Moldy roof sheathing/ stains at windows

[Brandon Whitmore]

I just did a 1996 single level ranch style home.

Roof slope is about 5:12 (lots of attic air volume), housewrap looked like kraft paper, plywood sheathing, good ventilation, etc.

Home sat on a fairly level lot with decent grading. The crawlspace soils were well covered with 6mil black plastic and the crawlspace was dry.

Along the perimeter of the attic there is mold/ mildew growth that is black/ gray in color... not too thick. The growth starts at the insulation line and extends up a few feet. There is an eave vent every 3rd truss bay with no growth in those bays.

There are water droplet stains on the vinyl windows at the head areas of the tracks along the E. end of the home (kitchen, bedroom areas). Seeing as how this is a single level ranch home with good eave overhangs, I see no way that flashing would matter at the windows as they are not exposed to the elements== I am ruling out improper flashing as a potential cause of the moisture stains.

I am pretty much stumped as to why there is mold growth in the attic with the water stains on some of the windows. By the way-- the worst mold staining is on the E. end of the attic above the windows with the stains.

Anyone have any ideas? This one has me stumped.

Oh yeah-- the vapor barrier is installed so the top edge of the barrier is secured to the sill plate at the top of the foundation stem wall-- this is a pretty typical installation for newer homes in this area. I was thinking that maybe condensation from the ground is migrating up to the vapor barrier, and moisture is entering the wall cavity where it condenses on the attic sheathing. Possible?

This building science stuff gives me a headache.

[hausdok]

Originally posted by Brandon Whitmore

There is an eave vent every 3rd truss bay with no growth in those bays.

There's your answer. you need to get air moving between these vents. Were there gable end vents as well? Add more vents under the eaves at every rafter bay, close the gable end vents and ensure that the total vent space at the eaves is evenly proportioned with that near the ridge.

There are water droplet stains on the vinyl windows at the head areas of the tracks along the E. end of the home (kitchen, bedroom areas). Seeing as how this is a single level ranch home with good eave overhangs, I see no way that flashing would matter at the windows as they are not exposed to the elements== I am ruling out improper flashing as a potential cause of the moisture stains.

Sounds like they need to do more to ventilate the home. I wouldn't associate one condition with the other.

Oh yeah-- the vapor barrier is installed so the top edge of the barrier is secured to the sill plate at the top of the foundation stem wall-- this is a pretty typical installation for newer homes in this area. I was thinking that maybe condensation from the ground is migrating up to the vapor barrier, and moisture is entering the wall cavity where it condenses on the attic sheathing. Possible?

Not if the barrier is installed properly. If you're not seeing moisture issues on the rim joists at the perimeter of the crawl where the framing is coldest, it's probably not moisture from the crawlspace that has anything to do with the attic issue.

This building science stuff gives me a headache.

Nah, it's just a few basic principles to understand. You want to talk headache? Give me a column of figures to add together and you can physically watch as my head deforms into putty.

ONE TEAM - ONE FIGHT!!!

Mike

[Brandon Whitmore]

Were there gable end vents as well? Add more vents under the eaves at every rafter bay, close the gable end vents and ensure that the total vent space at the eaves is evenly proportioned with that near the ridge

No gable vents. It had plenty of eave vents and can vents right up at the ridge.. ventilation looked great, which is what is throwing me off. I did not calculate the air balance between upper and lower ends, but it looked pretty good.

Thanks Mike-- I'll recommend they have a roofer try to figure out what is going on and/ or add ventilation.

[Brandon Whitmore]

What are some other causes of water stains see at the top of vinyl windows besides leakage at the windows. The stains I am referring to are where you typically see a few tan/ brown water droplet marks along the interior top edge of the windows. (head area track).

[Jim Katen]

Originally posted by Brandon Whitmore

What are some other causes of water stains see at the top of vinyl windows besides leakage at the windows. The stains I am referring to are where you typically see a few tan/ brown water droplet marks along the interior top edge of the windows. (head area track).

Well, the classic is a window with an unflashed deck ledger above it.

If there's enough condensation going on in the attic, I'd have no trouble believing that to be the cause.

I tracked down the source of these stains to clothes dryer exhaust in the attic.

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- Jim Katen, Oregon

[Brandon Whitmore]

Thanks Jim.

I've seen stains such as those and worse in some nasty rentals where the condensation rotted out sheathing and rafter tails as well. (above bathrooms).

Well, the classic is a window with an unflashed deck ledger above it.

I see more signs of leakage more often than not with replacement windows, where the original windows are plumb with the siding/ wall plane and they don't install flashing.