Pool wall/Rebar collapsed after gunite

[ashup]

We have just started our pool construction. Today was the gunite day. When they were shooting gunite, wall crumbled down along with the rebar. Rebars were bowed so much, so they have to cut it and take it out.
Builder says they will rewire new rebars to the broken end & repour gunite. They mentioned it happens and can be taken care. We were worried this patching up solution may bring problems to the structure of pool in future.
Pls share your experience & thoughts!

Attached a before & after picture.

 

[Bperry]

Do they know why it collapsed? I assumed rain, but don’t see evidence of that.

 

[BigPapaSmurf]

It does not appear that the pool gunite shell was fully shot. I believe they tried to apply a light coating to prevent a cave in since rain was in the forecast. I’m not expert but that mix, or what’s left of it, looks very loose and obviously did not have the strength to stop a cave in.

 

[HeyEng]

Oof. I would not be very happy about that. I have a lot of respect for those of you that have a pool installed. Ours was already here when we bought the house and I don't think I could be so brave as to have one installed!

 

[ashup]

It wasn’t raining. One guy was pouring the shotcrete on one side and other was trying to install a pole for the cover. Error totally by the crew.
My biggest worry is they are going to rewire and reapply shotcrete. Do you guys think it will hold good?
We did have a steel inspection before the wall collapsed. Builder says no inspection needed when they rewire. Pls let me know your thoughts.

 

[Oona]

Troubling that the rebar collapse with the gunite-I know you are worried about them having to rewire but it sounds like they really need to. Did they use the correct gauge of rebar

 

[HeyEng]

I would be leery of the "no inspection required"...as a matter of fact, I would call the inspection authority and ask them if this is indeed the case. Since it was already inspected and "passed", the contractor has no motivation to call out the inspector again. I don't know much of anything about these inspections, but I sure as heck would want to make sure the bases are covered. Last thing you want it a battle with the builder in a couple of years if/when the wall fails.

 

[JoyfulNoise]

Shotcrete collapse can happen particularly when the weather conditions are not favorable. It’s ok, it can be repaired. They need to redo the rebar and then reshoot the gunite. It’s fine don’t panic. Let the crew fix it and it’s the PBs responsibility to make it right. There should be no structural issues by them redoing it.

 

[AQUA~HOLICS]

A lot of things going on here.
What was done with the Gunit/Shotcrete that fell from the wall? Both types of products are designed to be pneumatically applied. If it was reused on steps or seats their could be problems in the future of delimitation.
The product had not been given proper time to set up before more was added on top. For it to pull the steel cage with the product as it fell is rare, I personally have never seen that happen.
The repair for this is the same as the initial requirement of the steel cage for inspection, proper clearance from the dirt shell, over lapping lengths with ties. The only reason no inspection is required is due to one already taken place prior and that the inspector is unaware of what just happened. I have been on many job sites that require a Shotcrete/Gunite inspector on site during this process.

 

[HeyEng]

A lot of things going on here.
What was done with the Gunit/Shotcrete that fell from the wall? Both types of products are designed to be pneumatically applied. If it was reused on steps or seats their could be problems in the future of delimitation.
The product had not been given proper time to set up before more was added on top. For it to pull the steel cage with the product as it fell is rare, I personally have never seen that happen.
The repair for this is the same as the initial requirement of the steel cage for inspection, proper clearance from the dirt shell, over lapping lengths with ties. The only reason no inspection is required is due to one already taken place prior and that the inspector is unaware of what just happened. I have been on many job sites that require a Shotcrete/Gunite inspector on site during this process.

This x1000. Construction lawyers make a LOT of money; there is a reason for that. There is NO WAY I would take the builder's word on "no inspection required"...I would say, "trust but verify", but I see no reason to trust this builder.

 

[JoyfulNoise]

A lot of things going on here.
What was done with the Gunit/Shotcrete that fell from the wall? Both types of products are designed to be pneumatically applied. If it was reused on steps or seats their could be problems in the future of delimitation.
The product had not been given proper time to set up before more was added on top. For it to pull the steel cage with the product as it fell is rare, I personally have never seen that happen.
The repair for this is the same as the initial requirement of the steel cage for inspection, proper clearance from the dirt shell, over lapping lengths with ties. The only reason no inspection is required is due to one already taken place prior and that the inspector is unaware of what just happened. I have been on many job sites that require a Shotcrete/Gunite inspector on site during this process.

This x1000. Construction lawyers make a LOT of money; there is a reason for that. There is NO WAY I would take the builder's word on "no inspection required"...I would say, "trust but verify", but I see no reason to trust this builder.

We're talking about a swimming pool here, not a bridge or freeway overpass. Maybe CA requires swimming pools to have gunite inspectors on site, but the vast majority of jurisdictions do not.

Shotcrete collapse can happen and we have seen many posts on TFP over the years with this type of failure. It happens and it's not a catastrophe. Its up to the pool builder who owns the job and hired to subs to figure this out and make it right. Stomping feet and throwing around the L-word (lawyers) and demanding reinspection will only make this situation 10,000 times worse. The rebar cage can be reassembled and the shotcrete redone with little or no impact to the structural integrity of the shell.

Talk to the PB, ask for a face to face meeting with him and the shotcrete sub and have a constructive conversation about what happened and how it will be avoided in the future. Look at your contact and see what it says about shell warranty. Perhaps you can get the PB to make a note on the contract about what happened so that if there is any future issues (small chance of that happening), it's all in writing.

Spoiling for a fight or making the PB "the bad guy" is the quickest way to turn your build into a nightmare.

 

[HeyEng]

We're talking about a swimming pool here, not a bridge or freeway overpass. Maybe CA requires swimming pools to have gunite inspectors on site, but the vast majority of jurisdictions do not.

Shotcrete collapse can happen and we have seen many posts on TFP over the years with this type of failure. It happens and it's not a catastrophe. Its up to the pool builder who owns the job and hired to subs to figure this out and make it right. Stomping feet and throwing around the L-word (lawyers) and demanding reinspection will only make this situation 10,000 times worse. The rebar cage can be reassembled and the shotcrete redone with little or no impact to the structural integrity of the shell.

Talk to the PB, ask for a face to face meeting with him and the shotcrete sub and have a constructive conversation about what happened and how it will be avoided in the future. Look at your contact and see what it says about shell warranty. Perhaps you can get the PB to make a note on the contract about what happened so that if there is any future issues (small chance of that happening), it's all in writing.

Spoiling for a fight or making the PB "the bad guy" is the quickest way to turn your build into a nightmare.

I stand by what I said. It's up to the OP to make a decision how they would like to proceed. I just stated what I would do...and that does NOT include the threat of using a lawyer or "stomping of feet"...I did NOT say that so please don't make that implication. I understand that most inspections will not have someone there when the shotcrete is done and I wasn't making that assumption. I was simply pointing out (and highlighted/bolded) what I felt was a good point made by a user that has identified themselves as "in the industry." To assume what an inspection requirement might be for a given jurisdiction is generally a bad idea so I would simply call the office that is responsible for the inspections and simply ASK A QUESTION.

 

[JoyfulNoise]

@ashup

Talk to your pool builder and try to get them onsite with the shotcrete sub. Please let us know what they say and feel free to post up pictures of what they do to rebuild the rebar cage. They are professionals and they know that they are on the hook to ensure that the shell is structurally sound. I’m sure they will make it right.

 

[darkrider]

Did they end up cutting out the rebar on the wall? It looks like it's sitting on the ground above the area that had the collapse. I'd have a number of questions, as it looks like they finished the spa. Are they starting from scratch, or redoing just the area of the collapse? If the later, how are they handling the cold joint and how much are they removing? I'd certainly have some concerns about the floor as well, as I don't see any signs that they're removing rebound.

 

[kimkats]

I agree with @JoyfulNoise While it is not fun to see or deal with it can be fixed. Breath in, breath out.........try to keep all emotions at bay. Work with them to make sure it gets fixed the right way-digging out the dirt, removing the fallen rebar and tying new rebar in place while keep the shape of the pool per the plans.

 

[JoyfulNoise]

Did they end up cutting out the rebar on the wall? It looks like it's sitting on the ground above the area that had the collapse. I'd have a number of questions, as it looks like they finished the spa. Are they starting from scratch, or redoing just the area of the collapse? If the later, how are they handling the cold joint and how much are they removing? I'd certainly have some concerns about the floor as well, as I don't see any signs that they're removing rebound.

“Cold joints” are mostly a myth as long as proper prep is done. From the TFP Wiki on Construction Best Practices -

Cold Joints​

Cold joints in shotcrete (gunite) are in some ways a myth. Laboratory testing has shown that multiple layer shotcrete has no anisotropic weakness (cold joint) when the layers are applied within 7 days of each other. In the real world a plane of weakness often develops between layers, but it's almost always due to improper surface prep. Dust, dirt, and rebound from shooting adjacent areas will accumulate on the first layer during/after the shoot, and if not thoroughly removed prior to applying the next layer a plane of weakness will develop. If the first layer is troweled smooth it can also impede bonding of the second layer. If too much time passes between layers a cold joint is possible, but in that case the reduction in strength is pretty minimal as long as the surface is properly prepped.[6]

 

[darkrider]

“Cold joints” are mostly a myth as long as proper prep is done. From the TFP Wiki on Construction Best Practices -

Agreed, but keep in mind we're not talking a new layer of gunite on top of what was previously shot. We're talking about an entirely new section of gunite marrying up at some cut point in the wall to what was previously shot. I think it can be done, but it will require expertise. For all intents and purposes, you're going to have an existing crack along the entire seam as they are two independent pieces of concrete. Any perpendicular or lateral shifting from either section is going to cause cracks in the plaster. The tie-ins with the rebar are going to be critical to ensure strength and avoid future cracking. I would guess that they will need to drill and anchor the new rebar into the existing gunite to prevent this from happening.

 

[ashup]

Thanks everyone for your timely suggestions. I contacted the city first and they wanted me to go ahead with the builder, at the same time they wanted me to send some pictures to the chief building inspector, so they have it in their record.
I talked to the concrete guy, he confirmed that they applied shotcrete up to 6ft at once, instead of gradually increasing the height from 3ft. That caused the collapse.
Now, it’s all rewired and the new iron rods are anchored to the existing shotcrete. In addition, they have also added short metal rods that goes from the rebar in to the sidewall, plus they have applied a flash of shotcrete to avoid any cave-ins from bad weather that’s coming in a day.
I went and checked again this morning. Rebar looks really strong.
Builder also agreed to include the incident in my contract.
I can’t thank enough for all your responses and suggestions for the last couple of days. It was very helpful for me to talk to the builder.
Happy weekend!!

 

[kimkats]

Sounds like they really owned the problem and took good care of it! Well done working with them to get the best fix possible!

 

[JoyfulNoise]

Excellent resolution. Sounds like the PB and shotcrete sub really stepped up to make everything right. Problems are always bound to happen on any construction job, big or small, but it’s how the people in charge respond to the problems that shows their character and quality.

And you can rest assured that the owner/foreman of the shotcrete company very likely chewed out all the guys on the original shoot for going too fast and not paying attention to the loads they were creating. And, the PB will likely make sure that the shotcrete sub never sends those guys to another one of his jobs again. This is how quality builders work, they eventually do enough builds and work with enough subs to know who does the job right and they’ll request certain foreman’s for their jobs when they really get to know the crews.