CHAPTER 5 - FOUNDATION REQUIREMENTS

**500. GENERAL.** This section outlines general material and quality
standards for all foundations in this manual.

**501. EXCAVATION**

**501-1. FOOTING DEPTH.** Excavation for footings or foundation walls
shall extend below depth of soil subjected to seasonal or characteristic
volume change to undisturbed soil that provides adequate bearing. Select
the greatest depth required by any of the provisions below, reference
Figure 5‑1.

**A. Maximum Frost Penetration Depth.** The bottom of footings shall
extend at least to the depth indicated on the map on page H‑4.

**B. Alternate Seasonal Wetting and Drying.** This is especially
important with expansive soils. If expansive soils exist, consult a
geotechnical engineer to obtain required footing depth.

**C. Footing Depth.** The footings shall be deep enough to provide
required uplift capacity. (This value may need to be determined for high
wind areas after the calculations needed to determine footing bearing
have been completed.)

**502. FOUNDATION MATERIALS.** Footings and foundations shall be
constructed of solid materials such as masonry, concrete, or treated
wood, based on the Foundation Design Concept Selection (Appendix A) and
Foundation Capacity Tables. (Appendix C) (For masonry and concrete refer
to CABO R‑302.2, R‑304.1 and R‑304.3; for wood refer to CABO R‑302.1 and
R‑304.5.)

**503. STRUCTURAL REQUIREMENTS**

**503-1. FOUNDATION REQUIREMENTS.** All exterior walls, marriage walls,
marriage wall posts, columns and piers, must be supported on an
acceptable foundation system that must be of sufficient design to
support safely the loads imposed, as determined from the character of
the soil.

**A. Height Above Grade.** Foundation walls shall extend at least 8\"
above the finished grade adjacent to the foundation at all points. See
Figure 5‑1.

**B. Minimum Foundation Wall and Wall Footing Thickness.** For masonry
or concrete construction, the minimum foundation wall will be 6 inches.
The minimum reinforced concrete footing thickness will be 6 inches or
1‑1/2 times the length of the footing projection from the foundation
wall, whichever is greater.

**503-2. PIER AND COLUMN FOOTING REQUIREMENTS.** Footings for pier
foundations shall be reinforced concrete and should be placed level on
firm undisturbed soil of adequate bearing capacity and below the frost
penetration depth. They can also be placed on engineered, compacted
fill, approved by a licensed geotechnical engineer.

**A. Unusual Conditions.** Where unusual conditions exist, the spacing
of piers and pier size and the load bearing capacity of the soil shall
be determined specifically for such conditions.

**B. Minimum Pier and Pier Footing Thickness.** The minimum thickness
for a pier is 8 inches. The minimum thickness for pier footings is 8
inches or 1‑1/2 times the length of the footing projection from the
pier, whichever is greater.

**503-3. FOOTING REINFORCING (HORIZONTAL).** Reinforce footings when the
projection on each side of the wall, pier, or column exceeds 2/3 of the
footing thickness, or when required because of soil conditions.

**503-4. MASONRY PIERS AND WALLS.** All masonry piers and walls shall
have mortared bed and head joints. Reinforcing and grouting shall be in
accordance with the foundation concept selected from Appendix A and
designed in Appendix C.

**503-5. CRAWL SPACE REQUIREMENTS** (Basementless spaces)

**A. Height Requirement.** Ground level must be at least 18 inches below
bottom of wood floor joists and 12 inches below bottom of chassis beam.
Where it is necessary to provide access for maintenance and repair of
mechanical equipment located in the under floor space, the ground level
in the affected area shall not be less than 2 feet below wood floor
joists. (Refer to CABO, Section R‑309.) See Figure 5‑1.

**B. Interior vs. Exterior Ground Level.** The interior ground level
must be above the outside finish grade unless:

1\. Adequate gravity drainage to a positive out fall is provided, or

2\. The permeability of the soil and the location of the water table is
such that water will not collect in the crawl space, or

3\. Drain tile and automatic sump pump system are provided.

**C. Openings.** Locations of crawl space openings and ventilation
openings should be on long foundation walls. Avoid any openings on short
foundation walls. Sill plates or other structural members should not be
randomly cut to accommodate openings. Continuity of structural members
must be maintained.

**503-6. FOUNDATION WALLS FOR BASEMENTS.** The design and reinforcing of
basement walls is **NOT** in the scope of this document. Refer to local
codes and ordinances for guidance. Refer also to CABO, Section R-304:
\"Foundation Walls.\" Design the unit's foundation based on soil
conditions present at the site.

**503-7. BACK FILL.** Material used for back fill must be clean and free
of wood scraps or other deleterious substances and must be placed
carefully against walls.

**503-8.** S**TEEL BEAMS AND COLUMNS**. The analysis and design of steel
transverse girders, steel longitudinal girders potentially used under
marriage walls to reduce the number of steel pipe columns within a
basement, and the steel pipe columns themselves are **NOT** within the
scope of this document for system Types **E5**, **E6** and **E7**