Client built a house over as 80 yea

[katesENGR]

Client built a house over as 80 year old basement (old school house boiler room), covering the ground on three sides outside basement walls. Ten years later, has major problem with water seeping through the old concrete walls of basement. The exterior of the basement walls can only be accessed on one side by excavation to permit installation of a waterproofing membrane. Anyone have recommendations on getting the other three sides dry (or at least, drier)? Basement is 35' long × 15' wide × 9' high, with concrete ceiling (floor of old school house); no data available on thickness of walls.

 

[oldestguy]

I'd be very reluctant to waterproof walls as you describe if there is any potential for them to cave in due to the pressure that retained water outside applies. Maybe a thick old foundation can withstand it, but some rough check of stability should be done.

Injection of grout into the "voids" may help, but if dirt is there also, later to be washed in, maybe not so good.

 

[cvg]

first, determine where the water is coming from. groundwater or surface water. if surface water, than surface water drainage should be improved and there may be no need for waterproofing the basement walls. if groundwater, than interior improvements could work including installing a drainage membrane, pipe and sump pump

 

[katesENGR]

Thanks, guys! In my PS to my initial post, I noted the client's house is in semi-arid west Texas; ground water should not be a problem, water table is 160'± below ground, bit one soil boring will tell.
The basement's foundation is of concern, as is the condition of the basement walls; thought about building a reinforced CMU wall all around the basement interior with mastic/membrane water proofing on sandwiched tightly against the inside surface of the existing concrete walls; two purposes, to support the basement roof & 2, to hold back the any hydro-static pressure that may come through the existing concrete walls trying to push the WP off. This would be very expensive labor vise since every bit of material would have to be hand carried through the house and down the stairs to the basement.
Surface water could be migrating around the basement from the one uncovered side and owner has been advised to correct the drainage problem there - to get positive drainage away from the foundation. When that's done, it may take months for the water that is present to percolate down and away (as well as in); another year waiting to see may not be unreasonable. Is there a "sealant" slurry of some sort (bentonite, maybe others - lime, flyash?) that could be injected into the soil around the outside of the basement walls - would have to drill holes walls the through the floor above outside the basement below and try to get slurry down to the basement floor level with a long pipe nozzle - never have ever seen it done before; effectiveness could not be verified without observation holes through the basement wall at/near interior floor level.

 

[Ron]

Take a look at silicate injection. You could also intercept the surface water and route around the structure with swales or shallow underdrains.

 

[katesENGR]

Thanks, Ron Lots on good info about this on WEBAC & BSAF web sites. Seems like the best way to fix the leaky basement walls. Thanks again.

 

[oldestguy]

Another thought. It is right that sloping the exterior to cause surface water to go away from the building, but once the water is into the ground there, surface slope is meaningless. What usually happens when basement walls are backfilled is that the pattern of filling creates easier flow path sloping downward the wall than vertically down. Any water infiltrating within the zone of wall backfill can get to that wall as a result. I have resolved surface infiltration and movement of water toward the building at several places such as schools, a church and even the house where I now live. It may not be perfect, but "waterproofing" the ground surface, in addition to downspouts extended way out (10 ft plus) and any sloping does an amazing job and has solved some completely. In the typical case in Wisconsin, with our weather this is what is done. First figure out hat can be done to divert surface water. A re-grading may be needed. Any sod is striped off. The re-shaped surface, or what you are stuck with, receives a "dose" of POWDERED (NOT GRANULATED) bentonite all the way out to the edge of all backfill. That distance easily can be 10 feet or more. About 3 pounds per sq1uare foot of the POWDERED bentonite is worked in with a rototiller to about 3 inches or so, so that the percentage of bentonite in that treated zone is roughly 10 to 15 percent, or possibly more for clean sand soil there. Too much and you can create a slippery mess. Not enough and it doesn't work. At bushes and trees work around them. Replace sod. Thorough mixing in of the bentonite is mandatory. At walkways, sometimes working a sand-bentonite mix can fill cracks and areas where access is limited.

At my house the former owner had landscapers do something that looks nice, but sure was wrong. All around the perimeter (except for walks and driveway) a trench was dug extending out about 3 feet and 8 inches deep. A fabric was placed in bottom and clear stone added to fill it up. No weeds can grow there, but that was a great place to catch surface water and then feed it to perimeter drains. In some weather, the sump pump ran continually. After the treatment, getting rid of that trench and surface regrading, extending downspouts way out the sump pump might run once a year off and on when ground water rises after big storm. House sits only a few feet above groundwater level.

Treated areas stay greener than elsewhere doe to bentonite holding moisture.

Stone area had then first the waterproofing, a black sheet of plastic and one inch layer of stone. It looks the same as before, except no seepage.