Roof sheathing is black and green!
I posted earlier in the week about plywood buckling up on a reroof job- complete tear off, replace bad sheets, etc. Well, I poked around in the attic of the house earlier today, and found the offending section, which I think just needs some screws in it to attach to a truss. Clearly from all the blocking between trusses, this problem was prexisting.
In any event, I noticed something odd. On the section of the roof over the porch, the underside of the sheathing is dark black/grey/green – looks almost like somebody took dark flat spraypaint to it. It is only over the porch- over the finished house, which is insulated by blown fiberglass, the plywood looks fine. The reroof was 6 months ago, and the places where the nails went through are normally colored, so it is obviously old or a slow process. Further down, near the soffit of the porch, looks almost crystalline. The area under the porch is uninsulated, and the ceiling of the porch is covered in 1/4 ply, with vinyl soffit under that. The discolored section ends immediately above the top plate of the main house. Weird. . .
Any ideas? Doesn’t seem to have to caused any problems. . .but bothers me. Maybe not enough ventilation? But in that case why discolored only above porch? Some weird air current? Fire-resistant plywood???
Thanks. . .
The discolored section ends immediately above the top plate of the main house. Was the porch originally without a ceiling, and maybe the previous HO spray painted the underside of the roof?
That was my guess too..
Excellence is its own reward!
>The discolored section ends immediately above the top plate of the main house. Was >the porch originally without a ceiling, and maybe the previous HO spray painted the >underside of the roof?
No. It definitely is not paint, maybe some type of mold/mildew/etc - I think!- I can sort of make old mildewey "blooms". The porch ceiling was sealed from construction- the pitch of the roof starts at the edge of porch and continues to the high point unbroken - single "A" trusses span the whole roof, and overhang the wall for the porch. Current homeowner is same for life of home (25 years), and said no paint. The only thing I can **think** happened is maybe the porch ceiling was left undone while the house interior etc was done, leaving the underside exposed until the house was complete. . .but why that would cause mildew or anything close beats me. Seems like this would happen under house side, where warm air would condense, not the porch part!
I'm still stumped.