voestalpine Metsec's offsite product, Metframe uses Light Gauge Steel Framing systems (LGSF) sections bolted together in a 2D panel format to create complete loadbearing structures up to 15 storeys.
Whilst efficiency, versatility and sustainability are desirable attributes for any building system, they count for little without certified proof of the system's ability to meet the required technical performance standards in the areas of acoustics, thermal efficiency, loadbearing and, most importantly, fire protection.
With LGSF, fire performance in accordance with Part B of the Building Regulations and thermal efficiency in accordance with Part L are achieved through the combination of materials that are used in conjunction with LGSF to construct the wall. For external wall constructions, from inside to out, this would typically consist of plasterboard dry lining, LGSF, insulation within the stud zone, sheathing board and insulation.
A more assured approach Since Grenfell, there has been increasing recognition for the need to undertake fire testing of the entire wall construction under laboratory controlled conditions rather than arriving at a theoretical figure through calculation. This testing provides a true 'through-wall' performance which gives designers and contractors added assurance of a solution's performance capabilities, in accordance with BS EN 1364-1 (non-loadbearing covering Infill, Continuous Walling and High Bay Walling applications) and BS EN 1365-1 and 2 (covering Loadbearing LGSF structure walls and floors).
The reason for the 'through-wall' concept is that, with so many exterior façade materials available, it wouldn't be impossible to test every possible wall construction. The 'through wall' approach to performance allows manufacturers to test a meaningful number of material combinations. The tested solutions will either be from the dry lining through to the sheathing board or from the dry lining to external insulation – all using non-combustible Class A1 or A2 materials.
Freedom and choice
This approach provides the design team with the freedom to choose the desired external façade, provided, of course, that the necessary performance requirements are met, including compliance with the 2022 update of Approved Document B 2022 which means that all materials in façades over 11m are to be non-combustible too.
Independent testing
In order to achieve 'through-wall' fire performance data, voestalpine Metsec constructs different complete wall build-ups for testing at UKAS accredited laboratories. The build ups measure 3m x 3m and comprise various combinations of boards and insulation materials applied to the LGSF. Each build-up is tested using a large-scale, high temperature test (reaching up to 600 degrees Centigrade in 5 minutes), which measures the performance of the entire wall by simulating fire trying to break through a solid wall. Tests are conducted to British Standards EN 1364-1 and BS 476-22 (for nonloadbearing walls) to achieve the 120-minute, 60-minute and 30-minute fire ratings typically required by building regulations. This vast suite of testing enables voestalpine Metsec to provide a 30-year though-wall warranty to support the system performance.
A positive step
Whatever the circumstances, through wall fire testing and the performance data it returns for the combinations of materials used in wall constructions is a positive step forward. The benefit this brings to the client is having choice of the various manufacturers of plasterboard, sheathing board and insulation, all at various thicknesses, which provides flexibility in supply and availability, commercial aspects and supply chain preferences.
Being able to determine if a particular thickness of plasterboard and number of layers the LGSF wall is being lined with has the capacity to achieve particular fire and acoustic performance is a key benefit to simplifying not only the specification but also the site installation to benefit logistics and programme. At voestalpine Metsec, we currently offer a choice of more than 400 configurations.
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