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MurphyMan 09-22-2013 12:48 PM

Unsure of small retaining wall materials.
6 Attachment(s)
I am building a stone patio. I had a small company remove the old concrete and they will lay down the gravel and sand bed. They have started their part of the job.

The grade is flat for about 1/2 of the patio, then it slopes down, as you can see.

I will have a small retaining wall/bench going around about 1/2 of the patio. In the attached photo I have laid the base course of 6" thick Unilock Estate stones on the ground, just to establish the pattern. Next, I will dig the trench, tamp, drop in 6" of gravel and tamp some more.

Once I have finished the wall, the contractor will bring in the rest of the gravel and bedding sand and I will lay down all of the stone.

These are the materials my local supplier recommended. We did not use a regular retaining wall block, with the set back flange, because I wanted it to transition into a 18" high seating wall. The regular flanged retaining wall blocks have the finish on one face, and the other face is flat. Hence, they would be unsuitable for the bench part of the wall.

At the very deepest section, the retaining wall will have to hold back about 20" of gravel, sand and paver stone. That will be in the area of the sharp turn. I asked the supplier about keeping the retaining wall in place, since we weren't using flanged block, and he gave me a bag of these little plastic tubes. Said they go one per block. Doesn't seem like it's enough to hold the blocks in place. I was unable to find any online information about the use of these tubes.

So, do you see any red flags here? Is my little retaining wall going to hold together? Is there a different material I should be using in the Uniblock grooves?

Here is what the block looks like at my dealer.

Msradell 09-23-2013 10:12 PM

Are those plastic tubes solid or hollow? If they are hollow can you crush them easily? At 1st look they certainly don't look like they would provide much strength. Do you know who the manufacturer of the blocks is? If so I would definitely consult their website or call them about the issue. 20" of gravel behind the wall it can provide quite a bit of force pushing outwards.

concretemasonry 09-23-2013 10:35 PM

The plastic tubes are there to provide some shear resistance to the gravity wall. The shear is low because of the height. My concern would be about the base and levelness of the first course (the most important part of a retaining wall). It is not level and the loads can easily be concentrated, leading to movement.

Those units shown are not the best, but they provide a low wall that stacks vertically with both sides having an architectural surface on both sides. They are not suitable for taller walls retaining more soil.

The base material seems a little high considering there will have to be a 1" screeded concrete sand setting bed plus the paver thickness to provide adequate distance from the wood siding.


MurphyMan 09-24-2013 07:15 AM

Thanks guys.

First off, the photos just show the thing being roughed in. Yes, I know the blocks aren't straight, I'm just kind of laying them out to establish the curves that are possible with this block.

I managed to get Unilock's installation instructions (file size too large to upload here), something that was not provided by my local distributor. It turns out the little plastic tubes are for locating the block, not providing shear protection.

Each bock has a groove on either side of it. The grooves do not line up. One of the sides has a dimple in it as well. If you are using the block as a retaining wall, you place the blocks dimple side up and place a single locator tube in the groove. This establishes a setback of about 3/4".

If you are building a vertical wall, you set the blocks so the dimples face each other. They also recommend using concrete adhesive when building a vertical wall.

Here is a link to their pdf: The Unilock Estate blocks are shown on page 21.

This brochure shows some kind of green locator, which I did not receive. I got the round tubes, which look like the Brussell blocks on page 18.

I now have a better idea how to proceed. I'm just not sure if these materials are suitable. Maybe I'll just use concrete cement for all the courses, just to make sure.


MurphyMan 09-30-2013 12:31 PM

Getting it done
1 Attachment(s)
I guess I worked through my questions. First off, I contacted Unilock's customer support and they sent over some instructions for working with this material. It clarified the use of the spacers and how they establish setback.

I only have three courses of block that will be acting as a retaining wall, so I think I am good to go. Here is another photo of how it is turning out. There will be another two vertical courses added for the seating bench, topped off with a coping block.

I think this will turn out fine. :thumbup:

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