Block Retaining Wall on Concrete

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  #1  
Old 05-29-12, 06:19 AM
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Block Retaining Wall on Concrete

Hi All,

I have a retaining wall that is approximately 27" high and 35' long that is comprised of cinder blocks that were mortared together, and then topped off with a 3" cap. It is currently really leaning, and I believe that is because the wall has no drainage system or weep holes, so water builds up behind it and pushes it forward.

Anyways, I have got a few quotes but just could not justify spending the money I was quoted for, so I have begun to think that I want to/can do it myself. I have read several articles online, a couple of books about block retaining walls (this is the style I am wanting to use), and seen a few videos too.

My current wall seperates the yard from the patio. The current yard is slopish. You do not feel like you are falling down when on the lawn, and it is
not like doing hill sprints going up, but there is a slope.

I understand the first layer is the most important, but I am wonderining if it is possible to build a block retaining wall on the concrete patio. The patio itself is about 7" thick. And, if I could just knock down the old wall, build the new wall on the patio, create a drain system in between the lawn and new wall, and then backfill, that would be the quickest fix for this.

However, can I build a block retaining wall on a conrete base? Should I adhere the first level to the concrete? If so, should I use a concrete to concrete adhesive? Mortar? Or is this just not a good idea, and should I knock down the old wall, excavate, and place it in soil and go from there.

I am in Massachusetts, so we do have freezes in the winter. Not sure how much that matters, but want to be as extensive as possible. I will also be using 6" high interlocking blocks (from Lowe's) and need to be 4 high, with a 3" cap, so 27" high total.

Thanks for your time, and any input. Let me know if you need any details, or additional info.

Dave
 
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Old 05-29-12, 02:42 PM
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Don't put the new wall on the patio. You will want to the first course of the wall to be below grade. That helps keep the wall from being pushed forward. You should get the manufacturer's instructions to make sure you build it to their specs. You will need to dig down enough to allow for your base material. The soil at the bottom should be compacted, then the base material added and compacted. Then you put your wall on top of that. Back fill your wall about 12" back with 3/4" crushed stone. Put landscape fabric between the crushed stone and the soil. That will prevent the stone from becoming clogged with silt. Also a drain pipe behind the wall that drains to daylight will help with drainage as well.
 
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Old 05-29-12, 03:11 PM
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drooplug hit the nail on the head.Flat/flexible fabric is many, many times superior to a "sock" and has many uses.

Dick
 
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Old 05-29-12, 05:51 PM
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Thanks for the input guys.

I figured that my "ideal" choice of putting it on the patio would be not so great an idea but I was hoping it would be "good enough".

I was planning on using fabric and a drain pipe to assist in removal of water, even if the wall sat on the patio.

Have either of you ever heard of a wall on a patio? Have you seen one fall over?

I do agree, the best thing would be to knock down the old wall, excavate back, and go from there (like said in the 2nd post), but, I was hoping building on the patio itself would hold up "good enough".

Let me know if you have heard of any walls being started on a concrete base.

Thanks again,
Dave
 
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Old 05-29-12, 06:01 PM
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Why are you so insistent on putting it on the patio? Your existing wall of concrete block is failing. Why do you want to put up a new one in a similar fashion? If you put it on the patio, it will just get pushed across it until it goes off the other side. Doing it right the first time is faster than doing it twice.
 
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Old 05-29-12, 06:46 PM
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I guess I am insistent on the patio because in my mind it seemed like an easy, straightforward approach that I thought would be good enough.

It certainly sounds like I am wrong in that respect though. Thinking about it, I see your point in doing something right once and that would be the best choice.

Going back a ways to create room for the drainage system and new wall, is that something I could get by doing with a shovel and a good day of sun and work?

Or should I consider renting something to help with the excavation?

Thanks again for the feedback.

Dave
 
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Old 05-29-12, 06:49 PM
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I forgot to add, I was insistent on the patio for the retaining wall because I thought the addition of a proper draining system after the lawn and before the new wall on the patio would be sufficient.

Thanks again.

Dave
 
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Old 05-29-12, 07:35 PM
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You have a lot of wall to work on. I guess it depends on if you feel able enough to dig by hand. I'm not experienced with machinery, so I would do it by hand. It will take a lot of time though.
 
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Old 05-29-12, 07:44 PM
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I am 25 and in pretty good shape (6'5"/220). I would imagine after removing the existing retaining wall it would be easy to knock back another 18" or so?

And then get low enough in the trench to start the process.

My goal would be to complete this in a weekend working with a buddy both days for about 10 hours each day.

Is that a realistic expectation? Last thing I want to do is start the process and then get rain and have it become a bigger problem than it was.

Please let me know if you think I have realistic expectations on this.

Thanks again,
Dave
 
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Old 05-29-12, 07:47 PM
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I meant to say easier*

I recently fenced the yard in and digging those holes were moderately difficult. I found a good rhythm with my post hole digger, wedge point crowbar, Sawz-all and hand spade. So knowing, after removing the existing wall that the lawn will be entirely visible, I feel that it would be easier to just knock it down, shovel it up and move it out of the way.

Dave
 
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Old 05-30-12, 02:58 PM
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I'm not exactly experienced in doing a ton of retaining walls. I think one weekend might be enough to excavate and start building the wall, but I don't think it will be finished. It also depends on what your soil is like. Mine is all clay. Very heavy, sticky, and a real pain to work in. Get yourself a pick. They work great for this kind of thing to break up the soil.

You may want to rent a compactor if you want to get tings done in a hurry. Hand tamping takes a lot of energy and time to do it right.
 
 

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