Narrow Retaining Wall / Barrier - Input Sought (Video)

uvascanyon(8A)January 14, 2011

I'm in the process of digging holes for what will be 16 Italian Cypress trees. A good number of them will get planted along a strip of land about 3' wide, right near the property line (location of dilapidated fence). Not easily seen due to dirt over it, is the blacktop driveway surface... And that's the problem here. How to best keep the earth from coming down onto the driveway?

Given these somewhat tight dimensions, I really can't use those retaining wall locking block as they'd take-up to much space. Pressure-treated planks, 2x10's, with 4x4 posts? I know these eat-up hardware (metal) now though...

Anything thin, flexible, that can go up 8 to 10" above ground level? Concrete pavers, stepping stones, inverted maybe? Thanks for any input you might have.

Here is a link that might be useful: YouTube Vid for Retaining Wall / Barrier Feedback

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Can't help with the dirt issue, but hope you will be doing a lot more prep for planting each of the cypresses. The post-hole digger holes won't do. Others will probably come in the tell you correct method.

    Bookmark   January 15, 2011 at 6:26AM
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A lot more prep? Do share, anyone...

I'll try a search here too, but the directions say a hole twice as large as the plant container. I had not mentioned the size, but these are small, one gallon pots. The holes are plenty deep (approx 2') already. The width is not done yet, but I'd say 80%. I want to be equidistant from the fence, so I had planned to add a few inches to the width, in the right direction later. Doing so thus far has been remarkably easy, with the post hole digger. Again, if I should not be doing that, I'll all ears...

Again, while in the process of locating and digging these holes, I realized that I need something to retain the soil, something not too bulky or wide.

Thank you.

    Bookmark   January 15, 2011 at 11:29AM
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You might use a 3.5 inch wide concrete wall a few inches tall to hold back the bed soil. Once you see how it's done most homeowners can build these walls. Check the end of the link below to see a 12 inch high wall of concrete.

Here is a link that might be useful: Poured concrete walls

    Bookmark   January 15, 2011 at 5:29PM
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That seems to be perfect! I've worked with concrete before on other projects, most recently this past Summer... Didn't even think about it here.

I saw the forms for the 3.5" wall. Any particular reason why that thickness? Also, it looks like some of the bolts used to keep the forms from blowing-out actually go through the concrete. I suppose that is necessary. Are those removed before it cures, or just hacksawed-off later?

Thanks again for the great idea!

    Bookmark   January 15, 2011 at 11:13PM
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The thickness of the wall matches the width of standard 2 x 4 lumber, so I don't have to cut lumber for a piece to put at the end of the forms.

The tie bolts do go through the wall, actually I often use all-thread cut to length instead of bolts. Inside the forms, 3/4 inch pvc pipe acts as a spacer to set the wall thickness. The bolts run through the pvc spacers which protect them from the concrete (see photo below). I coat the pvc spacers with full strength mop-n-glo and let it dry before form assembly. After the pour, remove panels, bolts, and spacers to be used on the next wall section.

For these little bed walls up to 12 inches high, I don't pour a footer. I level the soil to the bottom of the wall grade then about every 4 feet along the wall I dig a post hole a minimum of 1 ft deep plus an additional inch for each inch of wall height above 4 inches. The post hole is filled with concrete and a rebar inserted to extend upward into where the wall will be built.

    Bookmark   January 16, 2011 at 6:48AM
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3.5" explained, and makes perfect sense.

Don't know if the PVC spacer idea is your concoction, but it's ingenious. I'm guessing the Mop-n-Glo is used to make it easier to remove the PVC spacers. One last question... Do you later fill the spacer-created holes with concrete?

    Bookmark   January 16, 2011 at 3:43PM
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On larger walls the bottom row of holes are left open as weep holes. The others can be filled in as the walls are rendered or a veneer is applied.

The holes in parallel walls with steps between serve as a means to temporary bolt on standard forms with cleats to mount riser boards to pour the steps. The same form panel works for up to 5 steps with risers between 6_3/4 to 7_1/4, 11 inch treads.

    Bookmark   January 16, 2011 at 5:18PM
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Post-hole diggers seem to compact the soil on the sides. I think you'd get better results by breaking up soil all around each planting. Try filling one of the new holes with water and note how long it takes to drain. What you're aiming for is excellent drainage.

Sorry I wasn't clearer in first post. Thought someone else would (and could) explain this better.

Best, Rosie

    Bookmark   January 16, 2011 at 5:32PM
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pls8xx, you are an inspiration, thank you very much. I'm going to buy a concrete mixer as I plan to tackle this and larger jobs, now that I see what can be accomplished. I might add some color into the concrete just it case I decide to not go with a veneer...

Rosie, thanks for the follow-up. You make a good point as I've noticed that before, and here too on these holes. I plan to "scratch-up" the sides of the holes so they are more porous and more inviting for the roots to expand outward.

    Bookmark   January 17, 2011 at 4:14AM
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If you can, take some pictures or video of what you do. Around here, we learn from each other.

    Bookmark   January 17, 2011 at 3:15PM
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botann(z8 SEof Seattle)

Digging a ditch might be a better alternative to digging individual post holes. Way better for the plants, and might be quicker too. I guess that would depend on the spacing.

pls8xx, nice illustration! Anybody doing a concrete wall should see it. I used molasses instead of Mop-n-Glo.

You can use lampblack in the mix to darken the concrete, especially for patios. It cuts down on the glare. That, or do exposed conglomerate which takes some practice to do well.


    Bookmark   January 24, 2011 at 1:51PM
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We rented a "Post Hole Digger" or Auger on a trailer. 2 Man operation. To dig 20 holes for plants here in AZ. Ground was very very hard. Worked like a charm!

We tried the fill the hole with water and see how long it took to drain. Over a week. That is why we went with "more power!"

    Bookmark   January 31, 2011 at 12:00PM
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bernd ny zone5

I made a 1 ft wall out of 4x4s stacked with offsets, to protect my new fence from neighbor's soil. To anchor them I dug 18 inch deep postholes, spaced 3 ft, put a 1/2 in rebar in each of them and filled them with concrete. I had the 4x4s pre-drilled to fit them over the rebars, needed some careful calculation for that though.

    Bookmark   February 1, 2011 at 1:18PM
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