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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

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Chapter 6Standards for Floodplain Development and Building Protection


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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


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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.


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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


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Building Protection StandardsElevation on Fill

Fill


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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.


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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?


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Building Protection StandardsElevation 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


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Building Protection Standards

Elevation on Fill (cont.)

House built on fill

above the flood elevation


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Building Protection Standards Elevation on Solid Perimeter Walls

Opening

(typical)


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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


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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..


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Building Protection Standards Elevation on Solid Perimeter Walls (cont.)

Use of Enclosed Areas below the BFE

  • Parking

  • Limited Storage

  • Building Access


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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.


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Building Protection StandardsElevation on Solid Perimeter Walls (cont.)

TB 1-93



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Building Protection Standards

Special Notes About Basements

  • 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?




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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.


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Building Protection Standards Elevation on Posts or Piles


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Building Protection Standards Elevation on Posts or Piles (cont.)

Elevation on Post, Columns, Piers or Piles

  • 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.


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Building Protection StandardsElevation on Posts or Piles (cont.)

Piles


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Posts

Piers


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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)



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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


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NOT in the Gulf States.

Not while I’ve got a say!


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Building Protection StandardsCoastal 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.


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Building Protection StandardsCoastal 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.


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Building Protection StandardsCoastal High Hazard or V Zone Construction (cont.)

  • Bottom of the lowest horizontal structural member supporting the lowest floor


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Building Protection StandardsCoastal 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.


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Building Protection StandardsCoastal 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.



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Building Protection StandardsCoastal 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


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Building Protection StandardsCoastal 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.


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Building Protection StandardsCoastal 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.




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Building Protection StandardsCoastal 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.


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Permit Issuance (continued)

V Zones and Fill

  • 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.


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Building Protection StandardsManufactured 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!


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Building Protection StandardsManufactured 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.


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FEMA 85

Sept. 1985


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Building Protection Standards Non-Residential Floodproofing

  • ONLY NON-RESIDENTIAL STRUCTURES MAY BE FLOODPROOFED IN LIEU OF ELEVATION.


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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.


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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


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Building Protection StandardsWet 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.”


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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


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Building Protection StandardsWet Floodproofing / Minor Accessory Structures

Standards for wet floodproofing:

  • 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


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Building Protection StandardsWet Floodproofing / Minor Accessory Structures

FPE

Openings to allow floodwaters to flow in & out


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Building Protection StandardsWet 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.


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Building Protection StandardsWet Floodproofing / Minor Accessory Structures

Agricultural Structures: Variance Procedures

  • 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.


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Building Protection StandardsWet Floodproofing / Minor Accessory Structures

Temporary Structures

  • Common examples are:

    • Construction trailers;

    • Portable bathroom facilities;

    • Large trash receptacles; and,

    • Roadside stands.



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Building Protection Standards

RVs and Travel Trailers

  • Self propelled or towable by a light duty truck

  • No porch or deck

  • No permanent dwelling. Only seasonal use.

  • No more than 400 sq. ft.

  • Wheels on axles and inflated

  • Quick disconnect utilities

  • Licensed and titled as an RV

  • Supported by wheels or jacks. No blocks.


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Building Protection Standards

RVs and Travel Trailers

If an RV is on-site for more than 180 days, it must:


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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.


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Elevate me!

Utilities

125


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Utilities

Power Outlet

Base Flood Elevation

Vented area below elevated floor.


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Building Protection Standards Utilities and tanks

  • Duct work must be elevated above the BFE.


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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.



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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.


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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.


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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.


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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.


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Existing House

FPE

Original Ground


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Substantial Improvement

Existing House + Garage/FR/BR Addition

FPE

Added Fill

Original Ground

  • Raise Existing House & Build Addition above FPE


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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.


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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.


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AC

AC

AFTER

Vertical Addition

Compliant With

NFIP Criteria (Zone A)

Utility

Box

BEFORE

FPE

FPE

Existing Pre-FIRM

Residential Structure

After Substantial Improvement

Elevate on fill or crawl required


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Building Protection Standards Substantial Improvement

Vertical Additions

  • Second-story additions almost always trigger the 50% rule.


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Building Protection Standards Substantial Improvement

Determining BuildingValue

  • 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!


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Building Protection Standards Substantial Improvement

The formula

Cost of improvement project > 50% Market value of the building

_____________

$140,000 house

$75,000 project = 54%


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Building Protection Standards Substantial Improvement

Substantial Improvement tracking (one example)


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Building Protection Standards Subdivisions and large developments

  • Subdivisions


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Building Protection Standards Subdivisions and large developments

  • Subdivisions: Open Space Design


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NFIP Technical Bulletins

  • TB 1-93 Openings in Foundation Walls

  • TB 2-93 Flood-Resistant Material Requirements

  • TB 3-93 Non-Residential Floodproofing

  • TB 4-93 Elevator Installation

  • TB 5-93 Free of Obstruction Requirements in V Zone

  • TB 6-93 Below Grade Parking Requirements

  • TB 7-93 Wet Floodproofing Requirements

  • TB 8-06 Corrosion Protection for Metal Connectors

  • TB 9-99 Breakaway Walls

  • TB 10-01 Structures Built on Fill


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