Tracking Hidden Moisture In A Brick Apartment

79% humidity inside an apartment while the air conditioner is running is more than uncomfortable, it’s a building telling you something is wrong. We take a real call from a long term renter who feels increasingly ill and suspects mold, then we unpack how we investigate indoor air quality without falling into the trap of “one test equals the truth.” Our approach is simple: we combine environmental sampling with hands on moisture detection so we can connect symptoms, humidity, and the actual source of water.

We talk through what we saw in an older brick apartment setup and why small ceiling moisture spots weren’t the main story. The bigger clues were on the exterior: a raised flower bed pressed against brick, termite activity where moisture stays trapped, and painted brick peeling only near the bottom where poor grading sends water toward the wall. From there, we explain capillary action and brick wicking, how moisture can migrate upward and inward, and why that can quietly drive high indoor humidity and hidden mold growth behind drywall.

Then we get into mold testing details: why swab samples from HVAC registers can come back “hot” for molds like Alternaria, Penicillium/Aspergillus group, and Cladosporium even when air samples aren’t elevated at that moment. We break down why mold doesn’t always release spores, how timing matters, and why relying on the wrong screening tools can lead to bad decisions. If you care about mold inspection, moisture intrusion, and indoor air quality testing that actually helps you fix the problem, this conversation will save you time and stress. Subscribe, share this with a friend dealing with mystery humidity, and leave a review with your biggest home moisture question.

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Transcript

A Tenant Gets Seriously Sick

SPEAKER_02 0:01

Alright, Laura. Here is the situation. A person has been renting an apartment for four years. Yep. Several years. And they're I feel like they're getting sick. They don't know exactly why. They suspect uh molds.

SPEAKER_01 0:19

Getting sicker and actually off work at this point in time because they're so sick.

SPEAKER_02 0:25

That sucks. That sucks mightily. So the person contacted us, we went out there, and then how do we do this? Because you, for environmental consultants of Ohio, does air quality testing typically. That's what it does. Looks for chemicals, VOC. It can do phase ones, like somebody buying a commercial microtoxin testing. It does a lot of stuff. And I don't know if we did this under Habitation Investigation or Environmental Consultants of Ohio. I don't remember how we did this one.

SPEAKER_01 0:58

It really doesn't matter because it's both you and I, and they're so so here's how we handle things like that.

SPEAKER_02 1:04

If somebody is sick in the house, they don't know why, and they want some air quality testing. You come out, you're you're doing the testing after we consult with the person for a little bit, and then I'm there looking for as a home inspector, I'm looking for moisture and come with ideas and theories on how the moisture is coming in.

SPEAKER_01 1:21

Right. So we tag we tag team well.

SPEAKER_02 1:23

We tag team, yes. We have worked together for decades.

SPEAKER_00 1:28

Decades.

SPEAKER_02 1:30

So at this place, this is a place down in German village. Yes. What how do you want to describe the place?

SPEAKER_01 1:39

Old. Probably it was originally an old house that they divided up into apartments.

SPEAKER_02 1:47

Did she say it was like an old carriage house?

SPEAKER_01 1:49

I think it was an old carriage house. So it's on a slab. Like it's like an old garage. It's it's on a slab. That's it. Um, very little insulation. It was very reactive to the temperature and the humidity outside. That reflected a lot inside the apartment.

SPEAKER_02 2:08

Yeah, I and I looked at some things. She had two humidostats, uh, humidity gauges in the apartment, and they both said it was 79% humidity in there, which is crazy. For a house that has air conditioner running. It should not be that high.

SPEAKER_01 2:25

Well, and at what point does humidity start to deteriorate belongings and wood and things like that? Isn't it like 60 and over?

SPEAKER_02 2:37

Well, if you got 60% humidity, that is high enough where you start getting some molds growing typically. I'm not sure there's variation in that type of mold.

SPEAKER_01 2:45

Like rot, like wood rot.

SPEAKER_02 2:46

Uh if you're for wood, you're typically talking about 16% moisture content. 16% moisture content of the wool of the

Tag Team Approach To IAQ

SPEAKER_02 2:55

material. Okay. That's different than the relative humidity. True. Okay. Because you two different substances. But anyway, so 79% humidity in the place. There was uh I did find some moisture, elevated moisture in some areas of a ceiling, two areas, which are not very big and with all the rain we had, so not probably a small roof leak, you thought? Yeah, small, and definitely not a big contributor to the moisture in the apartment. There's not there's the leaks are not big enough. I mean they're they're tiny.

SPEAKER_01 3:31

No, but you did find something interesting outside that you thought was causing the issue.

SPEAKER_02 3:37

Yes. Well, here's also I found moisture up the walls in a couple areas of the house.

SPEAKER_01 3:43

Up, not down below.

SPEAKER_02 3:45

Two feet up the wall, there was moisture, and it was like 16-17% on the drywall, which is high. It shouldn't typically never get that high. So that is the rotting that is high enough for the whatever how are they framed in that bit that that wall there? There could definitely be some deterioration going along with where were they two by fours or one by two, who knows? You can't you don't know until you open it up. Right. But there that is high enough to cause some deterioration and definitely enough for mold growth. But so moisture, like two feet up the wall from the bottom, up higher, it was still moist, because I think overall humidity in the place, but not as high as about two feet up.

SPEAKER_01 4:33

Still kind of crazy to me that it was up, not down.

SPEAKER_02 4:36

Yes, so went outside. Curious here. But the one area where there's moisture up the wall, there was a raised bed put up against the actually this place is all brick on the outside.

79% Indoor Humidity Red Flags

SPEAKER_02 4:50

Raised bed, flower bed up on the brick. So, yeah, that's definitely gonna hold moisture against the bricks. That makes perfect sense to me why you'd have the moisture coming in that area of the wall because you're holding wet wood.

SPEAKER_01 5:03

Well, and that was also the termite area.

SPEAKER_02 5:06

There's also termites there, which moistures you need moisture for the termites to do well. But then the other side of the house, the apartment on the end of it, there was the brick had all been painted, and the lower, like foot and a half, two feet, the paint was peeling off on the lower levels. But it the paint looked fine up above. Right. That tells me that the brick, and there's bad grating outside. So the ground was too flat or sloped slightly toward the apartment, directing water in that area. So that peeling paint on the bottom edge is telling me that the brick is absorbing the water, and then during freeze-thaw cycles, it is you know expands and it's pushing the the paint off. The paint starts is peeling off because of all the moisture. So my theory is a lot of the moisture coming in that house is from the outside getting wicked capillary action, getting pulled up that brick, and then it gets on the wood that's just inside that brick, and then it gets transfers into the house. That's my theory of how all the moisture is coming in and explains why it's on the outside. So how drywall as well.

SPEAKER_01 6:22

How how would you fix that then if you let let's let's say that her landlady actually cares about fixing this? How would she fix it?

SPEAKER_00 6:33

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SPEAKER_02 6:58

I believe there are things that can be injected, like soaked into the brick. Because

Brick Wicking And Exterior Clues

SPEAKER_02 7:05

it's red, it's red brick, it's porous. You can soak that into the brick, and that will act as a vapor barrier and keep the keep the wall from getting wicked up the brick.

SPEAKER_01 7:17

Oh, that's cool.

SPEAKER_02 7:18

Because at this point, I mean, normally they would have some kind of a vapor barrier going up behind the brick, and but it's too late to do to do the unless they completely strip it down to studs, then they could do that. Yeah, and they can make you do it section by section, but the easy thing is probably put some kind of uh substance into the bricks to at least stop the capillary action from pulling the moisture up from the ground and up. Another thing they do is make certain they got good grading to prevent the moisture from coming up against the brick in the first place, and of course get rid of that stupid raised bed that's like a foot up the brick wall.

SPEAKER_01 8:00

Oh, easily.

SPEAKER_02 8:00

The moisture's gonna go in. Where else is it gonna go?

SPEAKER_01 8:04

It wasn't going out.

SPEAKER_02 8:06

So that there was that story. So Laura, so you did testing on it. You didn't we did swabs. I climbed I climbed up on a table or reached the reached the uh register that was up on the ceiling. We did first floor and then second floor. And then an outside sample, of course, as as a control.

SPEAKER_01 8:27

Both came back hot. They they were came back as unusual with with the new lab that we're using, meant meaning that there were molds in it.

SPEAKER_02 8:37

Did they say what type of molds are in there?

SPEAKER_01 8:39

Give me a second and let me see if I can pull that up.

SPEAKER_02 8:44

But there was mold in the swab. How was the air?

SPEAKER_01 8:55

I've got it already. So turn roll, please. Okay, so the first swab had mold present and it was alternaria. Um, it had roots in it, ascospores, and penicillium aspergillus.

SPEAKER_02 9:17

Not common mold, yes.

SPEAKER_01 9:19

So the air for the downstairs was not considered elevated as of yet. The upstairs vent had chlamydospores, cladosporium. Chlamydia? Yeah. Clemendospores.

Swabs Versus Air Samples

SPEAKER_01 9:45

Screw you.

SPEAKER_02 9:48

I was saying that's a whole old new what method of transfer I've never heard of, but okay.

SPEAKER_01 9:52

You know what? Come on, that's fine. I'm tired. You're picking on your wife because you're being mean.

SPEAKER_02 9:58

Swamps in the registers, found mold.

SPEAKER_01 10:00

Found mold. They they came back as unusual. But the air was not. Wait, I'm looking at this other one. And the other one was not elevated either.

SPEAKER_02 10:08

Okay. So here's the thing that some people or the some people believe, or they'll at least say, that if there's no spores, elevated spores in the air, that means you don't have a problem. That is bullshit. Because, like fruit trees, like apple trees, it's still an apple tree that's growing, but it doesn't always produce the apples. Which is my analogy for moles, because you can have moles growing, but they're not always going to be producing spores and releasing them. So when I see other home inspection companies and they do just two samples and they call it and they and they go, Hey, that we did a whole test, and like, well, wait a minute, did they swab this big ass piece of mold down?

SPEAKER_01 10:59

Like, well, don't you just do an air sample and a control and call it good, which is the test we just saw.

SPEAKER_02 11:03

We just saw an air, we just did an air sample in that area in the basement, the control side, and that's it. No, no, I mean that's a start, but no, you need to do, especially if you see something, you should do a swab.

SPEAKER_01 11:18

Well, that tells you if you've got stuff on that swab, and then let's say you have something in the air, but it's not on the swab, well, you've got another area somewhere where you've got a moisture issue because there's something giving that source. If you have something on a swab but not in the air, okay, well, it might not be fruiting, might not have been putting out spores, might not have been growing long enough. Or let's say it's like Stachyboctorus. There are a few that, like as they're growing, their spores are very, very heavy. And they do not actually put out spores until they're dried out. So once you fix the situation, you could be actually putting spores out if you haven't taken out that area and cleaned that up.

SPEAKER_02 12:02

Yep. So psychoboctorus, it's it's more seasonal. You're more likely to see it when things are dry.

SPEAKER_01 12:09

Right.

SPEAKER_02 12:10

Or the situation's been fixed and then dries out.

SPEAKER_01 12:13

So I read an article the other day, just as an interesting side note, because I didn't know this. All of the of all the researchers that go out and search for molds and do things outdoors, there has been no one ever that has found Stachyboctorus in

Why Mold Tests Get Misread

SPEAKER_01 12:30

the wild. Ever.

SPEAKER_02 12:33

That's interesting.

SPEAKER_01 12:34

Isn't that interesting?

SPEAKER_02 12:35

Not even a stachyboctorus needs lots of moisture for a long, continuous time. So I would think you would find it in like a swampy area.

SPEAKER_01 12:48

Nope. Not according to the article that I read. It has never been found in the wild by any researcher.

SPEAKER_02 12:55

That's crazy. So okay. So that's about it on this one. So yeah, sometimes it's not just a water, you know, plumbing leak. It's not just that. So if you need some clarification to see what's going to your house, man, somebody like Laura and I, where you got somebody who can do the air quad, and then somebody who's a home inspector can pair up.

SPEAKER_01 13:20

Because Laura, you got certifications for mold testing, clearance, mold assessor, mold writing protocol, water restoration tech, blah, blah, blah, blah, blah.

SPEAKER_02 13:30

Yeah, those certifications. I'm a home lowly home inspector.

SPEAKER_01 13:33

Yeah, I'm blowing my foot.

SPEAKER_02 13:35

But I mean, I like building science. To me, that's that that is interesting. Because there's there's physics to this that a lot of people don't even don't even think about that stuff. There's a lot of building science to this stuff. But uh, I think that's about it on this one. So, yeah, if you if you need some air quality testing done, look around. I'm sure there's people wherever you're at that can help you out, but make sure you just find someone that knows what they're doing. Yeah, don't get just any mold testing company or any old home inspector. Can I just make sure they got some good background and if you get two people of diverse you know experiences, that's even better.

SPEAKER_01 14:15

Can I please put a plug-in for something? Sure. Do not if somebody says, hey, we're gonna come out and do an ermie or a hurts me, find another company. Since 2013, the EPA has specifically said those tests are not to be used in a residential assessment of a mold or a moisture issue. And that's all I'm saying on that. Thank you.

SPEAKER_02 14:38

All right, that's it. All right, thanks, everybody. Bye bye.