[4runner freak]

I am going to be putting up 2 cinder block retaining walls in my back yard(hopefully this weekend) and wanted to get some advise on what is needed.
I know that for major load bearing applications and to make it bulletproof, it would need a concrete footer with re-bar set in it, the blocks assembled and filled with concrete.

For this application, each wall is going to be holding 20inches of earth(24" of block, with bottom row 4" below grade). This will be a stepped set up with the second wall sitting back a couple feet from the first.
This area does not see very much run off but is in Denver, CO(so it does see snow) and the ground is very clay like.

We were planning on tamping the ground beneath the wall, driving re-bar every couple blocks, and filling them with dirt and small rocks(pea gravel).

Am I mistaken on what we need for this?
Any help is greatly appreciated.
Thanks

[natural12]

Sounds like you got it. Dont forget to add drainage behind the wall. Gravel and a perforated pipe.
BTY they do not make cinder blocks any more. Concrete blocks or CMU.

Mike

[jshilan]

It's hard to tell from your description if you are actually using concrete block (not cinder block as was pointed out) that should be wet laid and is typically used for foundations and other masonry work. Or if you plan on using the CMU type of retaining wall stone that most landscape contractors use. If I had to guess, based on your description, it is the latter.

The process that you are describing is not correct and will not make it through a couple of freeze thaw cycles before it starts to move. Rebar is typically not required, and as per natural12 you need gravel, pipe and fabric for drainage, as well as at least a gravel or other appropriate stone footing. If the units you are using have voids that are to be filled with gravel, fill it with clean gravel not the existing clay soil.

All of the catalogues have details on how their walls should be built and I suggest looking through them and do a little more research before you do the weekend warrior thing.

See if you can get us some more info about the brand of stone etc. so we can guide you better.

Nice computer graphic for the walls.

[4runner freak]

Actually, I think they ARE cinder blocks.
These are being recycled! These are from a local green house, where they have been used as planters for ~30 years.

[4runner freak]

This is what we we going for.
In real life though, it will be different.

[jshilan]

They are indeed "cinder blocks". I don't quite understand your building process, but I am hoping you are a structural engineer.

Maybe someone else has some thoughts. Do think about some sort of drainage behind the walls to keep them from pushing out.

Good luck with the project and please send some finished photos.

[Stonehenge]

If you're going to use cinder blocks, that means you're going to need to do a wet (mortar) installation. By definition, this means you'll have to pour a footer below the frost line in your area for each wall. Zone 6, it might be 36", but I'm not sure.

Having rebar extend from the footing into the block is a good idea. The block will need to be mortared together and filled with mortar or concrete, not dirt or pea gravel.

Side note - if you were planning to have rebar extend into the dirt below the block to serve as a reinforcement, it's incorrect and a waste of the expense of rebar and your time - if that wall decide to fall, the rebar will slice through your soil like a knife through butter as the wall goes over. It adds nothing to the structural integrity of the wall.

Next, for your wet application, you'll need to provide for weep holes out the face of the wall (since each block will be mortared, sealing off the water behind the wall - gotta give the water a place to go). You'll also want some drainage material behind the wall to collect and daylight the water, otherwise, as Jody mentions, that wall will be tipping over after just a few freeze-thaw cycles.

Now, with all the work I just described, I would think the more economical and easier way to go would be to buy some retaining wall block, which are designed as a gravity (read: flexible) wall system that does not require a concrete footing, mortar or rebar. Sure, you won't be able to get the block for $.01 apiece, but you also won't have to spend $1,000 in concrete and mortar to do the job right. Plus, with that skid steer there, you can have the job done in a weekend, instead of a solid month. Not to mention, it'll look tons better than mortared gray block.

My $.02, anyway.

Then, your block

[Lanelle]

Are you going to mortar the blocks together?
Please consult your county/city's building codes for retaining walls.
Even though these are low walls, if they are going to be put on concrete and mortared together and filled with concrete, they need to go on a footing that is as deep as your soil frost depth.
How are you going to finish the face of the wall to make it more attractive?

[4runner freak]

Thanks for all the help.
The walls are mostly done.
Still have to put top caps on.
We ended up compacting the ground beneath and leveling with sand.
We mortared them together and filled with concrete.

We are going to leave the face as-is at this point.
They have been in a green house for the past ~30 years and have nice looking water lines on them. If the lines wash away or ? we may stucco or paint in the future.

[papercutter]

ok, the look of the blocks with the water stains? That's actually kind of cool. Color me surprised. Having done it on a sand footer scares me, but it's not in my backyard.

[4runner freak]

Originally Posted by papercutter

ok, the look of the blocks with the water stains? That's actually kind of cool. Color me surprised. Having done it on a sand footer scares me, but it's not in my backyard.

The ground there is like clay, so I don't see it being an issue anytime soon.

[Fine Edge]

Ummmm, .... where is the mortar between the top and bottom of the blocks?
Maybe I couldn't see it clearly but it looked non-existent.

The sand footer in Denver could be an issue but who knows?

[Lumas976]

On edge's note... is there any mortar on the blocks other than on the curve?