Water Appearing Through PT Slab on Grade

Hi Denverdamon

Start by giving information about the soil and rock formations on the site and down the slope.

Do you have slate, clay or dolomite in the area?

Clays do expand when they become saturated and will 'pump' water to the surface.

I have been to a site today (close to the cradle of human kind) where a new fountain sprung up on a high spot. (the closest higher spot is about 10 km away) This is in dolomite area and the source could be further away.

Welcome to CR4 and EXCELLENT first post!!!!

I can only suggest that you consult the original building specifications (and if they exist the inspection reports during construction) and if possible contact the people actually involved in the original pouring of the slab. There may be some additional detail there that could give you an indication of the cause.

As I said, EXCELLENT first post with good detail. If this is the quality of your questions, I'm waiting to see your responses when others seek your help.

www.post-tensioning.org

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My aunt had an artesian spring in her garage, whiereby she had controlled the flow and it fed into a drain where the water escaaped from the garage. I have never studied this type of spring, but it is a possibility that is what you are running into.

She lived on a level lot with a slight hill behind her and a slight drop in front of the house. A stream larger than the size of my thumb flowed continously. There were no other artesian springs within many miles of her home, as far as I know. She passed away, but the spring is still there for more than 50 years.

Location is a mile East of the Allegheny River in PA

Thanks for your reply. It's definitely not coming from any of the plumbing as we've seen the water when neither the waste or supply has been used in weeks.

We actually have an area where we could make that work, I appreciate your thouroughness.

Greetings,

You might also consider a fix similar to the previously mentioned one except 1st trying an auger to see if you could instead install a dry well. If a hole eight feet deep gets you to free draining gravel as it appears to be the case at the location 25 feet away you mentioned, then a hole filled with drain rock would accomplish the same desired results as a pump. You may very well have a case of an impervious layer of material under your slab, that due to its' location causes the moisture to wick up through the slab. Whatever the case, an exploration/ test hole should provide insights if not a solution.

Keep us posted

Sounds a lot like condensate to me.

ZZZGrinch & Bill both seem to be correct in my estimation. Wicking due to capillary action may be occurring depending on what subbase materials are present under your slab as well as the type of subgrade foundation material was placed and compacted directly under your concrete slab. Do you know if the Contractor placed a poly plastic vapor barrier under the subgrade material, and if yes, that they lapped the individual sheets of poly properly? Absence or poor lapping procedure of a vapor barrier may cause a condensate problem to occur as well.

You may also be experiencing an intermittent spring; then there is a high enough ground water level the spring or springs may become active.

Is there any way that you could install a new drainage ditch all around the hanger and still be able to daylight it to a nearby watercourse or low area? If this is possible, you may be able to alleve some of the pore pressure caused by the presence of ground water under the slab. This may or may not work as I see that you have a 60 feet wide hanger/slab, and that half of that distance is a long way to form an adequate cone of depression and thus relieve the water pressure under the slab.

Other than installing a sump and submersible pump to draw down the ground water, there may be three long term drainage alternatives, though expensive, that you could employ and will use no electricity to remove water:

1). Horizontal tunneling bores under the slab (each way in a grid) with perforated pipe installed with integral filter fabric. Spacing and depth to be determined by a Geotechnical Engineer. Perforated pipes to either connect to the afore-mention drainage ditch or a buried header pipe of sufficient diameter that finally daylights by gravity into a nearby water course or storm sewer system.

2). Install new subsurface drainage pipe wrapped w/ an integral filter fabric sock in a gravel trench under the slab in each direction forming a grid. This would require saw-cutting strips of the existing slab so as to install the new drainage system. Place new replacement slab as necessary. Depths and spacings per Geotech. Engineer.

3). Install a new vapor barrier and a new reinforced concrete slab atop the existing slab.

4). Demolish and remove existing slab and possible the existing subgrade and subbase materials under it IF Geotechnical Engineer deems them unsatisfactory. Install new underdrain system, subgrade foundation material and new dense concrete floor slab. I suggest that the concrete mix have at least 15 to 17% Pozzolan (a Fly Ash) by weight (supplanting an equal weight of cement) and no less than 650 pounds of Portland Cement by weight per Cubic Yard. Limit slump to 3-inches maximum and W/C ratio to 0.42 maximum. Aim for at least a minimum 5,000 psi compressive strength (at 28-days age). The intension here is to produce a very creamy and dense concrete, almost impervious to water capillary action and having an early high strength. Admixtures needed are: Air-entrainment, Mid-range Super-plasticizer, and Xypex (a waterproofing compound added during the mixing that prevents water migration through concrete member). The concrete will be expensive, but you will not regret placing it.

5). Before you do anything, install a number of vertical 8-inch diameter perforated HDPE drainage pipe sections around the hanger perimeter, no less greater than 20 feet apart, except where you already have asphalt pavement (assumed). You want install the bottoms of these no less that 10 or 12 feet below the ground surface and no closer to the hanger foundation/slab than 5 feet away. You may need to obtain an auger machine to dig the holes for you. Do not attempt to open excavate for these pipes as you may end up undermining the hanger foundations and the slab. These pipes are to be used for observing the water table. You should measure the groundwater level at each of them every few days, unless it rains then you may have to measure each and every one of them every few hours. Keep good records as you may end up turning these over to a Geotechnical Engineer and Structural Engineer.

Finally, did the Contractors who did the excavation and earthwork, install the slab and erected the hanger building keep any records of conditions at the jobsite? OBTAIN THEM IF THE EXIST.....YOUR ATTORNEY MAY NEED THEM.

Good luck and have a great sunny day!

Thank you all for the well thought out and detailed replies. I'll take all this info to a geotechnical engineer and at least be able to discuss a variety of solutions. I very much appreciate your time!

Before spending time, money and effort; consider that if the shower walls were (I assume) tiled, and properly spaced, and/or sealed before use.

How about the shower floor; is it a material that 'flexes' under the weight of the 'showeree', and allows leakage at the drain connection?

Is the shower floor/drain connection correctly sealed?

Not to disregard/diminish all others; remember K.I.S.S.

The sump is the best idea, you may need more than one. If you get flooding after a rain, consider putting a French drain close to the building, and a sidewalk around the building to divert runoff from the roof. I would definitely run gutter-pipes from the roof to the ditch. Get the rain away from your building.

Before you do any of these highly engineered fixes just do one simple thing; Raplace the closet flange seal, even if it looks O.K., replace it. I know you said it "seeps" even when the supply is shut off, but there is still some head pressure in the tank. It may seem highly unlikely to you, and if it doesn't work, you can hire a geo engineer and start spending money. However; I'd hate to see you spend all that time & money just to find out a $3.00 wax ring (I guess there are some poly seals now) will fix it.

Good suggestion, and I wish it were a simple solution. At one point in this process I colored water in the toilet with tablets and flushed several times (coloring it each time) and waited a couple of days....nada. Also ran water in the shower for an hour and no joy.

does the building have gutters all around?If so, where do they drain? If not, install gutters and drain the water away from the foundation.

Otherwise, install a french drain.

A day or two after significant percipitation.

Is there a plumbing vent pipe passing through the roof? Is the pipe metal or PVC? Is the roof flat or sloped?

If so, is the roof vent flashing properly sealed around the pipe? Is the vent properly sealed to the roof?

Good questions Hornetson,

Single plane roof sloped at approx 10 degrees. The only penetration through the roof is for heating exhaust, and it's been sealed and resealed by our HVAC people.

The only penetration through the roof is for heating exhaust.

Curious: If there are no plumbing penetrating the roof, how is the same vented?

A home sits next to the hangar (15ft) with a full height basement with a french drain/sump system that works well and no associated water problems exist.

Does this house's french drain system discharge it's effluence toward you?

The slab was poured about 18-24 inches above original grade on imported soil.

Was an analysis done on this 'imported' soil, and on the virgin soil?

I miss any reference to your inquiries, regarding this 'issue', to the construction manager, project engineer, or other on-site personnel (other than HVAC) involved in the construction before posting to this site.

Everything I know about gravity and water flowing downhill tells me that this is not possible.

For what's worth,I have, on more than one occasion, seen water 'percolate' up in coarse gravel filled residential basement window area wells in late April, early May, days after any rainfall, and upstream of the occurrence, to penetrate into the basement of the residence, in north shore, LI, NY.

Would be nice to see some pix of the problem area.

Ooh, ooh: How about a street address, or a lat/long so that we can GOOGLE-EARTH the site?

As an aside with the vapor barrier mentioned. When this 'stuff' (6 mil. polyetheylene, "Visqueen") started to be used back in the '50's on LI, it took a certain learning curve for the concrete guys to get used to. The concrete place (pour)didn't start to 'set-up' in the usual time-frame manner, as with place(pour)-on-grade, a.k.a. soak-into-the-soil, expections.

So imagine, after placing (pouring), and it's 5:30-6:00 pm and getting dark inside and the pour isn't setting-up like it should be to float properly, you're faced with the following options, so I've been told:

1. Spend,who knows, many long, cold hours waiting for the stuff to set, or,

2. Poke a bunch of holes into the plastic to expidite the drainage issue.

This not to suggest that this was done at your, or any other site, to my knowledge.

Hope that you can resolve the cause, and, not the effect of the problem.

I would suggest that you may have inadvertently discovered that you have a situation in which a spring has been created. This some times happens where the sub soil is sufficiently tight to slow the perk of the water downward to the normal water table. What often happens is that after the foundation fill has been compacted to the engineers intended standard, and the form work for the concrete slab has been installed, along comes the plumbing contractor who's employees now dig up this compacted material to install the underground plumbing. It clearly extends out side of the building. Rarely is this disturbed soil ever re-compacted back to the previous standard.

Any water migrating through the upper soil will find this loose soil around the plumbing to act as a highway for the flow, and as soon as the capacity of the disturbed soil area has been reached, the water then rises around the plumbing just like a spring in a desert.

The only cure for this example that I have seen to work is to have a company that injects soil filling/tightening materials around foundation walls of cellars to determine where the plumbing has been installed and injecting said material all around that area. It isn't a cheap fix, but it may work in your case.

TMF

I would have to agree with tomuchfun on this, I have seen this before and compacted soils play a big part in channeling the water around pipes under slabs.Also the line where natural ground meets the compacted fill can act like a dam in many cases especially on a hill side. I would suggest French drains with perforated pipes on the uphill side of the building , along with gutter's on the roof since there is alot of surface area there to contend with that could ad to the problem.