Attic space roof sheeting is black - InspectionNews

Bill Wieczorek · #1 (**permalink**) 08-02-2007, 09:36 AM

I've seen this in homes which seem to lack ventilation but I've also seen it in homes with vents. Mondays home had 2 power roof vents, in the attic space the sheeting color on two sides (West and South) was gray. I don't know if that's mildew or the sheeting turning color from lack of ventilation. Any information is appreciated.

Michael Thomas · #2 (**permalink**) 08-02-2007, 10:21 AM

Pictures?

Bill Wieczorek · #3 (**permalink**) 08-02-2007, 11:08 AM

I don't have the pictures, I was helping another inspector friend and he hads the pictures. The house was 6300 sq ft and had lots of roof. The buyer was concerned thinking it was mold. I think it's possibly mildew. I think he wrote it up as home should be evaluated by a roofing contractor.

wayne soper · #4 (**permalink**) 08-02-2007, 06:21 PM

were the vents original equipment? if added, disclosure from the homeowner as to past problems is required and take you out of the picture.
More than likley they were added. Poor ventilation design found after a few years would dictate mechanical upgrades. Was the plywood delaminated? were the bathroom vents terminating in the attic?
Did you probe the plywood for delamination?
Did you walk the roof?
Aside from pics, all these things lead to the right answer to your question.

Jon Randolph · #5 (**permalink**) 08-02-2007, 06:55 PM

I have seen the remnants of a prior house fire being painted in an effort to either hide the evidence or, most likely, to deal with the smoke smell. Was it only the decking or were the rafters/trusses also grey?

Matt Fellman · #6 (**permalink**) 08-02-2007, 07:11 PM

What you describe is fairly common in my area. Without pics it's tough to say for sure but it sounds like you're describing mildew or mold or some type. I notice it more is shady areas or the north/east sides but it can occur anywhere. It's an excessive amount of moisture and/or a lack of ventilation.

Given the hysteria around mold these days I usally recommended taking measures to properly ventilate the space and further evaluation from a mold remediation specialist to determine if any corrective action is needed at this time.

I kind of struggle with the ones where I just see a very minor amount of it. I don't personally think it's a big deal if it's minor but I never know how bad the next guy in is going to scare the people.

Most times when it's minor the mold guys recommend adding ventilation, getting all fans vented through to the outside (rather than just hanging the duct near a vent and hoping for the best) and washing it down with a bleach solution.... but I would never go that far on the report.

I had a moderate amount of it in a house I bought and had to replace 28 sheets of plywood when I did the roof. Some pics from my house are below.

As you can see the insulation installers were nice enough to completely block off the soffit vents when the house was built (1989). I came along in 03 and the roof was done in 04. Notice the black piece of plywood in contrast to the newer ones.

Michael Thomas · #7 (**permalink**) 08-02-2007, 08:33 PM

the sheeting color on two sides (West and South) was gray"

Bill,

It would be helpful to fill out your profile so others can see your location, for example here in Chicago I most frequently see this on the north side of the roof, due to condensation - it's not uncommon here see a lot of discoloration on the north side, and nothing anywhere else. If an inspector here observes this sort of discoloration in some other area and the north side is clean, or much less discolored, that's a clue to look for a localized moisture source such as a bathroom fan or dryer venting into the attic or to an improperly installed soffit vent in that area, or for blocked soffit vents or some other cause of poor ventilation on that side.

One other possibility (long shot, but it happens) in buildings from the 1980s: if the discoloration is widespread and fairly uniform on the south and west sides, consider the possibility that it's FRT plywood,

Fire retardant plywood - FRT Plywood - Fire Resistant Treated Plywood Failures on Building Roofs - Inspection & Testing Procedures

left over from a multi-family project and used by the builder on a SF home, and deteriorating faster on those exposures due to higher sheathing temperatures there.

Bill Wieczorek · #8 (**permalink**) 08-03-2007, 11:27 AM

I appreciate the replies. I'll try to obtain the pictures from the guy I was helping, he has them on his camera. To answer a couple questions.
The 2 power vents that were working were an add on about 10 years ago, one one was working. Those are the only vents, there are baffles for air thru the eves. but not enough in the roof in my opinion. The home was heavily shaded on the South side, not so for the West side. When you rubbed the sheeting nothing came off on your hand which I thought was strange.

The roof was walked in the areas where it wasn't too steep, parts of the roof have a 6/12 pitch. No thanks, there is difference between bravery and stupidity.

Bath vents were vented to the outside but it's possible that was done after the problem started, there was no way to tell. Its didn't look like they had been done recently. There was no plywood de-lamination. The shingles were 30 year architectural, they were black so any exterior color deterioration couldn't be seen.