How to Install a Cold Joint While Pouring a Large Concrete Floor

Install your form boards across the section where you want a cold joint to be. Use rebar stakes to hold the form boards in place. Lay the boards out across the length of your floor and hammer the stakes in place. Use the tape measure and pencil to mark any boards that need to be cut, and cut them down with a miter saw.

Call ahead and have the concrete company deliver a truck of pre-mixed concrete. Because you are working in a large area, you will not be mixing by hand. After the first section is poured, chop it down and work it across the area with a shovel, then smooth it down with a metal trowel. Use an extension arm and large flat trowel where necessary to help smooth across the longer sections. Use a hand trowel to smooth the concrete down against the edge of the form boards. Let it sit for 24 hours.

Remove the form boards and pour your next section. The joint against the first section is the cold joint. You can repeat this process across the length of your concrete slab as necessary, moving the form boards across and pouring each new section 24 hours after the first. A 24-hour period is necessary to allow the concrete time to set up so there isn’t a bond between the two sections, but rather a seam.