New Floors, Mold, Destroy, Rebuild, New Floors
March 11, 2013 10:52 PM   Subscribe

We refinished our hardwood floors. About three months later mold started growing up through the floor in a corner of the house. The moisture captured in the area buckled the floors. In the crawl space it looked like this (picture in linked version below) We removed all the fungus, and are now removing the area that was damaged. The big question was how this happened in the first place and why in this exact spot. This seems to be the answer. The spot where the moisture was getting in through the foundation was is a transition from the original foundation to a room addition that was done about 25 years ago. (yellow circle) (photo in linked version below) The transition has a crack in the foundation on both sides (yellow circle) There were NO foundation vents in this corner of the room, no ventilation. Moisture was getting in and trapped, fungus sprouted and destroyed the floors. Here is what I am trying to get information on: What do I do to the foundation wall, interior and exterior where this crack is to thwart any future moisture issues? Here is the same text with images
posted by silsurf to Home & Garden (15 answers total) 1 user marked this as a favorite
Well, there are a number of possible answers. Moisture in crawlspaces, as such, is fairly normal, so we can assume that an abnormal amount of moisture was getting in at this location. Where does it come from? What is the gutter/downspout situation, and how well does your ground slope away from the house at this point? Why was it collecting moisture in the first place, basically?

Second is mitigating the entry of the moisture. In extreme cases this can mean digging up the ground, installing french drains, sealing the outside of the foundation, and so forth. In this case you might be able to solve infiltration via a single crack using the standard repair of hydraulic cement. Get in there with a sturdy, somewhat sharp tool and open up the crack to accept the cement (and remove any loose material), then make up a slurry of the cement and put it in place like grout. It will actually expand as it cures to fill in gaps and seal up the crack, and barring significant movement, will last for many years.

Since you also have good access to the crawlspace and it's fairly clean, I would take the time to install a moisture barrier as well -- essentially a layer of 1-to-2-mil plastic laid over the bare ground. This will eliminate moisture that comes up from wet ground itself (although this comes back to the original point as to why it's there to begin with). Finally, consider installing foundation vents, ideally with seasonal flaps or some other way to regulate.
posted by dhartung at 1:44 AM on March 12, 2013

It takes quite a bit of moisture over a substantial period of time to do that and I am skeptical that the crack alone can explain it, so I have questions rather than answers.

Is the house in a low spot that generally doesn't drain well? Is the ground outside the crack sloped towards the house rather than away? Do you live in an especially wet climate? Was the soil in the crawlspace wet during this investigation? In the second pic, what is that perforated metal panel on the rim joist if not a vent? Did you have any extreme weather events just before this happened (i.e. hurricane Sandy)?

The foundation crack theory means you're talking about ground water flowing in, which doesn't explain how it gets to the wood. If it saturated the soil and then evaporated, making the crawlspace extremely humid and raising the moisture content of the wood, then I'd expect the fungus to be evenly distributed across all the wood surfaces, not concentrated in a particular area. But in the second pic the fungus appears to be concentrated along the left side, spreading out from the wall, and there appears to be a damp area just under the rim joist on the left wall. Has anyone considered the possibility of a roof, siding or window leak above this area? A steady trickle of water finding its way down to this area and wicking in-between the subfloor and finish flooring could have effects very much like this.
posted by jon1270 at 4:13 AM on March 12, 2013

It's odd that you're seeing fungus so far away, horizontally, from the crack. Water travels, sure, but it likes to go down more than across, and while wicking can explain a lot, it doesn't explain how there's no significant staining on the concrete in the crawlspace, which I would expect if the crack was leaking a lot. I'm sure the crack is leaking somewhat, but if the leak is in a room that was added on, I am going to suspect there's also a significant leak higher up where the rooflines were joined. Check the flashing and roofing up there, check the gutters, and if you can peek under the siding without doing too much damage do that. Alternately a little exploratory work on the inside wall might be good. Perhaps pull the outlets out of that box and have a look behind if you can.

More crawlspace venting would not hurt.
posted by seanmpuckett at 4:29 AM on March 12, 2013

We also laid down a vapor barrier over the dirt, while leaving the crawlspace vented (per assorted EPA recommendations), and it has done amazing things for the comfort of the house. Also makes doing stuff under the house (new plumbing, yay!) way more comfortable.
posted by straw at 8:55 AM on March 12, 2013

Thanks so much, here is some info based on the questions above.

The fungus was fast moving and happened in a matter of weeks, it forced its way into the wood floors, separating them, taking moisture with it and expanding the floors and buckling them. It was all radiating from the area in question, but found some areas in the corner where it was easier for it to break through.

Once the floor was up and the sub floor it was clear that the only area of moisture was at the crack area. Many people thought it was coming from other places, window seals, interior walls, underground pipes, etc. But that was all clearly not the case once everything was opened up.

The house has terrible irrigation and currently there are no gutters up. The rainy season is virtually over here in LA and I will be installing gutters before next year.

The soil has a lot of clay in it and is terrible at draining, this particular area is also at a corner of a roof where a lot of water came down.

I have been under the house many times and the foundation, venting and interiors walls are all in great shape, no signs of moisture anywhere except this one spot.

At this point, due to funds, what I am trying tin understand is the best method to deal with the crack and this area of foundation, it sounds like the hydraulic cement and a vapor barrier are the way to go. I would like a little better understanding of how to prepare and install the vapor barrier?
posted by silsurf at 9:22 AM on March 12, 2013

As far as the fungus starting, my theory is this: The area inside the crack was moist and there was NO foundation venting in that area. It was an addition done 25 years ago. They sealed one existing vent and added none, I now have two events kitty corner in the part of the house.

So, moisture got in, no ventilation, perfect environment for fungus? And starts adn spreads like wildfire.

Since cleanup there is no sign of any micro biological activity in that area
posted by silsurf at 9:25 AM on March 12, 2013

One other thing I should add is there is certainly a possibility of some of these things being a coincidence. The facts are:

-No ventilation

-Moisture in a single 18 inch round area


-Ruptured floors

Whether or not all of these are directly related is impossible to actually say
posted by silsurf at 10:19 AM on March 12, 2013

Seems likely then that the old flooring was permeable enough that the moisture from below was able to get into the interior and thus keep the mould just below real viability, and when you put the new flooring in it sealed up the moisture enough that the mould could really bloom.

So, yeah. Ventilate which you did, put down some vapour barrier on the soil under there, get gutters up and route the downspouts far away from the house ASAP and then as much earth sculpting as you can to route standing water away from the foundation.

Seems like you've got a good handle on it.
posted by seanmpuckett at 12:03 PM on March 12, 2013

thanks, is the vapor barrier for the crawlspace? Or is it something that gets applied from the outside?
posted by silsurf at 12:57 PM on March 12, 2013

My understanding is that moisture appears where hot meets cold. Your house is a warm zone and your crawlspace is a cold zone. The crawl space should be well vented and well drained so water doesn't collect in there. However there still needs to be a vapor barrier (which could be spray foam suited for this purpose I think) between the floor and the crawl space. It would be applied from the outside meaning someone would get into the crawlspace and spray the underside of your floor or wrap and tape it with suitable plastic sheeting. It must be completely and thoroughly sealed to work properly. The foam or sheeting now becomes the actual border between hot and cold. Since condensation occurs on the cold side, i.e. the crawlspace side of the foam/sheeting the moisture can't get through it and into the floor anymore. Win!
posted by Hairy Lobster at 4:44 PM on March 12, 2013

I believe that in modern new construction the whole under-house is sealed, but there's some controversy over that. After doing much reading of every possible source, and getting a quote from at least one contractor, we settled on putting the vapor barrier directly on the dirt and leaving the crawlspace ventilated. That seemed like the lowest risk option. Sealing the entire crawlspace means that if you didn't get it entirely right you could end up with the mold problem from hell. Sealing the dirt and leaving the crawlspace ventilated means you aren't going to have anything worse than what you have now.

In particular, we laid down two layers of six mil plastic, taped the seams, and glued (using construction adhesive) the plastic to the piers and sides of the foundation. If I had to do it again, I'd see if I could come up with a thicker plastic. We were quoted with like a 17 mil plastic, but the quote was so high and the use case for the thicker plastic seemed kind of gimmicky that we decided to do it ourselves.
posted by straw at 4:47 PM on March 12, 2013

Not sure if I'm misreading what seanmpuckett wrote but just putting vapor barrier down on the soil might not do much if the air itself is moist since you'd still have a vented cold zone making direct contact with the outside of the floor with no vapor barrier between them. If the air is generally very dry and all the moisture is coming from the soil then I guess it's possible it might have some sort of effect. Still, as I've stated above, my understanding is that some sort of vapor barrier needs to be installed that actually separates hot from cold zones to prevent this from happening.
posted by Hairy Lobster at 4:48 PM on March 12, 2013

straw: "Sealing the entire crawlspace means that if you didn't get it entirely right you could end up with the mold problem from hell."

Yeah, that seems like a bad idea. I saw them address a very similar problem on one of the Holmes shows (one of the few where they weren't dealing with a house with basement but one with crawlspace) they did not seal off the crawlspace. They sealed the underside of the floor with spray foam and left the crawlspace vented.
posted by Hairy Lobster at 4:51 PM on March 12, 2013

Thanks so much for the great information

posted by silsurf at 4:52 PM on March 12, 2013

To Hairy Lobster's comment, after a season with the vapor barrier, which was awesome, we added unfaced fiberglass insulation between the floor joists, which made the house even more awesome. However, unfaced because we didn't want any place for condensation to collect, and installing the insulation was a horrible horrible experience (did I get enough "horrible"s in there?). I got wore a full respirator, some paintball goggles with a fan through a foam filter, clothes with rubber bands around the cuffs, and still ended up taking a bath in clay to keep the itching under control. Next time it's Tyvek suits and springing for the $1300 for a full-on positive pressure respirator. Or not doing it at all.

Spray-in probably wouldn't fly in my household because of concerns, warranted or not, about out-gassing from funky plastics and foams. And even though the theory says that the hot-cold interface would be somewhere in the middle of the interface I'd get nervous with a non-permeable barrier below the moist warm air of the house. But if you're cool with that, it's got to be a more pleasant installation experience than fiberglass in a crawlspace.
posted by straw at 1:08 PM on March 13, 2013

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