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Thread: Anyone have a good idea to hold back my 'retaining wall'? (pictures inside)

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    nate81's Avatar
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    Anyone have a good idea to hold back my 'retaining wall'? (pictures inside)

    I intend on putting sand in the areas between the edging stones and the plastic edging....but on one side of the pool its a bit deeper.....should i fill it to the top with sand? This would mean sand would be on the pool walls about 2 or so feet. or....can someone give me a good idea to help support/hold the stones in place? Perhaps some way to tie them down.

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    Re: Anyone have a good idea to hold back my 'retaining wall'? (pictures inside)

    They use adhesive to hold them together and make the wall...

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    Re: Anyone have a good idea to hold back my 'retaining wall'? (pictures inside)

    noice I like the adhesive idea, conversely what do you think would happen if i 'backfilled' with sand? How would the pool handle that?
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    Re: Anyone have a good idea to hold back my 'retaining wall'? (pictures inside)

    Those bricks are not designed to build a retaining wall with. Even mortared together they will eventually get pushed over from the dirt behind them.
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    Re: Anyone have a good idea to hold back my 'retaining wall'? (pictures inside)

    Some worries about the sand:

    -It will hold moisture and and cause the legs to rust

    -it will settle and push against the pool causing problems with the pool form

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    Re: Anyone have a good idea to hold back my 'retaining wall'? (pictures inside)

    Quote Originally Posted by kimkats View Post
    Some worries about the sand:

    -It will hold moisture and and cause the legs to rust

    -it will settle and push against the pool causing problems with the pool form

    Kim
    Do you think I'm ok if I keep the sand between the plastic and concrete edging? Maybe I could use a few metal rods to help keep the concrete edging in place. There was no 'retaining wall' for the previous 3 years and there was very minimal wash out.....the stones are there just for a nice cleaner look really.
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    Re: Anyone have a good idea to hold back my 'retaining wall'? (pictures inside)

    That would be fine and look oh so nice. You might even want to put some pretty rocks on it as well.

    Kim
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    Re: Anyone have a good idea to hold back my 'retaining wall'? (pictures inside)

    All I can say is what I'd do and a couple of thoughts come to mind, assuming you're not keen to spend a lot more money. If you have enough $ to buy blocks intended for a retaining wall, I would do that, but otherwise, here's something that should work OK with what you've already got. Blocks intended for a retaining wall have a lip at the back or a key in the middle that stops them from slipping horizontally and yours don't have that.

    If you backfill between the blocks and your pool, you're countersinking the pool. The pool manufacturer may or may not allow this with respect to your warranty. I'll bet not, so based on that assumption, would you consider moving the blocks much closer to the pool? (like maybe an inch or two away) If so, here's what I'd do. To build a retaining wall, you need some room behind the blocks as you build it. First off, the bottom course of blocks needs to be countersunk into the ground. Half the height of the block would be enough. So get the blocks out of the way and then dig down so you can make a nice level bed of gravel under the bottom course and about 3" down from the current ground level. Use a rubber mallet to set the blocks all to same height and level. Backfill and compact to the original level to keep those blocks in place. That wall is pretty low - looks like maybe 12" or 18"? I think for that low of a wall, adhesive would work fine. Buy good stuff and be warned it's not cheap because you'll need a fair bit of it and you don't want to skimp on it. Follow the directions on the tube to the letter. Let the adhesive set before anything else. Behind the wall, put some perforated ag pipe with an outlet somewhere on the low side. If you can get it, buy the kind with a sock over it. Cover the ag pipe with drain rock maybe 4" to 6". Put some landscape cloth over the drain rock, then backfill with top soil for the lawn to grow into, or top it off with turf. Those aren't the right type of blocks for a retaining wall, so essentially you're building something more like a dry stack natural stone wall. Therefore, it would be a good idea to tip the wall out of vertical slightly, by setting the second and third courses back into the lawn a little away from the pool, maybe 1/2" back for each course of blocks.

    You could make it more solid by cutting some 3-foot long pieces of 1" wide galvanized strapping. Glue these pointed back toward the lawn between the top course and second course down, around about every 4 blocks or so. When backfilling behind the blocks, twist and then bend them at a right angle up against the original ground, so that they're tied into the backfill. You said it's not been getting any erosion, so this might be overkill, but it's pretty easy to do.

    A good thing you have going for you, is that the shape created by your blocks is an arch so movement is restricted as long as the blocks are touching, end to end.

    It's not quite kosher, but I think it would last a really long time. I haven't seen those particular blocks before, but if you know what they're called, the manufacturers often have websites with building advice. There may be mortared options if you don't mind doing some bricklaying. If that's possible for those, it would be sturdier and you could put some no. 3 rebar into the mortar poking out into the backfill. It's hard putting this all into words! Have fun with the project.
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    Re: Anyone have a good idea to hold back my 'retaining wall'? (pictures inside)

    As a structural engineer, i deal with things like this a lot. Here are my thoughts/comments:

    1) Those blocks will be fine to use as gravity stones. Your wall isn't tall enough to worry about anchoring them together with epoxy or reinforcing.
    2) The fact that you angled the blocks backwards toward the high side soil is a very good tactic. This is called "batter" and increases the resistance strength of the wall.
    3) Do not infill the front with sand, especially not 2 feet of it against the pool. Use #57 crushed stone or bigger, or free-draining rubber mulch just up to the top of the border.
    4) This part you may not like, but i highly recommend taking the wall down and re-placing it. The biggest issue I encounter with retaining walls is WATER. Especially in your location where you get a decent amount of rain, you need to provide a drainage path for water to get through and under the wall.
    - You need a granular stone base tamped down underneath the wall, or it will sink and rotate (BAD). At least 2-3" thick.
    - You need to dig the first course of stone blocks down - the first blocks at the bottom of the wall should be completely underground...or close to it. Otherwise the wall will slide (BAD).
    - you need a layer of stone behind the wall, at least a couple inches worth, so that water will drain down instead of pressing against the back of the wall. The force of the dirt on the retaining wall can TRIPLE from dry condition to saturated condition (VERY BAD). In at least 1 or 2 places i would take some 1" diameter PCV pipe and provide a "weep" holes horizontally between the stones (above the level of the fill in front of the wall) to allow water to freely pass from the back of the wall to the front.
    - try to avoid surcharging the soil directly behind the wall - i.e. don't drive your lawn tractor directly along the edge of the stones. Keep back a foot or 2 and push mow the edge zone.

    This illustrates the concept, although more complicated than your case:
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