Transcript CHAPTER 5 DEVELOPMENT AND BUILDING PROTECTION

Chapter 6
Standards for Floodplain
Development and Building
Protection
Development is…...
•Construction of new buildings
•Addition or substantial
improvements to existing buildings
•Manufactured (mobile) homes and
RVs
•Subdivisions or commercial
developments
•Storage of materials
•Fill, grading, excavating
•Fences, culverts, bridges, roads
•And ANYTHING else that changes
the floodplain
Standards of Floodplain
Development
Federal regulations at Subpart B, Section
59.22 (a)(3) require that communities
adopt the minimum provisions of 44 CFR
60.3.
These standards must be applied to all
development and structures built or
substantially improved in the SFHA.
Building Protection Standards
Methods to Elevate Buildings in an A Zone
• Elevation on Fill
• Elevation on flow-thru walls
• Elevation by poles, piers, or columns
Building Protection Standards
Elevation on Fill
Fill
Building Protection Standards
Elevation on Fill (cont.)
Elevation on Fill
•
Before allowing floodplain fill, decide if the fill will
increase flooding or cause drainage problems on
neighboring properties.
Building Protection Standards
Elevation on Fill (cont.)
Elevation on Fill
•
Before permitting floodplain fill, decide if the applicant
plans to excavate a basement into the fill. Basements
are not allowed in the SFHA!
What is a basement?
Building Protection Standards
Elevation on Fill (cont.)
• Usually limited to three or four feet in height
• Fill placed in 6’ layers and compacted (95% proctor)
• Extend fill 10’ around structure
• Side slopes 1’ vertical to 1.5’ horizontal
• Erosion control
Building Protection Standards
Elevation on Fill (cont.)
House built on fill
above the flood
elevation
Building Protection Standards
Elevation on Solid Perimeter Walls
Opening
(typical)
Building Protection Standards
Elevation on Solid Perimeter Walls (cont.)
•
Types of solid wall foundations:
• Chain walls
• Perimeter walls
• Unreinforced masonary block
• Unreinforced brick
• Some types are required to have flood vents
Building Protection Standards
Elevation on Solid Perimeter Walls (Cont.)
• Enclosed areas below the lowest floor must
have openings to equalize hydrostatic
pressures (1” per 1 sq. ft.).
• Openings no more than one foot above grade.
• Flood resistant materials
• NO HVAC, electric, utilities, etc..
Building Protection Standards
Elevation on Solid Perimeter Walls (cont.)
Use of Enclosed
Areas below the
BFE
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•
•
Parking
Limited Storage
Building Access
Building Protection Standards
Elevation on Solid Perimeter Walls (cont.)
Flood-Resistant Materials
•
All materials below the BFE must be
resistant to water damage.
•
TB 2-93 is the best source of
information.
Building Protection Standards
Elevation on Solid Perimeter Walls (cont.)
TB 1-93
House built on
elevated
foundation walls
Flow through
crawl space
Building Protection Standards
Special Notes About Basements
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•
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Definition of a basement?
Can a crawl space be defined as
a basement?
A “walk-out” basement is an
enclosure below the BFE. What
does that mean?
What do you notice about the vents?
Good vents?
Building Protection Standards
Elevation on Fill (cont.)
•
Example: In an area with a BFE of 6 ft, fill could be
placed for 3 ft and chain wall or crawl space built for the
additional 3 ft (plus any freeboard).
Or, a combo of slab and
raised floor.
Building Protection Standards
Elevation on Posts or Piles
Building Protection Standards
Elevation on Posts or Piles (cont.)
Elevation on Post, Columns, Piers or Piles
•
•
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Posts or columns are wood, steel, concrete, or
masonry supports.
Piers are vertical structural members supported by
concrete footings.
Piles are generally made of wood or prestressed
concrete.
Building Protection Standards
Elevation on Posts or Piles (cont.)
Piles
Posts
Piers
Building Protection Standards
Elevation on Posts or Piles (cont.)
• Should be used in areas of deep flooding
and/or high velocities (floodways)
• Properly anchored to resist wind and
water forces
• Lower area must remain open (not
enclosed later)
House built on
piers or poles
above the flood
elevation
Building Protection Standards
Crawlspace
• Total height no more than
4 feet.
• No more than 2’ below
grade.
• Flow through openings
• Interior drainage controls
• Flood resistant materials
Technical Bulletin 11-01
NOT in the Gulf States.
Not while I’ve got a say!
Building Protection Standards
Coastal High Hazard or V Zone Construction
•
Mean High Tide: All new construction in V Zones
must be located landward of the reach of mean
high tide.
•
Modification of Dunes: Prohibit man-made
alteration of sand dunes in V Zones.
Building Protection Standards
Coastal High Hazard or V Zone Construction (cont.)
Methods to Elevate Buildings in a V Zone
•
New and substantially improved structures must
have the bottom of the lowest horizontal member at
or above the BFE.
Building Protection Standards
Coastal High Hazard or V Zone Construction (cont.)
Bottom of the
lowest
horizontal
structural
member
supporting the
lowest floor
Building Protection Standards
Coastal High Hazard or V Zone Construction
(cont.)
Methods to Elevate Buildings in a V Zone
•
A certificate of the design foundations for buildings
in V zones is required to be submitted prior to
permit issuance.
Building Protection Standards
Coastal High Hazard or V Zone Construction (cont.)
Coastal High Hazard Areas or V Zones
•
Structural Fill is prohibited to support buildings.
•
Nonstructural fill, such as might be used for
landscaping, should be placed so that it does not
divert waves and surging floodwaters onto other
structures.
Building Protection Standards
Coastal High Hazard or V Zone Construction (cont.)
Connecting the Load Path in the V Zone
•
•
Continuous path from roof to wall to foundation
Materials that resist deterioration
Building Protection Standards
Coastal High Hazard or V Zone Construction (cont.)
V Zone / Breakaway Wall Certificate
•
In V Zones, the applicant must include the V
Zone Certificate and an engineer’s certification of
design on a breakaway wall.
Building Protection Standards
Coastal High Hazard or V Zone Construction (cont.)
Breakaway Walls (V Zone)
•
Minimum standard requires collapse after not
less than 10 and no more than 20 pounds per
square foot.
Pre-Event
35
Post-Event
Building Protection Standards
Coastal High Hazard or V Zone Construction (cont.)
Altering Sand Dunes
•
Your flood damage prevention ordinance
prohibits manmade alterations of sand dunes
that will increase potential flood damage.
CoBRA
•
•
NFIP insurance not available.
You must still review and issue permits.
Permit Issuance
(continued)
V Zones and Fill
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•
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Fill is not allowed as a method to elevate
buildings in V Zones.
FEMA does not allow placement of fill in V Zones
as a method to remove a site from the mapped
floodplain by means of a LOMR-F.
Non-structural fill may be used for landscaping
purposes and cannot divert waves and water
toward any building.
Building Protection Standards
Manufactured Homes
Manufactured Homes
•
Manufactured homes are treated the same as any
other structure in the SFHA.
Make it easy, require all units
to be at or above the BFE!
Building Protection Standards
Manufactured Homes (cont.)
Special Considerations
•
•
•
Manufactured Homes are extremely
vulnerable to flood damage.
You may wish to require that a
engineered foundation to ensure
structural stability.
Anchoring, tie-down, & permanent
foundation requirements must be
outlined in the FP permit.
FEMA 85
Sept. 1985
Building Protection Standards
Non-Residential Floodproofing
ONLY NONRESIDENTIAL
STRUCTURES MAY
BE FLOODPROOFED
IN LIEU OF
ELEVATION.
Building Protection Standards
Non-Residential Floodproofing (cont.)
1. Non-residential construction may be
floodproofed below the BFE so that the structure
is watertight with walls substantially
impermeable to the passage of water.
2. Have structural components capable of
resisting hydrostatic and hydrodynamic loads
and effects of buoyancy.
Building Protection Standards
Non-Residential Floodproofing (cont.)
•
A Floodproofing Certificate is required for all
floodproofed structures
• The Floodproofing Certificate must be signed by
an Engineer
• The form can be obtained at:
www.FEMA.gov/library/floodproof
Building Protection Standards
Wet Floodproofing / Minor Accessory Structures
“Permanent or
contingent measures
applied to a structure
and/or its contents
that prevent or
provide resistance to
damage from flooding
by allowing flood
waters to enter the
structure.”
Building Protection Standards
Wet Floodproofing / Minor Accessory Structures
When to Use Wet Floodproofing
• Enclosed areas below the BFE that are
•
•
used for parking, building access, or limited
storage
Attached or detached garages
Minimal value storage sheds and garages
Building Protection Standards
Wet Floodproofing / Minor Accessory Structures
Standards for wet floodproofing:
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Non-habitable
Anchored
Openings
No HVAC or electric
Used only for storage
No later modification
Flood resistant materials
Document elevation
Size and/or cost threshold
Building Protection Standards
Wet Floodproofing / Minor Accessory Structures
FPE
Openings to allow
floodwaters to
flow in & out
Building Protection Standards
Wet Floodproofing / Minor Accessory Structures
Agricultural Structures
•
•
•
May be elevated or;
Wet floodproofed under certain conditions with a
variance.
Call State NFIP Coordinator if you plan to use a variance.
Building Protection Standards
Wet Floodproofing / Minor Accessory Structures
Agricultural Structures: Variance Procedures
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Use limited to agricultural purposes;
Flood-resistant materials below the BFE;
Anchored and impact resistant;
Hydrostatic venting is required;
Mechanical, electrical, or other utilities either above the
BFE or floodproofed;
Floodway encroachments cannot be waived; and,
Major equipment or contents must be evacuated prior to
a flood.
Building Protection Standards
Wet Floodproofing / Minor Accessory Structures
Temporary Structures
•
Common examples are:
• Construction trailers;
• Portable bathroom facilities;
• Large trash receptacles; and,
• Roadside stands.
Temporary Structures
Building Protection Standards
RVs and Travel Trailers
1. Self propelled or towable by a
light duty truck
2. No porch or deck
3. No permanent dwelling. Only
seasonal use.
4. No more than 400 sq. ft.
5. Wheels on axles and inflated
6. Quick disconnect utilities
7. Licensed and titled as an RV
8. Supported by wheels or jacks.
No blocks.
Building Protection Standards
RVs and Travel Trailers
If an RV is on-site
for more than 180
days, it must:
Building Protection Standards
Utilities and tanks
•
Utility Service in Buildings: Plumbing, mechanical, heating,
A/C, toilets, sinks, showers, water heaters, furnaces, heat
pumps, generators, air distribution systems, and other
permanent plumbing, mechanical, and electrical
installations must be elevated to or above the flood
protection elevation.
!
Elevate me
Utilities
125
Utilities
Power
Outlet
Vented area below elevated floor.
Building Protection Standards
Utilities and tanks
•
Duct work must be elevated above the BFE.
Building Protection Standards
Utilities and tanks
Storage Tanks
•
•
Above ground tanks may be anchored or elevated up to
5-feet from grade.
Below ground tanks must be anchored, require
engineered installation.
Above ground tanks
Building Protection Standards
Utilities and tanks
Protecting Utilities
•
•
•
Private On-Site Utilities: On site waste disposal systems
such as septic tanks and septic fields should be
protected.
How?
Backflow valves,
watertight enclosures,
and platforms above the
BFE.
Standards of Floodplain
Development
Functionally Dependent Use
•
May only be approved
by a variance.
•
Does not relieve the
applicant or community
of responsibility to
reduce damage
potential.
Building Protection Standards
Substantial Improvement
Any combination of alteration or
improvement to a building taking place
(during the life of the structure or a 10-year
period), in which the cumulative percentage
of improvements equals or exceeds 50% of
the current market value of the structure.
Building Protection Standards
Substantial Improvement
Compliance
•
•
When the 50% rule is evoked, the original residential
building must be elevated.
Non-residential buildings can be floodproofed, with the
proper certifications.
Existing House
FPE
Original Ground
Substantial Improvement
Existing House + Garage/FR/BR Addition
FPE
Original Ground
Added
Fill
•Raise Existing House & Build Addition above
FPE
Building Protection Standards
Substantial Improvement
Horizontal or Lateral Additions
•
Only the addition must meet lowest floor requirements, if
the structure is Pre-FIRM and the cost is less than 50% of
the market value.
Building Protection Standards
Substantial Improvement
Horizontal Additions
•
If the structure is Pre-FIRM and the cost is more
than 50% of the market value, the entire structure
must be raised to or above the BFE.
AFTER
Vertical Addition
Compliant With
NFIP Criteria (Zone A)
BEFORE
Utility
Box
FPE
FPE
AC
AC
Existing Pre-FIRM
Residential Structure
After Substantial Improvement
Elevate on fill or crawl required
Building Protection Standards
Substantial Improvement
Vertical Additions
•
Second-story additions almost always trigger the
50% rule.
Building Protection Standards
Substantial Improvement
Determining Building Value
•
•
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Building value is the market value of the building prior
to the damage or improvement.
You can require a professional appraisal.
Tax assessor records can be used as a screening tool
only.
Apply your approach consistently!
Building Protection Standards
Substantial Improvement
The formula
Cost of improvement project > 50%
Market value of the building
$75,000
project
=
54%
_____________
$140,000 house
Building Protection Standards
Substantial Improvement
Substantial Improvement tracking (one example)
Building Protection Standards
Subdivisions and large developments
•
Subdivisions
Building Protection Standards
Subdivisions and large developments
• Subdivisions: Open Space Design
NFIP Technical Bulletins
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TB
TB
TB
TB
TB
TB
TB
TB
TB
TB
1-93
2-93
3-93
4-93
5-93
6-93
7-93
8-06
9-99
10-01
Openings in Foundation Walls
Flood-Resistant Material Requirements
Non-Residential Floodproofing
Elevator Installation
Free of Obstruction Requirements in V Zone
Below Grade Parking Requirements
Wet Floodproofing Requirements
Corrosion Protection for Metal Connectors
Breakaway Walls
Structures Built on Fill