Repairs, Remodeling, Additions, and Retrofitting
Home Builder’s Guide to Coastal Construction
FEMA 499/August 2005
Technical Fact Sheet No. 30
Purpose: To outline National Flood Insurance Program (NFIP) requirements for
repairs, remodeling, and additions, and opportunities for retrofitting in
coastal flood hazard areas (some communities may have more restrictive
requirements). To provide recommendations for exceeding those minimum
--Existing pre-FIRM (read Note 1) buildings that sustain substantial damage or
that are substantially improved will be treated as new construction, and must
meet the NFIP’s flood-resistant construction requirements (e.g., lowest floor
elevation, foundation, and enclosure requirements). (See box on next page for
definitions of substantial damage and substantial improvement.)
--Work on pre-FIRM (read Note 1) buildings that are not substantially damaged or
substantially improved is not subject to NFIP flood-resistant construction
requirements. (read Note 2)
--Work on post-FIRM (read Note 1) buildings that are not substantially damaged
or substantially improved must meet at least the NFIP's flood-resistant
construction requirements that were in effect when the building was originally
constructed. (read Note 2)
--Your Authority Having Jurisdiction (AHJ) will determine whether the building
is substantially damaged or substantially improved when you apply for permits.
--With a couple of minor exceptions (e.g., code violations and historic
buildings), substantial damage and substantial improvement requirements apply to
all buildings in the flood hazard area, whether or not a flood insurance policy
is in force.
--Buildings damaged by a flood and covered by flood insurance may be eligible
for additional payments through the Increased Cost of Compliance (ICC) policy
provisions. Check with an insurance agent and the AHJ for details.
--Repairs and remodeling – either before or after storm damage – provide many
opportunities for retrofitting homes and making them more resistant to storm
damage (see Figure 1).
Note 1: Existing pre-FIRM (Flood Insurance Rate Map) buildings are buildings
constructed before the jurisdiction’s first adoption of a floodplain management
ordinance. Post-FIRM buildings are buildings constructed after the jurisdiction
adopted these regulations.
Note 2: See Fact Sheet No. 2 for recommended requirements for exceeding the NFIP
regulatory requirements in V zones and in A zones in coastal areas.
Note: Repairs, remodeling, additions, and retrofitting may also be subject to
other community and code requirements, some of which may be more restrictive
than the NFIP requirements. Check with the AHJ before undertaking any work.
Figure 1: Storm-damaged homes need repairs, but also provide opportunities for
renovation, additions, and retrofitting. Review substantial damage and
substantial improvement regulations before undertaking any work.
Factors That Determine Whether and How Existing Buildings Must Comply With NFIP
Rules governing the applicability of NFIP new construction requirements to
existing buildings are confusing to many people – this fact sheet and Fact Sheet
No. 2 provide guidance on the subject.
When repairs, remodeling, additions, or improvements to an existing building are
undertaken, four basic factors determine whether and how the existing building
must comply with NFIP requirements for new construction:
--value of damage/work – whether the value of the building damage and/or work
triggers substantial damage or substantial improvement regulations (see box
--nature of work – whether the work involves remodeling of a building; expansion
of a building, either laterally or vertically (an addition); reconstruction of a
destroyed, damaged, or purposely demolished building; or relocation of an
--pre-FIRM or post-FIRM building – different requirements may apply to pre-FIRM
--flood hazard zone – different requirements may apply in V zones and A zones
Two other factors occasionally come into play (consult the AHJ regarding whether
and how these factors apply):
--code violations – NFIP regulations allow communities to exclude from
substantial damage and substantial improvement calculations the cost of certain
work to correct existing violations of state or local health, sanitary, or
safety code requirements that have been cited by a code official.
--historic structures – a building that is on the National Register of Historic
Places or that has been designated as historic by federally certified state or
local historic preservation offices (or that is eligible for such designation)
may be exempt from certain substantial damage and substantial improvement
requirements, provided any work on the building does not cause the building to
lose its historic designation.
A Zones Subject to Breaking Waves and Erosion. Home Builder’s Guide to Coastal
Construction (HGCC) Recommendations: Treat buildings and lateral additions in A
zones subject to breaking waves and erosion like V-zone buildings. Elevate these
lateral additions (except garages) such that the bottom of the lowest horizontal
structural member is at or above the BFE. For garages (in A zones subject to
breaking waves and erosion) below the BFE, construct with breakaway walls.
Substantial Damage and Substantial Improvement
It is not uncommon for existing coastal buildings to be modified or expanded
over time, often in conjunction with the repair of storm damage. All repairs,
remodeling, improvements, additions, and retrofitting to buildings in flood
hazard areas must be carried out in conformance with floodplain management
regulations adopted by the community pertaining to substantial damage and
What Is Substantial Damage?
Substantial damage is damage, of any origin, where the cost to restore the
building to its pre-damage condition equals or exceeds 50 percent of the
building’s market value before the damage occurred.
What Is Substantial Improvement?
Substantial improvement is any reconstruction, rehabilitation, addition, or
improvement of a building, the cost of which equals or exceeds 50 percent of the
building’s pre-improvement market value.
When repairs and improvements are made at the same time, all costs are totaled
and compared with the 50-percent-of-market-value threshold.
Note that some jurisdictions have enacted more restrictive requirements – some
use a less-than-50-percent damage/improvement threshold. Some track the
cumulative value of damage and improvements over time. Consult the AHJ for local
What Costs Are Included in Substantial Damage and Substantial Improvement
--all structural items and major building components (e.g., foundations; beams;
trusses; sheathing; walls and partitions; floors; ceilings; roof covering;
windows and doors; brick, stucco, and siding; attached decks and porches)
--interior finish elements (e.g., tile, linoleum, stone, carpet; plumbing
fixtures; drywall and wall finishes; built-in cabinets, bookcases and furniture;
--utility and service equipment (e.g., HVAC equipment; plumbing and wiring;
light fixtures and ceiling fans; security systems; built-in appliances; water
filtration and conditioning systems)
--market value of all labor and materials for repairs, demolition, and
improvements, including management, supervision, overhead, and profit (do not
discount volunteer or self labor or donated/discounted materials)
What Costs Are Not Included in Substantial Damage and Substantial Improvement
--design costs, including plans and specifications, surveys, and permits
--clean-up, debris removal, transportation, and landfill costs
--contents (e.g., furniture, rugs, appliances not built in)
--outside improvements (e.g., landscaping, irrigation systems, sidewalks and
patios, fences, lighting, swimming pools and hot tubs, sheds, gazebos, detached
Below are some examples of remodeling, additions, or repairs to buildings
described in Fact Sheet No. 2 that illustrate the NFIP substantial damage and
substantial improvement requirements. Check with the AHJ before undertaking any
work even if the building is not substantially damaged or being substantially
improved. The AHJ may have adopted more restrictive requirements than the NFIP
Substantial Improvement and Substantial Damage Examples
Example 1. Renovation/Remodeling
This example addresses the renovation/remodeling of an existing building that
does not affect the external dimensions of the building.
If the cost of remodeling a building is equal to or greater than 50 percent of
the market value of the building, the work constitutes a substantial improvement
and the existing building must meet current NFIP requirements for new
construction (see Figure 2).
Figure 2: Substantial Improvement: renovated/remodeled building in a V zone.
Requirement: renovated/remodeled building must be elevated to or above BFE on
open (pile/column) foundation with bottom of lowest horizontal structural member
at or above BFE.
Example 2. Lateral Addition
--If a lateral addition constitutes a substantial improvement to a V-zone
building, both the addition and the existing building must comply with the
current floor elevation, foundation, and other flood requirements for new V-zone
construction (see Figure 3).
--If a lateral addition constitutes a substantial improvement to an A-zone
building, only the addition must comply with the current floor elevation,
foundation, and other flood requirements for new construction, as long as the
alterations to the existing building are the minimum necessary.* Minimum
alterations necessary means the existing building is not altered, except for
cutting an entrance through the existing building wall into the addition, and
except for the minimum alterations necessary to tie the addition to the
building. If more extensive alterations are made to the existing building, it
too must be brought into compliance with the requirements for new construction.
Note: However, the Home Builders Guide to Coastal Construction (HGCC) recommends
that both the existing building and the addition be elevated to the current BFE,
in a manner consistent with current NFIP requirements, and using a V-zone-type
foundation in A zones subject to breaking waves or erosion.
--If a lateral addition does not constitute a substantial improvement, see Fact
Sheet No 2 for HGCC recommendations.
Figure 3: Substantial improvement: lateral addition to a pre-FIRM building in a
V zone. Requirement: both existing building and addition must be elevated to or
above BFE on open (pile/column) foundation with bottom of lowest horizontal
structural member at or above BFE. An attached garage does not have to be
elevated above BFE, but must be constructed with breakaway walls.
Example 3. Vertical Addition
--If a vertical addition to a V-zone or A-zone building constitutes a
substantial improvement, both the addition and the existing building must comply
with the current floor elevation, foundation, and other flood requirements for
new construction (see Figures 4 and 5).
--If a vertical addition does not constitute a substantial improvement, see Fact
Sheet No. 2 for HGCC recommendations.
Note: for requirements concerning enclosures below elevated buildings, see Fact
Sheet No. 27.
Figure 4: Vertical addition to a home damaged by Hurricane Fran. Preexisting 1-
story home became the second story of a home elevated to meet new foundation and
floor elevation requirements.
Figure 5: substantial improvement: vertical addition to a pre-FIRM building in a
V zone. Requirement: both existing building and addition must be elevated to or
Example 4. Reconstruction of a Destroyed or Razed Building
In all cases (pre-FIRM or post-FIRM, V zone or A zone) where an entire building
is destroyed, damaged, or purposefully demolished or razed, the replacement
building is considered “new construction” and the replacement building must meet
the current NFIP requirements, even if it is built on the foundation of the
Example 5. Moving an Existing Building
When an existing building is moved to a new location or site in a V zone or A
zone, the work is considered “new construction” and the relocated building must
comply with current NFIP requirements.
Designers and owners should know that the work described above may have
In general, most changes to an existing building that result from less-than-
substantial damage, or that do not constitute substantial improvement, will not
change the status from pre-FIRM to post-FIRM and thus would not affect the
insurance rate. However, failure to comply with the substantial damage or
substantial improvement requirements of the NFIP will result in a building's
status being changed and may result in higher flood insurance premiums.
Retrofit opportunities will present themselves every time repair or maintenance
work is undertaken for a major element of the building. Improvements to the
building that are made to increase resistance to the effects of natural hazards
should focus on those items that will potentially return the largest benefit to
the building owner. For example:
--When the roof covering is replaced, the attachment of the sheathing to the
trusses or rafters can be checked, and hurricane/seismic connectors can be
installed at the rafter-to-wall or truss-to-wall connections. When reroofing,
tear-off is recommended in lieu of re-covering.
--Gable ends can be braced in conjunction with other retrofits, or by
--If siding or roof sheathing has to be replaced, hurricane/seismic connectors
can be installed at the rafter-to-wall or truss-to-wall connections, the
exterior wall sheathing attachment can be checked, and structural sheathing can
be added to shearwalls. Adding wall-to-foundation ties may also be possible.
--Exterior siding attachment can be improved with more fasteners at the time the
exterior is re-coated.
--Window, door, and skylight reinforcement and attachment can be improved
whenever they are accessible.
--When windows and doors are replaced, glazing and framing can be used that is
impact-resistant and provides greater UV protection.
--Hurricane shutters can be added at any time (see Fact Sheet No. 26).
--Floor-framing-to-beam connections can be improved whenever they are
--Beam-to-pile connections can be improved whenever they are accessible.
--At any time, deficient light-gauge metal connectors that are accessible should
be replaced with stainless steel connectors, where available. Heavier-gauge
metal connectors can be replaced with either stainless steel connectors or metal
connectors with heavier galvanizing.
--When HVAC equipment is replaced, the replacement equipment should be more
durable — so that it will last longer in a coastal environment — and should be
elevated to or above the BFE and adequately anchored to resist wind and seismic
--Utility attachment can be improved when the outside equipment is replaced or
--In the attic space, at any time, straps should be added to rafters across the
ridge beam, straps should be added from rafters to top wall plates, and gable
wall framing should be braced. In addition, the uplift resistance of the roof
sheathing can be increased through the application of Engineered Wood
Association AFG-01-rated structural adhesive at the joints between the roof
sheathing and roof rafters or trusses. The adhesive should be applied in a
continuous bead and extended to the edges of the roof (where some of the highest
uplift pressures occur). At the last rafter or truss at gable ends, where only
one side of the joint is accessible, wood strips made of quarter-round molding
may be embedded in the adhesive to increase the strength of the joint. For more
information about the use of adhesive, see Additional Resources, below.
--At any time, reinforcement or replacement of garage doors with new wind- and
debris-resistant doors can be considered. However, the ability of the adjacent
walls and building to accommodate the increased wind loads and flood loads
(transferred from the garage door to the building) should first be determined.
If the existing building cannot accommodate the increased loads transferred from
the new/reinforced garage door, the structure will first require reinforcement.
This may or may not be feasible. Also, in a V zone, the new/reinforced garage
door must be designed and certified to break away during the Base Flood (see
Fact Sheet No. 27).
--To minimize the effects of corrosion, metal light fixtures can be replaced at
any time with fixtures that have either wood or vinyl exteriors. However, wood
may require frequent treatment or painting.
--To minimize the effects of corrosion, carbon steel handrails can be replaced
at any time with vinyl-coated, plastic, stainless steel, or wood handrails.
However, wood may require frequent treatment or painting.
Clemson University Department of Civil Engineering and South Carolina Sea Grant
Extension Program. Not Ready to Re-Roof? Use Structural Adhesives to Strengthen
the Attachment of Roof Sheathing and Holding on to Your Roof – A guide to
retrofitting your roof sheathing using adhesives.
FEMA. 1991. Answers to Questions about Substantially Damaged Buildings. FEMA
FEMA. 2000. Coastal Construction Manual, Chapter 14. FEMA-55.