WRB or metal flashing for vertical wall-t0-wall connections (using ZIP R6)
My addition project, being a porch-to-room conversion, involves negotiating the transitions between new and old, new construction and the existing house. Where the room’s new walls (will) meet the house, I want to make sure the corners are well sealed against water. For the room, we are using ZIP R6 sheathing; the house has cedar shakes siding, with some black paper protecting the sheathing. We are thinking of having a long strip of metal flashing, bent so as it follows the corner, nailed (and taped) against the house; that will require replacing some of the cedar shakes. On the side of the new walls, the flashing will be fastened to the sheathing with nails, and then taped. Is that a decent assembly? The alternative I though of would be Tyvek or similar house wrap, stapled (and taped?) to the sheathing. In either case, as tape, I am thinking that ZIP System flashing tape will be good, unless folks here think that, when connecting ZIP sheathing and metal, or metal to plywood, some other tapes are better.
Thanks for any input on this!
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
matt2021,
When you come to apply a WRB and clad the house, there is really no difference between whether it is a new room that was joined to an old one, or if it was all new construction. So if you wouldn't have used flashing on the inside corner of the two walls of a new build (and that would be unusual) there is no reason to do so on a renovation.
If you aren't convinced by that argument, and want to take a belt and suspenders approach, using a strip of Peel & stick membrane is an more appropriate choice than flashing.
Thanks Malcolm! That makes a lot of sense.
A follow-up question: since the house, under the siding (part of which we are removing, so as to be able to properly seal the corner) has black paper, should I ask that, upon removing the siding, the paper be ripped as little as possible, so as to apply the membrane over the paper’s edge? The sheathing on the house (built in 1970), of course, is not ZIP; so, that paper, I guess, is it’s water and air barrier.
Matt2021,
Yes, you want to overlap the existing building paper with a strip of WRB or membrane.
If you use a membrane there isn't much difference between them. You don't want too wide a piece as it will limit drying to the outside, and that can cause problems of its own.
https://www.homedepot.com/p/Typar-6-in-x-75-ft-Self-Adhering-Flashing-Roll-ATFLH-002/205056022
Thanks Malcolm! Any reason why the ZIP flashing tape would not be suitable? We are going to have that around anyway.
Malcolm, would either of these work?
https://www.homedepot.com/p/GAF-WeatherWatch-36-in-x-50-ft-150-sq-ft-Mineral-Surfaced-Peel-and-Stick-Roof-Leak-Barrier-Roll-0912000/100083257
https://www.homedepot.com/p/GCP-Applied-Technologies-Grace-Select-36-in-x-65-ft-Roll-Self-Adhered-Roofing-Underlayment-195-sq-ft-5003200/204423144