retaining wall advice


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Old 01-27-22, 08:34 PM
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retaining wall advice

I've been wanting to build a retaining wall along a sloped area that goes the length of my yard. It won't be holding any dirt back, just sitting in front of the slope for ornamental / looks better reasons. I am considering retaining wall blocks 4-6inches in height (see pictures) or 8ft landscape timber. I was thinking this wall will be 8-12inches high. So 2-3 blocks (depending on which one to use) or 3 timbers. Everything I read recommends using crushed rock underneath and as backfill (see third picture). How crucial is the crushed rock with such a short wall? Will the dirt give out underneath if I just lay blocks directly on the ground, i.e. not burying 1/2 of the first level? Will using the larger or smaller blocks or the timber make a difference if I don't use the crushed rock?



 
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Old 01-27-22, 11:13 PM
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The more "formal" the wall the more important a foundation is needed.

I have lots of bolder walls around the yard, some are 5' tall, no foundation installed because when they move due to the ground shifting or soill pressure I really dont care because you diont see it.

I have some small retaining walls, about ,16" tall, going around beds, they have crushed and compacted base and they stay nice and level.

If you just put them on the ground eventually they will shift and you will be repairing.
 
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Old 01-28-22, 04:02 AM
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Stone is laid to help build and maintain a level wall, together with other issues. I suspect it will be considerably easier to build a reasonably level wall with stone than without it. And I can just about guarantee the wall will keep its shape much better with stone underneath.
 
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Old 01-29-22, 11:04 AM
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Everything I read recommends using crushed rock underneath and as backfill (see third picture)
You know why? Because water needs to go through it. I would use pea gravel as base. 5 inch minimum base. I would also cement your blocks on top of the pea gravel with durawall because if the bottom block goes, the whole wall goes.
 
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Old 01-29-22, 12:16 PM
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I would use pea gravel as base.
Absolutely not!!

For wall base you want sharp gravel, crushed limestone is the best. When packed the sharp stone locks everything together and forms a solid foundation, pea gravel, kind of like sand, can not be compacted and is not the correct material for this application.

I would also cement your blocks
Incorrect, retaining wall blocks need some flexibility to move, mortaring them will simply break up

Block adhesive is a much better product to use!

 
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Old 01-29-22, 01:56 PM
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I don't like pea stone as a base for the reason Marq said. I once built a flagstone walk using 4" of pea stone as a base and it literally took years for it to stabilize.

I have a fire pit that I built out of the same block as in your picture. It's bedded on 4" of crusher run. The blocks are bonded with adhesive not mortar. It is 20 years old and I have never had to do any maintenance.
 
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Old 01-29-22, 09:29 PM
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Incorrect, retaining wall blocks need some flexibility to move, mortaring them will simply break up

Block adhesive is a much better product to use!
You might want to explain this a little better.
 
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Old 01-29-22, 09:32 PM
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I have a fire pit that I built out of the same block as in your picture. It's bedded on 4" of crusher run. The blocks are bonded with adhesive not mortar. It is 20 years old and I have never had to do any maintenance.
Crusher run is good if you have a water problem. So that's a good base. You use landscape adhesive in the northeast, it will come apart in a few years. Will not withstand the winter weather in the northeast.
 
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Old 01-29-22, 10:09 PM
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Regarding the earlier recommendation of pea gravel, note the comments of an aggregate company, who should know what they are talking about when they say that pea gravel mainly has rounded edges, does not compact well and can be problematic in landscaping projects.

https://www.ramco.us.com/crushed-gra...ction-project/



 
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Old 01-29-22, 11:53 PM
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Will not withstand the winter weather in the northeast.
​​​​​​​I'm in Michigan, it works fine!
 
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Old 01-30-22, 04:56 AM
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"Will not withstand the winter weather in the northeast."

I'm in New England and it works fine.
 
 

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