Q.: In an area 90 by 110 feet, completely enclosed against the weather, how important are control joints in a 2 1/2-inch topping with welded wire fabric on a 3 inch metal deck? The area will be heated in winter to keep a fairly constant temperature of 70 degrees F and cooled to the same temperature in the summer.

A.: Concrete slabs on metal decks are usually built with reinforcement and should not contain control joints. The topping containing welded wire fabric should not have control joints either. Cracks will generally occur over supporting beams in the negative moment regions.