Section 27-848.07. Masonry fireplaces

(a) Construction.
    (1)  Masonry fireplaces shall be constructed of solid masonry units of
  reinforced portland or refractory cement  concrete.  Masonry  fireplaces
  shall  be  supported on foundations of masonry or reinforced portland or
  refractory cement concrete,  or  on  other  noncombustible  construction
  having  a  fire  resistance  rating  of  not less than three hours. Such
  supports shall be designed to support the loadings.
    (2) Where a lining of low-duty fire clay refractory brick at least two
  inches thick laid in medium-duty  fireclay  refractory  mortar,  or  the
  equivalent two inches thick soapstone, three-sixteenths inch thick steel
  or   cast  iron,  or  equivalent  material  capable  of  withstanding  a
  temperature of 2000 degrees Fahrenheit without cracking or  spalling  or
  other  accepted  lining  is  provided,  the  total thickness of back and
  sides, including the lining, shall be not less than eight inches.
    (3) Where such lining is not provided, the thickness of the  back  and
  sides shall be not less than twelve inches.
    (4)  Where  the  masonry supporting a fireplace is designed to support
  vertical loads from the building and corbels are used to  support  beams
  or  girders,  corbeling  shall  be as described in reference standard RS
  14-18 as recommended for  masonry  chimneys.  The  lintel  spanning  the
  fireplace  shall  be  designed and constructed to support the additional
  load transferred by the member.
    (5) Masonry fireplaces shall be provided with  chimneys  designed  and
  constructed in accordance with the requirements of subchapter fifteen of
  this chapter for construction of masonry chimneys or, where permitted by
  the  individual  listing,  shall be provided with accepted factory-built
  chimneys having accepted adapters in accordance  with  the  requirements
  for factory-built chimneys of subchapter fifteen of this chapter.
    (b) Steel fireplace units.
    (1)  Steel  fireplace  units incorporating a firebox liner of not less
  than one quarter inch thick steel and an air chamber shall be  installed
  with  masonry  to provide a total thickness at the back and sides of not
  less than eight inches, of which not less  than  four  inches  shall  be
  solid  masonry.  Listed  firebox liners shall be installed in accordance
  with the terms of the listing.
    (2) Warm  air  ducts  employed  with  steel  fireplace  units  of  the
  circulating  air  type  shall be constructed of metal in accordance with
  reference standard RS 14-22, or of masonry.
    (c) Clearance.
    (1) All wood beams, joists, studs and other combustible material shall
  have a clearance of not less than two inches from the  front  faces  and
  sides of masonry fireplaces, and not less than four inches from the back
  faces  of masonry fireplaces. Headers of combustible material supporting
  masonry trimmer arches or concrete hearth extensions  shall  be  located
  not less than twenty inches from the face of the chimney breast.
    (2)  Spaces  between  headers  or trimmers of combustible material and
  masonry fireplaces shall be fire-stopped with  noncombustible  material.
  The material used for firestopping shall be galvanized sheet metal of at
  least  no.  14 U.S. standard gauge thickness, mineral board at least one
  quarter inch thick or equivalent rigid noncombustible sheet material not
  less than one half inch thick or other accepted noncombustible material.
    (3) Woodwork, such as wood trim  and  mantels,  or  other  combustible
  material  shall  not be placed within six inches of a fireplace opening.
  Combustible material above and projecting more  than  one  and  one-half
  inches  from  a  fireplace  opening shall not be placed less than twelve
  inches from the top of the fireplace opening.
    (4) Clearances specified in reference standard RS 14-18 shall apply if
  greater than those specified in this subdivision.

    (d) Hearth extensions.
    (1)   Masonry  fireplaces  shall  have  hearth  extensions  of  brick,
  concrete, stone, tile or other accepted noncombustible  materials.  Such
  hearths  shall  be  supported on trimmer arches of brick, stone, tile or
  concrete at least four inches thick, or of  other  equivalent  materials
  and  with  noncombustible material against the underside thereof. Wooden
  forms or centers used during the construction of the hearth  and  hearth
  extension shall be removed when the construction is completed.
    (2)  Where  the  fireplace  opening  is less than six square feet, the
  hearth extension shall extend at least sixteen inches in  front  of  the
  facing  material  and  at  least  eight  inches  beyond each side of the
  fireplace opening.
    (3) Where the fireplace opening is six  square  feet  or  larger,  the
  hearth  extension  shall  extend  at least twenty inches in front of the
  facing material, and at least twelve inches  beyond  each  side  of  the
  fireplace opening.
    (4)  Where  a  fireplace  is  elevated above or overhangs a floor, the
  hearth extension shall also extend over the area under the fireplace.
    (e) Fireplace dampers. Every fireplace shall be equipped with a damper
  able to  withstand  distortion,  binding,  cracking  or  corrosion  when
  exposed to the fireplace operating temperature.
    (f)   Accessories.  Factory-built  accessories  shall  be  listed  and
  accepted and shall be installed in accordance with the  terms  of  their
  listing and acceptance.