My garage had extremely poor flooring. I've removed it and dug down 11". I plan to use a plate compactor on the dirt, add 4" of crushed rock, compact that, add 2" of sand, wet that, wait for it to dry out, cover it with plastic sheeting, and then I'm ready for the concrete layer.

Thing is, I don't know how to make a flat, high quality concrete pour inside. If I'm outside I can add forms around the slab and use a flat 2x4 or 2x6 to even the surface.

My garage is 25' x 20' and has a small stairway I'm not removing as a bonus obstacle.

How do I pour inside for best results and a flat surface?

  • To get smooth and level concrete you normally level it out ("float" it) by hand. Not difficult but easier to demonstrate than to describe. There's probably a decent book on this at your local home center, or someone may be able to describe it better than I.
    – keshlam
    Aug 1, 2015 at 1:09

1 Answer 1


Sometimes hiring pros is the best option.

There are various approaches to the problem. You can set screed guides/rails that you first use to get it flat, then pull and fill in the void they leave. Some are designed to be left in place as expansion joints.

You can use a dense foam insulation around the edge of the slab and use that to guide your screeding.

You can attach 2x4 to the walls above your desired surface and use a screed with an offset guide that rides on the raised 2x4.

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