Base molding is a protective cover applied to a wall at the point where it meets a floor. Primarily designed to protect a wall's base from damage when struck by furniture and other objects, base molding also provides relatively easy access to the area behind the wall when a gap has been left between the wall's bottom edge and the floor. While a strip of wood about 4 inches (10.16 centimeters) wide is all that's generally necessary, decorative additions are added in nearly all residential applications and most commercial applications as well.
When internal walls are erected within a structure, they're generally made of drywall fastened to vertical wood or metal beams called studs. In many cases, the ceiling height is actually slightly higher than the standard 8 feet (2.44 meters). When this is the case, the drywall is butted up against the ceiling, which has already been installed, and a gap left between wall and floor. Base molding is essential to concealing this gap. In addition, if future work requires access, it's sometimes possible simply to remove the baseboard rather than cut a hole in the wall itself.
While drywall provides structure for interior space, it's not very strong. It will easily break when struck by a piece of furniture being moved or by many other objects, such as vacuum cleaners being propelled with vigor. Even if the drywall doesn't break, a sharp blow, as from a hammer, will crush the plaster content of the drywall, sometimes breaking the paper surface and leaving an unsightly dimple that will require repair. Since the chance of such damaging contact is greatest near the floor, because of moving furniture, base molding is routinely installed, even when there's no gap to conceal.
Walls in residences and some commercial spaces are often also protected by a molding called a chair rail, which is a strip of wood or plastic that measures from 4 inches (10.16 centimeters) wide to 6 inches (12.7 centimeters) wide, installed between 32 inches (81.28 centimeters) and 40 inches (1.016 meters) from the floor, to protect the wall from damage that might be inflicted when chair backs are in contact with the wall. Most residential applications also have molding installed where the wall meets the ceiling, but this is decorative in nature.
Commercial spaces' base moldings generally are not as decorative as those found in residences, and often consist of nothing more than a piece of flexible molded plastic that's fastened to the wall by means of an adhesive. These base moldings are extremely tough and durable, and will withstand the impact of cleaning equipment and furniture being moved even better than their wood counterparts.
Installation of base molding is relatively simple. In most cases, the the most important element is a board that measures 0.5 inches (1.25 cm) thick by 4 inches (10.16 centimeters) wide, cut to length for the wall it's to be installed on. If the wall is too long for a single length of board, two pieces are joined by a simple butt joint. Once the main element has been installed with its lower edge in direct contact with the floor, additional pieces are added. In many cases, a single quarter-round piece will be installed where the bottom edge of the base meets the floor, and another piece — sometimes quarter-round, sometimes ogee, and sometimes some other figure, is installed at the top edge of the base. There is an almost limitless selection of designs from which to choose, and there's not even any requirement that the main element be a 4- by 0.5-inch (10.16- by 1.25-centimeter) board, as long as the main purpose of protecting the joint where wall meets floor is achieved. Once installed, base molding is either stained or painted.