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We've got a 50' stretch of yard that has a very gentle side to side slope that we can't easily eliminate (fences on each side built at different heights). We want to build a retaining wall along that stretch. The wall will be 6" to 10" high. (Two or three layers of 4" block with the first layer dug 2" below the lower elevation.)

Can a retaining wall be built at a gentle side to side angle so that the top of the wall is flush to the gently sloping level of the higher elevation? We'd like to avoid stepping the wall. Are there any special considerations for a wall such as this?

Edit: the reason I'm asking is, much of what I've read says it's important that the first course of blocks is level both front to back and side to side.

Edit 2: Mark's post taught me you can add photos, so here are some:

From the house

Along the wall high to low

Along the wall low to high

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2 Answers 2

up vote 3 down vote accepted

I built a retaining wall in a situation very similar to what you described. In my case the wall drops approximately 12" over 40 feet. It has 3 courses of 6" Keystone wall blocks. The first course is mostly buried and the wall is about 12" high over most of it's length. I also put about 4" - 5" inches of drain rock behind it with a landscape fabric barrier.

This was 15 years ago and it seems to be holding up just fine. I would hope that the 4" blocks you want to use will be ok. However, I've worked with that size some doing garden walls and they are definitely less stable than the bigger blocks.

One other consideration here is aesthetics. Make sure looking at a retaining wall that isn't level doesn't bug you! Sometimes I look at mine and wish I had installed it level and stepped it down instead.

In the area where I live we have an assortment of gravity block retaining walls and the ones that follow the slope usually don't look as good in my opinion.

Here is a photo for reference: enter image description here

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This picture kind of exaggerates the slope. I haven't actually measured it, but I estimate the height difference between where the grass starts to back by the fence is approximately 16". The blocks on the far left ARE level and part of a raised planting bed. –  Mark Edington May 14 at 14:45
    
Yes! This. This is a very close analog to our situation. So for the blocks, we were planning on using the 12" long, 4" tall, interlocking blocks. But you say to go bigger? –  Jakerc May 14 at 14:52
    
As far as aesthetics, our house actually sits on the higher elevation that the wall will support, and the top of the wall will be flush with the lawn. It should, from the house just look like a stone border on the lawn. –  Jakerc May 14 at 14:54
    
Added some pictures to my original post –  Jakerc May 14 at 15:09
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Speaking of standard guidelines, Family Handyman magazine frequently runs articles on retaining walls with general best practices. Here's one you might read: familyhandyman.com/landscaping/retaining-wall/… –  Mark Edington May 14 at 16:06

If the wall isn't level gravity will be forever forcing it to fail.

It sounds like you're planning to run the wall in the direction of the slope, so what is it retaining? There are landscaping blocks with finish on both sides, but most are made to be backfilled behind them. And the backfilling isn't optional, its an integral part of the wall system.

It's one thing to place some garden blocks around a small area to hold back some mulch with the understanding that you'll probably have to redo it every few years to keep it looking nice, but if you want to build a nice looking long lasting wall, you have to go the whole nine yards. And that means for a 50' wall, you should use a full size wall block, excavate a few yards of soil (probably using a machine), backfill with a couple yards of crushed stone, compact the crushed stone (probably with a machine) and pound each base block into the crushed stone.

If you just scrape the ground a couple of inches and go 50' with small garden blocks, it will be a crooked mess in just a few years whether it's originally level or not.

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Thanks for the reply! In answer to what it is retaining, we've got a front to back yard elevation change also. We've got some raised bed planter boxes sitting on the lower elevation. The yard used to slope towards the front of the boxes but we've dug about 18" horizontally out of that slope and now have two distinct levels. The wall would split those levels and hold the upper, lawn part of the yard. –  Jakerc May 14 at 14:43
    
Added some pictures to hopefully illustrate the wall's purpose. –  Jakerc May 14 at 15:10
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The computer I'm on is blocking pictures, but I'll see them later today. –  Rand May 14 at 15:57
    
Another thing that can greatly improve the look of these walls are curves. Except that it adds some length, serpentining the wall is no harder than going straight. Curves not only soften the look of the block, but it's more attractive because it stops the mind's-eye from scrutinizing its straightness. It's the same phenomenon with a wall that's only a few degrees out of level, the mind doesn't want to accept it. –  Rand May 14 at 15:58

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