Curving Concrete Block Retaining Wall

[Toad]

I want to build an approximately 2 ft high concrete block retaining wall in my back yard. I would like a gentle curve instead of a right angle at the corners. Is it structuraly OK to just angle the blocks and fill the back gap with mortar? If so, how do you handle the second course in a running bond when the cells now won't line up? Any advice greatly appreciated!

RICK

[doyle]

First off, let me ask if you have considered using the mortarless-style retaining wall blocks? They are designed so that you can make curved-shaped walls.

It may be that you already have a supply of blocks and may just have your heart set on using the square blocks. If that's the case, then the curve would need to be fairly moderate to avoid the jaggedness you already have been thinking of. Of course, you can always apply several coats of mortar (stucco-style) over the surface when you are done, which will fill in all the areas where the staggered blocks are. You would eventually have a smooth curve. Just seems like a lot of extra work to me. Give me the 'stacked-stone' retaining blocks any day over having to mix up mortar...lol

[Toad]

Thanks for your reply, Doyle. Actually, the concrete block retaining wall will be faced with stucco. Since the wall will be an inside curve, the gaps in the blocks will occur on the back side, and the is the problem of the next course cells not lining up right which presents a problem with the vertical rebar placement.

I did look at the masonry blocks, but the Mrs. seems to want a stucco retaining wall to complement the slate tile patio that is yet to be built. Yes it is a lot of work!

I imagine there is some cutting that needs to be done to handle the curve and cell alignment, but wondered whether anyone had any direct experience with this particular issue?

[doyle]

Have you been to a concrete place that makes blocks? We have one here in town with dozens of different styles of blocks. Seems I remeber there being a special block for inside corners. Picture a big square block with a C shape cut into one corner. This would give you an inside curve, however it would be a small one, more along the lines of a 90 degree angle. Who knows, there may be other styles.

Look in the yellow pages under "Concrete Blocks and Shapes" or "Concrete Products". Both of those headings in the Atlanta book have places that carry blocks.

What the wife wants, the wife gets...LOL

[Shanley]

Jst lay it in stack bond, place your rebar every 16" (every other cell) and grout solid...You may want the top course to be a bond beam with a #4 rebar placed horizontally; you shouldn't have a problem putting a #4 rebar in a subtle radius.

[Toad]

Thanks for your replies. I may have a couple more questions on this. This is a great site!

[Toad]

More on the 3' high garden retaining wall. I went to a supply place and laid out some concrete blocks in an inside curve. Then I stacked a few in a second course in a running bond pattern. Although rebar placement through the staggered cells looks like no problem, the second course has significant (1.5" or so) insets and overhangs relative to the first course due to block joints meeting in different locations. I want to finish the face with stucco, and filling that kind of uneven surface seems like a lot to deal with.

Can I just lay the 3 or 4 courses on the curving portion of the wall in a straight stack (i.e. all the block joints in the same location) and just set rebar in each cell for added strength? Then I could use a half block to return to a running bond on the straight sections. I just don't know how important the running bond is structurally. Shanely, I am not sure what "stacked bond" is. Maybe you already answered the question.

Any thoughts greatly appreciated!

[Shanley]

I'd lay it all in stack bond (1 over 1 as opposed to 1 over 2 in running bond)...Rebar in every other cell should be plenty and a bond beam (ask for knockout bond beam block) course on top with a couple #4 bar horizontally...make sure the vertical rebar come up into the BB course just above the horizontal rebar...also use horizontal wire reinforcing (ie Duro-Wall) every other course...this should tie your wall together nicely and the stack bond will allow you to finish the exposed face...you may also want to consider an Architectural CMU like a Splitface block which is very forgiving for a novice installation and come in many colors...a stack bond with tooled joints looks great... just a suggestion to minimize your labor

[Toad]

Thanks, Shane. No, I think I will press on with the block, and just face it with stucco or cultured stone. I just wanted to be sure a stack bond was OK structurally. Your help is much appreciated.

RICK

[Toad]

In regard to the base material for the retaining wall concrete footing and a patio slab, most references I see call for compacted gravel as a subase for the pour. Others I have talked to say to use a compacted class II roadbase material. Others say both.

I live in northern CA in a non-freezing area. I have excavated about 12 inches below final grade. For the patio can I just compact about 6-7 inches of the class II roadbase then form & pour a 4 inch slab without using crushed rock? (The concrete will be finished with a mortored.slate tile)

How about the retaining wall footing? Can that be poured over the class II or is crushed rock required as well (or instead of). The backside of this low retaining wall will have proper drainage.

Back to the well of knowledge for the answers!

[Rich]

In my opinion it doesn't matter what you put down as long as it's a solid base.. either non disturbed earth or some type of rock base. Some rock will compact better than others.. personally I don't really care for roadbase unless it's for a road. That doesn't mean it won't do the job - I just don't like working with it.. hard to shovel compared to gravel.