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Is it possible to repair a SIP roof that is rotting?

Allan Poole | Posted in GBA Pro Help on

We built an SIP home using panels from ACH Foam Technologies. The roof was installed according to manufacturers specks. The panels were OSB on both sides of expanded polystyrene insulation, about 7″ thick. Block splines were installed with the prescribed Do All Ply sealant. This design had space between the lines of calk for air to move vertically. The OSB has begun to de-laminate at the seams visibly under the shingles. It is obvious that moist air is moving from the interior, especially during the winter, up along the seams and condensing on the undersides of the roofing tar paper and asphalt shingles. Roofing nails have let go. It is an 8/12 or a 12/12 pitch roof. Too steep to walk on. The panels are about 15′ long ranging from 3′ to 6′ wide

Has anyone come up with a plan to repair a situation like this. Somehow the leaks in the splines have to be addressed if such a thing is possible before a repair would even be feasible. Can the rotten osb be cleanly removed? can new osb or plywood be effectively applied and glued? Is the roof structurally safe to work on. Would it be less expensive and labor intensive to remove the panels with a crane and install a new roof?

A spot inspection at the bottom, middle and ridge have revealed that the osb has deteriorated and de- laminated most near the seams.

I would greatly appreciate any help and useful information I can get on this issue. Thanks
Allan Poole

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  1. Aj Builder, Upstate NY Zone 6a | | #1

    HIre a contractor that remodels, does framing and carpentry and repairs

    1-tear off shingles
    2-cut back bad OSB enough to seal the seams again.
    3-add vertical vent channels via 2x4 layed flat 24" O.C.
    4-resheath, I like Advantech or plywood
    5-reshingle, use Ice and water shield in all the normal locations.

    More money would be to add more insulation with taped seams as step 2.5 to achieve code level of insulation.

    On the inside the seams need to be sealed and taped if possible. (SEALING THE INSIDE IS THE MOST IMPORTANT WORK)

    Do more yourself if cost is an issue.

  2. Expert Member
    Malcolm Taylor | | #2

    What AJ's and similar solutions miss is that the panels rely on their exterior skin for their structural integrity. You need to get the manufacturer, or an engineer, involved to approve any remedial fixes.

  3. Aj Builder, Upstate NY Zone 6a | | #3

    Malcolm, I didn't miss. The edges of SIPs are not really the structural carrying aspect of the panels. Of course they will lose strength with rot and eyes on the actual roof is the only way to make a call as to the loss of structural strength.

    The body of the panel carries the load not the edge usually across structural members such as a post and beam frame in the cases I deal with, the edge is in very low to no shear.... I have not witnessed panel failures that are structural but plenty of rotting air leaky edges...

  4. Expert Member
    Malcolm Taylor | | #4

    Whose eyes? A contractor that remodels? It's not for them or you to make that call. Modifications to SIPs need either either an engineer or the manufacturers's approval.

  5. David Meiland | | #5

    Sounds like a major failure. I would get the manufacturer involved. A contractor with any sense knows that if they touch it, they own it, forever.

  6. GBA Editor
    Martin Holladay | | #6

    Good luck with your repair.

    If any GBA readers are considering a SIP roof, I strongly urge them to include ventilation channels above the SIPs.

    Here's what I wrote on the topic in my FHB article, "Air sealing SIP seams":

    "A so-called cold roof features ventilation channels above the SIPs and OSB or plywood sheathing over the channels. Ventilation channels add to the cost of a SIP roof, but they provide several benefits. Most asphalt-shingle manufacturers void their warranties when shingles are installed on an unventilated roof. In snowy climates, ventilation channels reduce the chance of ice-damming problems. Finally, if any roof-panel seams develop air leaks that permit condensation, ventilation channels will help dry out the damp OSB, reducing rot. (To ensure that these ventilation channels do their job, it’s important to specify a vapor-permeable roofing underlayment such as asphalt felt.)

    "“I built timber frames in the ’70s and ’80s and, like most other framers, we did not vent the roofs,” writes Bob Irving, a New Hampshire contractor who posts comments on “Every manufacturer I’ve spoken to (major in terms of the New England market at least) said they recommended the practice [of venting roofs] in their manuals. No manufacturer that I’m aware of ever mandated the practice.” Irving continues, “Since then, I have repaired several SIP roofs where the OSB has rotted.”

    "In short, if you are interested in reducing the chance that your roof SIPs will develop rot, ventilation channels are a good investment."

  7. Aj Builder, Upstate NY Zone 6a | | #7

    Malcolm, adding venting and sealing the seams is fine. Yes if the panels are shot then replace the panels with an engineered stamped plan.

    Happy labor day all

    (some people fly planes safely upside down... some watch from the safety of the ground) Malcolm, enjoy the show, my plane awaits.

  8. Allan Poole | | #8

    Martin Holiday, I would very much like to hear from a contractor or owner who has actually tried to separate and clean the deteriorating OSB from the expanded polystyrene. Did it work? Did they separate easily? What tools worked best. I would like to hear from Bob Irving.

    Others will be having this unfortunate experience. An engineer or the manufacturers must have come up with a plan. They will need to.
    Allan Poole

  9. GBA Editor
    Martin Holladay | | #9

    Q. "I would very much like to hear from a contractor or owner who has actually tried to separate and clean the deteriorating OSB from the expanded polystyrene. Did it work?"

    A. The SIP industry has extensive experience with these problems. The biggest cluster of SIP failures happened in Juneau, Alaska in the early 2000s. When I reported on these problems in 2003, I spoke to these experts in Juneau:
    Daniel Ulery, vice president of Four Eagles Construction in Juneau.
    Adrian Slater, a senior civil engineer at R & M Engineering in Juneau.
    John Cooper, a Juneau engineer who was hired by homeowners to investigate SIP problems.

    I'm not sure whether Ulery, Slater, and Cooper are still in business. With a little Googling, you might find out.

  10. Allan Poole | | #10

    I asked for help from the manufacturer of the panels. I am sure that they are familiar with what went wrong. the company was called R Control in 1979 when this building was built. They are at the same address; 90 Throwbridge Drive, Fond Du Lac, Wisconsin, but now operate under the name of ACH Foam Technologies. They refused to help me in any way. The methods they specified for sealing the seams of the panels ,I think, were inadequate. I think that because of this they should help their former customers with a solution that they know will work.

  11. Expert Member
    Malcolm Taylor | | #11

    I agree. it's an awful situation. I hope they live up to their obligations. Good luck.

  12. GBA Editor
    Martin Holladay | | #12

    You might want to contact a lawyer familiar with construction defect cases.

    You might also want to contact the Building Science Corporation. Joe Lstiburek was involved with the investigation of the SIP failures in Juneau, Alaska.

  13. Allan Poole | | #13

    Martin Holladay,GBA advisor. I have found a team of two roofing contractors who have started on the repair work this morning, monday, 8/1/2016. Removed the shingles and tar paper to reveal that 80 percent of the north side of the roof has rotten osb, which scrapes of easily with a hoe. If it were all rotten, it would make the job easier, forthe dry osb will be easier to fit in plywood around than remove.

    We have an adhedive for gluing the plywood to the foam panel once it is cleaned. It has a 5 minute working time.The SIP panel has a 7 1/4" thick core with osb on the inside also. Does anyone have a way to pressure or fasten the plywood down to the polystyrene in that 5 minutes till the adhesive dries? We would like to avoid bolting through to the inside osb. please respond as soon as you can. we had anticipated having at least some strips of good plywood across the roof from the middle of the 4 to 6 foot wide panels but now find we don't. Please respond as soon as you can. Also My phone number is 860-250-6742, Allan Poole.

  14. Allan Poole | | #14

    P.S. The polystyrene and the inside layer of 1/2' osb still has enough structural integrity to be safe to work on. It helps, I imagine that it is a 12/12 roof.

  15. GBA Editor
    Martin Holladay | | #15

    Lots of issues here.

    The first issue is, "Where did the moisture come from?"

    There is no reason to repair the SIPs until you are certain the you know the answer to that question.

    The second question is the basic structural question: "Will these SIPs be structurally adequate after repair?" The answer to that question is beyond my pay grade -- and it's a very important question.

    The third question -- the one you asked -- is the easy one. Weigh each plywood panel down with 12 or 20 concrete blocks (CMUs). Use a few drywall screws (into the plywood) to keep the concrete blocks from sliding.

  16. Allan Poole | | #16

    Martin Holladay, I have written about my successful effort to repair a Rotting SIP roof. I would like to include photos. I have a Google account. What is the best way to do this. A link ,àn article entered here or something else? Thank you Allan Poole

  17. GBA Editor
    Martin Holladay | | #17

    It sounds like you have the makings of a guest blog. That's great. Contact me directly at this email address:
    martin [at] greenbuildingadvisor [dot] com


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