Laying a concrete floor in an existing building takes some special skills and tools.
How to put a concrete floor in an existing garage.
Install either 2 by 2 2 by 4 or 2 by 6 joists over the garage floor depending on how much room you have floor to ceiling.
If more than 2 5 cm 1 inch shim the joists near the door trim the joists at the opposite end or do both.
You do not need to wait for the scratch coat layer to dry completely.
6 empty a 40 pound bag of concrete resurfacer into a 5 gallon bucket to make.
Pour concrete onto the existing slab until it is around where you want the final level to be.
You can set screed guides rails that you first use to get it flat then pull and fill in the void they leave.
Pour concrete for the new floor.
This is especially important in a wet climate.
You can use a dense foam insulation around the edge of the slab and use that to guide your screeding.
The taller the joists the more room for insulation and warmth of the floor.
Add all of the concrete right away so none of the mixture has a chance to dry out.
Place them 16 inches apart.
Place the steel rods or rebar around the edges of the freshly poured concrete mix and through the middle of your floor if working with a large area.
Make sure you have enough concrete to fill the entire area to the depth you desire.
Put in place a vapor barrier.
Place duct tape over existing expansion joints.
Lay an impermeable membrane on the raw concrete as a vapour barrier.
These bars will provide strength to the concrete.
Nail cross blocking boards to hold the joists together every 4 feet.
Have the bars prepared before pouring.
Some are designed to be left in place as expansion joints.
Divide the garage into sections no larger than 144 square feet each.
Lay the joists on edge across the width of the floor.
Allowing the concrete to dry too much between pours will create layers and make the concrete weaker.