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More on SIP Rot

Danidog | Posted in General Questions on

      Many thanks for all that has been posted about SIP rot and how to avoid it, but my timber frame home was built 22 years ago, and the problem is now appearing. I need cost effective advice about how to fix it.
      The panels are 4 inch with OSB exterior and blueboard interior. They were installed with seams following the roof joist beams. Drill and fill, nothing else to seal them.
    now they are weeping brown water and decay down my siding and some interiorly as well.
    Ok. I can fix the exterior with 2x strapping and new sheathing, etc. But from what I am reading, it is the interior moisture that is causing the issue. How do I retro-seal these now?

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  1. user-723121 | | #1

    I did some SIP roof repair many years ago as a result of leaking flashing and it was a mess. I would highly consider a roof overbuild (remove SIPS) if you have timber frame, do it right with the appropriate R-value for your climate, air sealing and ventilation.

    1. Danidog | | #2

      Financially devastating. I am sure there's a way to save the roof sips, and use their existing insulation value. Looking for a way to seal the moisture infiltration issue.

      1. user-723121 | | #3

        I get it, my experience was that repair of roof SIPS is difficult. The project I worked on had some serious failure of the exterior layer of OSB in some concentrated areas where the roof was leaking.. Yours may not be near as serious, get a number of qualified opinions.

  2. Expert Member


    You potentially have two related but distinct issues: The rot, and whether it has caused enough damage that the panels are structurally compromised. I think there are probably a variety of ways to retroactively air-seal SIPs, but first I'd want an engineer to say whether they were sound enough to be saved.

  3. gusfhb | | #6

    If my understanding is correct, an osb/foam/blueboard[or sheetrock] panel is a curtain wall or non structural panel. It holds itself up and the snow on top of it, but does not contribute to holding the house up. To me this means you could theoretically fix it from the top if the damage is not too severe. The problem being that you cannot see the level of the damage until you pull the roofing off, making it difficult to plan repairs

    1. Expert Member
      MALCOLM TAYLOR | | #7


      It's non-structural in that it doesn't hold anything else up, but just as is the case with roof sheathing, if it is rotten the roof is not structurally sound. The problem is that unlike roof sheathing, the panels usually span farther between load-bearing elements than the typical 24".

      1. gusfhb | | #8

        I guess my point is twofold.

        That in this type structure, I probably would not lose my mind if I peeled the roofing off and found the top foot of the peak rotten, where on a true SIP structure I would probably be in tears

        And that since any kind of reasonable planning involves having the materials onsite to do the job before you start, it really doesn't do you that much good.

        1. Expert Member
          MALCOLM TAYLOR | | #9


          You are probably right.

  4. Expert Member
    NICK KEENAN | | #10

    If the panels are non-structural, I assume they are supported by rafters? In that case I think your best repair is to lay a 2x4 over the panel at each rafter, screw it to the rafter with long screws, then sheath and roof. If the OSB along the rafter is suspect then it can be replaced as needed in spots to give the needed thickness.

    This means stripping the roof. If the OSB is failing I don't see any way out of this without stripping the roof.

    You need to nail down where the moisture is coming from. If the source is condensation from air leakage, while you have the roof off would be a good time to seal the panels from above.

    Do you know who manufactured your panels? They might be a good source for information.

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