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FEMA 550 - Recommended Residential Construction for the Gulf Coast

2. FEMA 550 - Recommended Residential Construction for the Gulf Coast. BackgroundHurricane Katrina confirmed that homes need to be higher to avoid flood damagesInterim 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.

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FEMA 550 - Recommended Residential Construction for the Gulf Coast

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    1. FEMA 550 - Recommended Residential Construction for the Gulf Coast Building on Strong and Safe Foundations

    2. 2 FEMA 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

    3. 3 Homes need to be built higher... Apartment complex with +/- 20 seaward buildings destroyed (only slabs are left) and washed back into other buildings. Documented 5 ft of stillwater flooding in standing building behind debris pile. Poorly constructed buildings (no building paper, minimal (no?) hurricane connectors, poor shingle attachment, cheap construction)Apartment complex with +/- 20 seaward buildings destroyed (only slabs are left) and washed back into other buildings. Documented 5 ft of stillwater flooding in standing building behind debris pile. Poorly constructed buildings (no building paper, minimal (no?) hurricane connectors, poor shingle attachment, cheap construction)

    4. 4 FEMA 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

    5. 5 FEMA 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

    6. 6 FEMA 550 - Recommended Residential Construction for the Gulf Coast Flood Issues

    7. 7 FEMA 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 < 1.5 feet Either open or enclosed foundations allowed

    8. 8 FEMA 550 - Recommended Residential Construction for the Gulf Coast

    9. 9 FEMA 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

    10. 10 FEMA 550 - Recommended Residential Construction for the Gulf Coast

    11. 11 FEMA 550 - Recommended Residential Construction for the Gulf Coast

    12. 12 FEMA 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

    13. 13 FEMA 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

    14. 14 FEMA 550 - Recommended Residential Construction for the Gulf Coast Wind Issues

    15. 15 FEMA 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

    16. 16 FEMA 550 - Recommended Residential Construction for the Gulf Coast

    17. 17 FEMA 550 - Recommended Residential Construction for the Gulf Coast Analysis and Design Issues

    18. 18 FEMA 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

    19. 19 FEMA 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

    20. 20 FEMA 550 - Recommended Residential Construction for the Gulf Coast Loads on Home

    21. 21 FEMA 550 - Recommended Residential Construction for the Gulf Coast Loads on Foundation

    22. 22 FEMA 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%)

    23. 23 FEMA 550 - Recommended Residential Construction for the Gulf Coast

    24. 24 FEMA 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

    25. 25 FEMA 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

    26. 26 FEMA 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

    27. 27 FEMA 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

    28. 28 FEMA 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

    29. 29 FEMA 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

    30. 30 FEMA 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

    31. 31 FEMA 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

    32. 32 FEMA 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

    33. 33 FEMA 550 - Recommended Residential Construction for the Gulf Coast

    34. 34 FEMA 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

    35. 35 FEMA 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

    36. 36 FEMA 550 - Recommended Residential Construction for the Gulf Coast

    37. 37 FEMA 550 - Recommended Residential Construction for the Gulf Coast Typical foundation footprint 24’ by 14’ bays Maximum 42’ depth (with additional row of piers)

    38. 38 FEMA 550 - Recommended Residential Construction for the Gulf Coast Gulf Coast Builder’s 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

    39. 39 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 FEMA 550 - Recommended Residential Construction for the Gulf Coast

    40. 40 FEMA 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

    41. 41 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 FEMA 550 - Recommended Residential Construction for the Gulf Coast

    42. 42 FEMA 550 - Recommended Residential Construction for the Gulf Coast Foundations for “Other Homes” - If home doesn’t 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 12:12 pitch Very heavy (gravity) or very light homes (uplift)

    43. 43 FEMA 550 - Recommended Residential Construction for the Gulf Coast If home doesn’t 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

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