BLM Standard Underlay is a non-woven, crimped filament poIyester, needle punched to allow air to circulate freely between the underside of the Lead Sheet and timber board decking with penny-air gaps, preventing condensation forming and corroding the underside of the Lead Sheet.
BLM Standard Underlay also serves to smooth out timber board substrate surfaces allowing the Lead to expand and contract with ease.
BLM Standard Underlay:
Allows Lead to breathe, preventing condensation forming and corroding the underside of the sheet
Protects against imperfections in timber board substrates, allowing the Lead to expand and contract freely during thermal movement
Resistant to high temperatures
Prolongs the life of correctly fitted Lead Sheet
Standard Underlay should be laid in adjacent sheets, either abutted or overlapped, across the fall of the roof
Must be fitted over the whole substrate area
All Rolled Sheet over 600mm wide should have an underlay fitted
Smaller widths may require an underlay depending on the application
Avoid forming joints above underlay
Not recommended for use when laying lead on to Plywood substrates
25m x 1.0m rolls
A Product Data Sheet providing handling, use and storage advice can be found on the download below