Moisture and polyiso
Help! I’m remodeling a 1948 ranch home in Tucson and we’ve had an unexpected bout of rain after the polyiso was installed. My question: Do we need to remove and replace the polyiso that was exposed?
The wall assembly includes interior plaster over double brick. We’re installing 1.5″ of polyiso directly over the brick, to be followed by chicken wire and stucco.
I’ve read the articles I can find here on the site, including the advice on moisture barriers and drainage behind the stucco, but am not sure whether this is necessary in our dry Tucson climate (zone 2b)in the long term, or whether our current wet weather has effectively ruined the exposed polyiso. Advice appreciated!
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Replies
Your polyiso will probably be fine. Polyiso does absorb water, but it’s not like a sponge — it won’t suck it up at lightning speed. Your polyiso most likely has a facing, leaving only the edges exposed. Assuming you’ve already taped the seams between panels, you probably only have a top and bottom edge exposed. The bottom edge will have some natural protection from gravity, unless it is in puddle of water or something like that. The top edge is probably somewhat protected by a roof overhang, at least from direct exposure.
Check the edges with your finger. Unless the polyiso is saturated with water, you should be ok. I’d be surprised if it will have absorbed enough water from a single rainstorm, even a big one, to be a serious problem.
Bill
The paper / fiberglass/ foil facers don't allow liquid moisture to pentrate quickly. The cut exposed edges can soak up moisture over a few hours if IMMERSED in water, but a quick hosing followed by drip-dry is nothing of concern.
Thank you so much for the very quick responses! We'll take a look later today to see how saturated it is. Two sides of the house are almost fully protected by porch roofs, but the other two have skimpier eaves.
Jacqui,
Chicken wire and stucco allow outward drying. Don't worry.
Very relieved to hear that. Thank you!
Even during Tucson's monsoon season there wouldn't be enough wetting to be an issue.
If the house is flooded and the bottom edge of the polyiso is under water for days, THEN it's an issue, but I suspect you'd have much bigger things to worry about in that unhappy circumstance.