2006 home. Tennessee crawl space with a new looking vapor barrier on the ground.
This apparent fungal growth is interestingly just around the outer perimeter. Moisture is around 14%. It also appears that there is no moisture barrier between the foundation and sill plate. There’s no plastic and when I look in the gaps I can see any plastic or foam.
Would lack of moisture barrier allow vapor to enter that area? Have any of you seen this before?
Looks like some water staining at the venting right there.
What is the exterior cladding?
My first thought would be moisture getting in at the floor level potentially
You said the perimeter…but is it isolated to the deck area/back door perchance? Or predominately the rear?
It’s called “sill seal” and it’s not for moisture. It’s used to help prevent heat loss due to air infiltration.
It was particularly along the ends of the home and the front portion not adjacent to the front porch. The rear of the home along the deck also did not show fungal growth.
Could you verify flashing at the brick ledge, and a Moisture resistant barrier behind the siding? That transition between the two may be suspect
I don’t believe crawl spaces are supposed to be air-tight or there would not be a need for wall vents (two in this picture) to ventilate the area.
Masonry clearance issues.
Wicking. No visible sill gasket.
Rim joists/Mudsill not insulated. No circulation.
Morning, Stephen.
From my understanding, a Sill Seal is a material gasket, one may refer to as a flashing, installed on ‘exterior walls’ that fill gaps between the sill plate/mudsill and a foundation wall and creates a capillary break to prevent wicking from the foundation material to wood sill plates.
The caveat; the seal is for 'above-grade sill plates/mudsills, adjacent to ‘conditioned spaces’ to minimize air leakage. Unfortunately in this example the space is not conditioned and 3/4 of the foundation is below grade.
Good question, Daniel. I wasn’t able to see any flashing or house wrap per se.
You should review the post: Floor joist, rim joist and subfloor rot
and Energy Vanguard
Venting a crawlapace during the humid summer is a source of moisture and mold. As stated, so is moisture from the exposed dirt and the foundation wall within the crawlspace, plus of course bulk water that enters the crawlspace because of factors such as a poor wall drainage plain and flashing, foundation wall vents, or a foundation wall less than 6 inches above grade.
I would break it down to two likely possibilities. (both of which has been mentioned above)
I’ll add a guess. The edge of the floor next to the exterior will be cooler due to conduction of cold from the exterior and you might have humidity in the crawlspace condensing on that cooler area creating conditions favorable for mold growth.
Certainly a good learning opportunity! Thank you all for the input! Air movement and condensation/moisture issues can be complex.
I concur.
Rim joist not insulated. Poor air circulation in that area.
Would you go so far as to recommend rim joist insulation be installed? My general recommendation is about apparent fungal growth, but I think it unlikely that a pest control company will make that assessment/recommendation.
Nope. This is definitely one of those instances where I would not make a recommendation for a cure.
I would report what I see and refer it out to an air quality specialist, IAQ or such.
If you do the below and you are wrong, guess who gets to pay?
I concur with you Larry! Thanks!
