as

(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 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 twoinch 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:

(i) Notches on the ends of joists shall not exceed one-fourth the joist 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

and (c) without exceeding the detions specified in § 3280.305(d). e connections between roof frame-k members and bearing walls shall fabricated in such a manner to proe for the transfer of design vertical I horizontal loads to the bearing ls and to resist uplift forces. 2) Roofing membranes shall be of ficient rigidity to prevent deflecn which would permit ponding of cer or separation of seams due to d, snow, ice, erection or transportan forces.

3) Cutting of roof framework mems for passage of electrical, plumb- or mechanical systems shall not be owed except where substantiated by gineering analysis.

4) All roof penetrations for electri1, plumbing or mechanical systems all be properly flashed and sealed. addition, where a metal roof memane is penetrated, a wood backer all be installed. The backer plate all be not less than 16 inch plypod, with exterior glues, secured to e roof framing system beneath the etal roof, and shall be of a size to sure that all screws securing the ashing are held by the backer plate. (i) Frame construction. The frame all be capable of transmitting all esign loads to stabilizing devices ithout exceeding the allowable load nd deflections of this section. The ame shall also be capable of withanding the effects of transportation nock 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 lesign of cold-formed steel structural nembers 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

required by $ 3280.203 shall be installed in the factory.

(e) Vertical clearance above cooking top. Ranges shall have a vertical clearance above the cooking top of not less than 24 inches to the bottom of combustible cabinets.

§ 3280.205 Carpeting.

Carpeting shall not be used in a space or compartment designed to contain only a furnace and/or water heater. Carpeting may be used in other areas where a furnace or water heater is installed, provided that it is not located under the furnace or water heater.

§ 3280.206 Firestopping.

(a) Firestopping of at least 1-inch nominal lumber, 5/16-inch thick gypsum board, or the equivalent, shall be provided to cut off concealed draft openings between walls and partitions, including furred spaces, and the roof or floors, so as to retard vertical movement of fire. In particular, such concealed spaces must be constructed so that floor-to-ceiling concealed spaces on one floor do not communicate with any concealed space on another floor, any concealed spaces in the floor, or any concealed space in the roof cavity. A barrier must be installed to prevent communication between adjacent concealed spaces.

(1) Where the barrier is vertical, it must be made of exterior or interior covering(s) equivalent to that used on the nearest exposed wall surface; and

(2) In all other cases, the barrier must be made of 1-inch nominal lumber, 16-inch thick gypsum board, or the equivalent.

(b) A space does not lose its character as a concealed draft opening if it is filled with insulation or other material or if it is blocked by a barrier other than as required by paragraph (a) of this section.

(c) All openings for pipes and vents and other penetrations in walls, floors, and ceilings of furnace and water heater spaces shall be tight-fitted or firestopped. Pipes, vents, and other penetrations are tight-fitted when they cannot be moved freely in the opening.

§ 3280.207 Requirements for foam plastic thermal insulating materials.

(a) General. Foam plastic therma insulating materials shall not be used within the cavity of walls (not includ ing doors) or ceilings or be exposed t the interior of the home unless:

(1) The foam plastic insulating mate rial is protected by an interior finish of 16-inch thick gypsum board o equivalent material for all cavities where the material is to be installed

or

(2) The foam plastic is used as sheathing or siding backerboard, an it: (i) Has a flame spread rating of 75 or less and a smoke-developed rating of 450 or less (not including outer cov ering of sheathing); (ii) does not exceed %-inch in thickness; and (iii) i separated from the interior of the manufactured home by a minimum of 2 inches of mineral fiber insulation or an equivalent thermal barrier; or

(3) The foam plastic insulating mate rial has been previously accepted by the Department for use in wall and/or ceiling cavities of manufactured homes, and it is installed in accordance with any restrictions imposed at the time of that acceptance; or

(4) The foam plastic insulating material has been tested as required for its location in wall and/or ceiling cavities in accordance with testing procedures described in the Illinois Institute of Technology Research Institute (IITRI) Report, "Development of Mobile Home Fire Test Methods to Judge the Fire Safe Performance of Foam Plastic, J-6461," or other fullscale fire tests accepted by the Depart ment, and it is installed in a manner consistent with the way the material was installed in the foam plastic test module. The materials shall be capa ble of meeting the following acceptance criteria required for their loca tion.

(i) Wall assemblies. The foam plastic system shall demonstrate equivalent or superior performance to the control module as determined by:

(A) Time to reach flashover (600°C in the upper part of the room);

(B) Time to reach an oxygen (0) level of 14% (rate of O2 depletion), a carbon monoxide (CO) level of 1%. a