A poured wall contracting firm of Mason, Michigan has been installing control joints with water stops it its walls for the past ten years. During this time, the firm reportedly has not had a single call-back to repair a leaky basement in which their technique was properly employed. Control joints, installed at predetermined wall locations, are the most effective method of preventing unsightly and potentially troublesome cracking. If a sizable expanse of concrete, such as a wall, is not provided with control joints to accommodate dry shrinkage and temperature contraction, the concrete may crack in a random manner. Control joints concentrate cracks in inconspicuous locations. Backing up each control joint midway in the wall thickness is a plastic water stop that prevents water leakage through any crack that may occur in the joint.
A pair of control joint forms is needed for each joint location. Pyramid-shaped rustication strips for these forms are made of wood or metal and are cut to the length of the form to which they will be attached. The strips should be about 1 inch wide at the base where they attach to the form and extend 1 « inches into the wall. This will leave a 1 «-inch-deep weakened plane joint in the wall, both sides. Some contractors attach the strips to the center of a 12-inch-wide panel and identify this panel as a control joint form. The Michigan firm prefers to attach their rustication strips 3 inches in from the edge of the form.
The person in charge of form layout should predetermine exactly where the control joints are to be located. In general, a joint is installed in the front, side and back walls when these walls are 30 feet or longer. A control joint usually is not needed for a garage wall as it normally will not leak even if a crack occurs.