Title: FEMA 550 Recommended Residential Construction for the Gulf Coast
1FEMA 550 -Recommended Residential Construction
for the Gulf Coast
- Building on Strong and Safe Foundations
April 2006
2FEMA 550 - Recommended Residential Construction
for the Gulf Coast
- Background
- Hurricane Katrina confirmed that homes need to be
higher to avoid flood damages - Interim Advisory Base Flood Elevations (ABFEs)
Issued Fall 2005 increase Base Flood Elevations
up to 15 feet (/-) - New BFEs are scheduled to be completed in 2006
3Homes need to be built higher...
4FEMA 550 - Recommended Residential Construction
for the Gulf Coast
- Many of the foundations historically used are not
adequate for the higher flood elevations - New Approaches to elevate homes are needed
5FEMA 550 - Recommended Residential Construction
for the Gulf Coast
- Project Goals
- Develop multi-hazard residential foundation
concepts - Provide designs for specific homes that can used
off the shelf - Provide designs that, when needed, can be
modified by local engineers with a minimal amount
of effort - Satisfy needs of 80 of homes being rebuilt in
the Gulf Coast - Use conventional materials and methods where
possible - Develop foundations that will support many of the
Mississippi Renewal Forum Pattern Book home
designs - Get input from local builders
6FEMA 550 - Recommended Residential Construction
for the Gulf Coast
7FEMA 550 - Recommended Residential Construction
for the Gulf Coast
- Flood Zones
- V Zone
- Breaking wave height Hb three feet or greater
- Open foundations required
- Coastal A Zone
- Breaking wave height Hb 1.5 feet to 3 feet
- Open foundations recommended
- Non Coastal A Zone
- Breaking wave height Hb lt 1.5 feet
- Either open or enclosed foundations allowed
8FEMA 550 - Recommended Residential Construction
for the Gulf Coast
9FEMA 550 - Recommended Residential Construction
for the Gulf Coast
- Elevation Required
- Homes must be elevated to the BFE
- BFEs are referenced to a vertical datum
(NAVD/NGVD) - Local topography provides some elevation
- Topography must be considered when determining
how high H above exterior grade a home must be
elevated - Many homes need to be elevated less than 8 feet
- Relatively few homes will need to be elevated
over 20 feet
10FEMA 550 - Recommended Residential Construction
for the Gulf Coast
11FEMA 550 - Recommended Residential Construction
for the Gulf Coast
Example Home located on site with an estimated
flood elevation of 18 ft. Site elevation is 14
ft NAVD. Home would need to be elevated 4 ft
(18 14) above grade.
12FEMA 550 - Recommended Residential Construction
for the Gulf Coast
- Elevation
- Designs provided for a range of foundation
heights - Enclosed foundations up to 8 feet
- Open foundations up to 15 feet
- Designs provided for one and two-story homes
- Designs for V-Zone, Coastal A-Zone and
Non-Coastal A Zone
13FEMA 550 - Recommended Residential Construction
for the Gulf Coast
- Flood Zones
- A Zone (enclosed foundations) limited wave action
- Coastal A Zone (recommended open foundations)
limited wave action - V Zone (open foundations) wave action
- Wave action taken into account for V Zone
foundations - Also
- Scour
- Erosion
14FEMA 550 - Recommended Residential Construction
for the Gulf Coast
15FEMA 550 - Recommended Residential Construction
for the Gulf Coast
- Wind Speed1
- Gulf Coast Communities
- 120 to 150 miles per hour (3-second gust)
- A small area SE of Pascagoula, MS and the SW tip
of Plaquemines Parish, LA have design wind speeds
in excess of 150 mph - 1ASCE 7-02/International Building Code
16FEMA 550 - Recommended Residential Construction
for the Gulf Coast
17FEMA 550 - Recommended Residential Construction
for the Gulf Coast
- Analysis and Design Issues
18FEMA 550 - Recommended Residential Construction
for the Gulf Coast
- Analysis
- Determine loads that the foundation must resist
- Includes loads on the elevated home
- Wind
- Dead loads
- Live loads
- Loads imposed directly on the foundation
- Dead loads
- Wind loads
- Flood loads
19FEMA 550 - Recommended Residential Construction
for the Gulf Coast
- Loads Determined for a Design Event
- 50 year (MRI) for wind MRI Mean Recurrence
Interval - 100 year (MRI) for flood
- Seismic (in some areas)
- Snow (in some areas)
- Others
- Building Codes
- IRC
- IBC
- Consensus Standards Guidance Documents
- ASCE 7-02 FEMA 55 Coastal Construction
- ASCE 24-98 Manual
20FEMA 550 - Recommended Residential Construction
for the Gulf Coast
21FEMA 550 - Recommended Residential Construction
for the Gulf Coast
22FEMA 550 - Recommended Residential Construction
for the Gulf Coast
- Load Combinations
- Address simultaneous loading
- Wind, flood, gravity, etc.
- Chapter 2 of ASCE 7
- Basic load combinations (apply everywhere)
- Dead load, live load, wind load, etc.
- Adds flood loads
- V and Coastal A (150)
- Non-Coastal A (75)
23FEMA 550 - Recommended Residential Construction
for the Gulf Coast
24FEMA 550 - Recommended Residential Construction
for the Gulf Coast
- Design
- After loads are determined design foundation to
resist those loads - Engineering Consensus Standards
- American Concrete Institute - ACI (concrete)
- American Institute of Steel Construction Inc -
AISC (steel) - National Design Standard NDS (wood)
- Others
25FEMA 550 - Recommended Residential Construction
for the Gulf Coast
- Designs
- Case A - Driven Braced Timber Pile - Deep
- Case B - Steel Pipe Pile with Grade Beam - Deep
- Case C - Driven Timber Pile with Grade Beam -
Deep - Case D - Grade Beam/Waffle Foundation - Shallow
- Case E - Masonry Crawl Space Foundation - Shallow
- Case F - Masonry Stem Wall Foundation - Shallow
- Case G - Grade Beam/Mat Foundation - Shallow
- Foundations reviewed by Gulf Coast Homebuilders
Association
26FEMA 550 - Recommended Residential Construction
for the Gulf Coast
- Case A - Driven Braced Timber Pile
- Good for V, Coastal A, or A Zones
- Maximum height above ground level is 10 feet
- Deep foundation
27FEMA 550 - Recommended Residential Construction
for the Gulf Coast
- Case B - Steel Pile with Grade Beam
- Concrete column above ground level
- Good for V, Coastal A, and A Zones
- Suitable for elevations up to 15 feet above grade
- Deep foundation
28FEMA 550 - Recommended Residential Construction
for the Gulf Coast
- Case C - Driven Braced Timber Pile with Pile Cap
- Concrete column above ground level
- Good for V, Coastal A, and A Zones
- Suitable for elevations up to 15 feet above grade
- Deep foundation
29FEMA 550 - Recommended Residential Construction
for the Gulf Coast
- Case D - Grade Beam/Waffle Foundation
- Good for A Zones (and Coastal A where scour and
erosion is limited) - Maximum height above ground level is 8 feet
- Shallow foundation
30FEMA 550 - Recommended Residential Construction
for the Gulf Coast
- Case G - Grade Beam/Mat Foundation
- Concrete column on concrete grade beam
- Reinforced slab provides additional uplift
resistance - Good for A zone
- Maximum height above ground level is 8 feet
- Shallow foundation
31FEMA 550 - Recommended Residential Construction
for the Gulf Coast
- Case E - Masonry Crawl Space Foundation
- Good for A Zone only
- Maximum height above ground level is 8 feet
- Shallow foundation
32FEMA 550 - Recommended Residential Construction
for the Gulf Coast
- Case F - Masonry Stem Wall Foundation
- Good for A Zone only
- Maximum height above ground level is 4 feet
- Shallow foundation
33FEMA 550 - Recommended Residential Construction
for the Gulf Coast
? Acceptable NR Not Recommended ?
Not Permitted
34FEMA 550 - Recommended Residential Construction
for the Gulf Coast
- Design Approach for use
- Design foundation in modules
- Combine modules to create an actual building
footprint - Modules are for one and two story homes
35FEMA 550 - Recommended Residential Construction
for the Gulf Coast
- Modules
- Design foundation in modules
- Design for minimum 24 by 28 house
- Design for maximum 42 depth
- Expand by 14 by 24 bay
- House widths can readily be increased by bay
widths (14 feet) - House depths can not readily be increased or
decreased and will require custom designs
36FEMA 550 - Recommended Residential Construction
for the Gulf Coast
37FEMA 550 - Recommended Residential Construction
for the Gulf Coast
- Typical foundation footprint
- 24 by 14 bays
- Maximum 42 depth (with additional row of piers)
38FEMA 550 - Recommended Residential Construction
for the Gulf Coast
- Gulf Coast Builders Review
- Deep Open Foundations (Cases A, B C)
- Piles are new approaches for residential
construction in many Gulf Coast areas - Pile Driving Contractors are not abundant in all
areas of the Gulf Coast - Minor adjustments to existing construction
methods required - not considered a major hurdle - Wood piles not anticipated to be widely used but
they wanted to have the option
39FEMA 550 - Recommended Residential Construction
for the Gulf Coast
- Shallow Open Foundations (Cases D G)
- Similar to existing coastal building practice
- Concrete columns are recommended where masonry
has historically been used - Minor adjustments to existing construction
methods required but not a major hurdle - Enclosed Foundations (Cases E F)
- Known construction technique
- Common practice for elevation in A zone
40FEMA 550 - Recommended Residential Construction
for the Gulf Coast
- Costs
- Cost in manual will be based on March 2006 prices
- General costs for the foundations have been
evaluated by construction contractors along the
coast. - Costs for Pile Driving have the greatest
variability in much of the Gulf Coast - Costs variations expected as reconstruction
commences - Labor prices rising due to demand
- Material prices rising with increased demand
- Economy of scale for homes reconstruction should
be sought
41FEMA 550 - Recommended Residential Construction
for the Gulf Coast
- Model Home evaluated for cost estimates as 28
foot by 42 foot home elevated 8 feet - Cost adjustments will be provided for taller and
shorter foundations - Open Deep Foundations 20K
- Open Shallow Foundations 10K
- Closed Shallow Foundations 8K
42FEMA 550 - Recommended Residential Construction
for the Gulf Coast
- Foundations for Other Homes - If home doesnt
match criteria used in the designs - Elevations greater than 15 feet
- Slender homes (less than 24 feet deep)
- Homes with flat roofs or roofs greater than 1212
pitch - Very heavy (gravity) or very light homes (uplift)
43FEMA 550 - Recommended Residential Construction
for the Gulf Coast
- If home doesnt match criteria used in the
designs - Consult with a licensed professional engineer to
design the foundation - Analyze loads per IBC/IRC or ASCE 7
- Use the Coastal Construction Manual, FEMA 55, for
guidance on issues not covered in the Model Codes
(IBC or NFPA 5000) and Standards (eg. ASCE-7,
ASCE-24) - Recommend following guidance found in other FEMA
publications to make homes more hazard resistant
than criteria contained in Model Codes
44(No Transcript)