Low density limestone retaining wall cracking everywhere

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  #1  
Old 05-23-19, 02:18 PM
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Low density limestone retaining wall cracking everywhere

Desperate homeowner here. I have been racking my brain on how to "dress" the existing low density retaining wall to stop it falling apart and to make it look uniform and "nice". Seems nearly every solution and quote I have received is way over my budget by at least 50%.

1) formwork and poured concrete in front of limestone wall - will probably crack due to hydraulic pressure from behind. Super expensive.
2) post and concrete panels then backfill with gravel. Again, not cheap... not DIY
3) 3000kg new uniform concrete blocks applied in front - $18000 materials only for wall 91 feet x 8 feet high. I have 2 tiers to do plus possible extensions. Still way too much. Not DIY. This would create a double retaining wall, which I think is overkill.
4) finally I looked at sandbags with barb wire between rows (taken from earthbag construction).... the polypropylene bags are cheap, I would need about 1700 of them.... the fill material is what I am not sure about..... filling with dirt would experience freeze/thaw problems which is what I am trying to avoid in the first place..... filling with just small gravel might be better..... what I am not so sure about is the cost of "dressing" the sandbag wall with cement stucco (lime, sand, cement) to protect the bags from the sun and give me the look I want. Anyone think this last option is the cheapest? I am not concerned about labour, obviously this would be a family endeavor to save money.

Seems the sandbag solution is DIY friendly and would allow me to extend the wall much longer than it is in order to help level off part of our 30 to 45 degree backyard. Right now we have zero useful space on almost 1/2 acre.

See attached pic.

thanks
Joseph



 
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  #2  
Old 05-23-19, 04:14 PM
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You have a massive wall. I'm afraid there is no cheap fix. You are trying to retain thousands of tons of soil so there is no cutting corners. Everything about your wall is measured in tons so nothing will be cheap just because of the volume of material required.

1. Formed and poured concrete retaining walls can work if done properly. When done properly water is drained from behind the wall so hydraulic pressure is not an issue.

2. Much like #1 when done properly it can work well.

3. I have a retaining wall four blocks high that is 18 years old with no troubles. It's fugly though so I would not advise it for your application. And they require a solid base/foundation to support the massive weight so it's not as simple as simply stacking blocks.

4. Sandbags are a temporary solution. Within a few years the plastic bags will degrade in the sun and start breaking apart.
 
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Old 05-23-19, 05:44 PM
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So what exactly is the issue?

I have a home with canyon back yard with many terraced bolder wall very similar to what you are showing.

No significant movement but installed a good drainage field behind every wall, some are 4 levels deep, approx 4' high!
 
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Old 05-23-19, 06:33 PM
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Thanks for the replies.

#4 - regarding sandbags falling apart. That's why I propose cement stucco as a finish over top the face and top of the new sandbag wall. To prevent the UV from degrading the bags.

A concrete wall in front would also suffice, however the amount of formwork and reinforced concrete would be staggering... don't forget I am planning on extending the wall from the original 91 feet to possibly 181 feet so as to make more of the property reasonably flat and usable. Concrete just seems very expensive give the amount of formwork that needs to go up... and not only that concrete requires a solid footing dug at least 4 feet deep....

that's why I keep coming back to sandbags with a cement stucco finish applied.
Here are some more pics.
 
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Old 05-23-19, 06:50 PM
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The issue is I hate the look of the low density and porous limestone blocks - you see what has happened in the picture from freeze/thaw year after year. They are basically falling apart. And there are too many holes and crevices for rodents going in a out all day long. I like clean, uniform, contemporary looking walls.... the mish mash of stone is just an eye sore for me. As long as my new wall lasts 15 to 20 years I am OK with that. Long enough for the kids to play, and we can enjoy some flat space instead of having to head to the park everyday. After that, we sell the property and let the new rich owners do what they want with the wall. Realistically this backyard of mine was meant for rich owners who have an extra $100,000 lying around for landscaping.

I've included a pic of the other end of the two tier wall.... you can see our property is steep.... it's a lot worse than it looks.... This is where I want to extend the 1st tier wall.... to create some usable flat space.... level it with the 2nd tier wall.
 
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Old 05-23-19, 07:06 PM
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A pic of the queen mother retaining wall essentially holding up 1/2 my backyard...

I won't be touching this thing.
 
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Old 05-24-19, 03:38 AM
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Any retaining wall you build is going to have to be structural. It will not be a cosmetic layer on the face. I do not know of a reasonable way to build a wall of sandbags that can resist the push of earth behind. Filling them with concrete doesn't make a difference. It can be done but it will be more like building an earthen dam or levee. You will need probably 10x more sandbags than you think you'll need. Then there is the problem of the clean look you want. A stuccoed facade on a segmented wall is going to crack. Because the sandbags are only held together by gravity there will be slight movement between the bags. You'll eventually see the joints between the sandbags telegraph through the stucco as cracks.

There are engineered, pre-cast concrete retaining block wall systems. They are available in many different appearances and are often used along highway bridges and commercial buildings. But, you still will see all the joints and segments and you already have an idea of the cost.

If you want a smooth, clean looking wall you'll need poured in place, reinforced concrete. The wall doesn't care about your finances. It's going to be expensive.
 
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Old 05-24-19, 11:29 AM
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I like clean, uniform, contemporary looking walls
I can't imagine any way of doing that without a lot of foundation work, reinforcement back into the hillside and poured concrete. Most cities would require stamped, engineered plans for a retaining wall of that size and weight. You're talking about holding up a tremendous amount of earth over a very short distance, and that's a civil engineering project; not landscaping.

Stucco on sandbags will have no retaining ability and will crack and fall apart after one season. Sandbags have no tensile strength and have the same density as the surrounding hillside -- they will move with the soil during normal seasonal shifts.
 
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Old 05-26-19, 01:44 PM
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Thanks for the opinions, I appreciate it.

Yes, I can see how even stablized sand bags would shift with the seasons....

However I am not convinced I need to re-engineer an existing retaining wall that has already been engineered to hold back tonnes and tonnes of earth.....that ship has sailed 10 years ago... they built it, it looks like crap, and somebody put a stamp on the drawings regardless of what it will look like 10 years later.

I will look further into the concrete post (placed 4 feet into the ground), and some sort of concrete panels in between..... it seems to me that would require a lot LESS concrete, no formwork, and simpler machines and labour to get it done. As long as the bottom panels rest above the frost line so as no to wick moisture, it should work.

Another advantage of the concrete posts is that they can be placed extremely close to the existing retaining wall, minimizing the amount of gravel backfill I would need. Hell, I would backfill with a lighter material like rubber waste if I have to, just to keep the pressure as low as possible.
 
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Old 05-26-19, 03:07 PM
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and somebody put a stamp on the drawings regardless of what it will look like
There was no engineering on that wall, it's just a landscape project that was installed with good intentions!

Regardless of your thoughts regarding the looks, it appears to have held up well despite some cracking.

As mentioned I have large quantity of bolder walls which shift due to weather and settling but hold integrity due to good foundation and drainage.

Wish you were in my area I'd love to have all that cracked limestone if you were to discard, there is a lot of $ invested there!
 
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Old 05-26-19, 03:30 PM
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trust me.... it was engineered.... nothing gets by the Town, especially a new subdivision. 8 houses have this limestone block, but I am the only one with 2 levels. They even carved out 1/4 of my property to build a cul-de-sac so emergency vehicles can make it around - that's the mother, 18 foot retaining wall you see in the pic above.. An engineer designed, but left it up to the builder to source out the stone. Builder got a deal on some real low density limestone - i.e. the cheaper stuff. They just care about the mass of the stone. Not the quality.
 
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