# Retaining Wall Design



## SMLWinds (Dec 19, 2012)

I have disaster in my own backyard and need some help if anyone has some information on retaining wall designs.

I don't do landscaping so hired another contractor to do a series of 3 retaining walls in my back yard. The first 2 walls were to be 6 feet and the top wall would be 4 feet high. There is 6 feet between the 1st and 2nd and 6 feet between the 2nd and 3rd walls. Thus, there are 3 walls that total 16 feet in height with 12 feet between the bottom wall and top wall.

We have serious issues because we keep getting significant movement in the walls. The contractor keeps rebuilding them (without taking out the backfill) and they have moved several times.

I am trying to find out how you calculate the amount, weight, and stretch of geogrid necessary. Not only are my bottom 2 walls 6' tall, but they are essentially tethered together since the second wall sits on the geogrid of the first. 

I believe he put 3 layers of geogrid into each of the bottom 2 walls. The geogrid was supposed to stretch back 6-8 feet. Gravel was placed immediately behind the blocks and then backfill, which was sort of a sandy topsoil. The blocks are 8" versalock.

Where did he go wrong? Is the geogrid too short? Not enough layers? Is it possible the weight is too light? Is the backfill the problem because of how is soaks up water?

Any rules of thumbs or equations to calculate what is necessary for stable walls is appreciated.


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## greg24k (May 19, 2007)

SMLWinds said:


> I have disaster in my own backyard and need some help if anyone has some information on retaining wall designs.
> 
> I don't do landscaping so hired another contractor to do a series of 3 retaining walls in my back yard. The first 2 walls were to be 6 feet and the top wall would be 4 feet high. There is 6 feet between the 1st and 2nd and 6 feet between the 2nd and 3rd walls. Thus, there are 3 walls that total 16 feet in height with 12 feet between the bottom wall and top wall.
> 
> ...


Does your contractor takes into consideration appropriate drainage measures to prevent surface water from infiltrating into the wall backfill? If not that should be included in the design of any retaining wall system. 
Even during construction, backfill surface should be graded back away from the wall at the end of each day of construction to prevent water from collecting behind the wall and saturating the soil. 

With that said, when doing walls this high, you should have an Engineering design, and also have your contractor to provide your Engineer with drainage and backfill material classifications he is planning to use, to make sure the materials comply with the applicable specifications.

Here is an image, to give you an idea of how wall should be constructed (each case is different and should have its own design and Engineering calculations)


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## peteo (Jan 8, 2011)

You may want to get your versa lock rep involved. The contractor may have missed something in the design process and not realized it. Also as stated above, an architect should have been called in due to the height involved. Not sure about your area but in my town anything over 4' has to be engineered. Good luck!


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## SMLWinds (Dec 19, 2012)

Thanks for the responses. Obviously there is something terribly wrong. What really happened is I was told the contractor was getting an engineer to sign off on the plans but he lied to me and never had an engineer review anything. Furthermore, as I began to realize this guy had no clue how to fix these walls, I also found out that despite being in business for several years he has never had a contractor's license. So, there are a lot of things going on. What I'm really trying to find out is exactly where the design is flawed. I want to know how much geogrid is necessary, what weight, how far back it has to stretch, etc. I know ultimately an engineer will make that call, but that will be his opinion. We will be getting an engineer, but just haven't done so yet so I'm doing initial detective work. I figured there have to be some guidelines regarding how much geogrid should be used. If anyone has any rules for calculating this, please let me know. Thanks!


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## Cole82 (Nov 22, 2008)

The engineer will use a program like such to see what is needed to keep the wall in place.










Some install


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## SMLWinds (Dec 19, 2012)

That is what I am looking for. Is that a program I can access or a licensed engineering program that only engineers have? I just need to know the geogrid recommendations for my walls. Thanks!


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## Cole82 (Nov 22, 2008)

SMLWinds said:


> That is what I am looking for. Is that a program I can access or a licensed engineering program that only engineers have? I just need to know the geogrid recommendations for my walls. Thanks!


You have to be a licensed engineer to get the software. If you have a good relationship with an engineer you should be able to just email them the specs and they will send you a screen shot like above with the numbers.


Cole


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## CarpenterSFO (Dec 12, 2012)

DIY alert. http://www.contractortalk.com/f59/anybody-have-carpel-tunnel-surgery-recently-118589/#post1657556 It appears to me that the O.P. is a surgeon; he hired an unlicensed contractor; and the fight begins. Get involved at your own risk.


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## CarpenterSFO (Dec 12, 2012)

mis-posted


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## SMLWinds (Dec 19, 2012)

Bob-good golly! Do you really think I am going to go to court and call "bathroomcrasherjoe" as my expert witness based upon something he said on a chat room? I was just trying to get some information from people who have experience building these walls. Similar to how in the post you linked to I tried to offer my expertise to others. Hopefully people will not be afraid to help me just like in your link I wasn't afraid to help others...


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## SMLWinds (Dec 19, 2012)

Bob-I do hold a license, but only for our rental properties LLC. I make my living mostly in the operating room. I didn't know being a full time contractor was a requirement here...I thought it was for anyone with a license. Obviously I didn't knowingly hire an unlicensed individual...he has been contracting in our area for years and has constructed several similar walls. He told me the plans were done by an engineer. No, I didn't check to be certain he wasn't lying...just like out of the 500 people I operated on last year not a single one ever asked to see my medical license. Did you ask to see your last doctors diploma?? Who said I was saving money? I have spent a million bucks on my house and almost 6 digits on the landscaping disaster so I resent the remark that I am "saving money." I am not a cheap person. I am uncertain as to why you are so bitter. Instead of being upset that someone is being fraudulent and making the jobs of honest contractors harder, you seem to be happy that the "affluent" person may lose some money. I grew up on a farm, I still farm, I do woodworking, I am a bit of a jack of all trades...I am probably more like yourself than I am most "affluent" people. I obtained references on this guy, I went to other projects, and I have learned all I can about building these walls...hindsight is 20/20 but you rejoicing that someone you have never even met got what they deserved is ridiculous and juvenile. You should be trying to help rid your profession of individuals like this guy who give contractors a bad name. I have hired professionals...I have a team of engineers but learning from past mistakes I also want to educate myself. I am very appreciative of the great advice I got from those above. Thanks!


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## concretemasonry (Dec 1, 2006)

Even with a program a person has to have enough sense on how to use it , what the real inputs should be and then, finally, enough intelligence to under stand what the computer/prints out to decide if it is garbage or not.

There is something seriously wrong with the designer and permitting authority to permit the construction of a multi-tiered wall system with the minimal setbacks described, unless the soil borings showed some rare, ideal situation. The contractor the put it up is equally ignorant. The walls must be spaced far enough apart for the walls to minimize the loads from above and the soil boring give that information.

Coles first shot of a wall on a concrete footing since segmental retaining walls are not placed on a concrete footing if they are expected to perform properly. The drawing shown was for a reinforced rigid retaining wall with cantilever action (note the wide footing) that must be heavily reinforced to retail the soil retained instead of anchoring and stabilizing the soil behind the walls.

The Versalok drawings are for conceptual use and not intended for actual construction a of specific walls, but their installation instructions are very good and have been developed over the last 25 years to get domestic and international approvals.

I could be expert engineering witness, but probably not acceptable because of my involvement and familiarity with the major SRW systems domestically and internationally for 25 years.


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## CarpenterSFO (Dec 12, 2012)

... rethinking..


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## CarpenterSFO (Dec 12, 2012)

Hire a professional contractor. He or she will hire an engineer, and they will sort it out for you.


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## CarpenterSFO (Dec 12, 2012)

SMLWinds said:


> Bob-I do hold a license, but only for our rental properties LLC. I make my living mostly in the operating room. I didn't know being a full time contractor was a requirement here...I thought it was for anyone with a license. Obviously I didn't knowingly hire an unlicensed individual...he has been contracting in our area for years and has constructed several similar walls. He told me the plans were done by an engineer. No, I didn't check to be certain he wasn't lying...just like out of the 500 people I operated on last year not a single one ever asked to see my medical license. Did you ask to see your last doctors diploma?? Who said I was saving money? I have spent a million bucks on my house and almost 6 digits on the landscaping disaster so I resent the remark that I am "saving money." I am not a cheap person. I am uncertain as to why you are so bitter. Instead of being upset that someone is being fraudulent and making the jobs of honest contractors harder, you seem to be happy that the "affluent" person may lose some money. I grew up on a farm, I still farm, I do woodworking, I am a bit of a jack of all trades...I am probably more like yourself than I am most "affluent" people. I obtained references on this guy, I went to other projects, and I have learned all I can about building these walls...hindsight is 20/20 but you rejoicing that someone you have never even met got what they deserved is ridiculous and juvenile. You should be trying to help rid your profession of individuals like this guy who give contractors a bad name. I have hired professionals...I have a team of engineers but learning from past mistakes I also want to educate myself. I am very appreciative of the great advice I got from those above. Thanks!


I'm not bitter and I'm not rejoicing, but I am occasionally ridiculous and juvenile. I try not to be, but sometimes I can't help myself. And well, yes, like every other person in America, of course I check my doctor's educational credentials, on-line. For your future reference, Virginia's contractor's license lookup page is here: http://www.dpor.virginia.gov/LicenseLookup/

As long as we're there, can I look up your license?

And why didn't you ask your team of engineers, for heaven's sake?

I'm really sorry, but this still just reads to me like DIYer trying to get free engineering advice.

In order not to get drawn in further, I'm unsubscribing from this thread - whether I'm right or wrong, I'm positive I have nothing more to contribute. I can be PM'd if anyone likes.


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## SMLWinds (Dec 19, 2012)

Bob-I am just about done with this, but as my "I am right" parting shot I will send you my license into when I get home.

Yes, it probably does read like a DIYer, because although I hold a license like just about anyone can obtain, I don't know about something until I do it. Do all contractors know about carpentry, cabinet making, painting, retaining walls, marine construction, etc? No, you know about what you do regularly...I guess I probably am a DIYer with a license.


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## SMLWinds (Dec 19, 2012)

Dick-Thanks for that message. Lots of good information. I have thoroughly reviewed the installation instructions, recommendations, etc. from Versa Lok. Sounds like you can stack walls close together, but you have to expand your geogrid in order to account for the extra weight (because you are essentially building one 16 foot wall). None of that was done.

Yes, I feel pretty stupid now but what this boils down to is that I get duped by a true con artist. I know an engineer is required and was told one was involved. He even gave me the name of the engineer who was reviewing the plans. All this came out when I personally contacted that engineer and he knew nothing about the project. This guy is a true con artist and I'll be the first to admit, I bit for a while before catching on that he couldn't be trusted.

You are correct about the approving folks as well. Our county administrators truly dropped the ball as well and they know it. For some reason, they let him proceed based on the same comments that he was going to get engineered plans.

I do have appropriate engineers involved now. I also have had to hire an attorney and he hasn't mobilized the engineers just yet. That is why I am doing my own homework--I'm waiting until we mobilize the engineering team. I will ultimately get all the answers but I was just anxious to figure out exactly what should have been done. 

Thanks again for your help!


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## Tinstaafl (Jan 6, 2008)

SMLWinds said:


> Bob-I do hold a license, but only for our rental properties LLC. I make my living mostly in the operating room. I didn't know being a full time contractor was a requirement here...I thought it was for anyone with a license.


Aside from a bit of medical advice (thank you), your participation here has consisted solely of soliciting advice on work around your own home. Since professional contractors do this sort of work for a living and you do not, I must conclude that you do not belong here.

Thanks for posting on ContractorTalk.com. The Moderators of this forum would prefer that you post Do It Yourself related topics on our sister site www.DIYChatroom.com 

ContractorTalk.com is designed for professional contractors to discuss issues and topics related to the construction and remodeling industries. Many of our professional contractors are also members at DIYChatroom.com and are looking forward to assist you with your needs.

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We apologize for any inconvenience that this may have caused. This thread has been closed.


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