Mark Location of Retaining Wall

Mark location of retaining wall

Excavate Wall Location

Excavate wall location

Compact the Base Trench

Compact the base trench

Install Drain Pipe, Wall Rock and Level

Install drain pipe, wall rock and level

Base Preparation

  • To start your layout, place stakes to represent the location of the front of the retaining wall. Using a string line or paint, mark out the entire length. A garden hose is an excellent tool to use when laying out curved walls.
  • Excavate the area by removing all surface vegetation and organic materials from the area. These cannot be used as backfill material.
  • If reinforcement is needed excavate behind the wall to accommodate the design length of the geogrid. Refer to your approved plans for exact length.
  • Starting at the lowest point, dig a base trench the length of the wall. More information on retaining walls where the base trench steps up a slope.
Retaining Wall Base Trench

Retaining Wall Base Trench

  • Dig a base trench 24 in. (600 mm) wide the length of the wall.**
  • The depth of the trench will be 6 in. (150 mm) plus an additional 1 in. (25 mm) for each 1 ft (300 mm) of wall height for the amount or buried block that is needed.**
  • Compact the base trench making a minimum of two passes with a walk behind plate compactor.
  • Foundation soils at the bottom of the base trench must be firm and solid. If the soils are made up of heavy clay or wet soils, or the areas have been previously excavated, remove this material and replace with a granular material, compacting in 8 in.(200mm) liffts or less.
    **For walls under 4 ft (1.2 m) dig the base trench 18 in. wide (460 mm) and 4 in. deep (100 mm) plus additional to account for the amount of buried block needed.

Base Material

How to prepare retaining wall base

Video: How to prepare the base

  • A drain pipe is required for any reinforced wall or any wall over 4 ft. (1.2 m) tall. Place the drain pipe at the lowest possible point toward the back of the trench and vent to daylight every 50 ft. (15 m). More information on drainage and water management.
  • Place a minimum of 6 in. (150 mm) of wall rock in the base trench and rake smooth.
  • Compact the wall rock making a minimum of two passes with a plate compactor.
  • Check the entire length for level, and adjust as needed.