Staggered Joints in a Concrete
Parking Lot

Hotline Question

We're constructing a concrete parking lot and the architect is insisting that joints be staggered as shown in the drawing below.

Joint Staggering

We think this jointing arrangement will cause mid-panel cracking, but the architect wants to see something in writing. Where can we find this information?

Hotline Answer

The proposed jointing arrangement will cause cracking at many (perhaps all) of the tee intersections of the joints. Here are two sources you can quote:

Guide for Design and Construction of Concrete Parking Lots (ACI 330R-92), Section 2.7.1, "Joint patterns across lanes should be continuous."

Finishing Concrete Slabs with Color and Texture, Portland Cement Association, PA124, page 28, 1991. "Joints should be continuous, not staggered or offset, unless made of divider strips."

In Concrete Construction article from February 1987, page 211, the author says "...tee intersections of joints will induce mid-panel cracking." That article also includes a photograph of cracking at a tee intersection even though the joints were formed with wood divider strips. This seems to indicate that even with divider strips, tee intersection can cause cracking.

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