(2) Hurricane Resistive (Zone II), (1) When a mobile home is designated as "Hurricane Resistive," the home and each wind resisting part and portion thereof shall be designed for horizontal wind loads not less than 25 psf and a net uplift not less than 15 psf. (ii) For exposures in coastal and other areas where wind records indicate significant differences, 125 mph or greater, from the wind loads stated above, the Department may establish more stringent requirements for homes known to be destined for such areas.

(3) Roof Loads. (i) Flat, curved and pitched roofs shall be designed to resist the following live loads, applied downward on the horizontal projection as appropriate for the design zone marked on the mobile home:

(11) For exposures in areas (mountaincus or other) where snow or wind records or experience indicate significant differences from the loads stated above, the Department may establish more stringent requirements for homes known to be destined for such areas. For snow loads, such requirements are to be based on a roof snow load of 0.6 of the ground snow load for areas exposed to wind and a roof snow load of 0.8 of the ground snow load for sheltered areas.

(ii) Eaves and cornices shall be designed for a net uplift pressure of 2.5 times the design uplift wind pressure cited in § 280.305(c) (1) and (2).

(4) The Data Plate posted in the mobile home (See § 280.5) shall show for which structural zone (s) of the USA the mobile home has been designed and the actual design external snow and/or wind live loads. The Data plate shall include reproduction of the Load Zone Maps shown in this Section and related information. The Load Zone Maps shall be not less than one-half the size illustrated.

Where L equals the clear span between supports or two times the length of a cantilever.

(e) Fastening of Structural Systems. Roof framing shall be securely fastened to wall framing, walls to floor structure, and floor structure to chassis to secure and maintain continuity between the floor and chassis, so as to resist wind overturning and sliding as imposed by design loads in this Part.

(f) Walls. The walls shall be of suffcient strength to withstand the load requirements as defined in § 280.305(c) of this part, without exceeding the deflections as specified in § 280.305(d). The connections between the bearing walls, floor, and roof framework members shall be fabricated in such a manner as to provide support for the material used to enclose the mobile home and to provide for transfer of all lateral and vertical loads to the floor and chassis.

(1) Except where substantiated by engineering analysis or tests, studs shall not be notched or drilled in the middle one-third of their length.

(2) Interior walls and partitions shall be constructed with structural capacity adequate for the intended purpose and shall be capable of resisting a horizontal load of not less than five pounds per square foot. Finish of walls and partitions shall be securely fastened to wall framing.

(g) Floors. (1) Floor assemblies shall be designed in accordance with accepted engineering practice standards to support a minimum uniform live load of 40 lb/ft' plus the dead load of the materials. In addition (but not simultaneously), floors shall be able to support a 200-pound concentrated load on a oneinch diameter disc at the most critical location with a maximum deflection not to exceed one-eighth inch relative to floor framing. Perimeter wood joists of more than six inches depth shall be stabilized against overturning from superimposed loads as follows: at ends by solid blocking not less than two-inch thickness by full depth of joist, or by connecting to a continuous header not

less than two-inch thickness and not less than the depth of the joist with connecting devices; at eight-feet maximum intermediate spacing by solid blocking or by wood cross-bridging of not less than one inch by three inches, metal crossbridging of equal strength, or by other approved methods.

(2) Wood, wood fibre or plywood floors or subfloors in kitchens, bathrooms (including toilet compartments), laundry rooms, water heater compartments, and any other areas subject to excessive moisture shall be moisture resistant or shall be made moisture resistant by sealing or by an overlay of nonabsorbent material applied with water-resistant adhesive. Carpets and/or carpet pads shall not be installed in concealed spaces subject to excessive moisture such as plumbing fixture spaces.

(3) Except where substantiated by engineering analysis or tests:

(1) Notches on the ends of joists shall not exceed one-fourth the joist depth.

(i) Holes bored in joists shall not be within 2 inches of the top or bottom of the joist, and the diameter of any such hole shall not exceed one-third the depth of the joist.

(iii) Notches in the top or bottom of the joists shall not exceed one-sixth the depth and shall not be located in the middle third of the span.

(4) Bottom board material (with or without patches) shall meet or exceed the level of 48 inch-pounds of puncture resistance as tested by the Beach Puncture Test in accordance with ASTM D781-68. The material shall be suitable for patches and the patch life shall be equivalent to the material life. Patch installation instruction shall be included in the mobile home manufacturer's instructions.

(h) Roofs. (1) Roofs shall be of sufficient strength to withstand the load requirements as defined in § 280.305 (b) and (c) without exceeding the deflections specified in § 280.305(d). The connections between roof framework members and bearing walls shall be fabricated in such a manner to provide for the transfer of design vertical and horizontal loads to the bearing walls and to resist uplift forces.

(2) Roofing membranes shall be of sufficient rigidity to prevent deflection which would permit ponding of water or separation of seams due to wind. snow, ice, erection or transportation forces.

(3) Cutting of roof framework members for passage of electrical, plumbing or mechanical systems shall not be allowed except where substantiated by engineering analysis

(4) All roof penetrations for electrical, plumbing or mechanical systems shall be properly flashed and sealed. In addition, where a metal roof membrane is penetrated, a wood backer shall be installed. The backer plate shall be not less than 5 inch plywood, with exterior glues, secured to the roof framing system beneath the metal roof, and shall be of a size to assure that all screws securing the flashing are held by the backer plate.

§ 280.306 Windstorm protection.

(a) Provisions for support and anchoring systems. Each mobile home shall have provisions for support and anchoring systems, which, when properly designed and installed, will resist overturning and lateral movement (sliding) of the moblie home as imposed by the respective design loads. The design wind loads to be utilized for calculating resistance to overturning and lateral movement shall be the wind loads indicated in § 280.305 (c) (1) and (2) increased by a factor of safety of 1.5. The basic allowable stresses of materials required to resist overturning and lateral movement shall not be increased in the design and proportioning these members.

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(1) The provisions of this section shall be followed and the support and anchoring systems shali be designed by a Registered Professional Engineer or Architect.

(2) The manufacturer of each mobile home is required to make provision for the support and anchoring systems but is not required to provide the anchoring equipment or stabilizing devices. When the manufacturer's installation instructions provide for the main frame structure to be used as the points for connection of diagonal ties, no specific connecuing devices need be provided on the main frame structure.

(b) The manufacturer shall provide printed instructions with each mobile home specifying the location and required capacity of stabilizing devices on which the design is based. The manufacturer shall provide drawings and specifications certified by a registered professional engineer indicating at least

one acceptable system of anchorage including the details of required straps or cables, their end connections and all other devices needed to transfer the wind loads from the mobile home to the ground anchors.

(c) The provisions made for anchoring systems shall be based on the following design criteria for mobile homes.

(1) The minimum number of ties required per side shall be as required to resist the design loads stated in § 280.305 (c) (1) and (2).

(2) Ties shall be as evenly spaced as practicable along the length of the mobile home with not more than 8 feet open-end spacing on each end.

(3) When continuous straps are provided as vertical ties, such ties shall be positioned at rafters and studs. Where a vertical tie and diagonal tie are located at the same place, both ties may be connected to a single ground anchor, provided that the anchor used is capable of carrying both loadings.

(4) Add-on sections of expandable mobile homes shall have provisions for vertical ties at the exposed ends.

(d) Double-wide mobile homes require only diagonal ties. These shall be placed along the main frame and below the outer side walls.

(e) Protection shall be provided at sharp corners where the anchoring system requires the use of external cables or straps. Protection shall also be provided to minimize damage to roofing or sliding by the cable or strap.

(f) Anchoring equipment shall be capable of resisting an allowable working load equal to or exceeding 3,150 pounds and shall be capable of withstanding a 50 percent overload (4,725 pounds total) without failure of either the anchoring equipment or the attachment point on the mobile home.

(g) Anchoring equipment exposed to weathering shall have a resistance to weather deterioration at least equivalent to that provided by a coating of zinc on steel of not less than 0.30 ounces per square foot of surface coated.

(1) Slit or cut edges of zinc-coated steel strapping do not need to be zinc coated.

(2) Type 1, Finish B. Grade 1 steel strapping, 14 inches wide and 0.035 inch thick, conforming with Federal Specification QQ-S-781-H, is judged to conform with the provisions of this section and paragraph (f) above.