Retaining Wall Basics – Article
Draw a plan showing measurements and grade elevations. The elevations are required to calculate how many retaining wall blocks are required and to estimate the cost.
Mark out the location of the wall. Before digging, call utility and cable companies to mark their wire locations (this is usually a free service.)
Excavate a minimum of 6-12 inch deep depending on the size of the wall unit you are using. Excavate more if the soil has been previously disturbed. Remove all loose soil. Remember that you need a minimum of 3 inches of a gravel base and at least 3 inches of the first wall unit course to be buried below grade level to help “toe in” the wall. You can save on materials if you step the wall up or down to accommodate the grade.
Place 3-6 inches of gravel in the trench and compact using a compactor. Compact until you have the best compaction possible. In areas with more than 6 inches of gravel, compact in layers of no more that 3 inches at a time. Leave enough room for the first row of the wall to be buried below grade level. The final height of your installation will determine the exact level you must set your base at.
Some wall styles come as “double units”, you must split these first. When placing the blocks, you must level each block individually using a mallet and a small level. Ensure that all blocks are leveled from side to side and front to back. After the first row is in the rest of the units can be stacked accordingly. Please note: You should always off set all vertical joints by starting with a block cut in half.
As you work you way to building courses to your wall start adding gravel after every two rows of blocks to aid in drainage. Use a well draining gravel like 6AC as a back fill (you may reference our installation guide for visuals.) Always use a filter fabric to separate the existing soils from your gravel.
When placing your final row of block (in some cases you may have a “coping” block or a “cap” that finishes off the wall) you must use a concrete adhesive. Always dry fit and cut any pieces required before applying any adhesive. After adhering the top row, place soil, sod or plant materials to complete your installation