N.Y.C. Admin. Code § BC 602: Section BC 602: Construction Classification

602.1 General.

Buildings and structures erected or to be erected, altered or extended in height or area shall be classified in one of the five construction types defined in Sections 602.2 through 602.5. The building elements shall have a fire-resistance rating not less than that specified in Table 601 and exterior walls shall have a fire-resistance rating not less than that specified in Table 602. Where required to have a fire-resistance rating by Table 601, building elements shall comply with the applicable provisions of Section 703.2. The protection of openings, ducts and air transfer openings in building elements shall not be required unless required by other provisions of this code. Buildings constructed or altered inside the fire district shall further comply with Appendix D.

602.1.1 Minimum requirements.

A building or portion thereof shall not be required to conform to the details of a type of construction higher than that type which meets the minimum requirements based on occupancy even though certain features of such a building actually conform to a higher type of construction. Classification shall be that of the minimum requirement unless all of the requirements for the higher type of construction are met.

Exception: Portions of buildings that cantilever over an adjacent building or tax lot shall also comply with the fire-resistance ratings of Section 705.12.

602.2 Types I and II.

Types I and II construction are those types of construction in which the building elements listed in Table 601 are of noncombustible materials, except as permitted in Section 603 and elsewhere in this code.

602.3 Type III.

Type III construction is that type of construction in which the exterior walls are of noncombustible materials and the interior building elements are of any material permitted by this code. Fire-retardant-treated wood framing complying with Section 2303.2 shall be permitted within exterior wall assemblies of a 2-hour rating or less.

Exceptions:

1. In Group I-1, R- 1, and R-2 occupancies, all exterior walls, fire walls, exit passageways, and shaft enclosures shall be noncombustible.

2. In Group F occupancies subject to Section 270(1) of the New York State Labor Law, all exterior wall assemblies and all structural elements shall meet the requirements for a "fireproof building" as such term is defined in Section 264 of such law.

3. Inside the fire district, exterior load-bearing walls shall be constructed of noncombustible material.

4. Inside the fire district, exterior nonload-bearing walls may be constructed with fire-retardant-treated wood complying with Section 2303.2 where the building is equipped throughout with an automatic sprinkler system in accordance with Sections 903.3.1.1 through 903.3.1.3, unless otherwise prohibited by Exception 1 or 2 above.

602.4 Type IV.

Type IV construction is that type of construction in which the exterior walls are of noncombustible materials or other materials permitted by Section 602.4.1 or 602.4.2, and the interior building elements are of solid wood, glue-laminated timber, heavy timber (HT), structural composite lumber (SCL), or cross-laminated timber (CLT) without concealed spaces. The minimum dimensions for permitted materials including solid timber, glued-laminated timber, SCL, and CLT and details of Type IV construction shall comply with the provisions of Section 2304.11 and this section. Interior walls and partitions not less than 1-hour fire-resistance rating or heavy timber complying with Section 2304.11.2.2 shall be permitted. Buildings of Type IV construction utilizing SCL or CLT shall be equipped throughout with an automatic sprinkler system where required by Section 903.2.13. In buildings of Type IV construction utilizing SCL or CLT, a fire watch shall be maintained in accordance with Section 901.7.2 of the New York City Fire Code and Section 3303.3 of this code.

Exceptions:

1. In Group I-1, R-1, and R-2 occupancies, all exterior walls, fire walls, exit passageways, and shaft enclosures shall be noncombustible.

2. In Group F occupancies subject to Section 270(1) of the New York State Labor Law, all exterior wall assemblies and all structural elements shall meet the requirements for a "fireproof building" as defined in Section 264 of such law.

3. Inside the fire district, exterior load-bearing walls shall be constructed of noncombustible material.

4. Inside the fire district, exterior nonbearing walls may be constructed with fire-retardant-treated wood complying with Section 2303.2 where the building is equipped throughout with an automatic sprinkler system in accordance with Sections 903.3.1.1 through 903.3.1.3, unless otherwise prohibited by Exception 1 or 2 above.

5. Inside the fire district, exterior nonbearing walls are permitted to be constructed with cross-laminated timber (CLT) complying with Section 602.4.2 of this code, unless otherwise prohibited by Exception 1 or 2 above.

602.4.1 Fire-retardant-treated wood in exterior walls.

Fire-retardant-treated wood framing and sheathing complying with Section 2303.2 shall be permitted within exterior wall assemblies not less than 6 inches (152.4 mm) in thickness with a 2-hour rating or less.

602.4.2 Cross-laminated timber in exterior walls.

Cross-laminated timber (CLT) complying with Section 2303.1.4 shall be permitted within exterior wall assemblies not less than 6 inches (152.4 mm) in thickness with a 2-hour rating or less, provided the exterior surface of the cross-laminated timber (CLT) is protected by one of the following:

1. Fire-retardant-treated wood sheathing complying with Section 2303.2 and not less than 15/32 inch (11.9 mm) thick;

2. Type X gypsum board not less than 5/8 inch (15.9 mm) thick; or

3. A noncombustible material.

602.4.3 Exterior structural members.

Where a horizontal separation of 20 feet (6096 mm) or more is provided, wood columns and arches conforming to heavy timber sizes in accordance with Section 2304.11 shall be permitted to be used externally.

Exception: Where prohibited by Exceptions 1, 2 or 3 of Section 602.4.

602.5 Type V.

Type V construction is that type of construction in which the structural elements, exterior walls and interior walls are of any materials permitted by this code. Type V construction shall not be permitted inside the fire district unless otherwise permitted by Section D105.1.

Exception: In Group F occupancies subject to Section 270(1) of the New York State Labor Law, all exterior wall assemblies and all structural elements shall meet the requirements for a "fireproof building" as defined in Section 264 of such law.