Section 718 Concealed Spaces
- Two-inch (51 mm) nominal lumber.
- Two thicknesses of 1-inch (25 mm) nominal lumber with broken lap joints.
- One thickness of 0.719-inch (18.3 mm) wood structural panels with joints backed by 0.719-inch (18.3 mm) wood structural panels.
- One thickness of 0.75-inch (19.1 mm) particleboard with joints backed by 0.75-inch (19 mm) particleboard.
- One-half-inch (12.7 mm) gypsum board.
- One-fourth-inch (6.4 mm) cement-based millboard.
- Batts or blankets of mineral wool, mineral fiber or other approved materials installed in such a manner as to be securely retained in place.
- Cellulose insulation installed as tested for the specific application.
- Fireblocking of cornices is not required in single-family dwellings. Fireblocking of cornices of a two-family dwelling is required only at the line of dwelling unit separation.
- Fireblocking shall not be required where the exterior wall covering is installed on noncombustible framing and the face of the exterior wall covering exposed to the concealed space is covered by one of the following materials:
- Aluminum having a minimum thickness of 0.019 inch (0.5 mm).
- Corrosion-resistant steel having a base metal thickness not less than 0.016 inch (0.4 mm) at any point.
- Other approved noncombustible materials.
- Fireblocking shall not be required where the exterior wall covering has been tested in accordance with, and complies with the acceptance criteria of, NFPA 285. The exterior wall covering shall be installed as tested in accordance with NFPA 285.
Where wood sleepers are used for laying wood flooring on masonry or concrete fire-resistance-rated floors, the space between the floor slab and the underside of the wood flooring shall be filled with an approved material to resist the free passage of flame and products of combustion or fireblocked in such a manner that open spaces under the flooring shall not exceed 100 square feet (9.3 m2) in area and such space shall be filled solidly under permanent partitions so that communication under the flooring between adjoining rooms shall not occur.
Draftstopping shall be installed to subdivide floor/ceiling assemblies where required by Section 708.4.2. In other than Group R occupancies, draftstopping shall be installed to subdivide combustible floor/ceiling assemblies so that horizontal floor areas do not exceed 1,000 square feet (93 m2).
Draftstopping shall be installed to subdivide attic spaces where required by Section 708.4.2. In other than Group R, draftstopping shall be installed to subdivide combustible attic spaces and combustible concealed roof spaces such that any horizontal area does not exceed 3,000 square feet (279 m2). Ventilation of concealed roof spaces shall be maintained in accordance with Section 1202.2.1.
Combustible materials shall not be permitted in concealed spaces of buildings of Type I or II construction.
- Combustible materials in accordance with Section 603.
- Combustible materials exposed within plenums complying with Section 602 of the International Mechanical Code.
- Class A interior finish materials classified in accordance with Section 803.
- Combustible piping within partitions or shaft enclosures installed in accordance with the provisions of this code.
- Combustible piping within concealed ceiling spaces installed in accordance with the International Mechanical Code and the International Plumbing Code.
- Combustible insulation and covering on pipe and tubing, installed in concealed spaces other than plenums, complying with Section 720.7.