Lowest Floor Guide
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Previous Section Table of Contents Next Section LOWEST FLOOR GUIDE This section is to be used as a guide for identifying • The enclosed space is finished (having more than 20 the lowest floor for rating buildings being considered linear feet of interior finished wall [paneling, etc.]); or for coverage under the National Flood Insurance Program (NFIP). • The unfinished enclosed space is used for other than building access (stairwells, elevators, etc.), parking, or storage; or I. LOWEST FLOOR DETERMINATION • The unfinished enclosed space has no proper The following guidance, along with the comments openings (flood vents). accompanying each building drawing provided in this section, will help insurance agents/producers NOTE: A garage attached to an elevated building is determine the lowest floor so that the appropriate rate considered an enclosure. can be applied. 1. Proper Opening Requirements A. Non-Elevated Buildings An elevated building with an enclosure or In a non-elevated building, the lowest floor used crawlspace below the elevated floor with proper for rating is the building’s lowest floor including a flood openings (flood vents) in the enclosure or basement, if any. crawlspace can be rated using the elevated floor as the lowest floor. (For elevated buildings with If a building described and rated as a single-family proper flood openings in an unfinished enclosure dwelling located in an A Zone has an attached garage or crawlspace, the Application should indicate floor elevation at or above the Base Flood Elevation “No” for enclosure.) This rule applies to buildings (BFE), the garage floor may be excluded for rating. in zones A, A1–A30, AE, AO, AH, AR, and AR Dual. An attached garage floor elevation below the BFE can All enclosures (including an elevator shaft, a be excluded as the lowest floor for rating if all of the garage, or a crawlspace) below the lowest elevated following conditions apply: floor must be designed to automatically equalize hydrostatic flood forces on exterior walls by • Building is described and rated as a single-family allowing for the entry and exit of floodwaters. One dwelling; of the following criteria must be met to satisfy this • Building is located in an A Zone (any flood zone proper openings requirement: beginning with the letter A); a. A minimum of 2 openings must be provided, • The garage floor elevation is below the elevation of with positioning on at least 2 walls, having a the top of the bottom floor; and total net area of not less than 1 square inch for every square foot of enclosed area. The bottom • The garage has proper openings with or without of all openings must be no higher than 1 machinery/equipment that is below the BFE. See foot above the higher of the exterior or interior “Proper Openings” in the Definitions section. grade (adjacent) or floor immediately below the openings. If a building not described and rated as a single-family dwelling located in an A Zone has an attached garage, b. If the enclosure floor is partially subgrade, and the floor level of the garage is below the level of a minimum of 2 openings must be provided, the building, use the garage floor as the lowest floor with positioning on a single wall adjacent to for rating. the lowest grade next to the building, having a total net area of not less than 1 square inch B. Elevated Buildings in A Zones for every square foot of enclosed area. The bottom of all openings must be no higher In an elevated building located in an A Zone (any flood than 1 foot above the higher of the exterior or zone beginning with the letter A), the lowest floor interior grade (adjacent) or floor immediately used for rating is the lowest elevated floor, with the below the openings. exceptions described below. If a building located in an A Zone has an enclosure 2. Alternative to the Openings Requirement above below the elevated floor, including an attached garage, For architectural or other reasons, a designer the enclosure or garage floor becomes the lowest floor or builder may use an alternative to satisfy the for rating if any of the following conditions exists: requirement for a building to have openings that LFG 1 May 1, 2011 Previous Section Table of Contents Next Section provide 1 square inch per square foot of enclosed documentation must include the model area below the BFE. These alternatives, which may numbers of the engineered openings, which be referred to as “engineered openings,” must must match the model numbers provided in the be certified as having been designed to provide International Code Council Evaluation Report. automatic equalization of hydrostatic flood forces by allowing for the entry and exit of floodwaters. 3. Crawlspaces Design requirements and specifications for certification statements are outlined in FEMA If a building elevated on a crawlspace is located Technical Bulletin 1-08, “Openings in Foundation in an A Zone and has an attached garage, use the Walls and Walls of Enclosures Below Elevated following guidelines to determine the lowest floor Buildings in Special Flood Hazard Areas,” at http:// for rating: www.fema.gov/library/viewRecord.do?id=1579. • Use the top of the crawlspace (under-floor If engineered openings are used as an alternative, space) floor or the garage floor, whichever is the Write Your Own (WYO) Company or NFIP lower, if neither the crawlspace nor the garage Servicing Agent must obtain a copy of the following has proper openings; or documentation for its underwriting files: • Use the top of the crawlspace floor, if the only a. For engineered openings designed for area that has proper openings is the garage; or installation in a specific building, a copy of • Use the top of the garage floor, if the only area the certification is required. This certification that has proper openings is the crawlspace; or will verify to community officials that the openings are designed in accordance with the • Use the top of the finished floor (habitable floor), requirements of the NFIP, applicable building if both the crawlspace and the garage have codes, and accepted standards of practice. The proper openings. original certification statement must include the design professional’s name, title, address, type Pre-FIRM buildings with subgrade crawlspaces of license, license number, the state in which that are below the BFE may use optional Post- the license was issued, and the signature and FIRM elevation rating. Follow the Submit-for- applied seal of the certifying registered design Rate procedures. professional. In addition, this certification shall identify the building in which the engineered C. Elevated Buildings in V Zones openings will be installed and it shall address the following: (1) a statement certifying that In zones V, VE, and V1–V30, the floor of an the openings are designed to automatically enclosed area below the lowest elevated floor is equalize hydrostatic flood loads on exterior the building’s lowest floor if any of the following walls by allowing for the automatic entry and conditions exists: exit of floodwaters; (2) description of the range • The enclosed space is finished (having more of flood characteristics tested or computed for than 20 linear feet of interior finished wall which the certification is valid, such as rates of [paneling, etc.]); or rise and fall of floodwaters; and (3) description of the installation requirements or limitations • The unfinished enclosed space is used for other that, if not followed, will void the certification; or than building access (stairwells, elevators, etc.), parking, or storage; or b. For engineered openings for which the International Code Council Evaluation Service, • The enclosed space is of any size, and there Inc., has issued an Evaluation Report, a copy of is machinery or equipment below the BFE the Evaluation Report is required. This report is located inside or outside the enclosed space. required to assure community officials that the (Machinery or equipment is defined as building openings are designed in accordance with the items permanently affixed to the building and requirements of the NFIP, applicable building that provide utility services for the building – codes, and accepted standards of practice. The i.e., furnaces, water heaters, heat pumps, air Evaluation Report identifies the model numbers conditioners, and elevators and their associated of the engineered openings addressed in the equipment. Washers, dryers, and food freezers report, specifies the number of engineered are contents items and are not considered openings that are required for a specified machinery or equipment.); or square footage of enclosed area below the BFE, and lists installation requirements. Acceptable LFG 2 May 1, 2011 • The enclosed space is constructed with non- In addition, the EC is optional in unnumbered A Zones breakaway walls. (A non-breakaway wall is (With or Without BFE), Zone AH, and Zone AO if the defined as a wall that is attached to the building has no basement or enclosure. structural support of the building and is not designed or constructed to collapse under C. Guidelines for Determining the Conversion from specific lateral loading forces. This type of NGVD 1929 to NAVD 1988 construction endangers the foundation system of the building.); or NAVD 1988 is replacing NGVD 1929 as the national standard reference datum for elevations. To determine • The enclosed space is 300 square feet or more the conversion from NGVD to NAVD, contact the and has breakaway walls; or community official. The surveyor may have applied the conversion factor to the elevations entered on • The enclosed space has load-bearing the EC. Unless the surveyor’s comments specifically (supporting) walls. state that the conversion was not performed, assume that line items C2.a–h have already been converted If the enclosed space (enclosure) is at or above the to the same elevation datum as the BFE reported in BFE, use the “Free of Obstruction” rate table in the box B9.