Unusual Attic Configuration Leading to Truss Rot
My house was built in 1999 in Michigan (48430) with a somewhat unusual layout in the attic. There are 2 windows in the attic on the east and west ends of the house and between those windows, a section of the attic was floored with OSB and drywalled. Under the OSB floor is poorly done R19 fiberglass (top plate gaps, unsealed penetrations, no even installed in one spot I pulled up, ...). Inside the drywalled area, which was fairly well air sealed from the rest of the attic, are 2 unsealed pulldown attic stairs on the east and west ends of the house. Outside the drywall area is about 6" of blown in celluose.
The issue is that the truss portions that contact the drywall are all showing various levels of rot / staining in the area where they meet the bottom chord at the mending plate. Several have rotted to the point of splitting, others just are somewhat soft. I'm guessing the drywall is leading to a temperature or moisture difference in this area of the truss but was looking for some more solid explanation.
As far moisture, the attic is probably somewhat under ventilated since only 12" soffit chutes are installed between the 24" OC trusses and had numerous areas which allowed house air directly into the attic. The upstairs bathroom fans are vented to the soffit as well. I have a long list of energy improvements to make in this area but need to stabilize / correct the truss situation first.
I tried to attach a few pictures, showing the layout of the drywall partitioning the attic, the truss staining/splitting behind the drywall, and better shot of a split truss where the drywall has been removed.
Thanks for any ideas,
Posted Sat, 09/07/2013 - 14:05
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