home does not meet these requirements.

(e) New materials and methods. (1) Any new material or method of construction not provided for in this standard and any material or method of questioned suitability proposed for use in the manufacture of the structure shall nevertheless conform in performance to the requirements of this standard.

(2) Unless based on accepted engineering design for the use indicated, all new mobile home materials, equipment, systems or methods of construction not provided for in this standard shall be subjected to the tests specified in paragraph (g) of this section.

(f) Allowable design stress. The design stresses of all materials shall conform to accepted engineering practice. The use of materials not certified as to strength or stress grade shail be limited to the minimum allowable stresses under accepted engineering practice.

(g) Alternate test procedures. In the absence of listed and prescribed standards, the manufacturer shall develop or cause to be developed necessary tests to demonstrate the structural properties and the significant characteristics of the method employed. Such tests shall be witnessed by an in

dependent licensed professional engineer or architect or by a recognized testing organization. Copies of the test results shall be kept on file by the mobile home manufacturer.

§ 280.304 Materials.

(a) Dimension and board lumber shall not exceed 19 percent moisture content at time of installation.

(b)(1) Standards for some of the generally used materials and methods of construction are listed in the following table. (2) Materials and methods of construction utilized in the design and construction of mobile homes which are covered by the standards in the following table, or any applicable portion thereof shall comply with these requirements. (3) Engineering analysis and testing methods contained in these references shall be utilized to judge conformance with accepted engineering practices required in § 280.303(c). (4) Materials and methods of installation conforming to these standards shall be considered acceptable when installed in conformance with the requirements of this Part. (5) Materials meeting the standards (or the applicable portion thereof) are considered acceptable unless otherwise specified herein or unless substantial doubt exists as to conformance.

Steel:

Wood and wood products:

Hardboard

Hardwood and decorative plywood.

Structural design guide for hardwood plywood

Timber, structural glued laminated-inspection..

Timber, structural glued laminated

AISC and SJI AISI-1973

PS 58, 59, and 60-1973 USDC PS 51-71

HPMA-SG-71

AITC-200-1973

USD PS 56-73

rials Bulletin No. UM25d

ANSI Z97.1-1972

(c) Wood products shall be identified as complying with the appropriate standards.

[40 FR 58752, Dec. 18, 1975, as amended at 42 FR 961, Jan. 4, 1977]

§ 280.305 Structural design requirements.

(a) Each mobile home shall be designed and constructed as a completely integrated structure capable of sustaining the design load requirements of this standard and shall be capable of transmitting these loads to stabilizing devices without exceeding the allowable loads stresses or deflections. Roof framing shall be securely fastened to wall framing, walls to floor structure, and floor structure to chasIsis 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. Uncompressed finished flooring greater than inch in thickness, shall not extend beneath load bearing walls which are fastened to the floor structure.

(b) Design Loads. (1) Design dead loads. Design dead loads shall be the actual dead load supported by the structural assembly under consideration. (2) Design live loads. The design live loads and wind and snow loads shall be as specified in this Section and shall be considered to be uniformly distributed. The roof live load or snow load shall not be considered as acting simultaneously with the wind load and the roof live or snow load and floor live loads shall not be considered as resisting the overturning moment

due to wind. (3) When engineering calculations are performed, allowable unit stresses may be increased as provided in the documents referenced in § 280.304 except as shown otherwise in § 280.306(a).

(c) Wind, Snow and Roof Loads. (1) Standard Wind (Zone I). When a mobile home is not designated as "Hurricane-Resistive," the mobile home and each wind resisting part and portion thereof shall be designed for horizontal wind loads not less than 15 psf and a net uplift load of not less than 9 psf.

(2) Hurricane Resistive (Zone II). (i) 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.

cant 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.

(iii) 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 onehalf the size illustrated.

(d) Design Load Deflection. When a structural assembly is subjected to total design live loads, the deflection for structural framing members shall not exceed the following:

(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 sufficient 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/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