In addition to local building codes, your fireplace hearth may also need to comply with national, state and international laws. The style of home (one- or two-family, for example) and the location of the fireplace in your house may also come into play.
Some states -- such as California and New York -- have specific building codes that cover the materials used to build fireplaces and hearths, in addition to clearances.
According to Buckley Rumford Fireplaces, codes previously used in the United States have included BOCA, NFPA, UBC, SBCCI and One and Two Family. These codes have merged into one International Building Code (IBC) and a residential counterpart, the International Residential Code (IRC).