Concrete overlays are finishes that cover up concrete slabs. People install these overlays for different reasons--sometimes they are necessary, as a repair step in fixing a badly flawed concrete floor. At other times, the overlays are made from epoxies and owners use them for decoration, painting them so they mimic other types of surfaces. While concrete overlays can have many purposes, owners must always install and care for them properly, or they can develop problems.
No matter the overlay, the layer must bond with the concrete beneath it. For many mortar layers, owners must first lay down a concrete adhesive to cement the two together--without this adhesive, the top layer can develop cracks and other structure problems. With more liquid-based overlays, owners must thoroughly clean the concrete of all dirt and oil, or the surface will not adhere properly.
Moisture is a common problem for concrete floors. When moisture enters the floor, it seeps easily through the concrete's porous material and causes mold and rot problems below the floor while creating structural issues throughout the concrete. When installing any type of overlay, owners must use sealants to protect it from moisture.
Concrete overlays are thin and do not last as long as the slabs beneath them. Some overlays show durability problems within several years. Acid etching and other types of concrete color work tend to fade away over time unless the floor is consistently sealed. Owners must pay close attention to maintenance and cleaning with their concrete overlays if they want them to last.
Concrete designs are imprinted and painted on epoxy layers. While this can give a concrete floor an entirely new appearance, it also requires considerable skill to make realistic stone or tile shapes, colors and designs. Owners cannot usually create these complex effects themselves, and must hire a professional for advanced work.