Frequently asked questions about the Roofing underlays and tapes category
What are Roofing underlays and tapes?
Roofing underlays and tapes are specialised materials for roof protection and seam sealing: breathable and non-breathable membranes (e.g. TYVEK SOFT, TYVEK SOLID, FORTEX EXTRA 140g) and adhesive tapes (GERBAND 586, TYVEK 50mm, FLEXWRAP) that manage vapour, windproofing and joint sealing.
What's the difference between breathable and waterproof underlay?
Breathable underlay (vapour-permeable) allows moisture vapour to escape from the roof structure and is suited to warm timber roofs; waterproof underlay protects against rain and wind, useful for temporary coverings. Products like TYVEK SOFT (breathable) and TYVEK SOLID illustrate these types.
What widths and roll sizes do tapes and membranes come in?
Tapes include GERBAND 586 50mm x 25m, TYVEK 50mm x 25m and FLEXWRAP EZ 60mm x 10m. Underlay membranes are sold in rolls such as 75 m2 (TYVEK SOFT, TYVEK SOLID, FORTEX EXTRA 140g) and 37.5 m2 (ULTIPRO SILVER 37.5m2).
Which underlay is best for a warm timber rafter roof?
Choose a breathable (vapour-permeable) underlay such as TYVEK SOFT or TYVEK PRO TEIBIGA for warm timber roofs; these allow vapour to escape while protecting the structure from moisture and wind.
Which tapes to use for ridge and eaves junctions?
Use profile and self-adhesive seam tapes with strong adhesion such as TYVEK PLUS 60mm x 25m or GERBAND 586 50mm x 25m for ridge and eaves junctions to ensure durable, weatherproof seals.
Are these materials suitable for repairing an old roof with slate or metal tiles?
Yes—underlays and tapes in this category are suitable for roof repairs under slate or metal tiles. Choose breathable or waterproof membranes depending on ventilation, and use tapes to seal joints and flashings.
How does TYVEK SOFT differ from FORTEX EXTRA 140g?
TYVEK SOFT is a breathable membrane designed to manage vapour in warm roofs; FORTEX EXTRA 140g is a heavier, more robust membrane (140 g) offering increased mechanical strength and protective waterproofing.
Can FLEXWRAP EZ tape be used to repair local cuts in the membrane?
Yes—FLEXWRAP EZ (60mm x 10m) is suitable for local repairs and sealing cuts due to its flexible material and good adhesion. Ensure the surface is clean and dry before application.
Is a vapour barrier required when using a breathable membrane?
Typically yes—when using a breathable underlay you still fit a vapour control layer on the warm side of the construction to manage internal moisture. Choose and install an appropriate vapour barrier to work with the breathable membrane in roof build-ups.
How should membrane rolls be joined and which tape seals the joints?
Join rolls with the manufacturer's recommended overlap (commonly 10–15 cm) and seal with specialist tapes such as TYVEK PLUS, GERBAND 586 or TYVEK 50mm. Ensure surfaces are clean and dry before taping for reliable adhesion.