Roofing Underlayment as WRB on Side Wall
ArchitectJL
| Posted in General Questions on
What are the problems, if any, with using Roofing Underlayment on the side wall as a weather-resistant barrier, provided that the product has the desired physical characteristics (perm rating, etc…)?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
J.L.,
All building codes require that a layer of asphalt felt, a roofing underlayment, be installed on walls as a water-resistive barrier (WRB). Other products, including plastic housewrap, have been approved as acceptable substitutes for the code-required layer of asphalt felt.
More information here: All About Water-Resistive Barriers.
Whatever you do, don't install synthetic roofing underlayment as a WRB on wall. Most synthetic roofing underlayments are vapor-impermeable. That's bad.