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fcastro 03-24-2010 08:47 PM

Basement Sump Pump & Dimpled Plastic Membrane Interior Questions
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Hi everyone, I was hoping I could get some questions answered about my basement. My basement has a wall that has all this dimpled plastic membrane running along the floor. On top of the plastic seems like the poured self leveling concrete. The plastic runs all along the wall and then wraps and runs about 3 feet on the side walls. In the corner theres a sump pump. My basement is 4 foot below grade btw. I noticed that all along the bottom of the wall they drilled huge holes.

Ok when it rains I see that the center of the cinder blocks (the hollow part) fills with water near the footing. The water then seems to come out of the relief holes in the interior and it seems to redirect the water to the sump pump pit. Basically the plastic is shields the water from making it to the basement floor which I am sure it was how its intended to work.

Today I dug up one of the walls on the outside to see if there was a weeping system in the footings and there wasn't. So I imagine when we get heavy rain the water gets by the tarred wall and into the block.

Does anyone have any images or directions on how this system works? I have another wall in my basement that water is makin into the basement and would like to install the membrane run it to the sump pit as well.

I have attached images of the system. I can't seem to dig up any info on this process. I know I have seen this dimpled material used on the exterior of walls.

itsreallyconc 03-25-2010 04:07 AM

it appears to be a professionally installed ' french drain ' & the blk material is known as ' miradrain ',,, the drain holes allow penetrating water to drain out & the dimples on the miradrain allow it to flow under the floor,,, i'm kind of surprised there's no collection pipe under the floor but won't 2nd guess the contractor. suspect the conc is std conc mix'd on-site [ cement, sand, coarse aggregate, & wtr )

the ' tar ' is actually an asphalt cement/wtr emulsion which, according to bldg code, is applied to exterior walls below-grade at a thickness of 3mil,,, its never been intended to be a waterproofing course.

on my w-site there's a diagram,,, w/o some individual bells & whistles :beer: we adopt, the industry std system's based on the 4 rules of wtr: 1, it runs downhill; 2, takes the path of least resistance; fills a void [ try making a hole in your tub full of wtr ]; & 4, seeks its own level.

fcastro 04-01-2010 10:57 AM

itsreallyconc thanks for the reply!

I ended up finding some more info on the system as you mentioned. Seems like the system was to break some of the concrete and curl the membrane and then run it to the sump pump.

handyguys 04-02-2010 12:23 PM

The systems are fine for under ground hydrostatic water pressure. I'm not a fan tho of controlling water inside a basement. I would much rather keep it out of the basement in the first place.

What is the problem you are trying to solve? You mention you dont have water on the floor.

The area where you noticed water inside the block at the bottom of the wall. Take and post a picture of the outside of the house, a wide shot that includes the whole house and landscaping, roof, siding, grade, etc. May have some suggestions for keeping the water outside.

itsreallyconc 04-02-2010 04:38 PM

it becomes a question of $$$$$$$$,,, invest lots more to excavate & do properly what should've been done when the structure was built OR treat the result,,, on balance, i agree w/any sr member ( top :banana: that they are )

doing this work professionally for 37 yrs, i will offer clients the choice & my HONEST ' what would i do if it were OUR home ! ' assessment.

grading & downspouts're the 1st thing everyone mentions however that penetrating water's been carving pathways to your foundation for years thru disturbed soil that was never properly compacted at the time of backfill,,, i'd bet a compaction test would show 70% at the MOST even 50 yrs after backfill compared to 100% below your topsoil at original grade.

in the end, it always comes down to $$$$$$$, value, & when am i going to move ! !

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