Abstract:
A sound and/or moisture barrier underlayment suited for use on a roof or floor surface to provide a substantially flat and level surface, comprises at least first and second strips of insulation membranes (10) laid down one next to the other in a coplanar relationship. The first and second strips (24, 26) have a thickness W1. An overlap joint (28) is provided between the first and second strips (24, 26). The overlap joint (28) has a thickness W2 substantially equal to or less than W1 to provide a free-bump transition between the first and second strips (24, 26) while preventing straight-through infiltration.