Alberta Building Code
Fireplace Hearth

9.22.5. Hearth

9.22.5.1.  Hearth Extension

1)  Except as required in Sentence (2), fireplaces shall
     have a non-combustible hearth extending not less than
     400 mm in front of the fireplace opening and not
     less than 200 mm beyond each side of the fireplace
     opening.
2)  Where the fire chamber floor is elevated more than
     150 mm above the hearth, the dimensions of the
     hearth measured perpendicular to the plane of the
     fireplace opening shall be increased by not less than
     a)  50 mm for an elevation above 150 mm and not
          more than 300 mm, and
     b)  An additional 25 mm for every 50 mm in
          elevation above 300 mm.
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9.22.5.2.  Support of Hearth

1)  Except as permitted in Sentence (2), the fire
     chamber floor and hearth shall be supported on a
     reinforced concrete slab not less than 100 mm thick
     at its supports and, if cantilevered, not less than 50
     mm thick at its unsupported edge.
2)  A hearth for a fireplace with an opening raised
     not less than 200 mm from a combustible floor is
     permitted to be supported on that floor provided the
     requirements of Clauses 5.3.6.5 to 5.3.6.7 of CAN/
     CSA-A405, “Design and Construction of Masonry
     Chimneys and Fireplaces” are followed.
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