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chimney height ircCHIMNEYS AND FIREPLACES 10-10 2015 INTERNATIONAL RESIDENTIAL CODE® COMMENTARY R1003.4.1 Anchorage. Two 3/16-inch by 1-inch (5 mm by 25mm) straps shall be embedded not less than 12 inches (305mm) into the chimney. Straps shall be hooked around theouter bars and extend 6 inches (152 mm) beyond the bend.Each strap shall be fastened to not less than four floor joistswith two 1/2-inch (12.7 mm) bolts. ❖The prescriptive requirements in this section are tradi- tional for typical fireplaces and chimneys. More sub- stantial anchorage may be required in areas of high seismicity, for large fireplaces or where the distance between floor and roof diaphragms is large. R1003.4.1.1 Cold-formed steel framing. Where cold-formed steel framing is used, the location where the 1/2-inch(12.7 mm) bolts are used to attach the straps to the framingshall be reinforced with not less than a 3-inch  3-inch 0.229-inch (76 mm  76 mm  5.8 mm) steel plate on top ofa strap that is screwed to the framing with not fewer thanseven No. 6 screws for each bolt. ❖The provisions in Section R1003.4.1 for anchoring masonry chimneys to residential buildings were devel- oped with the concept of anchoring to wood framing. Cold-formed steel framing can function equivalently in this respect to wood framing, except that the bearing area between the bolt and the cold-formed steel fram- ing is small and therefore needs to be reinforced to pre- vent the local failure of the steel. The 0.229-inch (essentially 1/4-inch) steel plate will provide this rein- forcement and spread the load from the bolt to a wider area in the framing to prevent the localized failure of the framing. The minimum of seven No. 6 screws (a total shear capacity transfer of 1,050 pounds in 33-mil cold-formed steel) provide the transfer mechanism to spread the force in the bolt (a maximum of 933 pounds for a 1/2-inch A307 bolt in 2-inch nominal Douglas-fir lumber with 1/4-inch-thick-steel side member). R1003.5 Corbeling. Masonry chimneys shall not be corbeledmore than one-half of the chimney’s wall thickness from awall or foundation, nor shall a chimney be corbeled from awall or foundation that is less than 12 inches (305 mm) thickunless it projects equally on each side of the wall, except thaton the second story of a two-story dwelling, corbeling of chim-neys on the exterior of the enclosing walls may equal the wallthickness. The projection of a single course shall not exceed For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.Figure R1003.2 TYPICAL MASONRY CHIMNEY Copyright © 2015 ICC. ALL RIGHTS RESERVED. Accessed by Louis Hasbrouck on Apr 2, 2018 10:20:26 AM pursuant to License Agreement with ICC. No further reproduction or distribution authorized. ANY UNAUTHORIZED REPRODUCTION OR DISTRIBUTION IS A VIOLATION OF THE FEDERAL COPYRIGHT ACT AND THE LICENSEAGREEMENT, AND SUBJECT TO CIVIL AND CRIMINAL PENALTIES THEREUNDER.