Heavy timber construction (construction class II-A).
NYC Admin. Code § 27-623
in effect§ 27-623 Heavy timber construction (construction class II-A).
(a) Minimum sizes of members. To conform to the fire resistance rating requirements for heavy timber construction (construction class II-A), members shall be solid sawn or solid glue-laminated and of the following minimum dimensions: (Sizes of wood members indicated in this section are nominal sizes).
(1) COLUMNS, FRAMES AND ARCHES.
a. Columns shall be at least eight inches in all dimensions when supporting floor loads, and at least six inches wide and eight inches deep when supporting roof and ceiling loads only.
b. Beams and girders shall be at least six inches wide and ten inches deep.
c. Frames or arches that spring from grade or the floor line and support floor loads shall be at least eight inches in all dimensions.
d. Timber trusses supporting floor loads shall have members at least eight inches in all dimensions.
e. Frames or arches for roof construction that spring from grade or the floor line and do not support floor loads shall have members at least six inches wide and eight inches deep for the lower half of the height, and at least six inches deep for the upper half.
f. Frames or arches for roof construction that spring from the top of walls or wall abutments, framed timber trusses, and other roof framing, which do not support floor loads, shall have members at least four inches wide and six inches deep. Spaced members may be composed of two or more pieces at least three inches thick when blocked solidly through their intervening spaces or when such spaces are tightly closed by a continuous wood cover plate at least two inches thick secured to the underside of the members. Splice plates shall be at least three inches thick. When protected by approved automatic sprinklers under the roof deck, framing members shall be at least three inches wide.
(2) FLOORS.
a. Planks shall be splined or tongue-and-groove, not less than three inches thick, covered with one inch tongue-and-groove flooring, laid crosswise or diagonally to the plank, or other surface having equivalent fire resistance; or shall be,
b. At least four inches wide, set on edge close together and well spiked, and covered the same as for three inch thick plank. The planks shall be laid so that there is no continuous line of end joints except at points of support. Floors shall not extend closer than one-half inch to walls to provide an expansion joint, but the joint shall be covered at top or bottom to avoid flue action.
(3) ROOF DECKS. Roof decks shall be splined or tongue-and-groove planks at least two inches thick; or tongue-and-groove plywood panels (bonded with exterior glue) at least one and one-eighth inch thick, with face grain perpendicular to supports that shall be spaced not more than forty-eight inches on center; or of planks at least three inches wide set on edge close together and laid as required for floors.
(b) Construction details. Self releasing type wall plate boxes or approved hangers shall be provided where beams and girders enter masonry.
Table 10-4
Nailing Schedule
Building Element Nail Type Number and Distribution
Stud to sole plate Common-toe-nail 4 – 8d
Stud to cap plate Common-end-nail 2 – 16d
Double studs Common-direct 10d 12 in. o. c. or 16d 30 in. o.c.
Corner studs Common-direct 16d 30 in. o.c.
Sole plate to joist or blocking Common 16d 16 in. o.c.
Double cap plate Common-direct 16d 24 in. o. c.
Cap plate laps Common-direct 3 – 16d
Ribbon strip, 6 in. or less Common-direct 2 – 10d each bearing
Ribbon strip, over 6 in. Common-direct 3 – 10d each bearing
Roof rafter to plate Common-toe-nail 3 – 16d
Roof rafter to ridge Common-toe-nail 2 – 16d
Jack rafter to hip Common-toe-nail 3 – 10d
Floor joists to studs (no ceiling joists) Common-direct 5 – 10d or 3 – 16d
Floor joists to studs (with ceiling joists) Common-direct 2 – 10d
Floor joists to sill or girder Common-toe-nail 2 – 16d
Double-joist to joist Common-direct 10d – staggered at 16 in.
Ledger strip Common-direct 3 – 16d at each joist
Ceiling joists to plate Common-toe-nail 2 – 16d
Ceiling joists to every rafter Common-direct (See table below)
Ceiling joists (laps over partitions) Common-direct 3 – 16d
Collar beam Common-direct 4 – 10d
Bridging to joists and rafters Common-direct 2 – 8d each end
Bridging to studs Common-direct or toe 2 – 10d each end
Diagonal brace (to stud and plate) Common-direct 2 – 8d each bearing
Tail beams to headers (when nailing permitted) Common-end 1 – 20d each 4 sq. ft. floor area
Header beams to trimmers (when nailing permitted) Common-end 1 – 20d each 8 sq. ft. floor area
1 in. Subflooring (6 in. or less in width) Common-direct 2 – 8d each joist
1 in. Subflooring (over 6 in. in width) Common-direct 3 – 8d each joist
2 in. Subflooring Common-direct 2 – 20d each joist
1 in. Wall sheathing (8 in. or less in width) Common-direct 2 – 8d each stud
1 in. Wall sheathing (over 8 in. in width) Common-direct 3 – 8d each stud
Plywood sheathing and subflooring a
1 in. Roof sheathing (6 in. or less in width) Common-direct 2 – 8d each rafter
1 in. Roof sheathing (over 6 in. in width) Common-direct 3 – 8d each rafter
Shingles, wood Corrosion-resistive 2 – No. 15 B&S each bearing
Weather boarding Corrosion-resistive 2 – 8d each bearing
1/2 in. Fiberboard sheathing 1 1/2 in. galvanized roofing nail 6d common nail 16 ga. galvanized staples, 1 1/8 in. long, 7/16 in. crown 3 in. c. c. on all edges and 6 in. c. c. at other bearings
25/32 in. Fiberboard sheathing 1 3/4 in. galvanized roofing nail 8d common nail 16 ga. galvanized staples, 1 1/2 in. long, 7/16 crown 3 in. c. c. on all edges and 6 in. c. c. at other bearings
1/2 in. Gypsumboard sheathing 1 1/2 in. galvanized roofing nail 11 ga., 3/8 in. to 7/16 in. head 16 ga. galvanized staples, 1 1/2 in. long, 7/16 crown 4 in. c. c. on all edges and 8 in. c. c. at other bearings
Note a. For nailing of plywood, see reference standard RS 10-9.
CEILING JOIST NAILING TO EVERY RAFTER
(Number of 16d nails)
Slope of Roof 4/12 5/12 6/12 7/12 9/12 12/12
Rafter Spacing, o.c. (in.) 16 24 16 24 16 24 16 24 16 24 16 24
Width of building
Up to 24 ft. 5 8 4 7 3 5 3 4 3 3 3 3
24 to 30 ft. 7 11 6 9 4 7 3 6 3 4 3 3
Source: City of New York, Charter, Administrative Code and Rules (American Legal Publishing XML export, codelibrary.amlegal.com)URL: https://codelibrary.amlegal.com/codes/newyorkcity/latest/NYCadmin/0-0-0-51048Fetched: 10/24/2026