Basement Walls/ Hydrostatic Pressure

I have a small crack in one of my basement walls. During heavy rains water leaks through the crack onto my basement floor. I wanted seal the crack with some water proofing seal but a few of my coworkers suggested that I bring in some basement waterproofing company to evaluate my basement. Well.. three companies later, I am more confused than ever. Company A told me that my basement is fine. They offered to seal the crack on my basement with some expandable sealer. Company B said that my 30yr old walls are going to start cracking and that I should consider putting in a trench around the perimeter of my basement. Company C said that all hell is going to break out soon and that I need to dig around the perimeter of my foundation to install some exterior drainage that will help relieve the hydrostatic pressure on my walls. I want to believe company A but I would hate to seal the crack, finish my basement, and discover that company C was right. The grading and gutter drainage around my house is good. Is their a way to measure the amount of hydrostatic pressure against your basement walls. Can I shine a black light against it to reveal some obvious message?
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Go with company A or do it yourself. 30 yr old is not that old and its hard to believe its what Companies B and C told you, of course they're looking for a pay check too remember.
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There are too many unknowns to give a specific assessment but my preferred way of dealing with water is, at the time of construction to place a perimeter drain around the structure at a level, just below the top of the footings that drains to daylight (assuming that there is enough slope to have some location that is below the basement floor and footings. It's a good idea to have another perimeter drain a bit higher up, 1 to 2 feet below grade that also drains to daylight.
Measuring hydrostatic pressure won't give you a lot of insight. The worst case is that there is water pooling at the surface at or around grade level. The pressure will then range linearly from 0 psi at the top to a maximum at the basement floor level. Since a column of water 12 inches tall and 1" x 1" in cross section weighs 0.433 pounds, the pressure will increase at 0.443 psi per foot of depth, measure from the top of the pooled water. For a 10 ft foundation wall this would give you about 4.33 psi of pressure at the basement floor level. But, when you have this information what do you do with it? Not much.
Remediating water leakage after construction is problematic and depends on what the specific problem is.
One company that intrigues me is Crack-X. http://www.crack-x.com /
I haven't used them but I have spoken with them and may have them do some work for a client in the future. It's possible to do the same thing yourself but probably not at a lesser price.
If you can find a good (licensed, experienced, and well educated) hydrogeologist in your area to look at your situation it may be worth his fee. I looked at a basement floor yesterday that had a spout of flowing water about 0.5 inches high and 0.5 inches in diameter flowing continuously at what I'd estimate is 1 gpm. I'm hiring a hydrogeologist to help, although I believe that I know what the problem is and how to address it.
Waterproofing from the inside is not a sure thing. It's much better to get outside, then try to think like the water, and devise a route to a lower elevation that is easier and more favorable to the flow of water. Fingers in dikes don't work in the long term.
Boden
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A small crack that leaks little I would not worry about to much, repair it to see if that is all you need, company B & C are just selling a job.
Repair it yourself but the prep is 99% of getting a bond that will last. Open it up with a chisel or grinder so you have depth you can access to remove loose material and clean out all dirt and mold, 1-4", Just don`t do a quicky surface repair . You need to get it cleaned out first with a brush, then hose it out. Use bleach to kill mold, sqiirt it in with a meat baister. Muriatic acid [ dangerous and fuming] squirted in the crack with a meat baster will remove dirt, and etch it. Depending on size and depth of hole, hydraulic cement, mortar mix, epoxy or special caulk can be used .
If you hire it out remember prep is 99% of the job, it is not a 5 min job, it must be clean and solid.
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