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Mold inside the roof sheathing, wet and rotting roof sheathing

Mold inside the roof sheathing, wet and rotting roof sheathing


Old 03-17-06, 06:25 PM
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Unhappy Mold inside the roof sheathing, wet and rotting roof sheathing

The more I dig into it, the worse it seems to get. Looking for pro advice, or if I were you, I'd.... kind of advice. I have a 36x28 chalet style loft house. The loft is only in the front half of the house, the back half is a great room. It has a 12 pitch vaulted ceiling from front to back, vaulted all the way to the ridge board at the peak. The front part where the loft is has a 6 ft. knee wall creating two small eave attics one on each side of the house. The back part has a tripple 2x10 beam at mid span. The vaulted ceiling is drywall throughout. This is all good, so far. Now for the bad part. The rafter ends are boxed with soffit and facia. The soffit is 1/2" plywood with 2" round soffit vents spaced every 32", which are largely painted over. And for the kicker, three kickers actually: no ridge vents or gable vents, the rafters are 2x6, and the whole ceiling is stuffed with R-19 insulation.

I've been in this house two years. The house is 18 years old. This winter I noticed a black tar-like liquid had dripped in from the roof and splattered all over some things that were stored in the eave attic. It looked like creosote. And when I took a look, I pulled back the insulation and was shocked by what I saw. Soaked, wet, saturated plywood roof sheathing that had turned black in places and had white mold here and there. The inside of the insulation facing the roof sheathing was all wet. I pulled back a bunch of the insulation from a number of rafter sections and found every roof section was wet, some were wetter than others, some were turning blacker than others, and some had more mold here and there than others, but they all had wet sheathing. In some places the sheathing was swollen and buckled, and in some areas I could push up on it and watch it push away from the rafter, and in a couple places I wouldnt have to push on the plywood very hard to just poke right through the roof. All this was just in the section of the roof where I could peel back the insulation, in the eve attics. I can access 1/4 of the roof from the eve attics. I shudder to think what the rest of the ceiling is like, where it is completely closed in by the vaulted ceiling. There is one water stain on a different section of the ceiling, but it looks old and doesn't appear to be from fresh leakage.

Now, here is what I think I have to do to correct all this. It looks to me like I'm going to have to pull down the whole ceiling and to check for mold and damage the whole roof over, and remove the R-19 insulation. I figure I'll have to strip the roof shingles and repair and replace damaged and rotten roof sheathing and re-shingle the roof. I'll replace the small soffit vents with continuous strip soffit vents. Then on the inside, I think I'll have to leave it open long enough to dry out completely, and treat it with a fungicide/moldicide of some sort, and let it dry out some more. Then I'll build a section of level ceiling about three feet wide at the top of the vaulted ceiling so the ceiling will no longer be vaulted to the very peak, but have an air-space up at the top between this new sub-ceiling and the peak. Then I'll have to install gable vents on both ends of the house, either with a switch or thermostat controlled fan on at least one end. That will provide the circulation from the soffits up to the peak and out the gable vents. Then I'll have to fir out the rafters to make them equivalent to 2x8, install the proper R-rated insulation with foam channel spacers between the roof sheathing and the insulation. and finnish it off with a new ceiling. I'll use t+g pine bead to put a warm-feeling plank ceiling up.

Am on the right track here? or am I about to derail? Anyone think I'm heading for high weeds or am I thinking along the right lines? This whole thing is going to be a huge headache since the peak of the ceiling is 20 feet above the living room floor. Any advice or suggestions will be received thankfully since I want to do it right and minimize the hassle this is all going to cause.

Richard in Virginia
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Old 03-17-06, 09:06 PM
airman.1994's Avatar
Join Date: Dec 2005
Location: VA
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Id do all work on outside of home! Replace insulation and sheathing! Make sure their is a free air space between insulation and sheathing! then make sure you have air circulation.
Old 03-18-06, 04:15 PM
Join Date: Dec 2005
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I would pretty much do the same. I would probably start by getting the roof resheathed and shingled. I would make sure that ridge vents were installed. I would install rafter pans (the styrofoam kind) to make sure that the soffit are able to vent through to the ridge. If you visit the mfg's web sites (i.e. Cobra) you can get an idea about how much roof ventilation is recommended. I would also make sure that my gable vents were properly sized for the area that I want to vent. A TC fan may not be necessary with a ridge vent and properly sized soffit vents.
The vaulted ceiling may not have a problem. Much less space there for moisture to gather. I would probably pull some sheathing over the vaulted ceiling when reroofing to check the condition. A ridge vent here would probably solve a moisture problem if there is one.
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