Understanding Gross Floor Area Calculation: Exclusions for Flood Zones

When constructing a home in a flood zone, ensuring compliance with building regulations is crucial. One common strategy is to build the home on pilings with breakaway walls to resist floodwaters. This article addresses whether the floor area under the house, typically not enclosed, should be included in the Gross Floor Area (GFA) calculation as per building codes and standards.

What is Gross Floor Area (GFA)?

Gross Floor Area (GFA) is a critical measurement used in construction and real estate to determine the total floor space of a building. It is essential for various purposes, including building permits, property taxes, and determining building density. GFA includes all enclosed spaces and structural components within the building, ensuring that every inhabitable and accessible space is counted. This includes tenant areas, common areas, corridors, clubhouses, meeting rooms, and others. However, it is important to understand what is excluded from this measurement.

What is Included in the GFA Calculation?

When calculating GFA, the following elements should be included:

All enclosed spaces and structural components: This includes any space that is enclosed and sealed from the external environment, such as storage rooms, closets, and structural beams.Tenant areas: Any spaces dedicated to tenants, such as rental units or apartments within a larger building.Common areas: These are areas shared by multiple tenants, such as lobbies, hallways, and elevators.Corridors: Open or enclosed passageways connecting different parts of the building.Clubhouses, meeting rooms, and break rooms: These are communal spaces designed for social gatherings, meetings, or rest periods.Atriums: These are open spaces surrounded by buildings, typically counted as part of the base level only.

What is Excluded from the GFA Calculation?

While many elements are included in GFA, there are several areas that are excluded from the calculation:

Non-enclosed roofed-over areas: Such as porches, terraces, exterior covered walkways, and roof overhangs. These areas are not enclosed and are typically not part of the living space.Air shafts, pipe trenches, and chimneys: As these are structural features rather than habitable spaces, they are usually excluded from GFA calculations.Floor area dedicated to parking and vehicle circulation: Spaces specifically allocated for parking and movement of vehicles are not considered in the GFA.Open terraces: Unenclosed outdoor areas with roof coverings are typically not included in GFA.Spaces used exclusively for mechanical services: Areas used for HVAC systems, electrical fixtures, and other mechanical services are not counted in the GFA.

Implications for Flood Zones

For a home built on pilings with breakaway walls in a flood zone, the floor area under the house is often left unenclosed. This is a common design choice to help the house float and avoid catastrophic damage. The question then arises: should this area also be excluded from the GFA calculation?

According to building codes, the GFA focuses on the inhabitable and enclosed spaces within the building. Therefore, the floor area under the house, although within the property boundaries, would not typically be included in the GFA. This is because it is not considered as part of the main, enclosed living area. However, it is essential to consult local building codes and regulations, as they may have specific provisions for such unique structures.

Conclusion

Accurately calculating the Gross Floor Area (GFA) of a building is crucial for compliance and building permits. By understanding what is included and excluded from the GFA calculation, builders can ensure that their homes, especially those in flood zones, are constructed in accordance with local regulations. For homes built on pilings with breakaway walls, the floor area under the house is generally excluded from the GFA as it is not considered as a habitable and enclosed space.

For more detailed information on building regulations and codes, consulting local authorities and professional architects is recommended.