Quick RefeRence Guide 

comparison of Select nfiP and Building code 

Requirements for Special flood Hazard Areas 

This guide illustrates the similarities and highlights the 

differences between the National Flood Insurance Program 

(NFIP) minimum requirements and the requirements of the 

International Code Series (I-Codes) and ASCE 24, Flood 

Resistant Design and Construction (ASCE 24), a standard 

referenced by the I-Codes. 

Communities that participate in the NFIP adopt regulations 

and codes that govern development in special flood hazard 

areas, and enforce those requirements through the issuance 

of permits. The International Residential Code (IRC) 

and International Building Code (IBC), by reference to 

ASCE 24, include requirements that govern the design and 

construction of buildings and structures in flood hazard 

areas. FEMA has determined that the flood provisions of the 

I-Codes are consistent with the requirements of the NFIP 

(the I-Code requirements shown either meet or exceed NFIP 

requirements). ASCE 24, a design standard developed by 

the American Society of Civil Engineers, expands on the 

minimum NFIP requirements with more specificity, additional 

requirements, and some limitations. 

The illustrations that follow highlight some of the key 

similarities and differences between foundation types, lowest 

floor elevations, enclosures below elevated buildings, and 

utilities requirements contained within the NFIP and I-Codes 

for most residential and commercial buildings (classified as 

“Category II” structures by the building codes). 

DiD you know? 

Lowest floor elevation requirements 

in IBC/ASCE 24 vary with structure 

category, and may be higher for 

certain high occupancy buildings 

and critical and essential facilities. 

DiD you know? 

The NFIP refers to the Base Flood 

Elevation (BFE) for lowest floor 

elevation requirements, while the 

I-Codes and ASCE 24 refer to the 

Design Flood Elevation (DFE). 

The DFE will always be the BFE or 

higher. Additional height above the 

BFE is known as freeboard. 

The NFIP, I-Codes, and ASCE 24 

require the use of flood damageresistant materials below the 

required lowest floor elevation 

(illustrated throughout this guide). 

FEMA Quick Reference Guide: Comparison of Select NFIP and Building Code Requirements for Special Flood Hazard Areas March 2012 page 1 of 8 
-

Flood Zone Maps 

nFIp I Codes 

DiD you know? 

The NFIP regulations do not have provisions for Coastal A Zone (CAZ), but the I-Codes do 

(see map on right). The IBC, by reference to ASCE 24, requires CAZ buildings to be treated 

like Zone V buildings. The IRC permits the use of ASCE 24 in the CAZ as an alternative to its 

flood provisions, which allows CAZ buildings to be treated like Zone V buildings. Starting in 

2008, revised and new coastal Digital Flood Insurance Rate Maps (FIRMs) show the Limit of 

Moderate Wave Action (LiMWA), which delineates the landward limit of the CAZ. 

The NFIP requires that all buildings in Zone V resist the effects of wind 

and water loads acting simultaneously. The prescriptive wind design 

requirements in the IRC are applicable in regions where the basic wind 

speed is under 110 mph, or under 100 mph in hurricane-prone regions, 

which extend farther inland than Zone V in most areas. Where basic wind 

speeds exceed these minimum values, engineered design is required. 

FEMA Quick Reference Guide: Comparison of Select NFIP and Building Code Requirements for Special Flood Hazard Areas March 2012 page 2 of 8 
 

Slab-on-fill Perimeter wall 

(crawlspace) 

Footing 

Fill 

Slab 

Open foundation – 

piers/posts/columns 

Open foundation – 

piles 

Column Foundation 

wall Pile 

F o U n daTI on T Y pe 

nFIp and IRC 

Alternative use of ASCE 24 for CAZ buildings does not permit the use of structural fill or foundation walls 

U TI l I TI e s an d e n C lo s U R e s below elevated buildings 

Comparison of Zone A Requirements: NFIP and IRC 

l oW e s T F l o o R e l e VaTI o n at top of lowest floor 

nFIp IRC 

LHSM = Lowest horizontal
 

structural member
 

Top of BFE = lowest 

BFE + 1 ft 

or DFE* Floor framing 

Top of DFE = lowest lowest floor floor elevation lowest floor floor elevation 

Floor framing Floor framing LHSM 

(beam) 

Foundation 

element Foundation Foundation 

element 

*whichever is higher 

element 

LHSM 

(beam) 

Utilities elevated 

to or above 

required lowest 

floor elevation 

Flood openings on 

different walls to 

provide automatic entry 

and exit of flood waters. 

A minimum of 2 flood 

openings is required, but 

the total number of 

openings depends on 

the type and size of the 

openings and the size of 

the enclosed area 

No more than 1 foot 

Use of enclosure is 

restricted to parking, 

building access, 

and storage 

nFIp and IRC 

Alternative use of ASCE 24 for CAZ buildings requires breakaway walls and utilities to be elevated based 

on the orientation of lowest horizontal structural members (see page 6). 

FEMA Quick Reference Guide: Comparison of Select NFIP and Building Code Requirements for Special Flood Hazard Areas March 2012 page 3 of 8 
 

= Not permitted 

Slab-on-fill Perimeter wall 

(crawlspace) 

Footing 

Fill 

Slab 

Open foundation – 

piers/posts/columns 

Open foundation – 

piles 

Erosion and scour 

Column Foundation 

wall Pile 

F o U n daTI on T Y pe 

l oW e s T F l o o R e l e VaTI o n at bottom of LHSM 

nFIp 

nFIp and IRC 

Comparison of Zone V Requirements: NFIP and IRC 

IRC 

The IRC and 

ASCE 24 require 

foundation designs 

to specifically 

account for erosion 

and scour. 

LHSM parallel LHSM perpendicular LHSM = Lowest horizontal 

structural member to wave direction to wave direction 

BFE + 1 ft or DFE* = 

lowest floor elevation 

LHSM 

(beam) 

BFE = 

lowest Foundation 

Floor framing Floor framing LHSM 

(beam) 

DFE = lowest Foundation Foundation 

element floor floor element element elevation elevation *whichever is higher 

U TI l I TI e s an d e n C lo s U R e s below elevated buildings 

Use of enclosure is 

Floor framing 

restricted to parking, 

building access, and 

storage 

nFIp and IRC 

Both the NFIP and IRC require design certification in Zone V. Design certification is also required for breakaway walls that 

exceed a design safe loading resistance of 20 pounds per square foot. 

Area under elevated 

building must be 

free of obstruction 

or use breakway 

walls, open lattice, 

or louvers 

Breakaway wall 

Utilities elevated 

to or above 

required lowest 

floor elevation 

The IRC specifically 

prohibits mounting 

or penetration 

of utilities on 

breakaway walls 

FEMA Quick Reference Guide: Comparison of Select NFIP and Building Code Requirements for Special Flood Hazard Areas March 2012 page 4 of 8 
Comparison of Zone A Requirements: NFIP and IBC/ASCE 24 

F o U n daTI on T Y pe 

nFIp and IBC/asCe 24 

Slab-on-fill Perimeter wall Open foundation – Open foundation – 

(crawlspace) piers/posts/columns piles 

Slab 

Floor framing 

Foundation 

element 

Top of 

lowest floor 

BFE + 1 ft or DFE* = 

lowest floor elevation 

LHSM 

(beam) 

LHSM = Lowest horizontal 

structural member 

*whichever is higher 

Floor framing 

Foundation 

element 

Top of 

lowest floor 

BFE = lowest 

floor elevation 

LHSM 

(beam) 

LHSM = Lowest horizontal 

structural member 

= Not permitted 

nFIp 

nFIp 

IBC/asCe 24 

IBC/asCe 24 

l oW e s T F l o o R e l e VaTI o n at top of lowest floor or bottom of LHSM 

Footing 

Fill 

ASCE 24 includes 

specifications for the 

use of structural fill 

Column Foundation 

wall Pile 

Floor framing 

BFE + 1 ft or DFE* =
 

lowest floor elevation
 

Floor framing LHSM 

(beam) 

DFE = lowest Foundation Foundation floor element element elevation 

*whichever is higher

LHSM parallel LHSM perpendicular 

to wave direction to wave direction 

DiD you know? 

The NFIP and IBC/ASCE 24 allow 

non-residential buildings in Zone A 

to be dry floodproofed. Residential 

buildings are not permitted to be dry 

floodproofed in any flood hazard zone. 

ASCE 24 includes limitations on the use 

of dry floodproofing and on measures 

that require human intervention. 

FEMA Quick Reference Guide: Comparison of Select NFIP and Building Code Requirements for Special Flood Hazard Areas March 2012 page 5 of 8 
BFE + 1 ft 

or DFE* 

BFE = utility 

elevation 

Same as Zone A 

(above) 

Breakaway wall 

IBC/ASCE 24 specify 

Zone V requirements 

in Coastal A Zones 

(see page 7), with the 

addition of openings 

in breakaway walls 

Flood openings on different walls 

to provide automatic entry and 

exit of flood waters. A minimum 

of 2 flood openings is required, 

but the total number of openings 

depends on the type and size of 

the openings and the size of the 

enclosed area 

No more than 1 foot 

Use of enclosure is 

restricted to parking, 

building access, 

and storage 

e n C l o s U R e s below elevated buildings 

nFIp 

nFIp 

nFIp and IBC/asCe 24 

Comparison of Zone A Requirements: NFIP and IBC/ASCE 24 

IBC/asCe 24 

IBC/asCe 24 

U T I l I T I e s 

BFE + 1 ft 

or DFE* = 

utility 

elevation 

BFE + 2 ft or 

DFE* = utility 

elevation 

LHSM parallel 

to wave direction 

LHSM perpendicular 

to wave direction 

DiD you know? 

Elevation requirements for utilities 

in IBC/ASCE 24 vary with structure 

category, and may be higher for 

certain high occupancy buildings 

and critical and essential facilities. 

*whichever is higher 

LHSM = lowest horizontal 

structural member 

FEMA Quick Reference Guide: Comparison of Select NFIP and Building Code Requirements for Special Flood Hazard Areas March 2012 page 6 of 8 
= Not permitted 

Slab-on-fill Perimeter wall 

(crawlspace) 

Footing 

Fill 

Slab 

Open foundation – 

piers/posts/columns 

Open foundation – 

piles 

Column Foundation 

wall Pile 

Erosion and scour 

F o U n daTI on T Y pe 

nFIp 

nFIp and IBC/asCe 24 

Comparison of Zone V Requirements: NFIP and IBC/ASCE 24 

IBC/asCe 24 

l oW e s T F l o o R e l e VaTI o n at bottom of LHSM 

The IBC/ASCE 24 

requires foundation 

designs to specifically 

account for erosion 

and scour. 

LHSM = Lowest horizontal LHSM parallel LHSM perpendicular 

structural member to wave direction to wave direction 

Floor framing 

BFE + 1 ft or DFE* = 

lowest floor elevation 

LHSM 

(beam) 

BFE = 

Floor framing Floor framing LHSM 

(beam) 

DFE = lowest lowest Foundation 

floor element 

Foundation floor element element elevation elevation 

*whichever is higher 

Use of enclosure is 

restricted to parking, 

building access, and 

storage 

The IBC/ASCE 24 

specifically 

prohibits mounting 

or penetration of 

utilities on 

breakaway walls 

Area under elevated 

building must be free 

of obstruction or use 

breakway walls, open 

lattice, or louvers 

Breakaway wall 

e n C l o 

Foundation 

s U R e s below elevated buildings 

nFIp and IBC/asCe 24 

FEMA Quick Reference Guide: Comparison of Select NFIP and Building Code Requirements for Special Flood Hazard Areas March 2012 page 7 of 8 
BFE = utility 

elevation BFE + 1 ft 

or DFE* = 

utility 

elevation 

BFE + 2 ft or 

DFE* = utility 

elevation 

LHSM parallel 

to wave direction 

LHSM perpendicular 

to wave direction 

U T I l I T I e s 

nFIp IBC/asCe 24 

Comparison of Zone V Requirements: NFIP and IBC/ASCE 24 

*whichever is higher 

LHSM = lowest horizontal structural member 

FEMA Quick Reference Guide: Comparison of Select NFIP and Building Code Requirements for Special Flood Hazard Areas March 2012 page 8 of 8 

DiD you know? 

The IBC/ASCE 24 places 

constraints on construction 

in high risk flood hazard 

areas, including alluvial 

fan, flash flood, mudslide, 

erosion-prone, high 

velocity flow, and ice jam 

and debris areas. 

for More information 

For a more detailed and comprehensive summary, see Flood Resistant 

Provisions of the 2009 I -Codes, Flood Resistant Provisions of the 2012 

I -Codes, Highlights of ASCE 24 -05 Flood Resistant Design and Construction, 

and Provisions of the 2009 I -Codes and ASCE 24 Compared to the NFIP at 

http://www.fema.gov/building-science/building-code-resources 

See also CodeMaster: Flood Resistant Design, an 8 -page guide to designing a 

structure for flood loads in accordance with the IBC, IRC, ASCE 7 and ASCE 24. 

It can be purchased at: http://shop.iccsafe.org/codemaster-flood-resistantdesign-2009-2012-ibc-2009-2012-irc-asce-7-05-7-10-asce-24-05.html 

If you need additional information, contact the FEMA Building Science Helpline 

by emailing FEMA -Buildingsciencehelp@fema.dhs.gov or calling (866) 927 -2104.