Water Infiltration Through Retaining Wall Into Crawl Space


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Old 03-23-07, 07:12 AM
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Question Water Infiltration Through Retaining Wall Into Crawl Space

I live in a townhouse and the surface of our concrete garage slab is always wet after a significant rain. I was curious if water was infiltrating through the retaining wall separating the garage slab from the crawl space under the house and went down to investigate. What I found was standing water near the retaining wall, moist and muddy soil throughout the crawl space that was covered with mold, and small roots just under the surface of the moist and muddy soil.

To get a good look at the footer and retaining wall I removed the soil within 18 inches of a section of the wall. As you can see from the picture link below there are horizontal and vertical openings in the first row of concrete blocks where the mortar is missing. When it rains this is where the water comes in. I was also surprised to find so much concrete waste around the foundation extending back at least 18 inches and it may go back even further. I actually canít see the footer due to all the concrete waste.

Paste picture link: http://www.fototime.com/F0BF25F7623A93D/orig.jpg

I located a drawing showing how our townhouse retaining wall was supposed to be built. Based on the amount of water infiltrating into the crawl space and percolating up through the garage slab it looks like the 18 inches of drain rock, 4 inch perforated pipe and retaining wall water proof membrane called out in the drawing were never installed.

QUESTIONS: Can anyone explain the missing mortar in the first row of cement block? Is this due to 20 years of water infiltration through the retaining wall? Does this represent eventual failure of the retaining wall and if it does, how should it be repaired?

NOTE: I live in a homeowners association and my property is located at the lowest point in the complex where subsurface drainage from the complex most likely converges. Myself and two other homeowners have proposed to our board that the street in front of our properties be trenched and a subsurface drain be installed to intercept and collect the subsurface drainage from the rest of the complex.

Thank you for taking the time to read this.
 
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Old 03-23-07, 08:39 AM
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The head joints (vertical joints) were probably left empty to allow water to weep out, thus avoiding hydrostatic pressure on the wall. Could you post a pic of the other side of the wall (Driveway)?
 
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Old 03-23-07, 10:47 AM
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Thank you very much for talking the time to respond to my question.

Here is a link to a photo I just took of the other side of the retaining wall in the garage. As you can see there is efflorescence on the slab surface and some remaining moisture spotting from the rain several weeks ago.

Paste picture link: http://www.fototime.com/9D3C833EFDA649E/orig.jpg

Regarding the vertical joints being left open intentionally to relieve hydrostatic pressure, that wound be gross incompetence on the part of the builder because there is nowhere for the water to go once it enters the crawl space. Especially considering the drawing called out a waterproof membrane, drain rock and 4” perforated pipe on the garage side to prevent water infiltration through the retaining wall.

Paste this link to see a copy of the retaining wall drawing I color coded and scanned in.

http://www.fototime.com/2190E3A815A848F/orig.jpg

In addition, below is a picture of the foundation wall on the other side of the crawl space that runs perpendicular to the retaining wall. This was taken one day after a good rain by a representative of a crawl space encapsulation company. I have not been able to access this area myself because it is to tight a space for me to reach.

Paste picture link: http://www.fototime.com/0EC31EC83CF2035/orig.jpg
 
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Old 03-23-07, 01:00 PM
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After seeing the plan detail, there is a serious issue, although it is not certain that the wall was not built to the plan. The missing head joints would still be a standard design of that wall, although they are generally 32" O.C.
 
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Old 03-23-07, 01:10 PM
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I donít understand. Why would the head joints be left out if a waterproof membrane was supposed to be installed on the other side of the retaining wall.
 
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Old 03-23-07, 01:15 PM
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To remove water from the wall itself.
 
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Old 03-23-07, 02:48 PM
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Thanks for clarifying. I did not realize this was done. How about the horizontal mortar that is missing?

I donít know if our HOA will go for it, but one of my neighbors proposed the drain system shown in the picture link below. The goal is to intercept subsurface drainage before it makes it way under our slab and through our retaining wall.

http://www.fototime.com/ECBF6AD555185A6/orig.jpg

In the meantime, I have moved all downspout drainage as far away as possible from the building foundation.
 
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Old 03-23-07, 03:06 PM
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It is probably rotted out. That drainage system looks to be the solution to your problem. Where exactly could water be getting under the slab? Isn't the area in front of the garage(s) paved?
 
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Old 03-23-07, 07:27 PM
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Being at the low spot in our complex we believe the subsurface drainage for the landscaping in the complex converges in front of our property. In addition, I believe a big contributor to the water under the garage slab was a utility pit that was in the path of the discharge from one of the downspouts.

http://www.fototime.com/9BE22F1F47AC63C/orig.jpg

I used 3 inch pipe to route the downspout discharge away from the pit and layered the pit cover with plastic sheeting. This action substantially reduced the amount of water percolating up to the surface of the concrete garage slab.

http://www.fototime.com/4F4E4FF2D39F306/orig.jpg

There is a similar situation on the other side of the house where surface runoff and downspout discharge percolates down through cracks in the concrete and utility pits.

http://www.fototime.com/D883339A0CF4E1D/orig.jpg
http://www.fototime.com/D67CB93C646FD99/orig.jpg

I ran more 3 inch pipe to route the downspout discharge to the street and covered the entire area in plastic sheeting.

http://www.fototime.com/AA036AA9E1AB7BB/orig.jpg
http://www.fototime.com/312E3EBAB3ACD7D/orig.jpg
 
 

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