Fibrefill is a compressible non-extruding bitumen impregnated fibreboard. It is designed primarily for use as an expansion joint filler for joints between concrete components. Other uses include the protection of Xeric and other similar waterproofing membranes, as a separation strip between partition walls and the building shell to accommodate movement, as an insulator between floor joists and wood floating floors, and as an insulator and acoustic barrier on top of floor slabs.