Control Joints in Plaster

Technical Tip: Control joints usually refer to a single formed metal section that separates plaster surfaces to minimize possible cracking due to shrinkage. Requirements for control joints in Portland Cement Plaster is 144 square feet maximum panel area, 16 feet maximum panel length, and 2-1/2:1 length to width ratio. Vertical control joints at all comers of openings.

Also, if "Back up materials" changes such as from steel.studs to concrete, a control joint must be used.

Plaster control joints may be filled with sealant to partially conceal joints visually or they may be left open depending on the arrangement and number of joints.