Wet basement - Need an opinion

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#1

Originally Posted By: ppetroska
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Today I received a call from an excavation contractor who wanted my opinion on a project he had worked on. He had excavated a cellar hole for a lakeside vacation home this past spring. The home had been lifted and moved to the side while the hole was dug and the concrete footings and foundation were poured. The home was then moved back and lowered over the main section of the foundation and a new addition was constructed over the remaining ell. The foundation was built into a hillside (30 degree slope) leading down to the lake, the floor is 20+ feet above the waterline of the lake below. At the customer’s request, the uphill side of the home was graded to within 2 inches of the top of the foundation and there is definitely a negative grade at this part of the foundation. The downhill side of the foundation is a halfwall and is mostly exposed. There are no gutters. The contractor said that he has 18" of stone under the floor and around the footings to deal with the downhill grade. He has perforated drain pipe installed all around the footings, under the stone. He has drain pipes in the footings all around, connecting the inside and outside. The stone outside the wall was covered with fabric and the outside wall was painted with sealant. The foundation was backfilled with gravel and was topped by loam. He does not know whether a vapor barrier was installed before the floor was poured. There is a floor drain installed at the base of the uphill wall but there was no water visible in the drain (not backing up into the cellar). A drain pipe runs from the rear wall about 25 feet out towards the lake and it was dry at the time of my visit. The cellarspace is 8’ deep.


The problem is that the bottom 1 to 2 feet of the uphill wall and the floor are wet (puddles) along the whole length of the wall (40'?) and also along the side wall of the ell and it has pretty much been this way ever since the home was put back. There are no visible cracks. The owners are not happy and claim that the contractor screwed up. I have an opinion as to the cause of the wetness but was curious as what you folks might come up with.

--
Phil Petroska, Certified Home Inspector
Maine Home Inspections
New Hampshire Home Inspections
http://northcountryhomeinspections.com

#2

Originally Posted By: ppetroska
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Well, I guess I have no takers on this one. Basically, I told the contractor that I thought he had a problem with condensation despite the amount of water on the floor. The basement wall on the uphill side of the home was cool enough at the bottom of the wall to have condensation form and drip down onto the floor, forming puddles of water. It takes a good year or two for concrete to shed hundreds of pounds of water into the air. The fact that there was no water backing up through the floor drain pretty much eliminated a problem with the drain system unless the footer drains were blocked which was unlikely on a new construction. Also, the fact that the top of the wall was graded to within 2 inches of the top, effectively prevented moisture from the concrete wall escaping to the exterior. It could only go inside. I suggested a dehumidifier and regrading the front of the home to expose more of the foundation. Insulating the wall after it has a chance to dry out was also a possibility.

–
Phil Petroska, Certified Home Inspector


Maine Home Inspections


New Hampshire Home Inspections


http://northcountryhomeinspections.com

#3

Originally Posted By: roconnor
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Condensation can give you somewhat of a wet wall surface, but I doubt it would be enough for a puddle on the floor. The fact that just the lower part of the wall and floor is wet also indicates it’s not condensation. In addition, the evaporation of moisture from the curing concrete is generally not enough to even get a wall surface wet. Foundation leaks can be tricky, and I would recommend having an engineer look at that.


Just my opinion and 2-nickels as an engineer also.

--
Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee

I am absolutely amazed sometimes by how much thought goes into doing things wrong

#4

Originally Posted By: jpulley
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It is difficult to diagnose something like this from my office chair, but


Mr. O’Conner is right when he says these situations can be tricky.


Based on my experience, I would ask a couple of questions.

  1. How much drop is in the french drains?

  2. What kind of perforated piping was used? I have had less than satisfactory results with the black plastic convoluted type.

  3. Was there no indication of moisture retention at the time of excavation?


    The possibilty of a wellspring at that height seems rather remote, but perhaps a channel was uncovered by the backhoe?


    Finally, if all else fails, stick a garden hose in a drain at the highest point and see if the water drains to the lowest point.


Good luck,
J.R. Pulley
Quality Assurance Consultants, Inc.
Deltona, Fla.

#5

Originally Posted By: sramos
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I see this stuff all the time. Homes that are built on the hill side almost always have water problems. Given the fact that the wetting is in the lower half of the wall indicates that the moisture is coming from the ground. If there is enough moisture in the ground most of it will not reach the drain before reaching the wall, especially if the drains are deep, as it appears in this case.


I don't think it would be out of course to recommend further evaluation, as was already stated, to rule out a leak or other significant problems. If that were to come back clear. You may want to contact a company that installs basement encapsulation systems. To manage the longer term water problem that will persist.

http://www.basementsystems.com/index.html

--
Steven Ramos
EnviroVue Home Inspection
866-541-2883

#6

Originally Posted By: ppetroska
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roconnor wrote:
Condensation can give you somewhat of a wet wall surface, but I doubt it would be enough for a puddle on the floor. The fact that just the lower part of the wall and floor is wet also indicates it's not condensation.


Rob, thanks for the response but I have to respectfully disagree. The fact that it is the lower wall that is wet makes sense to me because the lower part of the wall is colder than the upper part of the wall. The fact that the wetness extends along the entire wall also indicates to me that it is more likely due to condensation than another condition. In fact, at the corner, where the grade slopes downward, you can see the stain slope downward. Also, I wouldn't expect curing concrete to make a wall wet in and of itself, but it would contribute to the relative humidity of the air in the basement and redeposit itself on the cooler lower wall. Finally, the floor drain probably contributes a lot of moisture to the basement. I don't see them much anymore in new construction and the only reason this builder put it in is because the owner wanted to be able to drain his pipes into the drain when shutting down the place for the winter.

Again, this all assumes that the builder properly constructed the drains, footings and walls so that groundwater is not held against the wall and can freely flow into the drain system. If it's not condensation, than I would expect an engineer to tell me that it's not properly constructed. Based on what I've been able to find on the 'net, there is an easy test that the builder can try and which I've suggested. He can tape 1' by 1' piece of foil on the wet area of the wall and wait a few days. If the foil is wet, than it's definitely condensation.

One more point... I'm sure you've seen water supply pipes and how much they can sweat on a floor. Let's say a typical 3/4" supply pipe has probably what, 28 square inches of surface area per foot which can effectively dampen a 2" or more strip (24 square inches) on the floor if sweating profusely. Almost a 1:1 ratio. That corresponds with the amount of water we are seeing on the floor. Two feet on the wall resulting in a wet area extending two feet or more out on the floor with water supply pipes running along the wall and contributing to the situation. The bottom two feet of the wall are wet, just like a sweating pipe, not damp, so I can't begin to imagine that that much water would migrate up from the floor seam. Since I'm not an engineer, that's my two cents. Thanks again for the input.

Here's just a few of the sources that I used to research this:

http://www.inspectmichigan.com/watsonsj/June99WJ.htm

http://www.concretenetwork.com/concrete/finished_basements/the_number_one_problem.htm

http://real-estate-agents.com/tips/basement/wet.shtml

http://www.ruralhometech.com/drainage/drainage.php

--
Phil Petroska, Certified Home Inspector
Maine Home Inspections
New Hampshire Home Inspections
http://northcountryhomeinspections.com
#7

Originally Posted By: ppetroska
This post was automatically imported from our archived forum.


jpulley wrote:
1) How much drop is in the french drains?
2) What kind of perforated piping was used? I have had less than satisfactory results with the black plastic convoluted type.
3) Was there no indication of moisture retention at the time of excavation?
The possibilty of a wellspring at that height seems rather remote, but perhaps a channel was uncovered by the backhoe?
Finally, if all else fails, stick a garden hose in a drain at the highest point and see if the water drains to the lowest point.


Thanks for the response, J.R. These are all good question. As I stated, the possiblity exists that there might be problems with how the drains were constructed. What I was trying to determine was what other possibilities could cause the problem if the drainage system worked properly. Before this guy goes out and hires an engineer, I think he needs to eliminate condensation as a possibility first and that is what I have suggested to him.

To specifically answer your questions:

1. Not sure what you mean, I always understood a French drain was a stone filled trench without a pipe, so I assume you mean the pipe used around the footing which was covered in stone. I'm not sure but my guess is about 1" in 10'.
2. This pipe is white and is primarily used in leach fields for septic systems. It's pretty strong stuff so I don't think it would collapse if that's what you're suggesting.
3. The site was dug in April and was very wet. He had to put in almost 2 feet of stone so they could put the floor in. No water was visible at the floor drain however and the drain outlet is dry.

--
Phil Petroska, Certified Home Inspector
Maine Home Inspections
New Hampshire Home Inspections
http://northcountryhomeinspections.com
#8

Originally Posted By: jpulley
This post was automatically imported from our archived forum.


Well, the difference in nomenclature is interesting.


However, I must admit, I think about the only place a trench filled with stone would be of any value is here, only because of the sandy (porous) soil. If indeed you are in Maine, by my own recollection of my limited time spent there, the soil is more clay based than anything. And as such, compounds your problem.


The fact that this was performed in April, and the snow was melting in higher elevations, plus the rains from spring, it would be hard to say that some sort of leeching from below did not exist in the first place.


Have conditions dried out there in the meantime?


The percentage of drop you quoted could be enough to do the job, but personally, I would prefer a bit more.


PVC drain tile are your best bet, and yes, crushing of the black plastic is one consideration, the other is that the convolutions fill with soil and sediment (over an extended period) and quit draining. Obviously, not the case here, but I fail to see why anyone would use the stuff in the first place.


As all this is running through my feeble mind, I review what you have written about the elimination of possibilities, and I agree.


However, something tells me that hydrostatic pressure exists here, if indeed, this is not simply a wet summer for your part of the country.


Have you tried the water hose test? You would at least be able to verify that the drain tile is working if the results are positive.


Please keep me apprised of your findings. Drainage problems fascinate me because of my own experiences.


Sincerely,

J.R. Pulley

#9

Originally Posted By: roconnor
This post was automatically imported from our archived forum.


ppetroska wrote:
Rob, thanks for the response but I have to respectfully disagree.

I don't mind at all ... discussion, disagreement, and debate are all part of learning ... for everyone (including me, even though foundations is one of my specialty areas). Also be careful of what you read on the web (even here), and the source of that information. If ya really want to get deeper into foundations and leaks send me a PM/email and I can give ya a few good book references by highly respected experts in the fields ... ![icon_wink.gif](upload://ssT9V5t45yjlgXqiFRXL04eXtqw.gif)

Sounds like the contractor installed a typical foundation perimeter drain system, and not a french drain system which would traditionally have an interior drain system just inside the foundation wall in addition to a wet sump with a pump. Some engineers (including me) actually question installing foundation drain systems, as it wicks water towards foundations and easily clog.

Also, by installing a lot of porous backfill/gravel the contractor may have actually encouraged water to flow towards the foundation ... especially one that is built into a hill, and if I am reading the posts right may not have good surface drainage away from the foundation. Steve is pretty much on the money that it's a common cause of leaks ... especially for moisture along the higher back wall.

It's interesting that although the house is over 20' above the lake water line, the contractor had significant water infiltration/problems during construction ... to the point where he had to backfill with gravel in order to place the foundation. That's a red mind flag right there. That at least tells you there might be saturated soils near the foundation with no drainage capability, and might mean more.

While the owner may very well have some condensation on the walls, particularly for unconditioned basement space, my guess is it's not the reason for puddles of water. But keep us posted on the effect of installing a dehumidifier. Also, where is the surface drainage directed on the site, and are there gutters with leaders connected to something well away from the foundation?

--
Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee

I am absolutely amazed sometimes by how much thought goes into doing things wrong