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What is this exterior wall sheathing?

ChrisInIllinois | Posted in General Questions on

Forgive the crude photos, it is the only markings I have found and it needs alot of light to make the words visible.

The house built in 1975, the sheathing and siding both 1/2 inch thick.

I’m thinking it’s beaverboard or some type of fiber board I also have a cutaway of the material the sheathing has a black paper or felt adhered to both sides.

Thanks for your time.

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  1. Expert Member


    That looks like Tentest. It's a fibre board used as sheathing and in some party walls. Crumbly, holds fasteners poorly. Not sure I can think of a good use for it. No idea why it was so popular.

  2. ChrisInIllinois | | #2

    The top shots are from attic. The cutaway is from about 6 foot up from floor in the kitchen, during a Hood vent relocation. I am assuming the whole house is covered with it.

    Any issues I need to be aware of when I drywall, reside / add exterior foam, or fixing step flashing that's silicone to the siding.

    To be fair the step flashing is under a 2 foot overhang, and to be honest I'm not too sure how well Grace's ice & water barrier would stick to that. Wondering if I should leave that alone. This is definitely a new material to work with thanks for the info.

  3. Expert Member
    Peter Engle | | #3

    It is wood-fiber based sheathing. The asphalt-saturated facers provide a reasonably effective WRB. The board is very vapor permeable and not very water permeable, so makes a good sheathing. It also has an insulating value of somewhere are R3-R4 per inch. Anything that sticks to felt paper will probably stick to this. Hand pressure rolling will always help. Sometimes a primer is necessary. Other than that, don't let water get to the core and it'll last for quite a while. It was very popular around here in the mid-20th century and I still see it in good shape in those houses. It is still available, and can be a good choice when a vapor permeable non-structural sheathing is required.

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