ASCE 24-2024 - Flood-Resistant Design for 2024 Building Codes
The newly released ASCE 24-24, Flood Resistant Design and Construction, brings significant updates to how structures are designed in flood-prone areas.
Referenced in the 2024 International Building Code (IBC) and other national standards, ASCE 24-24 replaces the 2014 edition and reflects the latest FEMA guidance, lessons from recent flood events, and coordination with ASCE 7-22.
For engineers, architects and permitting authorities, this updated standard introduces revised elevation requirements, stricter provisions for floodproofing, and expanded criteria for materials and mechanical systems.
As jurisdictions adopt the 2024 codes, understanding these changes is crucial for maintaining compliance and ensuring resilient design in flood hazard zones.
Looking For Your Flood Zone?
Flood Elevation Requirements
ASCE 24-24 introduces a more structured and risk-based approach to determining how high buildings must be elevated in flood hazard areas. Elevation requirements are still based on the building’s Flood Design Class (FDC), which reflects how critical the structure is during a flood. For example, a house has a lower FDC than a hospital, which must remain operational in emergencies.
In previous versions of the standard, the minimum required height was typically calculated by adding freeboard (a safety margin) to the Base Flood Elevation (BFE). The BFE is the estimated elevation of floodwaters during a 100-year flood, a flood that has a 1 percent chance of occurring in any given year.
DFE = max(FEcom, FEMRI + ΔSLC)
Where:
• FEcom = Flood elevation established by the local authority or jurisdiction
• FEMRI = Flood elevation associated with the Mean Recurrence Interval (MRI) based on the building’s FDC
• ΔSLC = Allowance for relative sea level change (not less than zero)
Decision process for determining the Design Flood Elevation (DFE) according to ASCE 24-24, Table 1-3.
ASCE 24-24 also improves clarity by bringing all elevation requirements into one place : Chapter 1, with Table 1-2 serving as a quick reference for all building types and flood conditions.
Required Minimum Elevations for Buildings and Structures according to ASCE 24-24, Table 1-2.
Expanded Flood Hazard Area
One of the most important updates in ASCE 24-24 is the expanded definition of flood hazard areas. In the past, ASCE 24-14 applied mainly to the Special Flood Hazard Area (SFHA), also known as the 100-year floodplain, as shown on FEMA flood maps (FIRMs).
Now, the updated standard goes further. For most buildings (Flood Design Class 2, 3, and 4), ASCE 24-24 requires designers to consider the larger of:
• The 500-year floodplain (also known as the Shaded X Zone, or Zone B/C on older maps), if it’s available, and
• Any area that the local community designates as a flood hazard area, even if it’s outside of FEMA’s mapped zones.
For Flood Design Class 1 buildings (such as small storage sheds), the minimum area remains the 100-year floodplain, but local designations can still expand this if they’re more restrictive.
This change helps align ASCE 24-24 with the latest version of ASCE 7-22 Supplement 2 and reflects lessons learned from major storms in recent years. It ensures that more buildings are protected, especially in areas where flooding risks are known but not yet fully mapped.
Enhanced Dry Floodproofing Requirements
Mandatory Use of Certified Products
One of the most important changes is the mandatory use of ANSI/FM 2510-certified products. Any barriers used to protect openings, such as shields for doors and windows, must now meet this rigorous national testing standard. Designers must confirm that these products:
• Are certified for the required flood depth,
• Can be installed correctly and securely,
• And are part of a full plan that also seals any small wall openings.
Temporary Barriers and Deployment Time
Temporary barriers are still permitted, but ASCE 24-24 now clearly separates those used at building openings (like doors and windows) from temporary floodwalls that block water away from structures. Each must meet specific performance standards based on Flood Design Class and project type. There are also now time limits on how quickly these systems must be deployed before flooding.
Designer Responsibilities
ASCE 24-24 also places more responsibility on the design professional, who must:
• Conduct a vulnerability assessment of the building,
• Design proper attachment methods,
• Specify installation procedures, and
• Ensure floodproofed wall systems are clearly labeled to prevent accidental damage during renovations.
Ongoing Maintenance and Training
To avoid system failure during a flood, the standard also requires:
• A written inspection, maintenance, and operations plan,
• Annual drills or testing of the equipment (or more frequently, if required by the local authority),
• And proper training for personnel to know where the barriers are and how to install them correctly.
These changes reflect lessons learned from past storms, where dry floodproofing systems failed due to poor planning, missing equipment, or user error.
Other Notable Changes in ASCE 24-2024
Several smaller but important updates were also introduced to ASCE 24-24:
• Elevated slabs: Existing slab-on-grade floors must now be structurally assessed and reinforced if used as elevated floors.
• Utility protection: Gas and fuel lines require automatic pressure control valves; utilities can’t be placed in dry floodproofed enclosures for residential buildings.
• New material standards: ASCE 24-24 adopts updated ASTM methods to rate flood damage-resistant materials.
• Mixed-use clarification: Clearer rules define how to treat residential portions of mixed-use buildings.
• Coastal design: Projects must now account for future sea level rise using historical data trends.
• Additional provisions: New sections cover tents, membrane structures, helical piles, and use of glass fiber reinforced polymer (GFRP) bars.
This article has highlighted several important updates and requirements in ASCE 24-24, but it’s essential to consult your local building codes and authorities to ensure full compliance with all regulations. For complex floodproofing projects, always seek guidance from a licensed design professional to ensure your structure is safe, effective, and meets the latest standards.
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Last Update: August 4, 2025