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pilk00 07-20-2008 09:33 AM

Rebuilding a Retaining Wall
 
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Once upon a time I let a Sumac tree grow too tall and it broke my wall. This was in 1980. I used 24" drywall block to rebuild it. The internet wasn't around then, so I had a lot fewer resources. The wall I built stayed up for 28 years... but it was starting to lean a little too much so I'm building it again.

I want it to be safe, but I'd rather not spend a fortune on it. I've taken some photos. If you look at the pictures what you see is nearly all I want to do in terms of removing old brick. For the part of the wall that was leaning, I've been thinking about leaving the ground-level course (visible in the photos) and just building a wall up from just inside that course. Most of the part I'm talking about is near ground level already. It's the big corner section towards the back of the yard that I'd rather not tear down/rebuild.

Rather than tearing that part down, again I thought about rebuilding a second wall right inside the existing one.

The part I really don't want to rebuild is the corner - that's where all the slope is - plus it's tricky supporting the soil under the porch while I rebuild.

Any suggestions will be sincerely appreciated!

mgsproperties 07-21-2008 12:21 AM

oh boy!!!

The strength of the retaining wall is very much depended upon the footing and the wall being fully grouted with proper rebar.

If the footing is stable enough i guess you try to drill 1/2" - 3/4" holes in the footing I would go at least 18" deep. Then insert rebar along with epoxy to make them whole.

Start by rebuilding the wall with 8" or bigger blocks, make sure you have both horizontal & vertical rebar’s with at least 18" joints. Make sure you fully grout the wall as you are building it and use a vibrator or a rebar on a drill and vibrate the concrete. Make the corner area (L shape) overlap each other.

But if you want my honest opinion hire a licensed contractor, too much responsibility.

newpaint 07-26-2008 01:43 PM

Concrete footing
 
Tear out the bottom course, level and gravel the run and then pour at least a 4" concrete footing with rebar going down at least 18". As you lay the block in courses, continue to mortar but also move each course back about an inch, backfill as you go and tamp your earth down tight.

concretemasonry 07-26-2008 02:07 PM

Where are you located? - Climate with frost?

If so, forget about a mortared and reinforced wall unless you get it below your frost depth. Even a 1/4" frost heave will crack any reinforced wall.

You old wall moved if there was frost and you never saw the crack or heave. In the spring it comes back close to where it was. Your old wall just did not have any horizontal shear resistance other then the weight of the wall on a smooth surface with sand and water for lubrication.

When you built segmental retaining walls were not common in the U.S., so there were limited choces for a dry stacked wall. Today, there are more options. A segmental retaining wall (SRW) is built without a concrete footing (concrete not permitted!!) and specially shaped block are used. Because of the lack of demand for plain units, they are available only in split, colored units.

fungku 07-27-2008 01:31 AM

Where I come from there is a lot of frost and heaving. here is how I would do it, using Allen blocks or other morterless blocks. no concrete or mortar.

1. take out the bottom course, dig back some of the earth on the high end so it's sloped back while you work and doesn't come crashing down.

2. Where the bottom course is going to be, dig below grade on low side, maybe around 6 inches.

3. level, compact, and then put landscape fabric where the bottom course will go and up the slope.

4. Put 3/4 crushed rock, where bottom course will be. level and compact

5. lay your bottom course, keeping a straight line and keeping level.

6. keep laying courses straight and level while backfilling behind the wall with crushed rocks and the cut-offs of block (to save having to throw them out)

7. remember to keep compacting the backfilling of rock.

9. when you get near the top stop backfilling with rock, fold the landscape fabric back over all the rock you've been backfilling with and backfill the last course or two with soil.

10. Do the capstones and you're done.

it is a lot of work and will take a long time, but it should last you forever or close to it.

also, consider running drain tile behind the wall for drainage


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