Advice sought on retaining wall options

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Old 06-10-10, 10:20 AM
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Advice sought on retaining wall options

Hi all,

I am going to tackle a retaining wall project in the next month or so, and am considering a few different options.

I will be replacing an existing and very ugly cinderblock wall that is falling apart. About 50 feet of it is 3' tall, and one side (about 20 feet long) tapers from 3' tall to ground level. Here are the options I'm considering. I'd appreciate hearing your thoughts.

Option 1: I remove all the cinderblock and replace it with Versa-Lok cement blocks.

Option 2: I re-lay the cinderblock with the appropriate amount of backfill and mortar it in place. I then place a 6-8" stone veneer (fieldstone or bluestone) in front of the cinderblock.

Option 3: I get rid of the cinderblock and drystack fieldstone/bluestone. I didn't expect a drystack wall to be able to withstand the pressure of the amount of earth behind it (the ground behind slopes up to about 4'), but I read a mason-authored stonscaping book that asserted that as long as the base of the drystack wall is at least half as thick as its height, it will be fine.


I'd much rather have natural stone instead of Versa-Lok, but I'm not keen on using mortar (no experience with it). I am aware that working with stone would add a lot more time to the project, since the material isn't uniform and will need to be fitted together ... that extra time isn't a great concern of mine.
 
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Old 06-11-10, 01:27 PM
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Where in the USA are you? Local climate would flavor my response, as freeze / thaw cycles could effect what you are doing. How much earth is the 3' high section holding, ie a small planting bed or 30' of earth 3' tall.
 
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Old 06-11-10, 01:49 PM
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A VersaLok or similar wall (there are 3 other internationally used and recognized products) that would be adequate for up to 4' high of soil without engineering if the slope behind is reasonable.

This type of wall can go to 40' high with engineering, but 4' is not a problem.

All segmental retaining wall block should NOT be placed on a concrete footing, but on a level, well compacted base. No mortar is permitted in the construction.

The key to a good retaining walls is providing adequate drainage behind the wall.

A segmental wall is a flexible wall with lateral shear strength due to the unit shape as contrasted wither individual pieces used. This allows very small seasonal and moisture related movement even in the far north and is not plagued by the cracks common to rigid poured walls. A retaining wall is a very difficult structure for an engineer to design and that is why many city, county and state agencies have standard design plate for use by field engineers and individuals for walls under 4' high.

Dick
 
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Old 06-11-10, 08:50 PM
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Originally Posted by brickyard blues View Post
Where in the USA are you? Local climate would flavor my response, as freeze / thaw cycles could effect what you are doing. How much earth is the 3' high section holding, ie a small planting bed or 30' of earth 3' tall.
I'm in Pittsburgh, so there is a frost concern, plus we get quite a bit of rain ... so I do like the natural drainage and flexibility (in a frostheaving sense) that drystack would provide.

* 25 feet of the wall holds back about 20' feet of earth that rises from 3' to 4'. It's bordered on the sides by open area for steps and on the other by a part of the wall that tapers from 3' to 0'.

* On the other side of the steps, the wall stretches back about 15' and holds back only about 8'-10' of earth (same 3'-4' height).

Would a drystack wall with a base 2-2.5' thick do the trick? I know to angle the wall back by half an inch for each foot of height.
 

Last edited by brian113; 06-11-10 at 09:12 PM.
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Old 06-14-10, 09:09 AM
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Brian -

Your situation (cold climate/frost and low heights) are what the original units were designed for. Since the international acceptance, they branched out into the high walls (over 4' and up to 40') and tiered installations that should be the engineered because of the total or global soil/block system.

For low walls they are commonly use in many states, counties and local municipalities and the users have standard designs or detail plates in the manuals to avoid engineering on the common applications of new sidewalks or road widening.

The beauty of the system is being able to properly build without excessive, disruptive excavation, poured footings because they can move and come back seasonally and be used for inside and outside curves and on sloping sites.

For good information on applications and use/installations, take a look at the sites of the major products that are available world-wide (Allan Block, Anchor Wall Systems, Keystone and VersaLok) - good information and great photos of applications.

Dick
 
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Old 06-14-10, 02:43 PM
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Originally Posted by Concretemasonry View Post
Brian -

Your situation (cold climate/frost and low heights) are what the original units were designed for. Since the international acceptance, they branched out into the high walls (over 4' and up to 40') and tiered installations that should be the engineered because of the total or global soil/block system.

For low walls they are commonly use in many states, counties and local municipalities and the users have standard designs or detail plates in the manuals to avoid engineering on the common applications of new sidewalks or road widening.

The beauty of the system is being able to properly build without excessive, disruptive excavation, poured footings because they can move and come back seasonally and be used for inside and outside curves and on sloping sites.

For good information on applications and use/installations, take a look at the sites of the major products that are available world-wide (Allan Block, Anchor Wall Systems, Keystone and VersaLok) - good information and great photos of applications.

Dick
Dick, I appreciate the info. You don't have to sell me on these systems I've already priced Versa-Lok for my job, and I'm sure it will outlast me. At this point, it is the option to beat.

That said, I am trying to beat it. The one thing Versa-Lok has going against it, as far as I'm concerned, is aesthetics. I have two concerns:

1. I'm not saying that it's not an attractive product (it is), ... however, there is A LOT of Versa-Lok (or similar looking product) in my neighborhood, and I would like my wall to stand out. (I fell in love with the look of Techo-Bloc, but the price is FAR beyond my budget.)

2. There is an awful lot efflorescence stains on the blocks in my neighborhood. Yes, I know there are treatments to wash this away, but two of my neighbors have told me that the are not happy with the effectiveness or price of the treatments. Given the number of stains I see around me, I suspect the problem might be traced to the regional manufacturer of the block, and I'd like to avoid dealing with these stains, if possible.

Those two concerns have led me to explore the feasibility of a drystack natural stone wall. In a neighborhood where you can't swing a cat without hitting one of these wall systems, a natural rock wall certainly would be distinctive, and it would not have efflorescence problems. But those two drawbacks are secondary to my main question strictly speaking about the engineering involved, would a correctly built drystack stone wall be suitable for a hill that slopes to a maximum of 4 feet?

If the engineering won't work, I'll have no problem going with Versa-Lok (in fact, it would save me a few hundred dollars, based on price estimates), but I don't want to discount real stone if it would be sufficient for the job.
 
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