Concrete floor finish specifications take into account the kind of material that will ultimately be applied to the concrete as the final floor covering. Some materials will allow more tolerance for imperfections than others. Each product that is used as the final finish on concrete floors also has its own set of specifications.
Concrete floors should be level from front to back and side to side. When a floor slopes too much over its total length or width, the effect is the feeling of walking uphill or downhill. These changes in elevations also affect the walls of the building and ultimately the roof of the building, possibly causing the structure to take on a permanently leaning appearance.
The thickness of the floor needs to be adequate to support the loads that will be placed upon it. Most residential structures use 4-inch thick concrete floors. Another factor that affects the floor's strength is the reinforcement used and how it is placed within the floor. Most residential floors use woven wire mesh reinforcement while commercial concrete floors will most often require rebar placed in a grid as reinforcement. Finally, the floor's strength is also affected by the concrete's rated strength. Residential floors typically call for 3,000 psi concrete, while commercial floors use higher rated concrete depending upon the loads they will be subjected to.
Concrete may look like it is perfectly solid and immobile, but it actually moves quite a bit through expansion and contraction. Before concrete is poured for a floor, you have to consider where you can use control joints to minimise the effects of movement. The joints are created by inserting thin material, like asphalt impregnated fiberboard, between successively poured sections of the floor. They are also cut into the concrete with a concrete saw when it is still green. Control joints are placed around columns that have their own foundations, along the edges of the walls if necessary. Control joints are also used to break up large expanses of concrete into smaller sections. When the concrete cracks, as it will, it will crack along the control joints and be unnoticeable. Control joints are filled with a filler suitable for the final floor covering.
The finish specification relates to the finish of the concrete floor before any floor covering is applied. Concrete floors to be covered with tile will have different requirements than floors that will be stained or stamped. Unless the desire is for a distressed look, most concrete floors will receive a steel trowel finish or a broom finish. The steel trowel finish leaves a smooth, hard and uniform finish suitable for most floor coverings or staining. The broom finish leaves a rough surface that provides traction for utility-type floors like those in garages.