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Higher Standards: When Paying a Bit More Costs a Lot Less February 14, 2013
Eric D. Kenney, P.E., CFM
Georgia Association of Floodplain Management
Higher Standard (ASCE 24-05)
Technical Provisions of the Higher Standard
Comparison to Existing Standards and Current Uses
Implementation Benefits
Implementation Issues
Summary
Overview
ASCE 24-05 Standard
National consensus standard for flood resistant
design and construction developed by
ASCE/SEI.
Improved design and construction standards
identified through the consensus process to
address damage to new buildings constructed
consistent with NFIP requirements.
Second edition published in 2006 and the next
revision cycle is in progress.
ASCE 24-05 can be used for new construction,
as well as to guide repairs of existing buildings.
ASCE 24-05 directs design and construction
based on structure classification (criticality and
nature of occupancy) and based on flood
hazard classification.
Structure Category
Category Description
I Low hazard to human life in the event of a failure: includes agriculture facilities
and storage facilities.
II Encompasses all structure types except those specifically listed in Category I, III,
and IV; includes single- and multi-family residences.
III Represents a substantial hazard to human life in the event of a failure; includes
schools, colleges, healthcare facilities, and other structures where large numbers
of people congregate.
IV Essential facilities; includes fire stations and other emergency services (including
hospitals), as well as other critical infrastructure-type facilities (i.e., power
generation, aviation control, etc.).
ASCE – Flood Resistant Design and Construction (ASCE/SEI 24-05), 2006
ASCE – Flood Resistant Design and Construction (ASCE/SEI 24-05), 2006
Combining Flood Hazard and Structure Criticality
NFIP I II III IV
Elevation of Lowest
Floor
(A Zone)
A Zones not identified
as Coastal A Zones:
elevation of lowest
floor
DFE or
above
(based
on food
zone)
DFE BFE +1 ft
or DFE
BFE +1 ft
or DFE
BFE +2 ft
or DFE
Elevation of Lowest
Floor or Bottom of
Lowest Horizontal
Structural Member
(V Zone)
V Zones and Coastal
A Zones:
(lowest parallel
member)
DFE DFE BFE +1 ft
or DFE
BFE +1 ft
or DFE
V Zones and Coastal
A Zones:
(lowest perpendicular
member)
DFE BFE +1 ft
or DFE
BFE +2 ft
or DFE
BFE +2 ft
or DFE
Managing Flood Risk
Area Applicability
Flood Risk
Riverine AE, AH, AO Specific guidance on methods, materials, and
elevation requirements.
Coastal A, V Specific guidance on methods, materials, and
elevation requirements.
Decertified Flood
Protection System (AR)
Siting requirements (DFE determination
needed).
Hazard Risk Not
Identified
Siting requirements (DFE determination
needed).
Technical Applicability of ASCE 24-05: by Project Type
Area HMA NFIP
Project
Type
Structure Elevation Additional Requirements Additional Requirements
Dry Floodproofing Additional Requirements Additional Requirements
Mitigation
Reconstruction Generally Consistent Generally Consistent
Higher Standards and FEMA HMA Guidance
Project Type Use in FEMA Funded Projects
Structure Elevation Encouraged
Mitigation Reconstruction
Required
Dependent on flood hazard;
International Residential Code -
IRC 2006 for 1- and 2-family
dwellings; IBC 2006 for multi-
family dwellings)
Encouraged
(IBC 2009)
Dry Floodproofing - Historical
Residential / Non-Residential
Encouraged
Current Standards
Criteria NFIP Community Rating System (CRS) 24-05
Elevation BFE 100 Points for each foot of freeboard (deductions if utilities
are not included)
BFE / DFE may
require additional
freeboard (including
utilities).
Foundation No
specifics
35 Points – P.E. Certified or Fill Elevation is above BFE
(including beyond building limits)
Detailed foundation
requirements,
including elevation.
Critical
Facilities BFE
100 Points – Outside the 500-yr Flood Plain (new)
50 Points – Protected from 500-yr flood (new/substantially
improved)
BFE + 2 or DFE
Current Standards
Criteria NFIP CRS 24-05
Enclosures Below
the BFE
Vents /
Hydrostatic
Equilibrium
None allowed (300 pts)
None larger than 300 sq. ft (100 pts)
Non-conversion agreement with owner (50 pts)
DFE - Parking /
Storage Only w/
Flow Through
Requirements
Building Codes
NFIP Minimums
and
Enforcement
Adopting International Building Code, including ASCE 24,
and obtaining BC Effectiveness Grade above 7 (15 pts for
each grade above 7)
Adopting full IBC (100 pts) (190 Max)
-
Coastal A Zones A Zone
Requirements
Meet V Zone building requirements and A Zone opening
requirements (500)
No enclosures below BFE (150)
Section 4
(Coastal High
Hazard Areas
and Coastal A
Zones)
Implementation Considerations – Increased Cost
Flood Zone Freeboard (ft)
Cost of Freeboard
(% Increase)
Average Premium
Savings as a Percent
of Total Cost of
Construction
Average Payback
Period for Additional
Cost of Freeboard
(Years)
V Zone
BFE +1 0.4 – 1.8
0.45
2.0
BFE +2 0.8 – 3.6 0.87 2.5
BFE +3 1.3 - 5.4 1.09 2.7
BFE +4 1.7 – 7.2 1.19 3.1
Coastal A
Zone
BFE +1 0.5 – 3.9
0.18
4.4
BFE +2 0.7 – 4.8 0.24 6.0
BFE +3 1.1 – 6.1 0.26 7.9
BFE +4 1.4 – 8.1 0.25 9.6
A Zone
BFE +1 0.2 – 2.3
0.20
3.3
BFE +2 0.3 – 4.5 0.26 4.6
BFE +3 0.7 – 6.8 0.28 6.4
BFE +4 0.9 – 9.1 0.27 8.2
Jones, C.P, et al. Evaluation of the NFIP’s Building Standard, 2006
Implementation Considerations – Insurance Savings
V Zone A Zone
Freeboard Annual Savings 30-Year Savings Annual Savings 30-Year Savings
1’ Freeboard $1,360 (25%) $40,800 $502 (41%) $15,060
2’ Freeboard $2,730 (50%) $81,900 $678 (55%) $20,340
3’ Freeboard $3,415 (62%) $102,450 $743 (60%) $22,290
NFIP premiums are based on May 2007 rates for one-floor residential structures with no basement, built
after a FIRM was issued for the community (post-FIRM rates differ from pre-FIRM rates). The coverage
and deductibles are as follows: $500 Deductible/$250,000 Coverage for Building and $100,000
Coverage for Contents.
Jones, C.P, et al. Evaluation of the NFIP’s Building Standard, 2006
Implementation Considerations
• Higher Technical Standard
– Increased design requirements
– Requires better understanding of flood hazards
– Increased professional verification requirements
– But, increased survivability of structures
• Higher Initial Construction Costs
– Elevation projects – directly related to freeboard
– But, potential for reduced premiums, and decreased flood damages