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water coming under foundation in unfinished basement

water coming under foundation in unfinished basement

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  #1  
Old 06-14-05, 01:31 AM
L
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Location: Makakilo, Hawaii
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water coming under foundation in unfinished basement

i began a basement type project that got stalled before it was finished. the foundation and cmu wall are in place but the slab was never poured.

the outer perimeter of the wall has a drainage pipe and emulsion type waterproofing.

whenever it rains for as few days or more water bubbles up from underneath the footing and fills the slab area. it resembles an artesian well.

now that i am ready to complete the project and pour the slab i am concerned about this water problem. will the slab stop the water from coming in? is there any precautions i should take before pouring the slab? any info will help.

thanks
 
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  #2  
Old 06-14-05, 08:21 AM
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coming under foundation in unfinished basement

Since you do not have the slab poured, there is a reasonable solution. It entails some work, plastic pipe and some clean gravel or stone.

Your outside drain pipe apparently is plugged, not working or is installed too high. You are seeing water from the general water table that does not get into the installed system.

An interior drain slightly below the footing is in order. Keep it slightly away from the footing base sloping down at a 45 degree angle from the inside base. It just has to be slightly below the footing bottom to let gravity do the job. This should go into a sump with a pump.

An ideal system is a continous loop system feeding the sump from both sides, but ideals are not always possible because of obstructions. Since you seem to have a high water table and the opportunity, putting some similar crossing pipes in the center will reduce the upward pressure on the slab and minimize and leakage through shrinkage cracks.

A dual drain system is often used by quality builders, since the cost is minimal is done at the correct time.

Pour the inside slab as soon as possible since it helps to restain the walls from sliding inward due to soil pressures.

Good luck.

Dick
 
  #3  
Old 06-15-05, 01:36 AM
L
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thanks for the information.

i live in hawaii where many of the houses are erected on pier blocks w post and beam framing. my home was on a slope that is approximately 8' difference over 40' lenghth.

my "basement" is on the lower end of my lot resulting in a 5 course wall to 1 course over about 22'. the water that comes in is a result of the ground above becoming satureated from rain ( maybe once a year) and then it only seepes in for less than an hour.

i was told that when the water gets to the depth of the footing that the unpoured area is now higher than the wter level producing that bubbling up of the water. he said that the slab would divert the water underneath of the slab to more dry soil thus preventing this. it doesnot rain enough where i live to soak the whole lot.

most of the basement is under the main house so over one half of the area never encounters this problem. it mainly happens in just this one exposed corner.

is this possible? would a slab act as a "cap"? do i really need an interior drain system? the outside one is at its deepest only about three feet. should i redo the outside one instead?

please help because it all seems so labor intensive. is there a way to check the outside drainage? are there any resource sites that show a good way to put drainage systems?

thanks again.
 
  #4  
Old 06-15-05, 07:36 PM
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water coming under foundation in unfinished basement

Thanks for the information describing the physical location.

Since you do not have a traditional basement you do not have to worry about using the area. I do not see why you would need a slab unless there is some local condition that would require it.

Getting water in for an hour once a year does not sound like a concern for an uninhabited area.

Your exterior drain tile is only 3 feet down, which is still 5 feet above the area you are conerned with. I do not think it is worth the effort to re-do the exterior drain tile or to add interior drain tile unless there is a structural concern or a moisture problem. For an unused space, just make sure you have adequate vetilation to prevent any rot or mold.

If you really want to do something, you could try to put in a couple of perforated sumps (one on each side of the basement area). They would consist of a plastic drum with holes placed below ground level in the basement. Dig a hole about a foot larger than the size of a plastic drum and put about 6 inhes of rock or clean gravel in the bottom. Put in the drum and surround it with some more rock or gravel. You can then put in a sump pump to pump out the water as it accumulates. You can tie the two pits together with a pipe under the soil to use only one pump.

This should help to reduce the moisture in the soil and possibly eliminate the visible water seepage.

I am not familiar with your area, but you should check to see if any other homes have a similar problem.

Dick
 
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