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Least Expensive Air-Sealing Method for OSB

mikeysp | Posted in General Questions on

Hi. I am in zone 4a (Nashville area).

What is the cheapest effective option abailable for air sealing OSB seams and OSB to Concrete seams?

I am not looking to save labor. I am looking to save money.  So installation ease is not a priority.

I thought a sealant caulking or 5 gallon bucket might be the best bet. I also have seen images of the liquid sealants that show a width of a couple inches on OSB seams and it confuses me. I figured with a 1/16″ or 1/8″ gap that a 1/2″ wide sealant would more than suffice? For that matter, the tapes such as zip are about 4″ and I wonder at the need for so much width?

I acquired a whole bunch of repurposed 3’x8′ 7/16″ OSB a few months back for $3 a sheet and am using it for my house and shop.

I much appreciate your advice.


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  1. brian_wiley | | #1

    Hi Mike, not sure if you’ve seen this, but worth a read if you haven’t.

    It seems like 3M all weather flashing tape would be the most economical.

    For the concrete to osb seam, sausage tubes of Zip LA flashing seem to be the cheapest, but I’d still price out Siga Fentrim.

    All that said, don’t negate the potential cost of doing it wrong. Leaks and rot come to mind, but even choosing a material that won’t hold its air seal after five years could potentially end up costing quite a bit in additional energy costs spread out over 20 years.

    1. mikeysp | | #3

      Those concerns certainly are on my radar. The air sealing is my only concern that I have not resolved as of yet. As for moisture, I am going to use the typar I have on hand, 3-1/2" of polyiso I have, rainscreen, and siding. The wall assembly should be pretty sound as long as I get the air sealing and door window assemblies right.

  2. GBA Editor
    Kiley Jacques | | #2

    Hi Mike,

    Another reader asked the same question. Read through this Q&A thread for suggestions.

    1. mikeysp | | #4

      Thanks Kiley, that was actually me a little over a year ago. Can't believe so much time has passe dsince I started this build. I did not know how to find it. Thank you. I will read through it.

  3. andy_ | | #5

    My last build had a beveled edge to the foundation spec'd so I couldn't do any tape from sheathing to concrete. The solution was to use the neoprene gasket (from Conservation Technologies?) between the concrete and sill plate. The sheathing was Zip, so I taped from the face of the Zip sheathing over to the sill plate before tipping the walls up into place.

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