Alternative to Zip System
joenorm
| Posted in General Questions on
I am considering using Zip System as sheathing for a small build but am having a hard time with accepting the use of OSB, I just don’t really like it as a product compared to plywood.
My question is what is the best air sealing method if I choose to sheet with CDX ply?
Also a question on ZIP……is it accepted at this point as a durable and trustworthy product?
thanks
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Replies
Joe, the ZIP system has been around for over ten years so it has a pretty solid track record. It is not the most robust system available, but fast and adequate in most cases, especially if the assembly includes a rain screen. The seams can swell, as can nail head holes, and if the tape is not properly applied and allowed to set up for 72 hours the seams can leak (I've seen it first-hand). Their liquid-flashing product seems to be more resilient than their tape, though their tape is very good.
You can tape CDX to create an airtight layer at the sheathing. It can be more difficult because of the voids inherent to CDX, and of course CDX doesn't lay nice and flat on the framing the way ZIP does. For tape, you can use any of the high-quality products available with an acrylic adhesive. I just used 3M 8067 All-Weather Flashing Tape in this application, and others I know have used ZIP tape. Siga Wigluv or Fentrim, or Pro Clima Tescon Vana are other good options. Alternatively, you could use a fully adhered WRB such as Henry Blueskin, Siga Majrex SA, or Pro Clima Solitex Adhero, or a liquid flashing system such as Prosoco's.
I would just say that I only have good things to say about Huber, which also makes advantech subflooring. Both products will have less problems than plywood with edge swelling.
I have left zip panels exposed for somewhere around a year, with several months of that time being able to see what was going on inside the structure. No seams or nails let a drop of water in. The tape showed no evidence of decay when I was applying foam insulation. I also have never had an issue with adhesion after applying pressure to the tape, and I never waited for 'a good tape day.'
Pretty much the only time I will go for plywood is for cabinet making. Plywood also takes a nail or screw on edge better than OSB, which can make it better for things like stair subtreads.
This decision also depends on where you are and what level of quality plywood you can get. I am building now in NC and the plywood quality is atrocious. I just finished pulling off 50 delaminating sheets and replacing them. We special ordered some high quality ply(it's not stocked) and immediately wrapped it in Solitex Adhero. Zip is definitely easier, but I too question the longevity, especially with the installation methods I see around here. If I had to do it over again, I would probably spec some high quality plywood, inspect the plywood before it went on, and then have Tyvek fluid-applied put over it(or Prosoco).