Mold-like growth in attic

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Mold-like growth in attic

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Bill Smith

Smith Home Inspection
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Posted: Nov 20, 2005 11:09 AM       Post Subject:
I found this dark mold-like growth on the underside of the roof deck sheathing.

[ Image: https://www.nachi.org/bbsystem/usrimages/D/DSCF0024.JPG ]

There appeared to be water stains on the rafters but I don't think there is an active leak. The deck and roof were replaced about 4 years ago. No rust was seen on the protruding tips of the roofing nails so the ventilation seems proper. There is a ridge vent installed and two large (2' x 2') gable vents. A bathroom vent was discharging into the attic but it is at the end about 20' away. This growth is only in 5 bays on the eastern side in the center of the attic. Traces of the growth were seen on the closet ceiling under this area where the access hatch is. I'm stumped as to the possible cause of this growth. Any ideas?
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Roy Cooke

Roys Home Inspection
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Posted: Nov 20, 2005 11:39 AM       Post Subject:
bsmith wrote:
I found this dark mold-like growth on the underside of the roof deck sheathing.

[ Image: https://www.nachi.org/bbsystem/usrimages/D/DSCF0024.JPG ]

There appeared to be water stains on the rafters but I don't think there is an active leak. The deck and roof were replaced about 4 years ago. No rust was seen on the protruding tips of the roofing nails so the ventilation seems proper. There is a ridge vent installed and two large (2' x 2') gable vents. A bathroom vent was discharging into the attic but it is at the end about 20' away. This growth is only in 5 bays on the eastern side in the center of the attic. Traces of the growth were seen on the closet ceiling under this area where the access hatch is. I'm stumped as to the possible cause of this growth. Any ideas?

Sounds to me like there is air getting past the attic door allowing moisture into the attic .
The mould in the closet could be from cold air being drawn down into the closet from attic when negative pressure is in the home from a dryer running or ,kitchen or Bath room exhaust fans.
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Jay Moge
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Posted: Nov 20, 2005 9:16 PM       Post Subject:

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what if the roof wasn't finished before a rain storm and this was the only part left unfinished and the shingles were put on the next dry day? looks like a pretty heavy water flow to leave a water stain like that. just a thought. icon_cool.gif icon_wink.gif
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David Valley

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Posted: Nov 23, 2005 8:10 AM       Post Subject:
You say the deck and roofing material was replaced four years ago. It appears that the roofing material is failing.

What's the moisture content?

Do you utilize a moisture meter of some sort?

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David Valley
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"Some cause happiness wherever they go; others, whenever they go."

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Bill Smith

Smith Home Inspection
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Posted: Nov 23, 2005 4:04 PM       Post Subject:
I did a moisture meter check and it read 10% - not unusually high. It was consistant throughout the attic but the growth was localized.
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Paul Hinsperger

Hinsperger Inspection Services Ltd
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Posted: Nov 23, 2005 6:11 PM       Post Subject:
With the available information I tend to agree with Roy. I am at a loss however as two why the nails are not showing any signs of rust. Guess they must have been super galvanized.
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Marcel Cyr

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Posted: Nov 23, 2005 6:14 PM       Post Subject:
icon_smile.gif icon_smile.gif

Hi. Bill;

Would it be possible that over the years, with the inadequate soffitt venting and moisture intrusions from the dryer and bathroom exhaust that might or might not be the culprit, have caused the dripping of the melting frost during the warm seasoned days?
I have in the past noticed in the Winter months, that a frost would accummulate under the sheathing of the roof caused by warm moist air that hits cold substrate, and the Sun comes out and warms it up to cause the frost to turn to liquid moisture. It then at this point runs down or drips onto the substrate below.
This picture dose not look like a mold problem, but more of a moisture problem.

Just my thoughts.

Good luck.

Marcel
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Tyrone Wheeler

Guaranteed Residential Inspections Inc.
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Posted: Nov 24, 2005 6:17 PM       Post Subject:
First of all, I do not see any baffles, which will restrict air flow and contribute to poor ventialation, also the insulation r-value appear to be low, which will allow considerable heat loss. Combine the two, and you've got condensation, which leads to black mold. This mold not considered high toxic mold, but will eat away at the sheathing and result in failure of the roof.
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Caoimh?n P. Connell
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Posted: Nov 25, 2005 12:17 PM       Post Subject:

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Hello Bill:

I have frequently seen this type of growth. As an Industrial Hygienist, coming at these projects from a different objective, one of the next things I look for is to see if the mycelia from the growth ?bridges? over onto the roof joists (or trusses, or whatever they?re called). If the mycelia bridge the gap, then you know that significant moisture occurred or is occurring at some time after the roof decking was installed. If, on the other hand, the fungal mycelia do not bridge the gap, the colonization has been arrested shortly after the roof decking has been installed, and further colonization is not likely until something changes.

Next, find a nail that penetrates the roof decking in an area of definitive growth and see does the mycelia grow on the wood that was exposed as the nail pressed through the wood. If the mycelia is absent from the ?newly? exposed wood, then you know the roof decking was installed with the colonies already present.

Regarding the ?black mould? comment. The colour of a mould has nothing whatever to do with any inherent toxicity ? the whole ?toxic black mould? thing is a recent creation by the news media and has no basis in science. Pearly white fluffy mould, green mould, blue moulds and pink moulds can all become ?black mould? when the mould dies and oxidizes.

Anyway, just some thoughts?

Cheers,

Caoimh?n P. Connell
Forensic Industrial Hygienist

www.forensic-applications.com

(The opinions expressed here are exclusively my personal opinions and do not necessarily reflect my professional opinion, opinion of my employer, agency, peers, or professional affiliates. The above post is for information only and does not reflect professional advice and is not intended to supercede the professional advice of others.)

AMDG
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Dale Duffy

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Posted: Nov 25, 2005 1:26 PM       Post Subject:
Once again the perfect professional opinion from an expert. Which is needed before someone says something to a client which could cause possible unnecessary remediation from a thief.
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Bill Smith

Smith Home Inspection
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Posted: Nov 27, 2005 6:28 PM       Post Subject:
Marcel Cyr wrote:

Quote:
I have in the past noticed in the Winter months, that a frost would accummulate under the sheathing of the roof caused by warm moist air that hits cold substrate, and the Sun comes out and warms it up to cause the frost to turn to liquid moisture.


Marcel- that seems to make the most sense. The affected section of the roof faces east so it would experience the most severe temp. change - cold at night to the first rays of the sun. You may have hit it on the head.


Caoimh?n P. Connell wrote:

Quote:
If, on the other hand, the fungal mycelia do not bridge the gap, the colonization has been arrested shortly after the roof decking has been installed, and further colonization is not likely until something changes.


Caomhin- The growth did not bridge the gap between the rafters and roof sheathing. Excellent input.

Thanks to you all for your thoughts.
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David Andersen

David A. Andersen & Associates
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Posted: Nov 29, 2005 10:11 AM       Post Subject:
It appears that there is considerable condensation occurring. The OSB is discolored in its entirety as well as the rafters.

As far as locating the source, I think an intrusive inspection is required. Pulling up the installation etc. may be necessary.
Condensation occurs from the cold object coming in contact with air with a dewpoint temperature higher than that of the cool object (roof). Air with a high dewpoint temperature has a high sensible temperature (causes air to rise) and a high latent temperature (moisture). It is likely that this air is rising from directly below (seeing as it is isolated to one section of the roof). This air contains high moisture (latent heat) likely originating from the interior space (bathroom) versus a heat source (light, air duct etc.).

It sounds like there is sufficient attic ventilation overall. This would account for this localized condition in the immediate area of the exfiltration point.
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