Thicknesses of floor finishes vary from ⅛ inch (3 mm) or less for resilient flooring to 3 inches (76 mm) or more for brick flooring. Frequently, several different types of flooring are used on different areas of the same floor level of a building. If the differences in thickness of the flooring materials are not great, they can be resolved by using tapered edgings or thresholds at changes of material. Greater differences may be resolved with variations in the thickness of underlayment panels. Alternatively, gypsum or cementitious self-leveling toppings up to several inches thick can be poured over some portions of the subfloor to raise the finish floor level.
If none of these solutions can satisfactorily resolve the differences, the level of the top of the floor deck must be adjusted from one part of the building to the next to bring the finish floor surfaces to the same elevation. The architect should work out the necessary level changes in advance and indicate them clearly on the construction drawings. In many cases, special structural details must be drawn to indicate how the level changes should be made. In wood framing, they can usually be made either by notching the ends of the floor joists to lower the subfloor in parts of the building with thicker floor materials or by adding sheets of underlayment material of the proper thickness to areas of thinner flooring. In steel and concrete buildings, slab or topping thicknesses can change, or whole areas of the structure can be raised or lowered by the necessary amount.
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