Metsec's light gauge galvanised steel zed roof purlins have been specified for the Brigg County Primary School project.

Metsec used its own MetSPEC 9 building shell design software to identify the most structurally efficient and cost effective solution to support a combination of green 'sedum' roofing with some Cambrian slate on the school at Brigg in North Lincolnshire.

The complex design of the 2,200m² school - a series of interconnected buildings of different heights , set around a square central courtyard - meant Metsec had to design the purlin systems for ten separate mono pitch roof areas. Half the roofs face inwards, sloping down towards the courtyard with the remaining five sloping in the opposite direction.

From MetSPEC 9 analysis to wind code BS6399 : Part 2, the highest wind load (locally) adopted was 1.702kN/m² reducing to a general of 0.766kN/m². The abrupt changes in roof heights meant designing the roof purlins for snow drift loads up to 3.0kN/m² in places.

The solution involved a predominantly sleeved system of mainly 262mm and 302mm deep zed purlins, spanning up to 10m and spaced at 1.2m centres, to support a dead load of 0.82kN/m² for the sedum elements of the roof. The roof coverings are supported on a standing seam liner which offered no lateral restraint to the purlins so struts were used.

According to David Cartwright of engineers Andrew Russell Associates, the green roofing solution was chosen by the client, North Lincolnshire Council, for practicality: "The sedum roof will reduce noise ingress from a nearby motorway as well as cut solar gain. Its low maintenance properties were also a factor."

A growing number of education facilities are being designed with green roofs and several recently have been specified with Metsec lightweight galvanised steel zed purlins or lattice beams for their high strength to weight ratio, long span capabilities and ease of roof fixing. Metsec's design service also takes the responsibility for the roof covering support structure
away from the architect / engineer and provides the most technically efficient and cost effective solutions.

Steelwork fabricator on the Brigg School project is Pudsey Steel with Hull-based Hall Construction the main contractor.

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