Guide

about 4.80 metres (depending on the manufacturer).

That means they can be used as roof panels which in some cases don’t need traditional rafters or roof trusses, but simply sit on ridge beams and purlins where necessary.

They do need to be kept as dry as possible during construction and should be made weathertight as soon as possible. The usual buildup for a SIPs type roof is slates, tiles or metal roof cladding on a breathable roofing membrane, on sheathing board, on vertical battens giving a 50mm clear airspace between them.

The battens are fixed over a bottom layer of breathable roofing membrane which provides additional protection to the SIPs layer. Note that due to the difficulty in applying an effective air and vapour control layer (AVCL) to the warm side of a SIPs panel to prevent water vapour entering the panel, and the risk of trapping moisture in the panels during the construction period, SIPs panels are not regarded as suitable for warm flat roof construction.