BPC-016 Retaining Wall Designs
Revised 05/18/2010, Reviewed 01/2020
The following are five (5) approved retaining wall designs. They may be used in lieu of a retaining wall designed by an engineer or architect. A site evaluation (see form CNI-002) and a building permit is required. Deviations from these plans or surcharge loads from adjacent structures, driveways, parking areas, terraced retaining wall(s), or steep slopes within a 45 degree angle from the bottom of the footing require a complete engineer’s design.
6' Retaining Wall
- 1' minimum compacted fill soil cap shall be moisture conditioned to near optimum moisture content and compacted in 8" maximum lifts to provide an impermeable barrier to surface water infiltration.
- Per CBC 1803.3 the ground adjacent to a building foundation must slope away from the building at 5% minimum for at least 10feet, or to approved alternative method for diverting water away. Impervious surface within 10' of the foundation must be sloped 2% minimum.
- Minimum 12" wide, class 2 aggregate base rock or crushed rock wrapped in an approved non-woven filter membrane. A minimum of 2" must be below the drainage pipe and 6" minimum above the pipe.
- Minimum 4" schedule 40 perforated pipe, holes placed down, sloped 2$ minimum to an approved outlet location. Cleanouts shall be provided as necessary. All 90° bends shall be made with (2) 45° pieces or additional cleanouts may be required.