Temporary but permanent
April 1st 2005

While steel framed buildings with heavy duty tensioned PVC covers are generally regarded as temporary, in practice they are more frequently used as permanent structures, according to Collinson TMS.

The company supplies and erects BestHall tension membrane buildings from Finland and says when evaluating the lifespan of the structures it is necessary to consider four separate elements: the design specification, the fabric membrane, the steel frame and the method of fixing.

In terms of design specification, the buildings are designed in Finland to withstand the region’s harsh climate. The PVC membrane is manufactured by Ferrari SA in France using patented Preconstraint technology – which provides both long life expectancy and exceptional dimensional stability. German testing organisation TÜV has tested the material and states that “under normal conditions, a life expectancy of 25 years is confirmed.” Buildings having the original membrane are still in use after 30 years, which is comparable to the lifespan of sheet steel used for cladding conventional portal frame buildings. If necessary, after many years, the steel framework can easily be refurbished with a new PVC membrane to resemble a new building.

The strong steel frame sections are shot blasted and epoxy painted or can be hot dipped galvanised to EN ISO 1461 for specific applications. In terms of fixing, for buildings up to 50m span the BestHall ground anchor system uses steel rods pneumatically driven into asphalt at varying angles to depths of 1.2m; expansion or chemical anchor bolts are used on concrete.

For buildings with a span greater than 50m, a concrete ring beam around the entire periphery of the building is recommended.

According to Collinson, due to BestHall’s preengineered design, buildings can be erected quickly on site. For example, a 1,500m2 unit can be installed and ready for use in two weeks.

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