P 85 Fema P85 Apndx G

G. Wind Zone Comparisons

(HUD's MHCSS and

FEMA 85)

G.1 Background

HUD’s Manufactured Home Construction and Safety Standards (MHCSS; 24 CFR 3280) and its Model

Manufactured Home Installation Standards (24 CFR 3285) categorize the United States and many

of its territories and protectorates into three wind zones: Zone I, Zone II, and the highest wind

zone, Zone III.

FEMA 85, NFPA 225 Model Manufactured Home Installation Standard, and NFPA 501 Standard on

The HUD standards, FEMA 85, and the NFPA standards all contain wind provisions based on

ASCE 7, Minimum Design Loads for Buildings and Other Structures; however, they are not all based

on the same edition of ASCE 7. HUD documents are based on a modified version of the 1988

edition of ASCE 7. FEMA 85 and the NFPA standards are based on more recent editions. The

wind loads used to design FEMA 85 foundations comply with ASCE 7-02; the NFPA standards

reference ASCE 7-05.

Only minor differences exist between the wind provisions of ASCE 7-05 and ASCE 7-02; however,

the wind provisions of both ASCE 7-05 and ASCE 7-02 differ greatly from the wind provisions

of ASCE 7-88.

Two major differences exist between ASCE 7-88 and ASCE 7-05. The basic wind speed map (Fig-

fastest mile wind speeds; ASCE 7-02 and 7-05 use 3-second gust wind speeds. The wind speeds in

the older standard are numerically less than those in the contemporary standards. For example,

ASCE 7-88 required buildings in the interior portion of the U.S. to be designed for a 70-mph

(fastest mile) wind speed; ASCE 7-02 and 7-05 place the interior portions of the U.S. in a 90-mph

(3-second gust) wind speed area. While the wind speeds are numerically greater, the design wind

loads are often not greater and, in some areas, the wind loads are less.

G.3 Wind Zones

HUD Zone II: Areas where the basic wind speed is 100 mph (fastest mile)

Zone 3: Areas between the 110-mph and the 130-mph isotachs

Zone 4: Areas between the 130-mph and the 150-mph isotachs

Figure G-1 shows the HUD wind speed map contained in 24 CFR 3280. Figure G-2 shows the

wind speed map used for FEMA 85 and the NFPA standards.

Note that the 2006 IBC Section §1609.3.1 shows the relationship between fastest mile and 3-sec-

ond gust wind speeds.

Vfm = (V3 sec – 10.5)/1.05

Where: Vfm = Fastest mile wind speed (mph)

V3 sec = 3-second gust wind speed (mph)

WIND ZONE COMPARISONS (HUD'S MHCSS AND FEMA 85) g

WIND ZONE COMPARISONS (HUD'S MHCSS AND FEMA 85) g

G.4 Wind Speeds and County Lists

Wind speeds for communities are typically determined when building codes are adopted. The

wind speeds should agree with those specified by ASCE 7, but are often decided upon by local

officials particularly in large municipalities where several wind speeds apply.

For manufactured homes, wind zones are specified by the MHCSS and are listed by State and

County. The MHCSS lists Counties contained in Wind Zones II and III. By default, all Counties

not listed as either in Zone II or III are in HUD Zone I.

The following list identifies Counties by State for the various wind zones used in FEMA 85.

Counties that are not listed or that are within the 90-mph isotach are in Zone 1.

The U.S. Territories of Guam, Northern Mariana Islands, Puerto Rico, Trust Territory of the Pa-

cific Islands, and the United States Virgin Islands

Alabama: Baldwin, Mobile

Alaska: The coastal regions seaward of the 110-mph isotach on the ASCE 7 map

Connecticut: Middlesex, New London

Florida: Bay, Brevard, Calhoun, Charlotte, Citrus, Collier, DeSoto, Dixie, Duval, Escambia, Fla-

gler, Gulf, Hendry, Hernando, Hillsborough, Holmes, Indian River, Jackson, Lee, Levy, Liberty,

Manatee, Nassau, Okaloosa, Okeechobee, Pasco, Pinellas, Santa Rosa, Sarasota, St. Johns, St. Lu-

Mississippi: George, Greene, Hancock, Harrison, Pearl River, Perry, Stone

New Jersey: Atlantic, Cape May, Ocean

New York: Nassau, Suffolk

North Carolina: Beaufort, Camden, Chowan, Columbus, Craven, Currituck, Dare, Hyde, Jones,

New Hanover, Onslow, Pamlico, Pasquotank, Pender, Perquimans, Tyrrell, Washington

Rhode Island: Bristol, Kent, Newport, Washington

South Carolina: Beaufort, Charleston, Georgetown, Horry

Texas: Brazoria, Calhoun, Chambers, Galveston, Jefferson, Kenedy, Kleberg, Matagorda, Nuec-

es, Refugio, San Patricio, Willacy

Virginia: Accomack, Northampton

Florida: Alachua, Baker, Bradford, Clay, Columbia, De Soto, Gadsden, Gilchrist, Glades, Ham-

ilton, Hardee, Highlands, Jefferson, Lafayette, Lake, Leon, Madison, Marion, Orange, Osceola,

Putnam, Polk, Seminole, Sumter, Suwannee, Union

Georgia: Appling, Atkinson, Bacon, Baker, Baldwin, Ben Hill, Berrien, Bibb, Bleckley, Brant-

ley, Brooks, Bulloch, Burke, Calhoun, Charlton, Chattahoochee, Clay, Clinch, Coffee, Colquitt,

Columbia, Cook, Crawford, Crisp, Decatur, Dodge, Dooly, Dougherty, Early, Echols, Effingham,

Emanuel, Evans, Glascock, Grady, Hancock, Harris, Houston, Irwin, Jeff Davis, Jefferson, Jen-

kins, Johnson, Jones, Lamar, Lanier, Laurens, Lee, Long, Lowndes, Macon, Marion, McDuffie,

Meriwether, Miller, Mitchell, Monroe, Montgomery, Muscogee, Peach, Pierce, Pike, Pulaski,

Quitman, Randolph, Richmond, Schley, Screven, Seminole, Stewart, Sumter, Talbot, Tattnall,

WIND ZONE COMPARISONS (HUD'S MHCSS AND FEMA 85) g

Vernon, Washington, West Baton Rouge, West Feliciana

Maine: Androscoggin, Cumberland, Hancock, Kennebec, Knox, Lincoln, Sagadahoc, Waldo,

York

Maryland: Caroline, Dorchester, Queen Annes, Talbot, Wicomico

Massachusetts: Bristol, Essex, Franklin, Hampden, Hampshire, Middlesex, Norfolk, Suffolk,

Worcester

Mississippi: Adams, Amite, Claiborne, Clarke, Copiah, Covington, Forrest, Franklin, Hinds, Jas-

per, Jefferson, Jefferson Davis, Jones, Kemper, Lamar, Lauderdale, Lawrence, Leake, Lincoln,

Marion, Neshoba, Newton, Noxubee, Pike, Rankin, Scott, Simpson, Smith, Walthall, Wayne,

Wilkinson, Winston

Scotland, Wayne, Wilson

Pennsylvania: none

Rhode Island: Providence

South Carolina: Aiken, Allendale, Bamberg, Barnwell, Berkeley, Calhoun, Chesterfield, Claren-

don, Colleton, Darlington, Dillon, Dorchester, Fairfield, Florence, Hampton, Jasper, Kershaw,

Lancaster, Lee, Lexington, Marion, Marlboro, Orangeburg, Richland, Sumter, Williamsburg

Texas: Angelina, Atascosa, Austin, Bastrop, Bee, Brooks, Burleson, Caldwell, Colorado, De Witt,

Duval, Fayette, Fort Bend, Goliad, Gonzales, Grimes, Guadalupe, Hardin, Harris, Hidalgo, Jack-

son, Jasper, Jim Hogg, Jim Wells, Karnes, Lavaca, Lee, Liberty, Live Oak, McMullen, Montgomery,

Newton, Orange, Polk, San Jacinto, Starr, Trinity, Tyler, Victoria, Walker, Waller, Washington,