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Section G304 Post-Firm Construction and Substantial Improvements
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In addition to the requirements of ASCE 24, the following standards shall apply to post-FIRM construction and substantial improvements located within A-Zones, other than Coastal A-Zones.
For buildings or structures that are residential (for flood zone purposes), all post-FIRM new buildings and substantial improvements shall comply with the applicable requirements in Chapter G3 of this code and ASCE 24, and shall be elevated as follows:
- Lowest floor. The lowest floor, including the basement (for flood zone purposes), shall be elevated to at or above the design flood elevation specified in ASCE 24, Table 2-1;
- Enclosures below the design flood elevation. Enclosed spaces below the design flood elevation specified in ASCE 24, Table 2-1, shall be useable solely for parking of vehicles, building access, storage, or crawlspace, and shall be wet floodproofed in accordance with ASCE 24. Breakaway walls are not required in A-Zones;
- Under-floor spaces. The finished ground level of an under-floor space, such as a crawl space, shall be equal to or higher than the outside finished ground level on at least one side.
- Materials. Only flood-damage-resistant materials and finishes shall be utilized below the design flood elevation specified in ASCE 24, Table 5-1;
- Utilities and equipment. Utilities and attendant equipment shall be located at or above the design flood elevation specified in ASCE 24, Table 7-1, or shall be constructed so as to prevent water from entering or accumulating within the components during conditions of flooding in accordance with ASCE 24;
- Fire protection systems and equipment. The following fire protection systems and equipment shall be located at or above the design flood elevation specified in ASCE 24, Table 7-1, except that where the system or equipment or portion thereof serves only spaces located below such design flood elevation, the system or equipment or portion thereof may be located below such design flood elevation:
- Sprinkler control valves that are not outside stem and yoke valves;
- Fire standpipe control valves that are not outside stem and yoke valves;
- Sprinkler booster pumps and fire pumps;
- Dry pipe valve-related electrically operated alarm appurtenances;
- Alarm control panels for water and non-water fire extinguishing systems;
- Alarm control panels for sprinkler systems, pre-action sprinkler systems, deluge sprinkler systems, and combined dry pipe and pre-action sprinkler systems;
- Electrically operated waterflow detection devices serving sprinkler systems; and
- Air compressors serving sprinkler systems and pre-action sprinkler systems.
- Fire alarm systems and components. Where a zoning indicator panel is provided at the main building entrance in accordance with Section 907.6.3.1 and such panel is located at or below 5 feet (1524 mm) above the design flood elevation specified in ASCE 24, Table 7-1, at least one secondary zoning indicator panel complying with the following requirements shall be provided:
- The secondary zoning indicator panel, associated controls, power supplies and means of transferring control shall be provided at least 5 feet (1524 mm) above the design flood elevation specified in ASCE 24, Table 7-1, in a location accessible to responding Fire Department personnel and approved by the department and the Fire Department; and
- Where the secondary zoning indicator panel or associated controls are only operable upon transfer of control from another zoning indicator panel, such transfer shall be by a means that is approved by the Fire Department.
- Fuel-oil piping systems. The following requirements shall apply to fuel-oil piping systems, as defined by Section 202 of the New York City Mechanical Code:
- Fill piping that does not terminate in a watertight terminal approved by the department shall terminate at least 3 feet (914 mm) above the design flood elevation specified in ASCE 24, Table 7-1; and
- Normal vent piping and emergency vent piping shall terminate at least 3 feet (914 mm) above the design flood elevation specified in ASCE 24, Table 7-1.
- Plumbing systems and components. The structure shall comply with the following requirements:
- Relief vents and fresh air intakes. Relief vents and fresh air intakes serving building traps in accordance with Section 1002.6 of the New York City Plumbing Code shall be carried above grade and shall terminate in a screened outlet that is located outside of the building and at or above the design flood elevation specified in ASCE 24, Table 7-1; and
- Reduced pressure zone backflow preventers. Reduced pressure principle backflow preventers complying with Section 608.13.2 of the New York City Plumbing Code and backflow preventers with intermediate atmospheric vents complying with Section 608.13.3 of the New York City Plumbing Code shall be located at or above the design flood elevation specified in ASCE 24, Table 7.1.
- Fire protection systems and equipment. The following fire protection systems and equipment shall be located at or above the design flood elevation specified in ASCE 24, Table 7-1, except that where the system or equipment or portion thereof serves only spaces located below such design flood elevation, the system or equipment or portion thereof may be located below such design flood elevation:
- Certifications. Applications shall contain applicable certifications in accordance with Section G104.5; and
- Special inspections. Special inspections shall be as required by Section G105.
For buildings or structures that are nonresidential (for flood zone purposes), all post-FIRM new buildings and substantial improvements shall comply with the applicable requirements in Chapter G3 of this code and ASCE 24, and shall comply with either of the following:
- Elevation option. The structure shall comply with Items 1 through 7 of Section G304.1.1; or
- Dry floodproofing option. The structure shall comply with the following:
- Elevation of dry floodproofing. The structure shall be dry floodproofed to at or above the design flood elevation specified in ASCE 24, Table 6-1;
- Dwelling units, patient care areas (for flood zone purposes) and sleeping areas. Where dwelling units, patient care areas (for flood zone purposes) or spaces intended to be used by persons for sleeping purposes are located in a building utilizing the dry floodproofing option, the following additional requirements shall be met:
- All rooms and spaces within dwelling units, patient care areas (for flood zone purposes) and all spaces intended to be used by persons for sleeping purposes shall be located at or above the design flood elevation;
- A restrictive declaration noting the above restriction shall be filed with the City Register or County Clerk, and the page number and liber number shall be identified in the permit application and on the certificate of occupancy.
- Utilities and equipment. Utilities and attendant equipment shall be located within the dry floodproofed enclosure, or may be located outside the dry floodproofed enclosure provided that they are located at or above the design flood elevation specified in ASCE 24, Table 7-1, or are constructed so as to prevent water from entering or accumulating within the components during conditions of flooding in accordance with ASCE 24.
- Additional requirements. The structure shall comply with Items 5.1 through 5.4 of Section G304.1.1.
- Certifications. Applications shall contain applicable certifications in accordance with Section G104.5; and
- Special inspections. Special inspections shall be as required by Section G105.
In addition to the requirements of ASCE 24, the following standards shall apply to post-FIRM construction and substantial improvements located within V-Zones.
- Foundation. The lowest floor shall be elevated on adequately anchored pilings or columns and securely anchored to such piles or columns to prevent floatation, collapse and lateral movement resulting from wind and flood loads acting simultaneously on all building components, and other load requirements of Chapter 16 and this appendix.
- Lowest horizontal member. The lowest portion of the lowest horizontal structural member of the lowest floor (excluding the pilings or columns) shall be at or above the design flood elevation specified in ASCE 24, Table 4-1.
- Below the lowest horizontal member. Spaces below the lowest horizontal member shall be either:
- Free of obstructions; or
- Enclosed with breakaway walls providing unconditioned space useable solely for parking of vehicles, building access, storage or crawl space. Such breakaway walls shall:
- Be of an open lattice type construction only;
- Meet the load requirements of Section 5.3.3 of ASCE 7; and
- Meet the additional requirements of ASCE 24.
- Materials. Only flood-damage-resistant materials and finishes shall be utilized below the design flood elevation specified in ASCE 24, Table 5-1;
- Utilities and equipment. Utilities and attendant equipment shall be located at or above the design flood elevation specified in ASCE 24, Table 7-1, or shall be constructed so as to both resist the wave action and prevent water from entering or accumulating within the components during conditions of flooding in accordance with ASCE 24;
- Additional requirements. The structure shall comply with Items 5.1 through 5.4 of Section G304.1.1.
- Prohibitions. The following shall be prohibited in V-Zones:
- Development, including land-disturbing activities, seaward of the reach of mean high tide;
- Use of fill for structural support of buildings; and
- Man-made alterations of sand dunes that would increase potential damage to buildings.
- Certifications. Applications shall contain applicable certifications in accordance with Section G104.5; and
- Special inspections. Special inspections shall be as required by Section G105.
In addition to the requirements of ASCE 24, all post-FIRM new buildings and substantial improvements in a Coastal A-Zone shall comply with the V-Zone construction standards of Section G304.2.
Exceptions: The following structural systems shall be permitted in a Coastal A-Zone:
- Wave-resisting stem wall foundation. Stem walls supporting a floor system above, and backfilled with soil or gravel to the underside of the floor system, shall be permitted in Coastal A-Zones. The design and construction of the shallow foundation system shall comply with the following:
- The underside of such floor system shall be located at or above the design flood elevation specified in ASCE 24, Table 4-1.
- Stem walls enclosing areas below the design flood elevation shall not be permitted. Stem walls shall be designed to transfer all vertical and lateral forces to the slab above and to the foundation elements below;
- The design shall consider all forces resulting from flooding, including wave action, debris impact, erosion, and local scour;
- The design shall consider all forces resulting from soil pressure behind the walls, including the effect of hydrostatic loads, and all live and dead surcharge loads from the slab above;
- Flood openings shall not be required in stem walls constructed in accordance with this section;
- Where soils are susceptible to erosion and local scour, stem walls shall be supported by deep footings;
- Shallow foundations including spread footing, mat and raft foundations shall be designed to prevent sliding, uplift, or overturning when exposed to the combination of loads in ASCE Section 1.6.2.
- Wave-resisting dry floodproofing wall and foundation system. Buildings that are non-residential (for flood zone purposes) and that are located in Coastal A-Zones shall be permitted to be dry floodproofed in accordance with Section G304.1.2 provided the structure is dry floodproofed to at or above the design flood elevation specified in ASCE 24, Table 6-1. For buildings or structures utilizing this exception, construction documents shall include calculations demonstrating that the foundation and building, including flood shields if provided, will resist the wave action, including the combination of loads in ASCE Section 1.6, to at or above the design flood elevation specified in ASCE 24, Table 4-1.
In shaded X-Zones, buildings that include I-2 occupancies that are hospitals shall comply with the requirements of this chapter and the applicable provisions of ASCE 24 for A-Zone construction.
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