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.
How to put a concrete floor in an existing garage.
6 empty a 40 pound bag of concrete resurfacer into a 5 gallon bucket to make.
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 can use a dense foam insulation around the edge of the slab and use that to guide your screeding.
Lay the joists on edge across the width of the floor.
Install wire mesh or fiber mesh as reinforcement.
Place duct tape over existing expansion joints.
Put in place a vapor barrier.
Divide the garage into sections no larger than 144 square feet each.
This is especially important in a wet climate.
Measure the slope if any of the floor from the garage front to the door.
Pour concrete for the new floor.
The taller the joists the more room for insulation and warmth of the floor.
Lay an impermeable membrane on the raw concrete as a vapour barrier.
These bars will provide strength to the concrete.
Laying a concrete floor in an existing building takes some special skills and tools.
You can set screed guides rails that you first use to get it flat then pull and fill in the void they leave.
Allowing the concrete to dry too much between pours will create layers and make the concrete weaker.
Add all of the concrete right away so none of the mixture has a chance to dry out.
Pour concrete onto the existing slab until it is around where you want the final level to be.
Have the bars prepared before pouring.
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.
Fill in the area with gravel 3 4 and compact it.
Make sure you have enough concrete to fill the entire area to the depth you desire.
Some are designed to be left in place as expansion joints.