Check local codes.
Be sure to check any State, Local, or HOA codes and restrictions for an outdoor fireplace.
Create a Design
determine width, length, depth, and height of retaining walls.
Foundation
The success of your retaining wall depends on a level base. To create a solid foundation, dig a trench for the first course of your interlocking retaining wall blocks. Make sure the ground remains even throughout.
Begin digging into the ground with a shovel.
The trench should be deep enough to bury at least half the height of your first course of blocks as they sit on a 2- to 3-inch base of gravel. Depending on the size of your blocks, this depth will be about 4 to 6inches.
The trench should be twice as wide as a single block.
Once you’ve dug the trench, compact it with a hand tamper or vibrating plate compactor.
Place a standard level on a 2 x 4 in the trench to ensure that the bottom is smooth and level.