Dry material will be a waste of time and money since its purpose is meant to be to bond the block to the reinforcement. Only a wet grout mixture can do the job. Just grout in a wall does not do much for lateral strength and does increase the vertical strength, but the concern is not vertical strength. - Grout is not just concrete, it is a much wetter (higher slump) and has a smaller maximum rock size and more sand.

The unknown height of the wall and the type of soil behind it will determine the size and spacing of the vertical reinforcement. That is assuming you had put is a proper footing and have rebars coming out of it for tying the wall and footing together. I assume the footing is not sized properly and there are no rebars sticking out.

Dick

 

Illustration and Photos

Thanks, Dick. I appreciate your taking the time to respond. I had tried to keep it as simple as possible, initially. I've attached a rough drawing and three photos, which should make some of the following more clear if you view them first.

The footing is much wider than the recommended width (about 4 inches on each side of the block), but there is no rebar.

There are two walls and they are built on a downhill slope. The first is rectangular, about 5 1/2 ft tall, supporting a concrete pad patio which is against the house.

The second, in the shape of an almost-half circle, about 4 ft at its highest. This curved secondary retaining wall lies about 9 ft. in front of the rectangular wall.

The taller, rectangular wall supporting the patio has sand-clay in front of it (leaning against it), beginning about 2 ft from the top of the wall, sloping downward toward the secondary wall. The remaining space between the highest wall and the secondary wall is filled with sand.

Therefore, sand-clay is the primary soil pressing backward against the primary wall (supporting the concrete pad patio that connects to the house, and sand is the primary soil pressing forward against the secondary wall.

The secondary wall, the curved one, has a 2 ft high sand-clay support against it in the front.

There is a gravel, French drain system at the base of each wall.

Why does it need to be stabilized? There is some pulling away block from block, vertically in one section of the taller, rectangular wall (see photo). It seems to have halted at 1/2 inch gap. The idea behind rebar and concrete is to link the horizontal sections together, row upon row, to prevent this in the future. There are no problems on any other sections of the wall, but before any money goes into cladding the wall with stone, I want to be darned sure this is addressed to the extent possible at this point. My concern is that curved sections of the shorter wall are also under stress.

Why did the builder use 8" block instead of 12"? Well, lack of experience is my guess. Now, there is nothing left but to try to forestall -- to the extent possible -- future movement.

What grade grout do you recommend?

Since I'm cutting re-bar a little at a time, can I leave the cut pieces inside the wall for several weeks or will the slight rusting cause any problems once I finally insert the concrete.

Among my future questions, after this is addressed, will be: Will the soil base of mostly sand --but with clay sloping upward against the larger retaining wall be an acceptable base for a poured concrete patio? Or is the sand a poor base for a concrete pad? A concrete truck will be able to reach the edge of the location to be poured and damage will be minimal.

Thank you, again.

 

Thanks, Dick. I appreciate your taking the time to respond. I had tried to keep it as simple as possible, initially. I've attached a rough drawing and three photos, which should make some of the following more clear if you view them first.

The footing is much wider than the recommended width (about 4 inches on each side of the block), but there is no rebar.

There are two walls and they are built on a downhill slope. The first is rectangular, about 5 1/2 ft tall, supporting a concrete pad patio which is against the house.

The second, in the shape of an almost-half circle, about 4 ft at its highest. This curved secondary retaining wall lies about 9 ft. in front of the rectangular wall.

The taller, rectangular wall supporting the patio has sand-clay in front of it (leaning against it), beginning about 2 ft from the top of the wall, sloping downward toward the secondary wall. The remaining space between the highest wall and the secondary wall is filled with sand.

Therefore, sand-clay is the primary soil pressing backward against the primary wall (supporting the concrete pad patio that connects to the house, and sand is the primary soil pressing forward against the secondary wall.

The secondary wall, the curved one, has a 2 ft high sand-clay support against it in the front.

There is a gravel, French drain system at the base of each wall.

Why does it need to be stabilized? There is some pulling away block from block, vertically in one section of the taller, rectangular wall (see photo). It seems to have halted at 1/2 inch gap. The idea behind rebar and concrete is to link the horizontal sections together, row upon row, to prevent this in the future. There are no problems on any other sections of the wall, but before any money goes into cladding the wall with stone, I want to be darned sure this is addressed to the extent possible at this point. My concern is that curved sections of the shorter wall are also under stress.

Why did the builder use 8" block instead of 12"? Well, lack of experience is my guess. Now, there is nothing left but to try to forestall -- to the extent possible -- future movement.

What grade grout do you recommend?

Since I'm cutting re-bar a little at a time, can I leave the cut pieces inside the wall for several weeks or will the slight rusting cause any problems once I finally insert the concrete.

Among my future questions, after this is addressed, will be: Will the soil base of mostly sand --but with clay sloping upward against the larger retaining wall be an acceptable base for a poured concrete patio? Or is the sand a poor base for a concrete pad? A concrete truck will be able to reach the edge of the location to be poured and damage will be minimal.

Thank you, again.

Well, for the lower wall, it looks like you wouldn't have to excavate much to install deadmen. So I'd go that route for that wall.

As for the upper wall, if you don't want to bust up your patio to install dead-men or tiebacks, your only other option is to build another wall in front of it to create enough mass that gravity alone provides enough force to resist the lateral earth pressure.

I would consider building a boulder retaining wall in front of the upper wall. It is a different look from the stone veneer that you were probably going for originally. But it would provide the mass needed to retain the soil under the patio without deadmen or tiebacks.

 

Was welded-wire bonding used horizontally between any courses?
How about adding one more row of block using bonding beam block filled with mortar and rebar?

 

Judging by the cracks in the second to the last photo, there is not a good enough footing or there is not any steel to tie the wall to the make the wall to work with the footing. Steel and some 8" to 11" slump grout (not concrete) in the reinforced cores needed IF there are steel dowels for added steel to be lapped with.

Dick

 

Thank you, Bud, for your reply. No, welded-wire bonding was not used horizontally. I will research your suggestion about using bonding beam block and mortar + rebar as a top row.

 

So I suppose no "tie-backs" were used connecting the wall-rise to mother earth either.

So...the area shown with sand gets a slab on top is that correct?

 

Dick and Bud, it appears that the best thing to do would be to dismantle the weakened corner of the wall and address any foundation issues before re-laying the block. Does that sound like a reasonable solution?

As for the original question, will adding rebar and concrete strengthen the remainder of the wall? I had been told that, since this was for vertical strength, I need only use something along the lines of QuickKrete rather than a finer, fill grout which would be more expensive. Is this correct? No need to skimp on grout if it's the wrong type.

For the sections of the curved wall would it be worthwhile to add bent rebar that links neighboring blocks together as in the illustration below?

Do you see any reason why I couldn't leave the sand as a substrate for the concrete pad in this particular situation? In a Google search, I find it listed as suitable, but I prefer to hear it directly from someone who has seen the photos and might notice something prohibitive.

Do I need to fill the cores of the blocks first and let them cure long before the pad is poured so as to not further stress the curved wall? Or could I wait to see if...and how many... blocks could be reached by the concrete truck that will pour the pad?

 

Unfortunately, while adding rebar and concrete inside of the wall will make the wall itself stronger it won't keep the wall vertical. That wall certainly needed tie-backs at a minimum. While sand is acceptable to use under concrete in most conditions it's really not good here. Because it really never compacts it will keep exerting forces against the lower wall pushing it outward. What kind of fill is behind the upper wall?

 

Thank you for your reply to this important issue, Msradell. The upper wall is filled with sand-clay, common here in SC. I suspected that the sand might be a problem for the reason you stated. So, does it have to be dug out and replaced with sand-clay? Is there something other than sand clay that I should fill it with?

Will adding a concrete pad to the lower wall (if the pad isn't on sand) stabilize the upper wall? What options and solutions are available to me to strengthen the existing set up?

Would digging out the lower (curved wall), adding new footers to support "buttresses" for the upper wall or a secondary retaining wall that slopes backward and against the first one?

Would concrete and rebar inside the blocks improve this situation in any way at any point in the process (after new footers, secondary retaining wall, etc.)?

To be honest, --and this is NOT directed at you, Msradell -- I'm getting a lot of pointers about what is wrong, but few ideas for solutions.

I can't tear down the taller rectangular wall and start over; that would undermine the patio. What can I do at this point and before going any further with the landscaping and wall cladding?

 

BFarm -

Just some information for you -

If the walls are like the drawing you provided, they have no foundation and just act like dominos that are slightly braced by the sand-clay and sand (that has little structural strength unless the fill is the right material and compacted). What you have seems like a flat plates stuck in Jello that are not very stable.

I don't think a DIYer can provide enough stability to support the precious patio slab for the construction of new walls attached to a proper concrete footing. Dead men will require support if they are to be expected to work, but you would have to excavate almost all the material around the walls to make a connection between the dead-men and the present walls that are probably not sufficiently reinforced and grouted.

You also need an engineer that understands soil, load distribution and can determine the suitability of the existing walls.

Dick

 

The clay may also be an issue since clay is notorious for excessive expansion when moisture is present.

"I'm getting a lot of pointers about what is wrong, but few ideas for solutions."

• The solutions are in front of you. You don't have a proper footing/foundation.
• You didn't use any tie-backs or dead-men.
• You didn't use welded wire reinforcing.
• You didn't use rebar or mortar-fill any of the cells.
• The fill contains an unknown percentage of clay.
• The walls are not canted.

All of those issues are what is wrong - true, but all of those issues/elements are also what is needed to correct the problems.

Anything short of a re-do done at this point would be only a Band-Aide and not an everlasting fix. This is one of those projects that wasn't thoroughly investigated BEFORE the work commenced. We see this here all of the time. You have a sizeable investment there already but not doing the job properly would only be throwing good-money after bad.

 

Thank you Bud and Dick for your replies.

As noted in my text, the walls have extra-wide concrete footers. Wider than the walls by at least 4 inches or more. Other than that, they're all wrong.

The problems with the walls are well known to me NOW. Perhaps I should have researched wall construction but instead I hired a licensed contractor who claimed to know what he was doing. Besides, I was busy micro-managing the house construction, preventing workers from cutting corners and doing shoddy work (!), researching performance histories of appliances, selecting door knobs and garage door openers, paint, and flooring, and couldn't also do the job of the contractor hired to do the retaining walls. (I'll spare you additional information concerning the financial and emotional collapse of said contractor mid-way and the need for me to also step in as payroll master and supply-acquirer, etc.)

Instead, I employed a "licensed professional" with superb references. While I'm sure it frustrates you to see, yet again, that a job was done poorly and without proper research by the homeowner, let's be clear here that the fault lies with the contractor. This homeowner did all the due diligence in finding said contractor, but I was obviously not successful. Like the other people posting issues, I'm here to ask for your help because a "professional" failed me.

And so like other people, I turned to this message board and its contributors, hoping for a potential solution short of tearing everything down. After all, the wall does have footings, although it's clear from the cracks that there is a stability problem on at least one corner.

Although I failed to study wall construction myself prior to the build, I'm not sure why I should be the target of your frustrations about the problems you see over and over. Blaming the homeowner, me, for the failings of the wall is pretty lame when the homeowner comes to you all desperately seeking help. If I needed someone to cast blame at me for my oversight failings, I can assure you I'm already suffering the consequences.

I'm not proposing that I DIY the repairs, rather that I get your input prior to hiring yet another "licensed contractor" with superb references to (potentially) repair the problem. While I welcome all information about what is wrong, it is only useful to me if I am also provided with some potential corrective measures -- IF THERE ARE ANY. Castigating the homeowner serves no one. We've already been screwed by the contractors, we don't need it from you, too.

Diane

 

Well, Diane,
If you came in here and said my expert contractor was hired to add some numbers, 45 and 46 and he came up with 81 and you ask what was wrong and the kind knowledgable pros said your expert
contractor failed to carry the one to the tens place, how much more would you need to know?

Sucks that you're in a spot, but the people here didn't put you there and they're certainly not mind readers.

 

I think the lady's got a good point here and I've seen other condescending remarks by concretemasonry ("the precious patio") in other postings (along with some good advice). And Bud's approach is rather accusatory "YOU DIDN'T this and YOU DIDN'T that..." This doesn't help anyone who comes to this board for advice. It sounds like she did as much as any reasonable person to head off this disaster. Her contractor is to blame.

Advice givers should be fully prepared to hear of our bumbling and messed up efforts in an understanding way. If there's no solution, then just say so nicely or don't answer. Most of us are in the same situation either by our own fault or that of so-called pros and if you can't give advice politely to people that are in a fix, don't reply to them. We don't need more aggravation.

 

+1 Well said.

 

do not use dry. if this is DIY you can use 5gal pal and this mixing paddle to mix up small bags. filling that whole wall will take some time though. maybe rent a mixer and get a bunch of bags, use 5gal pal to pour. or maybe get a truck and wheelbarrow to a transfer spot, pour into 5gal pal and then into the block. that crack shown simply looks like poor support under that section, a fill would not necessarily have stopped that. why did contractor not use tie-backs?? i suspect the next big issue to be seen is when those sections of dirt get soaked with water. i see the drains, but the drains are after the water gets there, there can still be lateral forces.

if the repairs are not DIY then simply ask new guy "how would you fix this", take notes, ask around, post his answers here, etc etc.

the rebar in the block simply ties the blocks together, it doesnt tie the blocks to the footing. is there any rebar tied into the footing coming up into the blocks?

and yes, wait for blocks/fill to cure ~72hr before pouring the pad.

. I assume the footing is not sized properly and there are no rebars sticking out.

Dick

well, footing may be right size, but it wont perform if what its on is no good, etc.

 

Joe - The minimum width of the footing is based on soil under the strip footing. The minimum thickness is determined by the pressure on the the bottom from the resiting soil. - Usually contractors just go by what worked before with similar conditions and rely on that. Definitely not engineered or permitted.

So far I have not seen any real information on the footing under the walls, but I have missed it in the sketchy information provided by the OP. The 4" outside of the wall is a common amount for 8"thick footings. The OP somehow thinks it is a question of vertical strength of the wall (non-realistic), the the real concern is the lateral strength of the wall to support the loads induced (horizontal and vertical) by the walls above and behind it. - It is a domino process.

The OP could have gotten better answers if more inormation was supplied, so it is just a guessing game. Unlikely it is in SoCal, since they usually catch all of the problems to protect the people below. Other areas have frost that can totally ruin a tiered wall and the results when a lower wall fails and dumps the "precious patio (and house) on everyone below when the erosion happens. The walls look like they are set back from each other enough, which increases the loads on the ones below.

A good wall should obviously be built according to what kind of soil or "dirt"is under and behind it. Fortunately, they did put in some sort of drainage and assume it works. Looking for another contractor is a mistake, since this is something that should be engineered and then turned over to a contractor to follow the drawings and specs.

Dick

 

A good wall should obviously be built according to what kind of soil or "dirt"is under and behind it.

Dick

agreed in full.

just a note for my post #17, filling the OP's walls by hand mixing will take a very long time. filling just one pocket on my 2 row high wall is just about a 5gal pal!! OP's fill would have to be done by shute or pump.

two pics of my block wall. i am green brick/block person, my work is plumb/level but i am about 5x slower than a good brick/block person.

insignificant compared to the OP pics, but here i show the use of locking pins to lock end of blocks together. my wall is only 2 rows high but i have "expansive" soil, i have actual geo soil report from when developer put homes on this land.

this is a spa vault approx 18" deep.

 

Why are you getting upset? There were no mention of lack of useful advice given by the experienced and expert people. The OP was very appreciative of the advice. Look at her posts.

We know we are the uninformed and bumbling diyer's thats why we are seeking help from the experienced and the experts. But we are also looking for user friendly chatroom.

 

Where are you located in SC?

To be honest it looks like the upper wall needs to be taken down and rebuilt...in one of the pictures it appears the base course isn't bonded correctly and worse yet, the corner doesn't look bonded either. In the picture, there looks like a stack joint on three courses. That's a big structural problem that needs to be fixed.
Ladder wire wouldn't have helped in this scenario, that's installed primarily for controlling shrink cracking, not for controlling lateral pressure...it's omission wasn't a factor of this walls problems. Make sure any future work is properly bonded.
Since this isn't a timber wall, running deadmen into the fill won't help either, unless they are supported, as Dick mentioned. Buttresses would have been the best way to strengthen your single wythe wall, but you don't have a footer to do that now.

Also, make sure your drainage is adequate, clay soil will expand when saturated....weep holes can assist if the drainage is overwhelmed. Grouting and doweling will strengthen the wall, yes, but if there is too much pressure behind it, grouting won't prevent structural failure.

 

Where are you located in SC?

...in one of the pictures it appears the base course isn't bonded correctly and worse yet, the corner doesn't look bonded either. In the picture, there looks like a stack joint on three courses. That's a big structural problem that needs to be fixed.

I think it may just be an illusion, I think the crack goes right through the block shell.

If it were mine, and I wasn't willing to tear the wall down, I'd at least tear the top course down, form an overhang on the front face, dowel every few feet into the end of the patio, and pour concrete right over the top of the wall, getting rid of the gravel area. Only pour a few vertical cells, cap the rest. It's not ideal but I would be taking advantage of the size of the patio as a tieback. Also, you'll likely need some kind of railing if you went this route......

 

heres a tidbit about engineering it wrong. at least the signs of issue showed up early, as in that cracked corner. its a lot worse if the wall had filled cores and tied corners but will little tie into footings or no tiebacks.... this is bad scenario, hydraulics pushes the whole wall over.

 

The more or less vertical crack is wider at the top ans naroows at the bottom. This indicated the from facing wall as the top rotated outward from footing failure (settlement/rotation) orbreaking away from the footing below. It is they of construction that can be picked to death because it is so unique and unknown construction.

Cracks like that common follow head joints and then hop over to an adjacent core area and then downward to the next head joint (unless it is a good tight head joint).

Dick

 

According to experts, you will achieve more strength using mixed concrete. Dry concrete cannot give you the similar kind of strength. But going by the images, there are many things incorrect in the retaining wall. You must seek professional assistance to get that sorted at least cost possible.

 

fortunerestore -

Time to go and learn a little about retaining walls and soils. There are different types and are designed for different methods of construction. Some are internded to be rigid and some flexible. In landscaping and erosion control flexible walls are generally preferred for tiered arrangements.

This wall was an error from the beginning and all ready-mix and steel in the cores will not help, but just make the chunks coming down the hill bigger.

Dick