# Wet subfloor on second floor



## rickjames8 (Aug 19, 2012)

I should mention, all of these spots are interior-interior walls. None of them correspond to an exterior wall on the outside. Also, the siding and roof (just inspected) are in good shape, evidenced by the fact the attic is dry.


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## SPS-1 (Oct 21, 2008)

If the wet spots happen when it rains, you have issues with your roof regardless of how good it looks. The leak could quite some distance from the wet spot and be travelling down the sloped rafter. Could be vent pipe(s) flashing is bad. If you can get access to the roof (difficult on a two story) put a water hose onto suspect parts of the roof and look for intrusion on the inside. You may have to run the hose a half hour or hour before you see anything on inside. 

Is your AC in the attic?


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## joecaption (Nov 30, 2011)

That was my first thought to SPS-1, plugged up condensate drain line or leaking drain pan.
Any plumbing vent lines going through the roof in that general area?
Valleys, wall to roof joints, chimneys?
Pulled the insulation back and checked for staining on the back side of the drywall?
What's behind that vented door looking thing on the right in the last picture?


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## rickjames8 (Aug 19, 2012)

SPS-1 said:


> If the wet spots happen when it rains, you have issues with your roof regardless of how good it looks. The leak could quite some distance from the wet spot and be travelling down the sloped rafter. Could be vent pipe(s) flashing is bad. If you can get access to the roof (difficult on a two story) put a water hose onto suspect parts of the roof and look for intrusion on the inside. You may have to run the hose a half hour or hour before you see anything on inside.
> 
> Is your AC in the attic?


Thanks for the help.

The AC is not in the attic. It's outside with the air handler in the basement.

I have walked around in the attic and pulled back the insulation, and everything looks dry. 

The areas that are getting wet are oddly in the center of the house. If they were near the outside, I would suspect water traveling through the flashing. The areas along the interior-exterior wall edge are dry.

I am not able to reach the roof with a hose.


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## rickjames8 (Aug 19, 2012)

joecaption said:


> That was my first thought to SPS-1, plugged up condensate drain line or leaking drain pan.
> Any plumbing vent lines going through the roof in that general area?
> Valleys, wall to roof joints, chimneys?
> Pulled the insulation back and checked for staining on the back side of the drywall?
> What's behind that vented door looking thing on the right in the last picture?


Thanks for the reply!

There are some vents for the bathroom shower vents nearby, but not very close to the wet areas.

I pulled back the insulation in the attic and everything looked dry.

Attached are exterior photos of the house. The peak of the garage is near the wet areas. I'm wondering if the flashing is bad there and could seep over. That would not explain why the wall adjacent to the garage was not also wet. 

I am including a floor plan of the house, with the wet areas marked in red. The garage is to the right of that area. The roof most closely over that area would be near the larger of 2 the satellite dishes - which by the way are from the previous owner and could be removed if needed. The darkened area near the top most red spot is a laundry chute. No plumbing is in here that I know of.

The louvered thingy in the OP is a very outdated sink vanity. No signs of water under the sink at all.


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## rickjames8 (Aug 19, 2012)

I went back up the attic as I'm also convinced that it has to be something from up there. However, all studs, subfloor (the attic has floor in the center for walking) and insulation is bone dry and there are no marks on any wood to indicate previous water.

I took a pic to illustrate the rafter design. It would make sense that water trickling down one of the supports in the photo would be in the perfect location to make those wet spots, but there is no evidence that they were ever wet.

(Random stuff compliments of the seller)


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## SPS-1 (Oct 21, 2008)

I see two possibilities:

1) Leak in plumbing, and where you see stains is simply the low spots in the floor.

2) Water getting in through the roof. I see a dish, a bathroom exhaust vent, and a plumbing stack. Could be any of the three. Don't assume the leak is directly above where you see the water. Again, wet spots could be just the low spots in the floor. 

I once saw a similar stain when I pulled out a carpet. Turned out to be an old kitchen exhaust duct (which actually never had anything hooked up to it). Flashing was not right - leaked water, which ran down the rafter, eventually found the wall, and to the floor. Took me a few hours to put 2 +2 together, but it was more obvious in my case. By the time I noticed, sheathing around the roof vent was pretty rotted.

From the attic, check out the sheathing around each of those penetrations.


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## Bud9051 (Nov 11, 2015)

First, rent an infrared camera or talk to an energy auditor that uses one. I have resolved numerous water problems with mine, even some the home owners were unaware of. Very sensitive to temperature and the evaporation of moisture creates a distinct cool area.

Second, floors often consist of two layers where the walls are constructed on the subfloor, bottom layer, and then a second layer is added room by room. This might allow water to get in between the layers and move to the lower spots as mentioned.

Third, we can't rule out condensation entirely. Even though you aren't currently using the ac, it can still be cooler inside than outside. 80° air at 90% RH has a dew point of 77°. http://andrew.rsmas.miami.edu/bmcnoldy/Humidity.html
And, when it is cooler inside than outside that cool air drops to leak out the lower areas which is replaced by warmer more humid air leaking in from above. Above can be the attic and all of the penetrations from electric and plumbing. On rainy days that RH can increase to 100% so it would not take a lot of cooling to form condensation. My personal opinion is that does not look like condensation, just didn't want it off the list as yet. Looking at your floor plan there are probably a couple of plumbing stacks going into the attic. 

Bud


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## rickjames8 (Aug 19, 2012)

SPS and Bud-

Thanks for the replies. I will check the flashings a bit further, and if I cant find anything, I will get someone out, preferably someone with an infrared camera. 

Oddly, these spots are just above the kitchen exhaust fan, so we may have a very similar problem.

I had looked up a lot on condensation/humidity, as that was my first thought too, but the localized area also made me think something else was the likely culprit. 

I may also take out the wall by the most affected area to have a look inside. 

Thanks. I will post results if/when I find the answer.


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## rickjames8 (Aug 19, 2012)

So I had a bit of an epiphany on this!

The wettest spot of this 'leak' is right next to the laundry chute, which is a metal chute that runs all the way to the cold basement. We have been having humid days, and as Bud pointed out, when it rains, that RH gets even higher. Basically, I think that chute becomes like a frosty coke can on a summer day, just dripping with sweat inside the wall. I'm not entirely sure how it makes it to the adjacent walls, but the wetness gets less as it moves away from that point. Also, the walls where I have wetness are the only walls covered in wainscotting. The rest are just drywall. I'm wondering if/how this could contribute to the problem.

Lastly, we have NOT been running the AC, nor the dehumidifier. My wife has a dry eye condition and the humid weather is the only weather she is comfortable in, and being from the tropics I don't mind it either. But we ran the AC/dehumidifier the past 2 days, and the drain in the basement has a steady stream of water, and my wet spots are drying up, despite the fact we had rain today.

So other than running a dehumidifier all summer, any ideas on how to fix this? I'm not sure if it's enough wetness to ruin wood floors?


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## SPS-1 (Oct 21, 2008)

rickjames8 said:


> Basically, I think that chute becomes like a frosty coke can on a summer day, just dripping with sweat inside the wall.


 When you stick your hand (or a paper towel) in the laundry chute, does it come out all wet?

I like Bud's idea of the infrared camera.


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## miki209 (Nov 26, 2017)

Hi, I have same problem on my sub floor on 2nd floor. I removed carpet and found damp spots middle of the house, corner of the wall. No sign of water leak from ceiling. Attic is bone dry. House was vacant for 6 month so I don't think it's plumbing issue.
Did you fix your problem? What was the cause?


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## HomeOwner24 (Nov 18, 2020)

miki209 said:


> Hi, I have same problem on my sub floor on 2nd floor. I removed carpet and found damp spots middle of the house, corner of the wall. No sign of water leak from ceiling. Attic is bone dry. House was vacant for 6 month so I don't think it's plumbing issue.
> Did you fix your problem? What was the cause?


Hi Miki209 & RikiJames,

I am also getting the exact same problem in my house. So far 4 plumbers, 2 Water Restoration Service Person and 1 Leak Detection Agency has looked into the problem, but none of them are able to find the leak.

I will appreciate if you guys can share how did you guys finally managed to fix this problem.

Thanks.


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