Saw-Cutting Joints in New Concrete Floors: Timing and Spacing

Why joints are cut

Concrete loses volume as it hardens and dries. This shrinkage creates stress that is released as a crack somewhere. A cut joint gives that crack a prepared line.

Timing

Cut too early and the edges ravel; cut too late and the slab cracks on its own first. Timing depends on temperature and how quickly the concrete gains strength.

Spacing and depth

Joint spacing is designed according to slab thickness and concrete properties. Cut depth must be enough to make the crack form at the joint.

Columns and corners

Stress concentrates around columns and at re-entrant corners, so the joint layout needs extra thought there.

Joint filling

Where forklifts run, a suitable joint filler protects the edges and extends the life of any coating applied later.