Drain Tile under Slab

[swamplife]

As my name implies, I live in a swamp. Last week we had a pretty bad rain event. I'm not sure of the exact totals where I was (weather service says 1.5'', but reality is closer to 5 or 6), but I ended up with my garage flooding pretty badly last week.

Damp floors have been pretty normal. I don't have any inside OSB or insulation or walls in the garage because of this. The garage was in rough shape when I bought the house; slab cracked in a few spots, foundation is cracked in a few spots and the silplate on the northern wall (load bearing) is missing completely.

With that all said, the garage slab is a 2'' slab originally. Everything has moved around it over the years. The storm last week did it in. I had water spraying up through the cracks in the slab. There were a few spots where the slab lifted up, cracked worse, then went back into place.

It looks like next summer I'll be doing a slab. I will be DIYing it myself, likely in multiple sections with fiber added to the mix and with rebar in the sections. Planning on a 6'' slab and importing / compacting gravel before it.

What would be the best way to run the drain tile under the slab and connect into yard drainage? The part where it would pass under / through the foundation has no current existing foundation, so that won't be bad.

But I won't be able to bury it completely under the slab; the slab would be poured on top of the drain tile but it would only be 3 or 4 inches thick on top of the drain tile. When the ground water comes up, in theory, it would spill into the bottom of the drain tile and into the yard drainage.

Thoughts? I can get some pictures later tonight if needed. I will also have a bunch more questions and will post progress!

I'm not in a position to knock down and rebuild, it's too close to the property line. But I can (and will) raise it!

Would this work or would it immediately crack?

 

[SGKent]

am puzzled that the garage could be wet and not the yard, so much so that you could drain it to the yard. That almost implies that the garage is built on a spring. If you can drain water out of the garage the way you are describing, it may take a lot more than a thicker slab and drain tiles to stop it. Not to get technical but ground water rises to the levels of the nearby ponds and creeks, except where there are springs. Those springs are usually fed by higher ground nearby thru underground streams. Those create sinkholes too. If your garage is the only really wet spot in your yard, and the ground is moving a lot you might want a geologist to look at it before you make any commitments to solutions.

 

[Kaizen]

Yea it would crack and probably crush it. I’d build it up and do something like a French drain to move water away from it. Might have to excavate a lot though. Take up a broken piece and dig to see what’s there. I live high and dry and still had to truck in two feet of gravel as I had to remove that much loam


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[swamplife]

Oh - the back yard had over a foot of water in it when I got home from work. The water level went up a few inches between 530 and 8pm and it started coming in the garage slab and walls.

That was with a 3600 GPH sump pump running full bore.

In the spring , I am going to be undertaking a pretty large drainage project. I am permitted to connect my sump pumps and yard to the storm sewer. As long as I DO NOT put any drains in the garage floor itself.

My property is graded away from the road and the storm sewer. There is a point about halfway through my back yard where the yard is too low to drain into the storm sewer, for that, I'll leave my 3600GPH pump and connect it into the rest of the drainage.

Yea it would crack and probably crush it. I’d build it up and do something like a French drain to move water away from it. Might have to excavate a lot though. Take up a broken piece and dig to see what’s there. I live high and dry and still had to truck in two feet of gravel as I had to remove that much loam


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I am pretty low. It doesn't take much to hit the water table. If I go down 5 or 6 inches the wrong time of year, I'll be hitting water. French drain around the perimieter might work, but I'm not sure how effective it would be at getting water out from underneath the garage slab.

 

[Mick56]

If you want to keep the water out, you will need to raise the slab. May need about 3' of shellrock, or other type of sand base, and then some gravel on top of that before pouring the slab.

 

[SGKent]

If you want to keep the water out, you will need to raise the slab. May need about 3' of shellrock, or other type of sand base, and then some gravel on top of that before pouring the slab.

that is the kind of solution I am seeing, or you build a berm around the property, and a big sump, then constantly pump out when the water is high. When the power fails you will be back to where you started. Gotta wonder why the Native Americans built all those city mounds so high. When you get high water after a rain, have to ask yourself if it is the rain not being able to run off that is causing the problem, or if it is you are in the path of drainage for other areas. In other words is it rain or flood that is driving the water. Besides how to solve the problem, that is material for insurance purposes also.

 

[Bretny]

Make sure you use a concrete underlayment under your new slab. Concrete isnt waterproof alone.

 

[swamplife]

Make sure you use a concrete underlayment under your new slab. Concrete isnt waterproof alone.

Oh definitely! I think that's some of the problems the previous owners ran into when trying to patch the slab. There were a few spots where the previous people tried to patch it and when it rains, the concrete turns back into mix and sets up once it dries. I had an engine hoist get stuck in it and had to wait a month so it could get out. That will also keep the garage dryer.

that is the kind of solution I am seeing, or you build a berm around the property, and a big sump, then constantly pump out when the water is high. When the power fails you will be back to where you started. Gotta wonder why the Native Americans built all those city mounds so high. When you get high water after a rain, have to ask yourself if it is the rain not being able to run off that is causing the problem, or if it is you are in the path of drainage for other areas. In other words is it rain or flood that is driving the water. Besides how to solve the problem, that is material for insurance purposes also.

Building up or out isn't really an option. I don't want to draw too much attention to myself.

The current plan is definitely to try to drain around the garage and then pump to the storm sewer. Part of the problem is the neighborhood was build up around my property since it was originally built. And of course those are things the home inspector missed.

What happens is the rain runs off of the higher ground towards the lake and can't get past my property. THANKFULLY the road is graded away from my place, otherwise I'd really be in trouble!