As a kid and even as an adult, I admit I try not to step on the cracks between the blocks of sidewalks. Remember the old childhood chant, “Step on a crack and you’ll break your mothers back?” Did you know that those purposely aligned cracks are strategically placed to allow movement of the sidewalk without compromising the integrity? You see, concrete, a cement product, tends to crack in squares, so the “cracks” along the walk are placed at intervals to match the width of the walk (i.e., squares).
In our wall cladding industry, one may think of stucco as a thinner, vertical version of a poured-in-place concrete slab, which too, is subject to the “square-cracking” phenomenon. This thought is not necessarily correct. Our building code addresses stucco panel size and dimension in ASTM C-1063, Standard Specification for Installation of Lathing and Furring to Receive Interior and Exterior Portland Cement-Based Plaster.Specifically, sections 7.11.4.1 and 7.11.4.2 call out for maximum areas no larger than 144-square-feet and distances between control joints of no greater than 18 feet in either direction. Because the stucco is applied in a vertical plane, section 7.11.4.2 also allows a maximum length to width ration of 2½ to 1. So, if a contractor places the control joints at these intervals, can you expect no cracking? Probably not—but maybe.