Most sidewalk failures are caused by inadequate thickness, soil settlement, poor-quality concrete, or improper construction methods. Recognizing these causes and acting to prevent them can go a long way toward avoiding sidewalk failures. Be sure the sidewalk is thick enough. A 5- or 6-inch thickness is needed in most commercial or business areas. For residential areas, a 4-inch thickness is adequate, increased to 5 inches where a driveway crosses the sidewalk. Controlling sidewalk thickness requires accurate form setting. When using wood forms, set forms so that the bottom of the form is about one-half inch above the trimmed subgrade for a 4-inch-thick sidewalk or 1.5 inches above for a 5-inch thickness.
Bullfloat or darby the surface right after it's struck off, before any bleedwater has appeared on the surface. Once the bleedwater has evaporated from the surface, edging and jointing should be the first finishing operations. Floating should follow in order to fill in holes, cut off high spots, and remove ridges. Start curing the concrete as soon as possible without marring the surface. If uniform color is important, first cover the sidewalk with wet burlap, then cover the burlap with plastic sheets.