Control Joints define plaster panels. They are used to minimize shrinkage cracking as Portland Cement Plaster panels lose volume during the setting and curing process. They are over rated when used for Expansion Joints as you can see in the picture above.
Advances in building science and plaster cements brought us products enhanced with acrylic modifiers or additives like PRF. PRF is a wonderful additive to increase consistent color in stucco. It also, when added to basecoats like scratch or brown coats, helps plasticize the plaster material without the use of additional lime.
The control joint was unable to minimize the building movement stress that created the crack pictures above and a bunch more in the same building. I don’t believe that an expansion joint, which is designed to provide significantly more movement stress relief could have prevented this crack.
So why did the cracks occur? Because the framing attachments weren’t done according to Building Standards and the building inspector didn’t catch it. In fact the amount of cracking was the clue to do destructive testing and find out why the cracking was so extensive. We found out it was a wood stud framing issue.
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