Type III-A, heavy timber construction, shall have interior structural elements of heavy timber material as required in this section.
Wood members of heavy timber construction shall be arranged so that there will be no concealed spaces within the construction.
Columns shall have a minimum dimension of eight inches.
Floor framing members shall have minimum nominal dimensions of six by ten inches.
Roof framing members, except trusses, shall have a minimum nominal dimension of six inches.
The members of roof trusses shall have minimum nominal dimensions of four inches by six inches with the following exceptions:
Members may consist of two or more pieces of three-inch nominal thickness with intervening spaces blocked solidly or tightly closed by a continuous wood cover plate of not less than two-inch nominal thickness.
Any member may be reduced to three- inch nominal thickness when protected by an approved automatic sprinkler system under the roof deck.
Wood floors shall be splined or tongue and grooved planks of not less than three-inch nominal thickness or of laminated planking laid on edge of not less than four-inch nominal thickness. A top flooring of not less than one inch nominal thickness shall be added to the structural floor.
Roof construction shall be of construction not less fire resistive than splined or tongue and grooved planks of not less than two-inch nominal thickness or laminated planking laid on edge of not less than three- inch nominal thickness.
Construction conforming to the requirements of Type I construction may be used.
In existing heavy timber buildings which do not conform to the floor and roof planking and joist minimum thickness as noted in (c), (d), (f) and (g) above, the floor, roof, joist, and planking systems shall be protected with a minimum of 1/2: type “X” gypsum board, or shall be fully protected by a Class 1 (0-25) flame spread rated intumescent coating. Where gypsum board is applied to the underside of joists, the joist spaces shall be fire-stopped at all beams. Existing metal columns shall be protected with one-hour fireproofing.
(Prior code § 49-4.1)