Thread: Mold on attic sheathing

Here we go with another mold on sheathing case.
This house was built in the 80's and had new roof with sheathing replaced in 2001. The sheathing that was replaced was in the rear only and is now covered with mold.
The rear of the house is facing north.
The insulation is fiberglass with no vapor barrier.
The soffit vents are blocked with insulation.
The ridge vent is the type where it has that fiber material that blocks the opening.

So with the moisture content of this Sheathing at approximately 20% and 80% covered with a layer of mold, should it be replaced?
Does anyone have any info about the different types of ridge vents?
Also, would you go as far as recommending that the insulation be replaced with the type that has a vapor barrier?

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What you have is cold roof decking, and a moist attic.
Vent the attic.
Find and stop the moisture from getting into the attic.

Unless the decking is swollen or otherwise damaged, it should not need to be replaced.
No moisture, no problem

The ventilation needs to be remedied. With that being the north side, was their moss buildup on the exterior?

There are continual ridge vents and roof caps/turtle caps and gable end vents that could help.

The mold can be remediated in place with chemicals by a remediation company. Very spendy, and in my opinion, a racket.

If the company that put that new roof on, to include the sheathing, did not clear/baffle the soffits, I would make a phone call to them. They knew there was a mold issue before, so they should have made sure that the attic cavity was venting properly.

As far as the insulation goes, no. It does not need to be replaced with an insulation with vapor barrier/paper backing. The majority of insulation installed today is loose fill, no vapor barrier.

How much of that sheathing was 80%. That should have been dripping.

Rob Jones

Seattle Home Inspection

"As far as the insulation goes, no. It does not need to be replaced with an insulation with vapor barrier/paper backing. The majority of insulation installed today is loose fill, no vapor barrier"


Are you sure? Did you do your homework?

Were there two layers of insulation?
Did you expose the backside of the plasterboard and check the 1st layer. [if 2 layers]

Originally Posted by Jon mackay

Does anyone have any info about the different types of ridge vents?

Although everyone does not agree with some of this information, I find this to be a good attic ventilation document.

Originally Posted by Robert Jones

The ventilation needs to be remedied. With that being the north side, was their moss buildup on the exterior?

There are continual ridge vents and roof caps/turtle caps and gable end vents that could help.

The mold can be remediated in place with chemicals by a remediation company. Very spendy, and in my opinion, a racket.

If the company that put that new roof on, to include the sheathing, did not clear/baffle the soffits, I would make a phone call to them. They knew there was a mold issue before, so they should have made sure that the attic cavity was venting properly.

As far as the insulation goes, no. It does not need to be replaced with an insulation with vapor barrier/paper backing. The majority of insulation installed today is loose fill, no vapor barrier.

How much of that sheathing was 80%. That should have been dripping.

Rob Jones

Seattle Home Inspection

There was som moss beginning to form at the roof surface, Yes.
The sheathing was not 80% wet, it was covered approx. 80% with mold. Only about 20% moisture.

Originally Posted by Michael Garrity

"As far as the insulation goes, no. It does not need to be replaced with an insulation with vapor barrier/paper backing. The majority of insulation installed today is loose fill, no vapor barrier"


Are you sure? Did you do your homework?

Were there two layers of insulation?
Did you expose the backside of the plasterboard and check the 1st layer. [if 2 layers]

The insulation was one layer of 12" fiberglass.

There really is no way for me to determine the structural integrity of the sheathing.
Being moist, won't delamination be an issue?
Even if you fix the moisture problem, what damage has been done?

In the past, I have said to fix the moisture problem and move on but I have never seen this much before.

There's a reason why it's called a vapor barrier.

Originally Posted by Jon mackay

The sheathing was not 80% wet, it was covered approx. 80% with mold.
.
Only about 20% moisture.

.
Mold Will Grow @ 20% Moisture.
* The Sheathing needs to be below 20% moisture content.
.

Originally Posted by Michael Garrity

"As far as the insulation goes, no. It does not need to be replaced with an insulation with vapor barrier/paper backing. The majority of insulation installed today is loose fill, no vapor barrier"


Are you sure? Did you do your homework?

Were there two layers of insulation?
Did you expose the backside of the plasterboard and check the 1st layer. [if 2 layers]

Am I sure of what? That the majority of the insulation installed nowadays is loose fill? Or that the insulation does not need to be replaced to one with a vapor barrier?

I'm leaning toward sticking with the facts on this one.

#1) Ventilation needs repair.

#2) Sheathing has mold at the rear portion which has accumulated in 9 years.
The front sheathing may be the original sheathing as there is no visible date stamp like at the rear. (Front soffit vent baffles also look to be intact)

#3) Unable to verify the structural integrity of the sheathing at the rear or how the exposure to moisture will accelerate wear.

any other thoughts?

Jon
Do mention that there is moisture in the attic. Mold does not grow unless there is moisture.