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Title 24

Displaying title 24, up to date as of 9/16/2021. Title 24 was last amended 9/13/2021.

Title 24

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§ 3285.303 Piers.

(a) General. The piers used must be capable of transmitting the vertical live and dead loads to the footings or foundation.

(b) Acceptable piers - materials specification.

(1) Piers are permitted to be concrete blocks; pressure-treated wood with a water borne preservative, in accordance with AWPA Standard U1-04 (incorporated by reference, see § 3285.4) for Use Category 4B ground contact applications; or adjustable metal or concrete piers.

(2) Manufactured piers must be listed or labeled for the required vertical load capacity, and, where required by design, for the appropriate horizontal load capacity.

(c) Design requirements.

(1) Load-bearing capacity. The load bearing capacity for each pier must be designed to include consideration for the dimensions of the home, the design dead and live loads, the spacing of the piers, and the way the piers are used to support the home.

(2) Center beam/mating wall support must be required for multi-section homes and designs must be consistent with Tables 2 and 3 to § 3285.303 and Figures A, B, and C to § 3285.310.

(d) Pier loads.

(1) Design support configurations for the pier loads, pier spacing, and roof live loads must be in accordance with Tables 1, 2, and 3 to § 3285.303 and the MHCSS. Other pier designs are permitted in accordance with the provisions of this subpart.

(2) Manufactured piers must be rated at least to the loads required to safely support the dead and live loads, as required by § 3285.301, and the installation instructions for those piers must be consistent with Tables 1, 2, and 3 to this section.

Table 1 to § 3285.303 - Frame Blocking Only/Perimeter Support Not Required Except at Openings

Pier spacing Roof live load (psf) Location Load (lbs.)
20 Frame 2,900
4 ft. 0 in. 30 Frame 3,300
40 Frame 3,600
20 Frame 4,200
6 ft. 0 in. 30 Frame 4,700
40 Frame 5,200
20 Frame 5,500
8 ft. 0 in. 30 Frame 6,200
40 Frame 6,900
20 Frame 6,800
10 ft. 0 in. 30 Frame 7,600
40 Frame 8,500
Notes:

1. See Table to § 3285.312 for cast-in-place footing design by using the noted loads.

2. Table 1 is based on the following design assumptions: maximum 16 ft. nominal section width (15 ft. actual width), 12” eave, 10” I-beam size, 300 lbs. pier dead load, 10 psf roof dead load, 6 psf floor dead load, 35 plf wall dead load, and 10 plf chassis dead load.

3. Interpolation for other pier spacing is permitted.

4. The pier spacing and loads shown in the above table do not consider flood or seismic loads and are not intended for use in flood or seismic hazard areas. In those areas, the foundation support system is to be designed by a professional engineer or architect.

5. See Table to § 3285.312 for sizing of footings.

Table 2 to § 3285.303 - Frame Plus Perimeter Blocking/Perimeter Blocking Required

Maximum pier spacing Roof live load(psf) Location Load (lbs.)
Frame 1,400
4 ft. 0 in. 20 Perimeter 1,900
Mating 3,200
Frame 1,400
4 ft. 0 in. 30 Perimeter 2,300
Mating 3,800
Frame 1,400
4 ft. 0 in. 40 Perimeter 2,600
Mating 4,400
Frame 1,900
6 ft. 0 in. 20 Perimeter 2,700
Mating 4,700
Frame 1,900
6 ft. 0 in. 30 Perimeter 3,200
Mating 5,600
Frame 1,900
6 ft. 0 in. 40 Perimeter 3,700
Mating 6,500
Frame 2,400
8 ft. 0 in. 20 Perimeter 3,500
Mating 6,100
Frame 2,400
8 ft. 0 in. 30 Perimeter 4,200
Mating 7,300
Frame 2,400
8 ft. 0 in. 40 Perimeter 4,800
Mating 8,500
Frame 2,900
10 ft. 0 in. 20 Perimeter 4,300
Mating 7,600
Frame 2,900
10 ft. 0 in. 30 Perimeter 5,100
Mating 9,100
Frame 2,900
10 ft. 0 in. 40 Perimeter 6,000
Mating 10,600
Notes:

1. See Table to § 3285.312 for cast-in-place footing design by using the noted loads.

2. Mating wall perimeter piers and footings only required under full height mating walls supporting roof loads. Refer to Figures A and B to § 3285.310.

3. Table 2 is based on the following design assumptions: maximum 16 ft. nominal section width (15 ft. actual width), 12” eave, 10” I-beam size, 300 lbs. pier dead load, 10 psf roof dead load, 6 psf floor dead load, 35 plf wall dead load, and 10 plf chassis dead load.

4. Interpolation for other pier spacing is permitted.

5. The pier spacing and loads shown in the above table do not consider flood or seismic loads and are not intended for use in flood or seismic hazard areas. In those areas, the foundation support system is to be designed by a professional engineer or architect.

6. See Table to § 3285.312 for sizing of footings.

Table 3 to § 3285.303 - Ridge Beam Span Footing Capacity

Mating wall opening (ft) Roof live load (psf) Pier and footing load (lbs.)
20 1,200
5 30 1,600
40 1,900
20 2,300
10 30 3,100
40 3,800
20 3,500
15 30 4,700
40 5,800
20 4,700
20 30 6,200
40 7,500
20 5,800
25 30 7,800
40 9,700
20 7,000
30 30 9,300
40 11,600
20 8,100
35 30 10,900
40 13,600
Notes:

1. See Table to § 3285.312 for cast-in-place footing design by using the noted loads.

2. Table 3 is based on the following design assumptions: maximum 16 ft. nominal section width (15 ft. actual width), 10″ I-beam size, 300 lbs. pier dead load, 10 psf roof dead load, 6 psf floor dead load, 35 plf wall dead load, and 10 plf chassis dead load.

3. Loads listed are maximum column loads for each section of the manufactured home.

4. Interpolation for maximum allowable pier and column loads is permitted for mate-line openings between those shown in the table.

5. The pier spacing and loads shown in the above table do not consider flood or seismic loads and are not intended for use in flood or seismic hazard areas. In those areas, the foundation support system must be designed by a professional engineer or registered architect.

6. See Table to § 3285.312 for sizing of footings.