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CGofMP 02-08-2006 12:38 AM

Block Retaining Wall - Best Practices Question
Okay - this is kinda basic.

I am going to build a retaining wall about 18 inches high to serve as a planter. We are talking about 50 feet all told. I will be using the cheaper Home Depot (Yes I am sorry) blocks and it will look similar to the photo below - only it will be three straight intersecting runs instead of curved. Picture a "U" with the sides bent open. The bricks in question will also be flat faced not curved.:

The bricks have this sort of interlock:

Everything that I have read online shows similar technique to the following:

That is set in some sort of gravel.
I was actually expecting to have to lay a footer of cement.

I want this job to be as professional as I can make it, and I also want to make sure the darn thing does not get bumpy or wavy in the future etc. So I am not above using cement, at the same time however I would not be at all unhappy with avoiding the time and effort of cement and making a footer.

So whats the right way to go about this?

Also anyone having any experience with this sort of wall/block who wants to share hints would be most appreciated.

Hints tips ideas thoughts?

jmic 02-08-2006 08:29 PM

I've used Uni-lock before on retaining walls with great success following manufacturers directions. Just set in gravel, not cement.

Alan Mesmer 02-08-2006 08:45 PM

You are on the right track. Just make sure that your base is set on landscape fabric and use a crushed ag base and compact it very well. You can rent a plate compactor or you can use a large hand tamper to compact the base. The most important thing is to adjust your base grade to exact level and keep it level. Each block on your first row needs to be exact. Use a level on each block from front to back and from each block to the next. Even a small variance in the first row will show up a lot as the rows go up. Time spent on the first row will be time well spent.


tgeb 02-11-2006 05:58 PM

I agree, no concrete needed. :)

Make sure that you have at least 1/2 of one block below grade for support.

There is nothing wrong with the HD blocks. :)

Good luck,


CGofMP 02-14-2006 12:07 AM


thank you very kindly for the replies. I will forgoe the concrete and see what I can do with this one. The project looks kinda fun and message received on all the above particularly the comments on keeping them level... had already planned to be a bit anal about that.

Is there a particular type of base rock that would be best for this project? I have use pea gravel a lot but I'm pretty sure that would be way too big and certainly would not make for a good 'set'. So wjhat is the proper screen size or common name for what you'd reccomend for this?

The soil is pretty interesting stuff. Its a clay/loammix it gets hard as hell in the summer but when it gets soaked when loose the mud it makes is quicksand like (way overstated but you get the drift)

Thanks again guys

johnlvs2run 03-28-2006 02:03 AM

block retaining wall
I'm planning to do a similar retaining wall in a month or so.

Here are some links that I've found in the meantime.

johnlvs2run 05-05-2006 02:12 AM

question about retaining well
I am starting a 60 foot retaining wall and have a few questions. All that has been there have been railroad ties. When we moved in, the soil was at the bottom front (left) of the ties, but is now at the top. I am going to remove the soil back to the bottom when the wall is completed.
Click to see larger image.

My plan is to dig to the bottom back (right side) of the railroad ties, compact 3 or 4 inches of crushed rock, then set the blocks on the rocks. I am planning to have 1/2 of the first blocks below the top of the ties. Also I might turn the first block upside down, though it won't look as good that way it will be easier to set in the first layer.

I am using 16 x 10 x 6" blocks from HD that weigh 60 pounds each. Their rep suggested I might not need rocks as the soil is hard clay and to just set the blocks on the soil. I am planning to use the rocks though, as there are also gophers here and the rocks will help to deter them.

Question: Is this a good plan, or would it be better to remove the railroad ties and dig deeper, to set the first blocks below the bottom of the removed railroad ties. Or is it fine to build up the wall behind the ties where they are.

axel 05-07-2006 02:31 PM

In response to an old thread question by CGofMP and more recently by johnlvs2run, the stone base I've always used is a material called "crusher-run" or "ABC" which is a mixture of crushed stone with rock dust. If you wet it down and tamp it properly, you will have a base that feels as hard as concrete. But if your wall is retaining less than four feet of earth fill, I believe just about any type of stone will work just fine. And, of course, follow the manufacturer's installation instructions.

johnlvs2run 05-07-2006 03:14 PM


Thanks much for your reply. I was about to ask that question again, and will go with the ABC mix.

I pulled out a small 3' long railroad tie this morning, which was quite rotted and weighed about 40 pounds. I'm estimating the 8' foot ones are 100 to 120 pounds, and not rotted much at all. I'm going to see about having someone cut them up with a chain saw. Then they will be easier to move around and get rid of. I have also dug out more of the trench.

My plan at this point is to get the ABC mix and then make 2 tiers of the blocks, with 3 rows in the lower tier and 2 rows in the upper one. The upper tier will start 2 inches back from the top of the first one. The ABC mix will go along the bottoms and backs of the tiers. I feel the advantage of having 2 tiers is less pressure from the back compared to if the 5 rows were contiguous. Also having 2 of tiers will give a step up and also plenty of places for sitting and relaxing.

The railroad ties haven't had any base or drainage and just sat on the ground, albeit only one row of them. The blocks are much heavier so I am figuring they won't need to be anchored much below the soil line, and also as the tiers are not very high. Anyone, feel free to let me know if you think this will not be enough.

1crazygirl 05-09-2006 04:17 PM

I did a similar planter project recently and it looks like you have eveything covered. Good luck :)

johnlvs2run 05-16-2006 10:36 AM

I pulled out all the railroad ties with a pick, lifting one side then the other. They came out quickly. This took only a few minutes and I had them all out, then rolled them along the ground and stacked them up in a pile. A couple of the big ones were rotted through and parts of them came apart. Then my neighbors came over and said they could use the remaining ties for a small raised garden. I will help them move the ties when the wall is completed.

The trench was down to the base of the ties in back and I dug it down another 6 inches and going 15 inches to the back. Another place only 4 miles from me had recycled base material and delivered a cubic yard to the driveway. I have been filling the trench and have it up to where the bottom of the ties were but in back.

I made a tamper out of a long scrap piece of 3/4 inch plywood 4 inches wide, screwed in a dowel near the top, and a couple pieces of 2 x 4 at the sides of the base with a 9 inch square piece of plywood on the bottom. It works very well! Using a rake at an angle, as it is wider than the trench, worked very well for getting the base material level, and also spreading it around with my feet.

By the time I went down the line quickly with the tamper then watered the material it was already as hard as a rock.

The second place tried to sell me some Allan blocks that were 33 pounds and cost slightly more than the ones from HD. They said they were made of better materials, easier to handle and could be filled with more rocks, however when the guy walked off I could easily flake the front material off with my fingers. They looked cheap. I came home and looked at the 60 pound block from HD and decided to stick with these as they looked much more substantial. I got a brick chisel and have been knocking the fringe off of 45 of them for the base.

Now I am taking some time to make sure the recycled base is level, and then will be laying the first course of blocks.

johnlvs2run 05-21-2006 06:43 PM

I am learning this as it is coming along. Most is getting completed much more quickly than originally planned, and some parts are taking longer than my current expectations. Overall the project is coming along well.

Having a string the length of the base helped a lot. Originally the string was 2 inches above the base of the first level of blocks, then I lowered it to be just 1/4 of an inch above. I found it helps a lot to level the length first, and not worry about front to back, then to tamp as level as possible front to back without checking it. Then I checked the front to back leveling just before placing each block. What helps the most is having the lengthwise leveled, tamped and watered before this. Then it is easy to add some base here and there and tamp it done well while placing the blocks.

It took me all of one day to set the first row of blocks. They are 60 pounds each and so it is slow moving with each of them. Often I would need to pull them up again and add some base material here and there, tamp it and then set them again. This was the longest day so I took the next one off for a rest.

Then the next day I tossed pea gravel behind the 1st row and set 24 of the next 44 blocks. I am happy about getting the pea gravel instead of 3/4 inch, as it fills in much better. Today I just set the other 20 so the 2nd row is complete. The next few days will be tossing the pea gravel behind and setting up the 3rd and 4th rows. I will be using some fabric to keep the pea gravel from going back too far, and will be pulling the dirt down behind it.

I had knocked the flange off the first row so they would set evenly on the base material. I was going to throw away the flanges today, then decided they could just be tossed behind with the pea gravel for fill. So I will do this tomorrow.

While setting the 2nd row, I found it helped to first use the brick chisel to scrape the rough parts off the bottoms. Then I would set them down, lift them up on edge to brush off the top of the 1st row, then set them in place. This helps them to set more evenly.

johnlvs2run 05-29-2006 01:41 AM

The retaining wall is now complete!

I will post a picture of it when available.

Now I have the idea of replacing the 60 foot wood plank fence in back with a 6 foot block wall filled with rebar and concrete.

I will post about it on a different thread.

mr_trotta 06-28-2006 07:16 PM

That looks amazing. I can't wait to see finished photos. How many bricks at how much a piece? That wall sure cost quite a bit, but I'm sure it'll look like a milliion bucks when it's all finished.

johnlvs2run 06-29-2006 01:13 AM


This was the left side before pulling out the railroad ties:

Here is after completion:

The blocks were $4.26 each at home depot. The rows have 45, 44, 43, and 42 blocks. The ends taper up which looks fine. The wall did cost a bit but looks great and is well worth having done it.

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