TOOLS YOU WILL NEED: Gloves, 4′ level, 10″ level, line level, string line, knife, rubber mallet, shovels, rake, broom, caulking gun, jumping jack compactor, vibrating plate. You will also need a container or a dumper. OPTIONAL: mini-excavator and skid steer (recommended if your wall is more than 10ft long).
MATERIALS YOU WILL NEED: Retaining wall system (make sure it’s right for what you’re trying to accomplish), geo-grid, geotextile, crushed gravel (preferably 0 3/4 gravel or HPB), perforated drain, PL adhesive
Step 1 – Preparation
Establish the area where you wish to install your retaining wall system and mark the area with orange spray paint.
Step 2 – Excavation
Excavate the area to the proper depth. Keep in mind that the depth of excavation varies depending on the height of the wall. For retaining walls we recommend excavating a minimum depth of 12″ to 18″ as well as a minimum width of 24″ to 36″ for backfill and your geogrid. The first foot of the wall will be installed below ground level for base support, and the back of the wall needs extra excavation because you will have to backfill the retaining wall for proper drainage flow. At Milton Stone Group, we like to go well above those numbers for optimum results).
Step 3 – Compaction of the sub-grade
For this part, you will need a compactor (a Jumping jack) to compact the sub-grade. Pass it 3 to 4 times to achieve maximum compaction, and take your time for this step. Once done, lay the geotextile fabric on the ground starting at your base going all the way up to the excavated area. This will prevent cross-contamination while allowing proper water filtration (always overlap the geotextile fabric).
Step 4 – Add your gravel and compact
It is extremely crucial that you take your time to do this right. As in every construction, the base/foundation is the most important aspect of the wall, a solid base means your wall will be durable. Subtract the height of your block wall to establish how much gravel to put on the compacted area. Once done, add gravel to the desired height, level it and proceed with compaction process once again. Put stakes at each corner of your area with a string line and line level at the desired height of your gravel, this will let you know how much gravel you will need. Add crushed 0 3/4 gravel to the compacted area please not: If using more than 6″ of gravel we like to add it in layers of 6″ and compact it with a compactor as we build it up). Compact the area the same way you did it with the sub-grade. The more time you spend compacting, the better the longevity. (For this part we use a compaction meter to assure 98% compaction)
Step 5 – Start building your base
If your wall is straight, put stakes on both ends in the direction you want your wall to go, attach a string line for direction and height. Start on one side and lay your blocks using a mallet to place them firmly into place, and a level to make sure your blocks are straight. Your blocks should be perfectly levelled in all directions. At this point, you will install your french-drain behind the wall (make sure your perforated drain is placed 1ft. above the base level).
Step 6 – Erect the wall
Make sure the joints of the wall NEVER end in line with one another, they must ALWAYS interlock. This will make sure it is stable, solid, and durable, without creating a weak spot. We recommend using a geogrid to reinforce the wall. Add the geogrid every two rows of the wall, backfill, and compact with a lightweight vibratory compactor plate. Repeat until you reach your desired height while always backfilling your wall as it erects. Very important to always make sure your geotextile fabric is always properly in place while you’re backfilling. NOTE: Your final blocks that are used as coping must be glued with PL construction adhesive. Congratulations, You’ve built a retaining wall.