Roof SolutionsSigma® II Build System offers two roof solutions, to suit the varying needs of individual projects, roof shapes and performance requirements. Conventional Trussed Roof SystemThe system utilises pre-fabricated roof trusses, spandrel and gable panels and verge ladder frames. These come pre-designed, complete with all structural fixings and bracing requirements. Party wall spandrel panels can be pre-sheeted with limited combustible boards.Where air tightness less than 3 is specified, we recommend the fitting of an air tightness membrane to the underside of the roof trusses, with a batten to the underside to accommodate services. The membrane should be taped to the perimeter wall heads and sealed at laps and junctions, penetrations should be limited, but where required, taped and sealed accordingly. The fitting of membrane should be sequenced after the building is weather tight and before first fix, to allow an interim air tightness test to be completed, before services installation. Where air tightness is greater than 3, the ceiling plasterboard can act as the air barrier, with appropriate sealing at edges and joints. Fitting of plasterboard should be similar to that required for the air membrane solution. Care should be taken if using roof mounted equipment, such as ventilation systems, to provide access and safe working decks, above the insulation layer and without compromising the air tightness layer. Air tightness membranes are normally supplied and fitted by the contractor. Ceiling Cassette System The Sigma® II Build System can offer a horizontal ceiling cassette system. This is particularly attractive for:
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