The TuffStuff® Raised Ridge Roll/Expansion Joint is used to create an expansion joint on roofs that are over 50 square metres. A minimum 25mm gap should be left between decking boards to allow for expansion/contraction. The expansion joint should then be mechanical fixed and each side covered in 75mm CSM Bandage before re-inforcement matting is applied. An expansion joint closure is also available for sealing off exposed edges.