Howdy, friends! It’s been two weeks since our last update. Thanks for being patient with us. We have not stopped working in the front yard. In fact, we were digging and building every Saturdays and Sundays. But landscape work is physical and it usually takes us more than one weekend to get a particular task done. Today, I want to share a fun “hardscape” project we completed recently – a retaining wall DIY! We loved the result and hope you find it interesting too.
“Hardscape” is a word I did not know until three weeks ago. Oh guys, it is really hard! I bet the person who came up with the name was exhausted from his/her hardscape project and just went for the most straightforward name possible. We built the wall ten days ago and I still feel exhausted when I see it!
What exactly is hardscape? It means that “the man-made features used in landscape architecture, e.g. paths or walls, as contrasted with vegetation.” So things like flagstone path, brick path, retaining walls, garden beds, water features, are all counted as hardscape. Hardscape not only decorates a garden and makes it beautiful, but also provides access and utility. In our case, our front yard is sloped, so a retaining wall is the best solution for preventing top soil and mulch from washing into the street.
Retaining walls can be constructed with different materials. Railroad sleepers, bricks, concrete, stones, or even tires. Retaining walls that hold significant amount of soil require some engineering and are usually done by professionals. We were able to DIY ours because it is just a couple feet tall and mostly for holding back light materials such as mulch.
We ended up using concrete blocks. Originally we considered wood sleepers, but upon walking around neighborhood, we realized that they do not hold up very well to the heavy clay soil in our neighborhood. Without a clear vision, we visited a few stores to see which material might work better. That was when we came across these chunky concrete blocks at Resource Central’s retail store.
These blocks are 16″ long and 8″ deep, much bigger than the big box store product. I’ve only seen them used in commercial building projects, such as shopping centers and city streets. The retail store of Resource Central’s is a second hand store for reclaimed materials, so these blocks are likely coming from commercial projects. Being second hand, they were significantly cheaper than the 12″ long blocks in big box stores (we got 102 of them for $120!). Needless to say we do not mind to overbuild with a good deal, so all 102 blocks came home with us.
Believe or not, it took us three trips to the retail store to transport all the blocks back, because they are heavy! Our car can only toll 40 of them at a given time (!), so the whole shopping and transportation took a day. Comparably, the building process was actually pretty straightforward. We knew that this wall would reside along the sidewalk, which is already straight. All we need to make sure was to build the wall at level and step the blocks up with the slope. So the first thing we did was to get a leveled string line along the whole length of the retaining wall, which should tell us the slope we had to follow.
We did not bother to set up professional strings and posts. Our whole system was pretty primitive. Well, it got the job done. You can see from the picture below how steep the slope is. With the string more or less level and one end on the ground, the other end was 37″ above the ground level! The whole string was 37′ long, so the average of the slope is about 1 inch per foot.
The slope of the sidewalk is fairly consistent between the two ends, so we basically followed the slope and stepped up our blocks gradually.
Retaining wall step up has some rules. The last block before stepping up needs to be completely buried, and the first block on the next level needs to sit on the buried block. We followed the instructions from this website, which has very helpful videos and schematic for how to correctly construct a step-up retaining wall.
Our blocks are 6″ tall and 16″ long. Since we have 37″ vertical space to go, we need to step up 6 times. Our slope is 1″ per 1′, that means we need to step up every 4.5 blocks (4.5 x 16″=72″=6′).
We marked the ground next to the wall every 6′ with spray paint, then started digging the trench. We used a tamper to compact the soil below till level before setting the blocks in.
The first row was the hardest. The ground needs to be fairly level and all the blocks needs to be level with each other. But after the first row was in, the rest went up quickly.
As shown in the picture above, the blocks were gradually buried into the ground due to the slope of the side walk. When we had one completely buried, we would level the dirt next to it and put the next one on top of the dirt and the one buried.
On each end of the wall we used a half block to create a clean edge.
I was pretty useless in this operation – Slav was the one who dug the trench, compacted the soil, and moved the blocks. These blocks were so heavy that I could barely move one by myself. So all I did was to smooth the soil after it was compacted and made sure the neighboring blocks were level with each other. It took us two afternoons to construct this 37′ wall. And guess what, we used exactly 102 blocks!
Slav gave the whole wall a power wash until the blocks showed their rich red color. I followed with sand to fill the gaps between the wall and the sidewalk to prevent ock weeds growth.
Just to clarify, we did not use adhesive in this project. The blocks were simply stacked on top of each other. Each block also has a small lip on the back (you can see it better in this image which pictures a block similar to the ones we used), so the blocks on top can lock onto the blocks below tightly. This lip provides some strength to endure the soil behind, but for retaining walls that need to hold back large amount of soil, the blocks need to be glued together with masonry adhesive. In our case, we will have very little soil behind the wall once we remove all the grass Slav turned over. We are confident that this retaining wall is steady enough for any rain or snow we might receive.
There has been a few T-storm since the wall was completed, and we did not lose a single drop of soil due to run off, even though the blocks are just set next to each other. We love this look a lot better than just the grass meeting the street. Incidentally, it makes a pretty comfortable place to sit. I found myself sipping drinks on it whenever I am out and about in the front yard. What do you think? Do you like it?