I missed another blog post again last week. I’m not proud of it and there’s no real excuses this time. Back on track this week with the final part of the retaining wall installation.
After removing the old chain link fence and digging the trench for the new retaining wall, I could get down to the actual wall install. I made sure to dig the trench to about 8” below grade prior to installing the first row of 6” x 6” x 8’ timbers. With ~2” of gravel as a base for leveling and stability, that meant that the first row of timbers would be completely buried in the end. This helps make the base of the wall secure for the long run.
Another key piece of installing the first row of timbers was to make sure that they were level. Behind the wall a perforated tube is added to facilitate drainage from the high point to low point of the wall. This tube needs to have a slight slope from high to low point, but I made sure to keep the actual timbers themselves as level as possible.
Our retaining wall did not have a single row of timbers from one side of our yard to the other. Because our neighbors’ yards are at different levels, I actually had to step a couple of rows down to allow for a level wall. A couple of the different steps can be seen in the photo below. I worked from the lowest part of the wall to establish a full timber placement. I then made the next level up level with the top of the timber, and overlapped that level slightly with the one below it. Continuing that method led to 4 different “base” timbers for my yard, each one stepped down exactly 6” and with overlapping seams to keep the wall a continuous unit.
The final step of installing the base layer of the wall was to drill 2 holes in each timber and drive ½” #3 rebar through the holes and into the ground below. I used 2’ rebar, meaning 1 ½’ were buried into the ground to provide stability for the wall.
From there the rest of the wall moved quickly. I used 10” spikes to connect each new row to the row below it (pre-drilling a ¼” hole in the top timber to help make driving the spike easier). As I built the wall up, I made sure to offset each row ~¼” towards the side of the wall holding back the soil. This is recommended to provide stability against leaning in the future and should help the wall to last for decades.
After getting the first couple of rows installed, I started to backfill behind the wall with gravel. I installed the perforated tube with a 90deg elbow to allow drainage from the backside of the wall to the front.
As I continued building up the wall, I continued to backfill with gravel. Once the wall was finished I left about 6” of space behind the wall that I then backfilled with soil on top of the gravel. I also backfilled the frontside of the wall to bury the entire first row of timbers. While everything went smoothly after establishing the base row of timbers, I did have to make sure I was staggering seams at least 1’. I did this by cutting timbers at the start of a row, so that each row always ended on a full beam if possible.
The absolute final step was to cut the old chain link fence posts away. At the high end of the wall, I left them level with the retaining wall. They can’t be seen since they are behind the workshop and hidden by our neighbor’s fence. By leaving them I can provide extra stability to the most taxed part of the wall. The posts by the lower part of the wall were cut back to as low as possible at ground level. We’ll eventually put in a small cattle panel fence in that area since that section backs up to neighbors with kids. Overall, I am pretty pleased with the end result. It was a lot of manual labor, but not too technically difficult and something I think most people can handle if they don’t mind putting in the work.