15.07.050 Installation.
A. Building Site Preparation: A mobile home may not be installed at a building site unless the ground at the site has adequate compaction and load-bearing ability to meet the foundation system footing support requirements. The installer or, if the building site is in a mobile home park, the park owner must ensure that the ground on which the mobile home is to be installed has been improved as necessary to provide proper base for the mobile home and that the area beneath the mobile home has adequate drainage. To provide adequate drainage, the installer by need to slope the finish grade or install drain tile.
B. Foundation System Footing:
1. Footings shall be constructed of:
a. solid concrete or an approved alternate that is at least 3 1/2 inches thick by 16 inches square; or,
b. two 8 inch by 16 inch by 4 inch solid concrete blocks that are laid with their joint parallel to the main frame longitudinal member.
2. Footings shall be:
a. evenly bedded and leveled;
b. placed on firm, undisturbed, or compacted soil that is free of organic material;
c. centered in a line directly under the main frame longitudinal members on both sides of a mobile home;
d. spaced not more than 8 feet apart; and not more than 2 feet from the ends of the main frame: a closer spacing may be required depending on the loadbearing capacity of the soil.
3. A mobile home with more than one section must have center line blocking at end walls and at any other point of connection of the sections of the mobile home that are ridgebeam bearing support. Blocking is also required at both ends of a door opening that is 6 feet or more wide in an exterior wall.
4. If a mobile home requires footings on its exterior perimeter, the footings shall be installed below the frost line. The footings for the main frame longitudinal members must be recessed only if frost heave is likely to occur.
5. A footing shall be constructed so that seventy-five percent (75%) of the area under the mobile home has at least 18 inches clearance between the bottom of the main chassis members and the ground level. The area beneath furnace crossovers and fireplaces, however, must always have at least 18 inches clearance. At no point under the mobile home may clearance be less than 12 inches.
C. Foundation System Piers: An installer must build and position piers and loadbearing supports or devices to distribute the required loads evenly. An installer may use manufactured piers or loadbearing supports or devices that are listed or approved for the intended use, or may build piers that comply with the following requirements. All blocks must be concrete blocks.
1. A pier may be made out of a single stack of 8 inch by 8 inch by 16 inch blocks if the blocks are not stacked more than three blocks high. A pier made of a single stack of blocks shall be installed at a right angle to the main frame longitudinal member and shall be capped with no more than 2 inch by 8 inch by 16 inch wood blocks or one 4 inch by 8 inch concrete block.
2. A pier may be made of a double stack of 8 inch by 8 inch by 16 inch blocks if the blocks are not stacked more than five blocks high. Each row of blocks in such a pier shall be stacked at right angles to the abutting rows of blocks. The wood blocks must be of hem fir, douglas fir or spruce pine fir. The pier shall be capped with 2 inch by 8 inch by 16 inch wood or concrete blocks. The pier shall be installed so that the joint between the cap blocks is at right angle to the main frame longitudinal member.
3. A pier may be made with more than five rows of blocks if the stacked blocks are filled with 2000 psi concrete or mortar. A licensed architect or professional engineer must approve a foundation system that includes a pier that is higher than 72 inches (9 blocks) high, or in which more than 20 percent of the piers exceed 40 inches (5 blocks) high.
4. All blocks shall be set with the cores placed vertically.
D. Foundation System Plates and Shims: An installer may fill a gap between the top of a pier and the main frame with a wood plate that is not more than 2 inches thick and two opposing wedge-shaped shims that are not more than 2 inches thick. A shim shall be at least 4 inches wide and 6 inches long. The installer shall fit the shim properly and drive it tight between the wood plate or pier and the main frame to insure that the mobile home is level and properly supported at all loadbearing points. A block that abuts a wedge-shaped shim shall be solid.
E. Foundation Fascia: A mobile home shall have an approved foundation fascia around its entire perimeter. The wood of the fascia shall be at least 3 inches from the ground unless it is pressure treated wood. Metal fasteners shall be galvanized, stainless steel, or other corrosion resistant material. Ferrous metal members in contact with the earth, other than those that are galvanized or stainless steel, shall be coated with an asphaltic emulsion.
A mobile home that is installed on a nonrecessed site and that has a metal foundation fascia shall have ventilation openings with a net area of at least 1 1/2 square inches per linear foot. A mobile home that has been installed on a recessed site or that has a foundation fascia that is not made of metal shall have ventilation openings in the foundation fascia with a net area of at least 1 1/2 square inches for each 25 linear feet of fascia. The openings shall be designed to provide cross ventilation on at least two approximately opposite sides of the mobile home. The installer shall locate the openings as close to the corners of the mobile home as practical, and shall cover the openings with corrosion resistant wire mesh or louvers.
Dryer vents and hot water tank pressure relief valves shall exhaust on the exterior of the foundation fascia. The fascia for each section of a mobile home shall have an opening of at least 18 inches by 24 inches, with a cover of metal or pressure-treated wood, to allow access to the crawl space.
F. Anchoring Systems: The City may require mobile homes to have an anchoring system which meets the following requirements:
1. Components of the anchoring system shall have a resistance to weather deterioration that is at least equivalent to that of a zinc coating that is not less than 0.3 ounces per square foot of coated surface. Cut edges if zinc coated strapping do not need to be coated.
2. An installer shall install, preload and adjust a ground anchor in accordance with the anchor manufacturer’s instructions. The installer must supply a copy of the instructions to the building inspector, as appropriate. A ground anchor, when installed, must be able to resist a working load of 3,150 pounds in the direction of the tie plus fifty percent (50%) overload (4,725 pounds total) without failure. Failure occurs if the point of connection of a vertical tie to an anchor is withdrawn more than 2 inches at 3,150 pounds, or when the point of connection of a diagonal tie is moved more than 4 inches horizontally when a load of 3,150 pounds is applied at 45 degrees from the horizontal. Ground anchors shall be marked with the manufacturer’s identification and model number in a location that is visible after the anchor is installed. The manufacturer of a ground anchor must provide instructions with each anchor that specify the kinds of soil for which the anchor is suitable.
3. If concrete slabs or continuous footings are used to transfer the anchoring loads to the ground, the following requirements apply.
a. steel rods cast in concrete shall be able to resist the loads and corrosion as specified for ground anchors;
b. a deadman anchor may be used in place of a listed anchor: it shall be constructed of solid concrete at least 6 inches in diameter and 2 feet long; reinforced with two #4 steel rods; and installed at least 5 feet below the surface of the ground;
c. a concrete slab may be used in place of a ground anchor if it provides holding strength equal to that required for ground anchors.
4. Ties shall be of cable, strapping or other approved materials. Ties shall be fastened to ground anchors and drawn tight with turnbuckles, yoke fasteners or other approved tensioning devices.
Tension devices shall end in clevis, forged or welded eyes. Hook ends are not permitted. Tension devices shall be designed to prevent self disconnection if the tie becomes slack. Cable ties shall be secured with two U-bolt cable clamps or an approved equivalent.
Tie materials must resist a working load of 3,150 pounds with no more than 2 percent (2%) elongation and must withstand a fifty percent (50%) overload (4,725 pounds total).
Ties shall connect the ground anchor to the main frame longitudinal members. Ties may not connect to steel outrigger beams that fasten to the main frame, unless the manufacturer’s installation instructions specifically approve the connection.
Diagonal ties must lie at least 40 degrees from the vertical. Vertical ties must be substantially vertical. If a vertical tie is not substantially vertical, the anchor must be placed outboard of the tie’s connection to the main frame.
A cable frame tie shall be connected to the main frame by a 5/8 inch drop forged closed eye bolt through a hole drilled in the center of the I-beam web, or by an approved alternative. The installer shall reinforce the web if necessary to maintain the strength of the I-beam.
The installer shall space the ties as evenly as practical, and shall locate a tie within 8 feet of each end of the mobile home. The installer may attach two or more ties to a single ground anchor if the anchor can carry a total required load. The installer shall install vertical ties at each detached corner of a clerestory roof and of add-on sections of expandable mobile homes.
As a minimum, the installer shall install the following number of ties for each main frame longitudinal member:
Length of Home (feet) (Excluding Hitch) | Number of Vertical Ties | Number of Diagonal Ties |
|---|---|---|
32-54 | 2 | 3 |
55-73 | 2 | 4 |
Multiple section mobile homes require only diagonal ties. Vertical ties are not required.
G. Assembly:
1. Sections of a multiple section mobile home shall be aligned, closed, and securely fastened at the required points along the ridge beam, endwalls and floor line. Head ducts, electrical connections and other fixtures and connections required between sections of a mobile home shall be properly installed. The floor of the mobile home shall be level within the tolerances given in the following table.
Tolerances may not exceed the amounts in the table (L equals the clear span between supports, twice the length of a contilever):
Floor | L/240 |
Roof and Ceilings | L/180 |
Headers, Beams, Girders (Vertical Load) | L/180 |
Walls and Partitions | L/180 |
2. The installer shall provide adequate clearance to ensure that the cross-over heat duct does not touch the ground and is not compressed. The installer shall insulate the cross-over duct at the intersection. The installer shall insulate and shall seal areas of potential water leaks with metal flashing or trim, if required, and with putty tape or other approved caulking to ensure the mobile home is water tight.
3. Utility connections to the mobile home, including water, sewer, electricity and gas, shall comply with local codes. Accessory structures attached to or located next to a home, such as awnings, carports, garages, porches, or steps, shall be constructed in conformance with local codes. (Ord. 1476, 1991).