Please comment on the photos below of water damage to the exposed soffit area of a SIP roof framed house that I have been asked to evaluate. It appears to me that the problem is related to condensation and not a roof leak. The seams on the North side of the house are the only ones with this problem, and the worst is below a plumbing vent penetration. The roof seems to be solid. The owners did not finish covering the soffits because of seeing mold under some boards that they had applied. Please comment. Thanks

Posted By r.anger on 20 Feb 2012 11:32 PM
Please comment on the photos below of water damage to the exposed soffit area of a SIP roof framed house that I have been asked to evaluate. It appears to me that the problem is related to condensation and not a roof leak. The seams on the North side of the house are the only ones with this problem, and the worst is below a plumbing vent penetration. The roof seems to be solid. The owners did not finish covering the soffits because of seeing mold under some boards that they had applied. 

VERY, VERY COMMON problem with OSB SIPs. Hence the reason why I wouldn't ever go with wood SIPS, especially in the roof area. It's either steel SIPs are no SIPs for me.

It looks like either a problem with roof venting and excessive moisture build-up in the roof area. Or a problem where the two SIPs meet. These are the areas where wood OSB SIPs have problems. When the 2 wood SIPs meet, that area creates a cold spot where moisture forms. The wood roof SIPs seem particularly prone to air leakage along joints. Once again, it is the roofs that have these problems, the walls are usually OK.

Here is a report about rotting in OSB SIP roofs:

SIP ROT STUDY

This is actually a HUGE problem in the wood SIP industry but like many such issues, they will deny that it exists, but just do a Google search and you will find THOUSANDS of hits on this issue.


What state is this in?

Does the owner have a ERV or HRV?

Was this a DIY install?


My solution would be to rip the wood SIP roof out and redo it with a truss design and insulate/vent the attic OR get steel roof SIPs. Replacing the rotted SIPs with other wood SIPs will NOT solve the problem. The problem is inherent in the design of the wood SIP joints.

Lbear,

Thanks for posting the link to the OSB SIP roof failures.  I read about this problem several years ago but needed the reminder.

Lbear,
You have confirmed my suspicions. This building is on Whidbey Island in western Washington State. Even higher humidity than Juneau. I do not know yet if they have an ERV or a HRV, I didn't know to look for one at the time. I suspect the installation was DIY, as the soffits remain uncovered. Glad I listened to my gut feeling, did the research and didn't tear into the roof.

Thanks again for your comments and the link to the rot study.

Ron

Those alaskan roofs are the bane of the industry.

If I'm looking at the pictures right and the worst damage is in line with the plumbing vent, then I would want to know about what appears to be a kitchen exhaust vent on the sidewall. If it is, it's expelling moist humid indoor air and accumulating under the soffit. I've seen similar results quite often with soffit mounted vents for bath fans many times.

The damage in your pictures of the soffit are worst at the fascia, so how is that related to leaking seam interior air damage like those in Alaska? It probably isn't. Have you considered ice dams? Localized air leakage from exterior wall wiring or other penetrations?

Blower door test the house and use an ir camera to check panel seams.

Could be alot of possibilites, but one thing is for sure, that purple door sure looks good against the green fascia.

Greentree,

Western Washington gets very little freezing weather, especially here on the island. Ice dams simply do not happen. The seams at the soffits are exposed and open (not caulked), so this seems to be the easiest outlet for condensation running down the panels and an easy inlet for cool air. Am I on the wrong track?

I don't think your on the wrong track, that's all I can do to try to help you out is offer possibilities that you can consider. The possibilities are based on 3 pictures and a brief description so it's definately not gospel.

Based on my experience, at times the source of the problem is something not initially considered. Good luck with it.

If the panel joints have air spaces in them then warm moist interior air will meet cold exterior air inside the panel joint and condensation will form. It will then run down the joint to the lowest point of the roof being the fascia. The north side of the roof is the coldest even during the day and the north soffit never sees the sun, so the problem is exacerbated on that side.

A solution would be to fill all the voids in the joints with spray applied expansion foam.

A thermal camera will reveal the issue. About 1 foot to the interior of the exterior wall on the underside of the roof will show cold spots at the joints and from the outside the reverse.

At the very least, the joints should be air sealed. Perhaps paint + tape. Vapor retarder on the inside and a gap vent (rain screen) under the shingles should be considered.

At the risk of a lot of flack, the roof problems first reared it’d ugly head in Alaska. The problem was closely inspected, and it was determined that there were air leaks at the roof seams. Warm moist air would leak up through these cracks, hit the cold air and form condensation at the seams, deteriating the OSB. Upon inspection, obvious, major deficiencies were found, such as missing spline connections, missing pieces of lumber, missing foam and missing adhesives. This wasn’t an inherent problem with the SIP panels, but a direct result of poor assembly methods and shoddy workmanship. I've seen many rotten roofs around poorly sealed plumbing penetrations and skylights.

As anyone who has built a SIP home knows, it specifically states in the assembly instructions to apply a special sealing caulk to all surfaces of the panel splines and the manufactures supply a sealing tape to apply to the inside of the roof panel seams. Like any other roof, all roof penetrations and valleys must be very carefully sealed up, inside and outside and as a part of normal roof maintenance, should be checked at least once a year. A couple of tubes of Black Jack is a whole lot cheaper than a new roof.

Carefully follow the factory assembly instructions, use recommended roofing practices and check your roof, siding, windows, weather stripping and anything else that protects the outside of your house once a year as a matter of yearly preventative maintenance.

Steve
GrandCountySIPS.com