To protect the underside of Lead Sheet from corrosive attack from certain substrates, the Lead should be isolated from the substrate using Grade A1F Building Paper. BLM Grade A1F Building Paper is a traditional, reinforced bitumen-bonded building paper laminate, manufactured with wet-strength Kraft paper, meeting the technical requirements of BS 1521 Class A.
BLM Grade A1F Building Paper should be used to provide a vapour barrier when laying Lead on to concrete, stone, screed, plywood and oak surfaces.
Protects the underside of the Lead from alkalis in concrete, stone and screed
Reduces corrosive attack when laying Lead onto plywood and oak
Building Paper should be laid in adjacent sheets across the fall of a roof and overlapped
Must be fitted over the whole substrate area
All Rolled Lead Sheet over 600mm wide should have an underlay fitted
Smaller widths may require an underlay depending on the application
Dimensions: 25m x 1.0m rolls
A Product Data Sheet providing handling, use and storage advice can be found on the download below