Master Flash Roof Flashing

Master Flash roof flashings — the industry-standard flexible cone flashing for sealing round duct and pipe penetrations through roofs. Ten overlapping sizes cover pipe and duct diameters from just 6mm up to 724mm, so there is a Master Flash for everything from a small cable or pipe up to a large ventilation stack.

Fitting a Master Flash

Each flashing is a stepped flexible cone on a flexible metal-edged base. Cut the cone at the step matching your duct diameter for a snug interference fit, slide it over the duct, then dress the base down onto the roof — it conforms to profiled metal sheeting, corrugated roofs and flat coverings alike. Fix and seal around the perimeter and the penetration is weathertight, with enough flexibility to absorb duct movement and vibration without cracking the seal.

Because the size ranges overlap (for example 70mm–177mm, 101mm–209mm, 140mm–292mm), pick the flashing whose range puts your duct diameter comfortably within its span. For hot ducts and flues — kitchen extract, process exhaust — use the high-temperature version in the same sizes. Stocked flashings ordered by 3pm are despatched for next-day delivery.