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(f) Walls. The walls shall be of sufficient strength to withstand the load requirements defined in § 3280.305(c) of this part, without exceeding the deflections as specified in § 3280.305(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 manufactured 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/ft2 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 one-inch 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 ince depth shall be stabilized against o turning from superimposed loads a follows: at ends by solid blocking less than two-inch thickness by depth of joist, or by connecting w. continuous header not less than t inch thickness and not less than t depth of the joist with connecting > vices; at eight-feet maximum intern diate spacing by solid blocking or = wood cross-bridging of not less tha one inch by three inches, metal cros bridging of equal strength, or by othe approved methods.

(2) Wood, wood fibre or plywood floors or subfloors in kitchens, bath rooms (including toilet compar ments), laundry rooms, water heate compartments, and any other area subject to excessive moisture shall & moisture resistant or shall be mad moisture resistant by sealing or by ar overlay of nonabsorbent material ap plied 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:

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

(ii) 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 puncture and stiffness of paperboard, corrogated and solid fiberboard. ASTM D-781-1968. 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 manufactured home manufacturer's instructions.

(h) Roofs. (1) Roofs shall be of sufficient strength to withstand the load requirements as defined in § 3280.305

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(c) without exceeding the de

specified in § 3280.305(d). nnections between roof frameembers and bearing walls shall icated in such a manner to pror the transfer of design vertical orizontal loads to the bearing nd to resist uplift forces. Roofing membranes shall be of ent rigidity to prevent deflecwhich would permit ponding of or separation of seams due to snow, ice, erection or transportaorces.

Cutting of roof framework memfor passage of electrical, plumb· mechanical systems shall not be ed except where substantiated by eering analysis.

All roof penetrations for electriplumbing or mechanical systems be properly flashed and sealed. ddition, where a metal roof meme is penetrated, a wood backer I be installed. The backer plate 1 be not less than 5/16 inch plyd, with exterior glues, secured to roof framing system beneath the al roof, and shall be of a size to ure that all screws securing the hing are held by the backer plate. ) Frame construction. The frame ll be capable of transmitting all sign loads to stabilizing devices Chout exceeding the allowable load d deflections of this section. The me shall also be capable of withanding the effects of transportation ock and vibration without degradaon as required by Subpart J.

(1) Welded connections. (i) All welds hall be made in accordance with the pplicable provisions of the specificaion for the design, fabrication, and rection of structural steel for buildngs, with supplements 1, 2 and 3, AISC-1973. The specification for the design of cold-formed steel structural members with addendum 1, AISI-1968 and the specification for the design of stainless steel cold-formed structural design manual, AISI 1974.

(ii) Regardless of the provisions of any reference standard contained in this subpart, deposits of weld slag or flux shall be required to be removed only from welded joints at the following locations:

(A) Drawbar and coupling mechanisms;

(B) Main member splices, and

(C) Spring hanger to main member connections.

(2) Protection of metal frames against corrosion. Metal frames shall be made corrosion resistant or protected against corrosion. Metal frames may be protected against corrosion by painting.

(Sec. 625 of the National Manufactured Housing Construction and Safety Standards Act of 1974, 42 U.S.C. 5424)

[40 FR 58752, Dec. 18, 1975. Redesignated at 44 FR 20679, Apr. 6, 1979, and amended at 44 FR 66195, Nov. 19, 1979; 47 FR 49386, Nov. 1, 1982; 48 FR 5267, Feb. 4, 1983; 48 FR 13165, Mar. 30, 1983]

§ 3280.306 Windstorm protection.

(a) Provisions for support and anchoring systems. Each manufactured home shall have provisions for support and anchoring systems, which, when properly designed and installed, will resist overturning and lateral movement (sliding) of the manufactured 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 § 3280.305(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 of these members.

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

(2) The manufacturer of each manufactured 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 connecting devices need be provided on the main frame structure.

(b) The manufacturer shall provide printed instructions with each manu

factured 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 manufactured home to the ground anchors.

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

(1) The minimum number of ties required per side shall be as required to resist the design loads stated in § 3280.305(c) (1) and (2).

(2) Ties shall be as evenly spaced as practicable along the length of the manufactured 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 ties 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 manufactured homes shall have provisions for vertical ties at the exposed ends.

(d) Double-wide manufactured 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 manufactured home.

(g) Anchoring equipment exposed to weathering shall have a resistance to weather deterioration at least equiva lent to that provided by a coating of zinc on steel of not less than 0.31 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 stee strapping, 14 inches wide and 0.035 inch thick, conforming with Federal Specification strapping, steel and seals FS QQ-S-781H-1974 is judged to conform with the provisions of this sec tion and paragraph (f) of this section

(Sec. 625 of the National Manufactured Housing Construction and Safety Standard Act of 1974, 42 U.S.C. 5424)

[40 FR 58752, Dec. 18, 1975. Redesignated & 44 FR 20679, Apr. 6, 1979, and amended at 47 FR 49386, Nov. 1, 1982; 48 FR 5267, Feb. 4, 1983]

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§ 3280.307 Resistance to elements and use (a) Exterior coverings shall be of moisture and weather resistive materi-g als attached with corrosion resistant in fasteners to resist wind, snow and rain Metal coverings and exposed metal structural members shall be of corrosion resistant materials or shall be protected to resist corrosion. All joints between portions of the exterior covering shall be designed, and assembled to protect against the infiltration of air and water, except for any designed ventilation of wall or roof cavity.

(b) Joints between dissimilar materials and joints between exterior coverings and frames of openings shall be protected with a compatible sealant suitable to resist infiltration of air or water.

(c) Where adjoining materials or assemblies of materials are of such nature that separation can occur due to expansion, contraction, wind loads or other loads induced by erection or transportation, sealants shall be of a type that maintains protection against infiltration or penetration by air.

moisture or vermin.

(d) Exterior surfaces shall be sealed to resist the entrance of rodents

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