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 D-781-68. 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 16 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 mobile 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 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 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 connecting 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 ties are lo

cated 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) of this section.

§ 280.307 Resistance to elements and use. (a) Exterior coverings shall be of moisture and weather resistive materials attached with corrosion resistant 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 cover

ings 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. Subpart E-Testing

§ 280.401 Structural load tests.

Every structural assembly tested shall be capable of meeting the Proof Load Test or the Ultimate Load Test as follows:

(a) Proof load tests. Every structural assembly tested shall be capable of sustaining its dead load plus superimposed live loads equal to 1.75 times the required live loads for a period of 12 hours without failure. Tests shall be conducted with loads applied and deflections recorded in 1⁄4 design live load increments at 10-minute intervals until 1.25 times design live load plus dead load has been reached. Additional load shall then be applied continuously until 1.75 times design live load plus dead load has been reached. Assembly failure shall be considered as design live load deflection (or residual deflection measured 12 hours after live load removal) which is greater than the limits set in § 280.305(d), rupture, fracture, or excessive yielding. An assembly to be tested shall be of the minimum quality of materials and workmanship of the production. Each test assembly, component or subassembly shall be identified as to type and quality or grade of material. All assemblies, components or subassemblies qualifying under this section shall be subject to a continuing qualification testing program acceptable to the Department.

(b) Ultimate load tests. Ultimate load tests shall be performed on a minimum of three assemblies to generally evaluate the structural design. Every structural assembly tested shall be capable of sustaining its total dead load plus live loads increased by a

factor of safety consistent with the material being tested. Factors of safety shall be based on nationally recognized standards and approved by the Department. Tests shall be conducted with loads applied and deflections recorded in 4 design live load increments at 10-minute intervals until 1.25 times design live load plus dead load has been reached. Additional loading shall then be applied continuously until failure occurs or 1.50 times the factor of safety times the design live load plus the dead load is reached. Assembly failure shall be considered as design live load deflection greater than the limits set in § 208.305(d) rupture, fracture, or excessive yielding. Assemblies to be tested shall be representative of average quality or materials and workmanship of the production. Each test assembly, component, or subassembly shall be identified as to type and quality or grade of material. All assemblies, components, or subassemblies qualifying under this section shall be subject to a periodic qualification testing program acceptable to the Department.

§ 280.402 Test procedure for roof trusses. (a) Roof load tests. The following is an acceptable test procedure, consistent with the provisions of § 280.401, for roof trusses that are supported at the ends and support design loads. Where roof trusses act as support for other members, act as cantilevers, or support concentrated loads, they shall be tested accordingly.

(b) General. Trusses may be tested in pairs or singly in a suitable test facility. When tested singly, simulated lateral support of the test assembly may be provided, but in no case shall this lateral support exceed that which is specified for the completed mobile home. When tested in pairs, the trusses shall be spaced at the design spacing and shall be mounted on solid support accurately positioned to give the required clear span distance (L) as specified in the design. The top and bottom chords shall be braced and covered with the material, with connections or method of attachment, as specified by the completed mobile home.

(1) As an alternate test procedure, the top chord may be sheathed with

inch by 12 inch plywood strips. The plywood strips shall be at least long enough to cover the top chords of the trusses at the designated design truss spacing. Adjacent plywood strips must be separated by at least 8 inch. The plywood strip shall be nailed with 4d nails or equivalent staples not closer than 8 inches on center along the top chord. The bottom chords of the adjacent trusses may be either: (i) Unbraced, (ii) laterally braced together (not cross braced) with 1" x 2" stripping not closer than 24 inches on center nailed with only one 6d nail at each truss, or (iii) covered with the material, with connections or methods of attachment, as specified for the completed mobile home.

(2) Truss deflections will be measured relative to a taut wire running over the support and weighted at the end to insure constant tension or other approved methods. Deflections I will be measured at the two quarter points and at midspan. Loading shall be applied to the top chord through a suitable hydraulic, pneumatic, or mechanical system, masonry units, or weights to simulate design loads. Load units for uniformly distributed loads shall be separated so that arch action does not occur, and shall be spaced not greater than 12 inches on center so as to simulate uniform loading.

(c) Nondestructive test procedure(1) Dead load plus live load. (i) Noting figure A-1, measure and record initial elevation of the truss in test position at no load. (ii) Apply load units to the top chord of the truss equal to the full dead load of roof and ceiling. Measure and record deflections. (iii) Maintaining the dead load, add live load in approximate 4 design live load increments. Measure the deflections after each loading increment. Apply incremental loads at a uniform rate such that approximately one-half hour is required to establish the total design load condition. Measure and record the deflections five minutes after loads have been applied. The maximum deflection due to design live load (deflection measured in step (iii) minus step (ii)) shall not exceed L/180, where L is a clear span measured in the same units. (iv) Continue to load truss to dead load plus 1.75 times the

design live load. Maintain this loading for 12 hours and inspect the truss for failure. (v) Remove the total superimposed live load. Trusses not recovering to at least the L/180 position within 12 hours shall be considered as failing.

(2) Uplift loads. This test shall only be required for truss designs which may be critical under uplift load conditions. (i) Measure and record initial elevation of the truss in an inverted test position at no load. Bottom chord of the truss shall be mounted in the horizontal position. (ii) Apply the uplift load as stated in § 280.305(c) to the bottom chord of the truss. Measure and record the deflections 5 minutes after the load has been applied. (iii) Continue to load the truss to 1.75 times the design uplift load. Maintain this load for 3 hours and inspect the truss for failure. (iv) Remove applied loads and within three hours the truss must recover to at least L/180 position, where L is a clear span measured in the same units.

(d) Destructive test procedure. (1) Destructive tests shall be performed on three trusses to generally evaluate the truss design. (2) Noting figure A-1, apply the load units to the top chord

Bracing and covering as specified for completed mobilehome

of the truss assembly equal to full dead load of roof and ceiling. Measure and record deflections. Then apply load and record deflections in design live load increments at 10minute intervals until 1.25 times design live load plus dead load has been reached. (3) Additional loading shall then be applied continuously until failure occurs or the factor of safety times the design live load plus the dead load is reached. (4) Assembly failure shall be considered as design live load deflection greater than the limits set in § 280.305(d), rupture, fracture, or excessive yielding. (5) The assembly shall be capable of sustaining the dead load plus the applicable factor of safety times the design live load (the applicable factor of safety for wood trusses shall be taken as 2.50).

(e) Trusses qualifying under the nondestructive test procedure. Tests §§ 208.402(c) (1) and (2) (when required), shall be subject to a continuing qualification testing program acceptable to the Department. Trusses qualifying under the destructive test procedures, Tests § 280.402 (c)(2) (when required), and (d), shall be subject to periodic tests only.

Bricks or other uniform loading units, spaced,

apart to prevent arching

Solid supports

Sheathing

§ 280.403 Standard for windows and slid

ing glass doors used in mobile homes. (a) Scope. This section sets the requirements for prime windows and sliding glass doors used in mobile homes except for windows used in entry doors. Windows so mounted are components of the door and thus are excluded from this standard.

(b) Materials and methods. Any material or method of construction, whether or not provided for in this standard, and any material or method of questioned suitability, proposed for use in manufacture, shall nevertheless conform in performance as outlined in paragraph (c) of this Section and proof of capability of structural integrity shall be presented. If applicable, units shall comply with the following:

(1) Wood and wood based products. (i) Wood. Wood parts including plywood and particleboard parts of window units shall have a moisture content of 6 to 12 percent at the time of fabrication. Wood parts, except inside stops and trim shall be manufactured utilizing wet-use adhesive requirements as defined in ASTM D3110 and preservative treated in accordance with NWMA IS-4. (ii) Plywood. Plywood parts except for inside stops and trim shall be exterior type plywood and preservative treated in accordance with NWMA IS-4. (iii) Particleboard. Particleboard parts except for inside stops and trim shall be type2 particleboard and preservative treated in accordance with NWMA IS-4.

(2) Aluminum. (i) Alloys. Aluminum shall be of a commercial quality and of proper alloy for window construction, free from defects impairing strength and/or durability, as follows:

Wrought aluminum alloys shall be those in which the alloying elements do not exceed the following maximum limits:

These limits apply to both bare products and to the core clad products. The cladding of clad products shall be within the same limits except that the maximum zinc limit may be 3.0 percent in order to assure that the cladIding is anodic to the core. Where aluminum extrusions are used for the main frame and sash or ventilator sections, they shall have a minimum ultimate tensile strength of 22,000 psi and a yield of 16,000 psi.

(ii) Finish. The exposed surface of all aluminum members shall be clean and free from serious surface blemishes. If exposed welded joints are used, they shall be dressed and finished.

(3) Glass. (i) Safety glazing materials, where used, shall meet ANSI Z97.1-1972. Tempered glass, where used, shall also meet FS DD-G-1403A. (ii) Insulated glass, when used, shall meet or exceed the requirements of Sealed Insulating Glass Manufacturers Association (SIGMA) and shall be permanently identified with the name of the insulating glass manufacturer. (iii) Glass tolerances and areas shall meet or exceed the values shown in the Glass Table below.

For other types of glass see Federal Specification DD-G-451c, dated Jan. 15, 1968.

"Maximum areas shown are based on minimum glass thicknesses set forth. Maximum areas shown apply for rectangular lites of annealed glass firmly supported on all 4 sides in a vertical position.

Tabulated areas may be increased as noted for use of tempered, heat strengthened or sealed insulating glass and shall be decreased as noted for use of sandblasted, wire or laminated glass. Glass louvers installed in jalousies shall be not less than 32" thick