Retaining walls help us offset grade changes to create usable land on our property. There are two ways a wall will be constructed, and they are referenced as a “cut” or a “fill” site. A cut site is one in which you will cut into the hillside to add flat land, and a fill site is one which you will add soil to and raise the land to flatten out the area.
In order to properly size the wall, we will need to have a detailed understanding of site elevations and grade changes to determine wall heights. Starting at the lowest point on your site, mark your grade changes in 1 ft. (0.3 m) increments on the plan. Mark your elevations on a drawing like the one pictured.
You may find it easiest to use string lines and line levels to create the elevations on your site. Determine the elevation (height) you want to “fill to” or the elevation point you want to place your wall and “cut” into. This point, or elevation, will be your standard/benchmark. From the point you just created, run a string line away from it towards the low spot on your property and/or to the point that will be the low part of your wall. Keep the string level by using a “line level” and pull the string all the way to the low spot on your site. Use a stake to hold the string in place and ensure it is pulled tight. Now, mark the elevations in 1 ft. (0.3 m) increments up to the standard/benchmark identified at the beginning. Using this technique will help you understand how tall of a retaining wall you will need to build.