Install floor drains in yet to be poured garage slab?


Old 11-27-15, 10:59 AM
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Question Install floor drains in yet to be poured garage slab?

I'm installing two floor drains in my 32 x 44' thickened edge slab. Slab is still not poured and I still need to add 5-6" of stone inside my forms before I'm ready to pour. Should I wait until stone is in place before I install drains or try and add them first?

I know I'd have to dig part of a trench in the stone, but stone trench would also help hold everything in place.
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Old 11-27-15, 11:18 AM
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I have done it both ways. The big thing is usually which is easier. If I can get in with equipment to move the stone I do that then shovel or rake out trenches for the pipes. If installing the drains and piping first I block under everything with rocks or bricks and drive rebar into the ground to hold it in place. Then make sure stone gets pushed solidly under everything to support the drains. Doing the piping first can make access more difficult for moving stone and leaves it susceptible to damage when spreading the stone.
Old 11-27-15, 12:29 PM
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Generally speaking, you just dig trenches for your drains after you have your base graded.
Old 11-28-15, 08:03 PM
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When I lived in snow country (Wisconsin), I had a tri-level house built with heated garage on the lower level. After several winters of living there, and getting tired of salty runoff pooling up against the garage door, I made 2 parallel full-depth sawcuts in the concrete for drainage, about 2' from the garage door. Didn't live there long enough to break out the concrete and install a grating system, but the sawcuts themselves carried away most of the runoff from the cars. The house's builder had put in close to 6" of compacted gravel under the garage floor, so I'm sure that played a big part in wicking away water.

If I ever was to build another house in a cold climate, I think I'd use a self-contained (transverse) galvanized steel drainage system, cast into the garage floor. No complications from pipes except where the system exits the garage, and the concrete finishing wouldn't require having fancy slopes to accommodate individual drain placements.

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