Thread: Black stains in attic?

This was on the under side of the roof decking. The house was thirty years old. Are these just stains? There did not appear to be any mold or mildew on the surface but I could see black spots. No moisture detected and the roof is new.

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Best

Ron

Soffit and gabel, no ridge. It was ok. There was nothing on the suface of the decking though, it was absorbed into the wood.

looks like the homeowner did the roofing himself. watch your head!

No S$%#T I got one in the head trying to scape some of the roof decking.

That is a stain caused by mold (mould). The variety I see most often is fuzzy green when active and goes black like that when dormant or dead. Attic moisture and poor ventilation are the causes. The new roof doesn't help much, most of the moist air is likely coming up from below.

John,
I know what you are saying and I see the same black fuzzy mold often as well. But this appeared to be absorbed into the decking. You could not scrape it off.

Did you check the nail points from the roofing? That should help indicate whether this is an on- going ventilation/ moisture issue or not. If the fasteners are corroded, with stains on the sheathing directly around them, it would indicate to me that this is an issue. If the fasteners are shiny new looking, it may indicate a past issue (sounds like ventilation is poor though).

Originally Posted by mathew stouffer

John,
I know what you are saying and I see the same black fuzzy mold often as well. But this appeared to be absorbed into the decking. You could not scrape it off.

I see fresh splinters and clean nails, so yes, it is possible that the problem was addressed. I think I would describe what you see now and recommend monitoring.

Originally Posted by mathew stouffer

There did not appear to be any mold or mildew on the surface but I could see black spots. No moisture detected and the roof is new.

This is dried water stains. The condensation appears in winter, normally underneath the frosted roof slopes at north and east. Poor ventilation in attic, and/or no exhausting duct for bathroom/laundry vent caused it.

I agree with Daniel. I see it pretty often here, and it's almost always on the north side of the house. Warm air escaping from inside (various ways) hits the cold roof and condenses.

Originally Posted by Jim Robinson

I agree with Daniel. I see it pretty often here, and it's almost always on the north side of the house. Warm air escaping from inside (various ways) hits the cold roof and condenses.

Same thing here... it's actually pretty common. There's really no risk of harm to the occupants of the house due to a lack of air exchange between the two areas.... I'd never tell buyers that though since it's outside my area of expertise. Also, the remediation can be expensive. Something I've never understood is why sometimes it's black and other times it's white. In any case I always take pictures and put it in the report.

Originally Posted by Matt Fellman

Something I've never understood is why sometimes it's black and other times it's white.

I think there are many varieties of mould which can grow on attic sheathing. Water is clear, wood is brown, so it takes a mold growth to change the color to black, white or green, IMO.

In any case I always take pictures and put it in the report.

Yes, it may not be physically harmful, or no longer active, but it can sure scare off buyers, so that affects property value big time.

I agree that the discoloration was likely caused by humidity, rather than a leak event. The even discoloration over a large area is a clue. There are many thousands of species of fungus. So having different colors is not surprising.

Originally Posted by Daniel Leung

This is dried water stains. The condensation appears in winter, normally underneath the frosted roof slopes at north and east. Poor ventilation in attic, and/or no exhausting duct for bathroom/laundry vent caused it.

Originally Posted by Jim Robinson

I agree with Daniel. I see it pretty often here, and it's almost always on the north side of the house. Warm air escaping from inside (various ways) hits the cold roof and condenses.

Our house is about 24 years old and the original owners had replaced the roof early because of such condensation building up in the attic. We later found out that one of the major problems was when they put in the bathroom vent they only used a single wall exhaust pipe and while poking my head into the attic during last winter I could all the frost built up on the sheathing.

Another problem that we found was that there was a couple of spots where there was insulation missing so the only thing stopping the heat from escaping was the popcorn covered sheetrock. Both of which issues have been addressed this summer and should hopefully never be an issue again.

A ton of moisture willl be driven up and out of an average house. I see this a lot in older brick veneer homes too. There can be a flow up the air space and that emanates from the crawl space. So all that good stuff rises and damned few attics are vented sufficiently. Result: mold. I've even had it tested. Usually benign-pennicillium, aspergilla. Around here it's ubiquitous. Plus you just can't do much about it other than scare people and queer the occasional deal.

JLMathis

I didn't make a big deal out of the mold but strongly recommended additional ridge and soffit venting. The buyer looked at the mold and said they would spray kilz on it

Originally Posted by Adam Goodale

We later found out that one of the major problems was when they put in the bathroom vent they only used a single wall exhaust pipe ...

That is not a major problem, that is not even a problem, basically the only ducts used for bathroom exhaust fans are single wall rigid metal, single wall flexible metal, or single wall foil flexible ducts - nothing more is required, and I have never seen anything else.

While one *could* use an appropriately sized insulated duct for the bathroom exhaust, if the ends are not sealed up properly, the inner duct is still exposed to long term attic conditions and nothing will have been gained.

Now, the most likely cause of moisture in an attic from a bathroom is that the exhaust fan is not ducted to the outdoors ... at all ... and yes, that can be a problem, but even that, in the scope problems with houses would not be a "major problem" - a "problem", yes.

As the others have said, there are so many holes and openings leaking air and moisture from the house into the attic (all of which are *required* to be sealed, by the way) that moisture in a cold attic can be a problem, but I would not blame it on a bathroom exhaust fan which is vented to the outdoors - if that was the problem I would look for where the duct is separated and 'not venting to the outdoors', but is really 'venting to the attic'.

FYI: I see this many of times as well here in MI attics. Just make sure there is no HVAC ductwork leaks (if HVAC is present) which could comprimise the indoor air quality for the occupants.

So far no one has discussed attic bypasses. The age of the house is consistent with those where penetrations into the attic were typically not sealed. Here in MN we find that the primary cause of frosted attics in winter is NOT the lack of ventilation, but rather, the presence of many attic bypasses. I encourage you to look closely for the bypasses (air leaks from house to attic).

Kurt Solomon, a HI from SLC may also be able to counsel you on these matters.

Best wishes and happy ski season in a few months. I love Park City, too bad its so far from MN.

Originally Posted by mathew stouffer

This was on the under side of the roof decking. The house was thirty years old. Are these just stains? There did not appear to be any mold or mildew on the surface but I could see black spots. No moisture detected and the roof is new.

Hey Matt,

I'm not seeing any discoloration on the truss members in your photo's. Also, I thought I read in one of you posts that the nails/ staples and adjacent splinters appeared shiney and fresh. Could it be possible that the discoloration occurred pre-installation. I have seen stacked CDX get rained on before installation and this type of discoloration be present after it is then installed.

Just a thought! Maybe, just maybe, there is no problem with venilation in attic or infiltration from living space at all.

Good luck. Mitch Toelle

Thanks for all the help.

This is a very common problem here in Northern Illinois, in my opinion generally caused by excess humidity in attic, bypasses as mentioned before, whole house fans, high humidity levels on furnace mounted humidifiers and especially wet crawl spaces. All the moisture in a crawl space will eventually find itself on the underside of the roof decking and condensating there when the temperature is low enough. I saw this localized once over a 100 gallon fish tank in a north side bedroom.

Look up "blue stain fungi" and you will discover that it is indeed possible to have a visible biological growth pattern on lumber products without having the presence of a heavy powdery or filamentacious fungal growth.

You can actually do a white glove wipe of these fungal stained areas and still not find any visible residue on the glove. An unnecessary surface test sent to the lab however might reveal the presence of Ophiostoma minus or some other fungal stain producing variant.

In this case however there has definitely been post construction moisture problem in the attic and a stain producing fungus has indeed manage to dominate the visible landscape. This is not a wood rot fungus by the way and does not result in structural problems.

It is however very unsightly and will cause the "hand wringers" among us to lose a lot of sleep and file law suits against you if you fail to point it out and refer it to an "appropriate expert".

In my opinion the root issue here is a moisture problem in the attic likely related to ventilation problems as previously stated by others.

Thanks so much for all this good information!

I have the same staining in my attic, and it is localized at the spot I have a known wall section that is without insulation. I will be addressing that issue this summer.

Looks like organic growth of some kind. Quite difficult to think of a potential recommendation/solution for that.

I feel like it is infested by some pests since the discoloration is not normal.
Also, this is an old thread 10 years ago and I am sure that the OP have managed to figure out what is that stain.