Interior drainage trench stone foundation

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Interior drainage trench stone foundation

Post by Gordsid »

My winter stay in shape project - trenching beside my stone foundation inside house- but it is not sitting on wider footing stones so I am worried about destabilizing the foundation (5’-8”headroom 4-10 in ground). Old crappy concrete slab is poured right at the bottom of the bottom stones. Water is coming in via hydraulic pressure at bottom of foundation and up through slab cracks and slab to stones joint- should I trench for the perimeter drainage in about a foot or can I do it right next to the stones? Was thinking of pouring a curb to support the stones when done and frame walls on top of it with vapour barrier against stones - the stone walls don’t leak but the mortar is a little suspect in areas…… just really worried about the foundation while I have it all trenched say 8-10” below bottom stone - in the wet winter time - thinking about removing slab and adding vapour barrier and repouring after curb is in - don’t want to lose any headroom!! I’m 5-8 and already have a lumpy head from being down there!! Thanks ahead for any support on this - Gord

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Re: Interior drainage trench stone foundation

Post by V-Man »

yeah, years ago when I was trying to solve my basement/foundation water issues a contractor wanted to trench the interior but I nixed that for the same reason. I was concerned about destabilizing the fieldstone foundation. I swear he wasn't the least concerned digging up against the foundation. Turns out years later my hydraulic water intrusion was due to roof, chimney and exterior problems and the trenching would not have solved the problem. Took me a few years and seasons to figure it out. I'd suggest you do some more sleuthing to confirm where the water is coming from before committing to any expensive/extensive course of action. Do you have a high water table? Even the smallest leaks from the roof, fascia, eaves etc. can allow enough water to wick its way down.
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Re: Interior drainage trench stone foundation

Post by HB »

A couple of ideas for consideration ….

If the water is coming through the floor, that does indicate a high water table. One way to prevent your problem is to redirect the water before it gets high enough to come up through the floor and the base of the wall.

I have the same issue with my house and I am fortunate enough to have the hand dug well alongside the foundation at the exterior of the house. My solution is to pump water out of that well whenever there’s a significant rain event. This drops the wTer table And provides the groundwater an easier avenue to escape than pushing through the floor and walls. I have also resolved exterior drainage issues around the house like sloping the ground away from the house and directing gutter flow far away from the foundation. These improvements drastically reduced the of times I’ve had to rum the pump.

You could attempt to have a shallow well dug outside your foundation wall, but if the underlying soils are not permeable enough, you would wind up having to poke multiple holes in the ground around the perimeter in order to have the desired effect.

A better approach might be to excavate an area in the center of your basement and fill it with clean stone. You could even run a few trenches out toward the walls ( like fingers radiating out from your hand) to increase your capture area while not actually excavating too much area directly against the foundation. Once you Backfill ( and compact) with clean stone place a perforated sump pit and pump in one of the areas where you can easily pump the water outside and away from the house. Depending in the volume if water expected, you could also lay perforated pipe in the bottom if the trenches to be sure that the path of least resistance for the water is directly to your sump pit and pump.

As an FYI - your basement floor should then be repaired with concrete or some other impervious material and a tight fitting lid put on the sump pit. This is because some areas of the country are subject to radon emitted from the soils - so you don't want to assist that stuff in off gassing into your basement.

Good luck!

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Re: Interior drainage trench stone foundation

Post by RalphT394 »

That was a good piece of information.

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