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-   -   Concrete moisture issue (https://www.thehulltruth.com/dockside-chat/650095-concrete-moisture-issue.html)

willie g 02-08-2015 07:40 PM

Concrete moisture issue
 
A buddy of mine has a house that was built in 74, parts of the house
continue to mold (just the parts touching the concrete). Evidently the vapor barrier has been compromised and the slab is porous and my guess is the HVAC unit pulls the water through the slab.

I checked the concrete with a moisture meter and cut out the concrete in a couple areas where the readings were high, in one spot about 3' below the slab I hit water. All the soil is damp, even muddy under the concrete UNDER a covered patio, in the backyard.

I've done test to see if the water supply was leaking and I did a hydrostatic test on the plumbing/sewer lines, both checked out fine.

The house is located in a suburb north of Houston, it's: slab on grade, monolithic construction, the backyard does have a pool, thats my next guess as a source.

I called a company that locates and repairs these type issues and they said I had already done everything they would do, that theres no need in paying them to come. That it was likely a ground water issue.

Any thoughts? I suggested leaving a hole in the concrete and installing a huge dehumidifier to try and dry out the water under the slab.

Bamby 02-09-2015 04:52 AM

Has this problem always existed?

Is the house located in a low laying area in comparison to the terrain around it?

Is the municipal water meter located at the house or on street or ally? You could have a pretty major leak between meter and municipal supply line.

You may also have a leak in the municipal water supply line itself somewhere in it's proximity where it passes by the house. C/C Same potential for municipal sewage.

For the ground saturation you're describing I'm thinking it's originating from a un-metered source somewhere in the general area of the house. Ground saturation to the point of standing water so close to the surface would involve so much water that if it were going through a meter and paying someone would have looked and fixed the leak on the first billing cycle.

Moving on, a big dehumidifier would just dry the air not the soil and it would also create a lot of surplus heat in the house. Digging out the hole and installing a sump pump may be the best method that would remove some of the excess water.

willie g 02-09-2015 07:16 AM

[quote=Bamby;7545581]

Has this problem always existed?
I'm not sure, they mentioned noticing a musty smell for years


Is the house located in a low laying area in comparison to the terrain around it?
No


Is the municipal water meter located at the house or on street or ally? You could have a pretty major leak between meter and municipal supply line.
The particular properties have a ditch next to the street, just inside the ditch is where the meter is located.


You may also have a leak in the municipal water supply line itself somewhere in it's proximity where it passes by the house. C/C Same potential for municipal sewage.

For the ground saturation you're describing I'm thinking it's originating from a un-metered source somewhere in the general area of the house. Ground saturation to the point of standing water so close to the surface would involve so much water that if it were going through a meter and paying someone would have looked and fixed the leak on the first billing cycle
.is there a way to have the city check that, whiteout creating a bunch of unwanted attention?


Moving on, a big dehumidifier would just dry the air not the soil and it would also create a lot of surplus heat in the house. Digging out the hole and installing a sump pump may be the best method that would remove some of the excess water.
I considered installing the dehumidifier in a sealed closet, I'm not sure if closing it in would cause it to burn up prematurely?

Squidd Vicious 02-09-2015 08:00 AM

Is the swimming pool above or below grade ? If below, what is the construction of the pool vinyl/concrete? Does the swimming pool have an auto-fill ?

Where is the nearest large body of water (i.e.; lake, river, etc.).

willie g 02-09-2015 09:09 AM


Originally Posted by Squidd Vicious (Post 7546133)
Is the swimming pool above or below grade ? If below, what is the construction of the pool vinyl/concrete? Does the swimming pool have an auto-fill ?

Where is the nearest large body of water (i.e.; lake, river, etc.).

Gunite pool, below ground. no auto fill, he said he doesn't have to add a lot of water


I noticed on the opposite side of the house from where I found the water, the water supply is dripping at about a drip per second (bad valve)

I ran a sewer camera into a drain only a few feet from there, hit a blockage then busted the concrete, then dug a hole. There is no water in that area. The water was found 30 or so feet further from there on the opposite side of the house.

The house is a couple miles from a river. I've lived in this area for 25 years or so and have never heard anyone with issues like this.

bsmit24 02-09-2015 11:50 AM

If you use a humidifier it will only dry the air as mentioned above and will likely only end up with more water wicking up through the slab.

Did you check any other places in the yard or just the one location in the slab for "ground" water? You could install monitoring wells around the exterior to help determine if the source from one particular direction.

Mjv2744 02-09-2015 12:00 PM

Oh the joys of Houston. Clay soil so will hold water. I had a house that had similar and what had happened is that it had settled and was in the water table you have 2 main things to look at.

The grading I am assuming that it is good but a lot of times the house had beds etc that trap the water in particular if they have built them up over the weep holes.

Does that side of the house have settlement issues if so you may need to pier it and lift.

JoCo34 02-09-2015 12:04 PM

Sounds like you need to install a french drain around the slab. I had a simular issue with ground water seeping into the crawl space. Filled around the foundation with 57 stone and daylighted at a low point. Took a few days but it dried right up.

bsmit24 02-09-2015 12:23 PM


Originally Posted by JoCo34 (Post 7547111)
Sounds like you need to install a french drain around the slab. I had a simular issue with ground water seeping into the crawl space. Filled around the foundation with 57 stone and daylighted at a low point. Took a few days but it dried right up.

For slab on grade there is a possibility of differential movement and the slab cracking when you dewater depending on the soils and subgrade.

Thalasso 02-09-2015 12:45 PM

French drain under the floor (in the house) into a sump. Drill weep holes in the bottom course of block so water doesn't set in the block. You will not have any more dampness issues.


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