Air Barrier Integrity with Penetrating Fasteners
Hi all, to my understanding nailbase roof exterior insulation manufacturers allow (in some instances insist) installing the nailbase fasteners directly to the plywood roof deck, with the screws driven ¾” past the bottom of the plywood. Whether using a nailbase system, or making your own site built nailbase, this screwing method is also easier to install, as the installers can just follow a screw pattern for the plywood, without having to worry about finding rafters through the foam.
But if you tally 20-30 screws per nailbase unit driven into the plywood deck, you will have thousands of screws driven through the air barrier and the plywood deck.
If using a peel and stick membrane, is it safe to assume that the membrane will self seal around every screw or is it required to liquid flash each screw penetration going through the plywood roof deck to maintain air barrier continuity?
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Replies
DamionL,
Exterior sheathing on roofs and walls is often used as the primary air-barrier. That sheathing gets penetrated by thousands of screws and nails - for furring strips, nail-base, roofing, or cladding attachment. Luckily they don't make any appreciable difference to the effectiveness of the air-barrier. Fasteners work by resistance between themselves and the material they go through. There is no void around them for air to travel.