8' Retaining Wall

[Sulla]

I recently built a seven foot retaining wall to support a driveway spur. The first thing we (my son and I) did was to grade the embankment back about 115 degrees. We then covered the hill with landscaping cloth to ****** weed growth.

I went to Home Depot and bought a truck load of 6"x8"x4" more or less, pavers. My wall was rounded so having the front of the paver curved worked well, but there are plenty of others. The pavers have a lip on the back so that when stacked upside down they interlock and lean back about 110 degrees.

We trenched the bottom of the wall and filled it with stone for the base and the proceeded to stack and lock the bricks. About half way up the bricks and the wall began to diverge. From that point on we filled the gap with river stones. At the top we finished with loom and seed, though the grass didn't have time to come in before the frost.

We also created a dry well of sorts in the middle of the spur by digging a whole and a trench that exits through the wall. We placed crushed stone as a base, then perforated PVC pipe, more stone and the covered the whole thing with loom and seed.

So far so good.


I have to say however, that the wall faces down hill into the woods and failure is not likely to injure anyone. If life and limb where at stake I might have used blocks filled with concrete and rebar.

If I can get through the snow I will try to post some pictures.

 

[Duffster]

Based on a couple of responses, seems like poured concrete will the way to go. Where can I find some design guidelines? I am envisioning a monolithic pour w/ an oversize footer that offset - the cross section would look like 'L' with the backfill then pushing on the bottom to resist the overturning moment. Perhaps some integrally poured gussets if strength at base (once again, the overturning moment) will be a concern? Obviously, I will plan on backfilling with stone & draing pipe for good drainage.

A poured wall contractor would be a good start.

 

[jdonovan]

Where can I find some design guidelines? I am envisioning ...

Its going to have to be an engineered solution, so the guy putting his stamp on the plans will tell you how it has to be done... and probably tell you how is contractor is going to do it.

 

[Duffster]

Its going to have to be an engineered solution.

Not necessarily.

 

[CurlyDave]

I think a poured wall is stronger than any other kind, but in most cases an 8' wall can be built from block and be "strong enough", especially if you are willing to use 12" block.

It will need a footer, and it can be engineered with the footer-wall combination in a T-shape, or in an L-shape with the bottom of the L facing either way with respect to the dirt behind the wall.

If I am understanding your situation correctly, I would consider a combination retaining wall/foundation, where the wall becomes part of the foundation of the house. I have actually done this in adding a walk-out basement to an existing house, and it is entirely possible.

Considering the possible consequences of wall failure, I would consult with a local engineer.

Several hundred dollars now can save you an awful lot of grief in the near future.

 

[jake98]

Anybody know what the angle of the slope needs to be before it's considered a cliff?

 

[jdonovan]

you either have a level slope behind the wall, or a surcharge you have to design for.

 

[hitekcountry]

One of the strongest shapes is the arch. I've built a few retaining walls with this shape. The one I have pictures of is only about 40 inches tall but it's enough to give you an idea of one way to build a retaining wall.

It's built of concrete block the ones with the open ends. It has a footer with two strips of rebar running horizontal. In the wall rebar runs both horizontal and vertical and is completely filled with concrete. There is a perforated drain pipe behind and at the base of the wall.

 

[dstig1]

There are a lot of ways to do this, but as many have already said - you probably need to have in engineered. Around here there are a lot of retaining wall block places. Anchor Block and Versalok are both local, I believe. I have seen some wall built with those things that are 15' high, supporting parking lots at strip malls around the area. But of course they were engineered. There is another option in that there are large size blocks such as these folks:
RETAINING WALLS - RECON RETAINING WALLS INC.

These require serious heavy equipment to place of course, as the blocks are 1500-3500 lbs each, but I have seen some nice walls done with them.

And yes a poured wall is always an option. You can get decorative with the forms on the show side and stain or pigment the concrete too, so it doesn't look so bland.

Just throwing out options. But you will still need an engineer. Even if your town does not require it, you are in the danger zone here and it is well advised to do it right.

 

[crbr]

It's built of concrete block the ones with the open ends. It has a footer with two strips of rebar running horizontal. In the wall rebar runs both horizontal and vertical and is completely filled with concrete. There is a perforated drain pipe behind and at the base of the wall.

For the homebound engineering, that's the proper way it should be done. Hopefully the perforations are on the top side of the layout.

Accolades to your planning.


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