NB: I am not going to build a retaining wall anytime in the near future. I like to sit on the deck and woolgather, and I’m looking for an answer to occupy my mind.
The back yard slopes down to a creek. The part nearer the house isn’t particularly steep, so we might have a bit more usable space if I built a retaining wall and back-filled it. For the sake of argument, let’s say the wall would be four feet high. How to go about building one?
I imagined digging a trench two feet deep and three feet wide, making plywood forms a little wider than a cinderblock, putting in rebar such that there would be two pieces of rebar for each cinderblock, and pouring a concrete footing. When the concrete dries, knock the forms apart (hence the wide trench), and start stacking blocks for the rest of the wall. Backfill with the free fill the County gives away.
That’s how I imagine it; but I’m not a mason. How do you actually go about building a retaining wall?
Here’s a guide. The base is usually compacted gravel and then bedding sand.
The landscaping bricks I used had a line indicating where to set the next course of bricks. Each course is set back a few inches. I only went up about 3 ft. That was enough work for me.
I wouldn’t go through that experience again. It’s to easy to hurt your back. I took it slow and careful. Worked short 4 to 5 hour days. Still ended up sore all over.
Hire a contractor who knows what he’s doing, and knows the local type of soil and weather conditions, how deep the frost line is in your area, how many drain openings you need, etc, etc.
For example:
You said you might “put two pieces of rebar” in each block, etc. But you probably need to be a lot more specific…The rebar should be bent and anchored in the wider footing, etc.
To further occupy your mind while relaxing on your deck, you might want to research affixing your vertical rebar to “deadmen” and consider installing appropriate “weep holes” to maintain the integrity of a wall and eliminate the possibility of it acting like a dam.
I had a professional install a concrete brick retaining wall so my house wouldn’t slide into the next door neighbors yard.
After the wall was built, I decided that it would look nicer with another layer of bricks, so I bought the right amount and placed them myself. Should be an inconsequential chore - each brick has a lip that butts against the back edge of the lower brick. Just need to stagger them properly to look right.
The staggering was not a problem. But I couldn’t get the damn things straight despite having a perfectly straight guideline to work with.
The other thing I think about is putting a fence or wall on the property line (downslope). Again, I thought of a concrete footing. Or a series of concrete footings, rather, going down the slope. Then a wall about four cinderblocks high. A fence would be cheaper, but a concrete footing would help keep the neighbour’s brush out.
A four foot high wall is high enough that you’ll want reinforcement (probably Geogrid). And reinforcement means you’ll want to get the wall properly engineered.
You don’t need a concrete foundation for a modular block retaining wall. A 6" depth course of gravel about 24" wide should suffice. You bury the first course or two (probably two for a 4’ wall) and go up from there. You’ll want 12-18" of stone behind the wall for drainage and the rest of the backfill can be compacted clay or similar. You want something that compacts well enough that it’s not going anywhere. You’d probably have two layers of geogrid going 4’ back behind the wall (so 5’ lengths since the first foot is under the blocks) so you’d need to excavate extra soil if you don’t have that much area available behind the wall.
