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Retaining Wall Rebuild

 
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Old 03-12-2012, 08:08 PM   #1
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Retaining Wall Rebuild


I purchased a home several months ago with a retaining wall build out of 6x6's about 3' x 100'. The wall has a noticeable bow in several areas due to poor drainage I am guessing. There is also substantial erosion on the top side of the wall where several of the sleepers are becoming exposed. This elevated area of the lawn is the primary play area for our children and I need to address this as it has become a safety issue. Due to the size of the wall and the cost associated with replacing this wall with a new block wall I am thinking of rebuilding the existing wall.
Here is my plan. I am open to suggestions as to weather or not this will work and if I am on the right path of logic as far as correcting this issue.
I plan on renting a small excavator to dig out the 3'x3' area behind the wall. I will then plumb the wall and secure in place with 2x4's staked into the ground and attached to the face of the retaining wall. I will then lay down landscape fabric in the area that has been excavated, lay down about 4" of rocks / gravel put in a french drain and fill with rock and then another layer of fabric and topsoil.
Am I on the right track with this project?
Any feedback would be greatly appreciated.
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Old 03-12-2012, 09:02 PM   #2
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Re: Retaining Wall Rebuild


If it is a typical segmental retaining wall (SRW), you need a compacted base for under the wall and it must be ABSOLUTELY level or you go nuts and regret it. - No concrete footing allowed for a SRW wall and just follow the instructions from the company that licenses (there are 4 internationally) your particular block. - If it a "knock-off" unit, good luck on getting assistance.

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Old 03-13-2012, 12:50 AM   #3
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Re: Retaining Wall Rebuild


Post a picture. Sounds like it is made of wood.
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Old 03-13-2012, 07:53 AM   #4
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Re: Retaining Wall Rebuild


Sorry, I missed the word "rebuild" since normally other materials are used, but the base preparation is the same with no concrete footing.
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Old 03-13-2012, 08:59 AM   #5
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Re: Retaining Wall Rebuild


My experience with "rebuilding" wood tie walls is that they rebuilt wall will fail almost exactly as the old wall only much faster.

If you do not use new material, the wall will return to its current position. I don't know why, but that has been my observations.
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Old 03-13-2012, 04:36 PM   #6
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Re: Retaining Wall Rebuild


here are a few pictures of the wall. I appreciate the feedback and look forward to more suggestions. I can send better quality pics upon request
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Old 03-13-2012, 04:43 PM   #7
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Re: Retaining Wall Rebuild


thanks guys
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Old 03-13-2012, 05:11 PM   #8
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Re: Retaining Wall Rebuild


Uh. That whole scenario looks odd. I would seriously consider a complete replacement. Can you get a photo in smaller scale like of the whole yard and back of house to see what overall drainage looks like?
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Old 03-13-2012, 06:17 PM   #9
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Re: Retaining Wall Rebuild


we are on the side of a hill /mountain. there is a pretty steep grade behind our lawn area that is landscaped
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Old 03-14-2012, 07:53 PM   #10
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Re: Retaining Wall Rebuild


In my opinion it is a complete redo. I notice there is no way near enough dead men on that wall. i would space the dead men every 8' staggered every other course. Ideally you want to "box" the dead men. A lot of wood but much stronger. Also, no drainage behind that wall. Strong reason why it failed.
A simple french drain is inadequate. The entire back side of the wall need 12" deep gravel with drain pipe.

I would spend the time to redo it. Why do it half assed then have it fail next year.
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Old 03-14-2012, 08:21 PM   #11
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Re: Retaining Wall Rebuild


So the concensus is a complete redo. Any advice on what type of product to use?

Also. Would a french drain work better at the back side of the yard before the grass?

Continued thanks for the input..
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Old 03-14-2012, 08:59 PM   #12
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Re: Retaining Wall Rebuild


It is situation with a very large contributory area on a substantial slope for rainfall/moisture coupled with poor backfill and no real way to get rid of it and reduce the pressure on any wall. I have seen 40' high segmental block retaining walls on mountainside sites over 10 years old with no problems because of the materials used and the ability to get rid of the runoff.

Even on a 3' high wall a few scattered dead men do not have much of a long term effect.

Definitely, a proper drain in a granular backfill is a step in the right direction. The wood does not provide much mass, since you are trying to build a gravity wall.
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Old 03-14-2012, 11:10 PM   #13
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Re: Retaining Wall Rebuild


In a state build job there would be two walls constructed locking in an eight foot deadman at least every second tie on each course. The hydrostatic pressure against the wall from the rain water run off is what is pushing this wall out. Also the material that the ties are made out of now are crap. Block wall with geo grid and drainage is the answer there Mr. Homeowner
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Old 03-15-2012, 11:33 AM   #14
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Re: Retaining Wall Rebuild


are the deadmen secured into the ground in any way? can't really tell from the pictures. usually i've seen them secured using rebar or even another deadman attached parallel to the wall. if not secured then they're just moving along with everything else.
another way to do it is to introduce steel ibeams that go vertically into the soil and then the 6x6s drop down into the pockets of the steel.
definitely have to fix the drainage, though, no matter what you do.
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Old 03-15-2012, 02:24 PM   #15
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Re: Retaining Wall Rebuild


Sometimes deadmen are just for appearance and a "warm and fuzzy" security. For a 6" timber wall, it does not appear there anough ends showing even though the wall is not really high.

I could not tell from the photos, but where does all the water that accumulates behind the wall go?
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Old 03-15-2012, 03:31 PM   #16
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Re: Retaining Wall Rebuild


The 6x6's and dead men are secured with rebar. I was thinking that if it was a rebuild (considering the wall has held up for 22 years so far) I would also use horizontal reinforcements on the deadmen to help with the reinforcement. However, after much suggestion and a few price comps a new interlocking block wall might not be as expensive as I originally anticipated.

Drainage....where does it go??? Well I guess that there is no real plan for this and I am assuming that this is the root of all problems associated with this project. I was hoping for budgetary reasons that I could go with my original plan:
1-excavate a 3'x3' area behind wall
2- Plumb wall and secure / brace from the front
3- install french drain and back fill

If I can get the water running to either side of my home the property continues to slope in a way that ther water would carry away from any structure and end up in a gully / drainage ditch on the side of my road.
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Old 03-15-2012, 04:03 PM   #17
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Re: Retaining Wall Rebuild


question regarding drainage:

Would I be better off with a drainage system at the rear of the yard, the foot of the steep slope before the grass (see red line in pics). Or would I be better off with the drainage directly behind the wall (see yellow line in pics)

Thanks again for all of the help

James
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Old 03-15-2012, 06:02 PM   #18
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Re: Retaining Wall Rebuild


No question - You collect and get rid of the water before it creates a structural or deflection problem. The location of the red line may be preferred because a drain at the base of the wall coupled with a proper backfill would minimize the effects of both ground water and surface water.

Your wall is only 3' high and can be built with segmental retaining walls and most local codes allow 4' or 5' heights without engineering, but the licensors of the major systems (Allan Block, Anchor Wall systems, Keystone and Versalok) that have international experience usually put the max at 5', even though there have been many engineered installations up to 40' with engineering and geo-grid. The installations do give recommendations on backfill material and the use of drain tile even though the systems does permit drainage though the open joints.
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Old 03-15-2012, 07:11 PM   #19
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Re: Retaining Wall Rebuild


Dovetail, What is your anticipated budget for rebuilding the wall?

If I understand you correctly, you are want to keep the retaining wall materials you currently have, reinforce it, and/or rebuild it.

The timbers look like treated 6 x 6 to me and yes there appears to be to few deadmen or tiebacks. But it has held for 22 years?

I personally think, that if your are on a limited budget, I would do as you say, excavate behind it, straighten it up somehow, secure it with some new dead men of some sort, install a french drain, back fill with clean rock and call it good.
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Old 03-15-2012, 07:39 PM   #20
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Re: Retaining Wall Rebuild


My original budget was to remain around $1,000. $500 for excavator rental over the weekend and another 500 for materials associated with the project.
I feel like i might be able to rebuild a new wall for $4,000 after some quick estimates. Now this would be for the most basic segmented block wall, no frills. And if i am going to spend this kind of $$$ I might as well go big or go home in which case i would be adding a paver patio to match the new block wall. I am not sure that I am ready to see the price tag for all of this material and work.

My original plan is meant to be a mid term band aid, 2-3 years, until I am ready to invest in a project of this dollar amount. My main concern is the safety issue with the erosion of the soil at the top of the wall and the fact that my children (2 & 4 yrs) play there. I am willing to spend the $1,000 to prevent a trip to the ER this year and completly redo the work of 2012 in 2015.
Also, we have been in this house for less than a year and there are other large scale renovations that are goint to take precident over this project. I am planning a 30k kitchen remodel and a the following year a 10k master bath project. Putting in a 10k patio project before these projects get done might mean a divorce for me.

Thanks again. i appreciate all of the comments and feedback regarding this project.

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