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Pay to have engineer oversee pour?


mossman's Avatar
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10-10-17, 05:40 AM   #1 (permalink)  
Pay to have engineer oversee pour?

I'm having a 35' x 13' structural slab with 3 grade beams poured at my home next week, and am curious if I should pay the engineer that designed the slab to inspect the excavation, rebar, mesh, etc. prior to the pour, and oversee the pour as well to ensure it is done properly. I've seen the design, and it looks text book, but I don't have a lot of confidence in the contractor (let alone any contractor). Seems like it would be worth paying to have the engineer on site to ensure everything goes as planned (e.g. rebar, mesh doesn't get damaged, moved around, concrete is of proper consistency, concrete is finished properly, etc.). Is it uncommon for an engineer to oversee a relatively small residential job like this? Any idea what I can expect to be charged for such a service? The site will be inspected by the same company that did the design, but my concern is how the actual pour and finishing is carried out once the concrete contractor takes over.


Last edited by mossman; 10-10-17 at 05:57 AM.
 
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Bruce H's Avatar
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10-10-17, 06:13 AM   #2 (permalink)  
Based on your previous posts, I'd say it wouldn't be a bad idea. The engineer will want to see the reinforcing prior to anything being poured. You might also ask the engineer to review the structural calcs, if you have them, including the concrete mix design. You'll probably have to find a small engineering firm for this small of a job; I have no clue what labor rates are in your area, or even my area for that matter. I've been retired for too long and no reason to keep up on rates.

 
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10-10-17, 07:15 AM   #3 (permalink)  
Having watched your other threads to some degree, I know you're not going to be happy if you don't.

 
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10-10-17, 07:35 AM   #4 (permalink)  
Is this living space, a level pour, or a garage where you want some slope. Too many garages end up with low areas in the middle.
Anchor pins need to be set and mesh needs to be pulled up off the bottom and not walked on until the mix stiffens.

Unfortunately doing it right has to be part of their normal practices, you don't have a lot of time once they start to say do this or do that.

Bud

 
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10-10-17, 08:53 AM   #5 (permalink)  
This will be the floor in an unconditionted garage. Someone from the firm will be inspecting the rebar, etc beforehand, likely not the engineer that did the design. The rear 1/3rd will be flat and the remaining will have a slope of 1/8"/ft to the garage door. I have asked them to use rebar/remesh chairs to elevate the rebar and mesh off the ground. The design calls for #4 rebar 12" O.C. and center of the slab the entire length, as well as $4 rebar 2" from the bottom of the grade beams.

 
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10-10-17, 09:42 AM   #6 (permalink)  
Maybe not much help, but any pour around here is observed by a City Inspector. If the city doesn't provide that inspection, then it would make sense to have an observer.


Brian

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10-10-17, 09:55 AM   #7 (permalink)  
Good luck on the slope, not being sarcastic, just realistic. Not sure how they will access this to do the pour without walking on the rebar, but a 12" x 12" is a challenge for big boots slogging through the mud. At some point they won't be able to see the rebar. They can bull float from the side but that makes setting the slope difficult. And I don't know where the mesh will be, but if it is on chairs no one will be able to walk out there.

Yes, I'm a pessimist, sorry.

Bud

 
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10-10-17, 10:27 AM   #8 (permalink)  
Good luck on the slope, not being sarcastic, just realistic. Not sure how they will access this to do the pour without walking on the rebar, but a 12" x 12" is a challenge for big boots slogging through the mud. At some point they won't be able to see the rebar. They can bull float from the side but that makes setting the slope difficult. And I don't know where the mesh will be, but if it is on chairs no one will be able to walk out there.

Yes, I'm a pessimist, sorry.

Those are some of my concerns as well, and exactly why I want the engineer on site while this is done. My thought is they could lay the center mesh down as they pour and work their way towards the door (the left and right would be laid ahead of time). This way they wouldn't have to walk on it at all. I've asked them to use sheets, so I believe this should be a viable solution. Each sheet is 4' x 7'. As an alternative, couldn't they also lay some 3/4" plywood down to spread the load and walk on top of that?

 
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10-10-17, 11:53 AM   #9 (permalink)  
Anything that changes the way they normally do a pour will cause delays and problems. Lifting the mesh as they pour is standard procedure but they don't always do it and no one will ever know. If someone needs to walk out through what has been poured they will, and just fix the footprints but not lift the wire.

The good news is, the slab will be just fine regardless where the mesh ends up. Of more concern is your slope and getting an apron for the garage door.

Bud

 
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10-10-17, 04:28 PM   #10 (permalink)  
The design calls for rebar the entire length in the center of the slab. Surely they wouldn't just throw the rebar on the ground and lay the mesh on top. Thus is structural slab and will be self supporting. They must use rebar chairs. Laying it on the ground would be entirely unacceptable.

 
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10-10-17, 05:35 PM   #11 (permalink)  
I hate to second guess the engineer of record, but I have to say, I've never seen a structural slab with the rebar in the center; it's always been near the bottom of the slab where the concrete is in tension. Unless this isn't truly a structural slab. Maybe a good reason to hire an independent engineer to take a look at the design. But you need to do that sooner than later. Like someone earlier said, the contractor isn't going to change anything once the concrete truck is sitting in the street waiting to unload.

 
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10-10-17, 06:35 PM   #12 (permalink)  
The grade beams are 12" tall and 12" wide and have rebar 2" from the bottom. The slab will be 4" thick with rebar running perpendicular to the beams 12" O.C. and in the middle of the slab. There is a 4" ledge around three of the four sides, which the slab will rest on. Span between beams will be 8'. The grade beams will be supported by pockets cut inside the foundation walls. Everything will be poured together/monolithically. The plans have a couple sheets with load calculations /data and a bunch of numbers I don't understand. Obviously computer generated. I assume it is correct.

This is a third party/independent structural and geotechnical engineering firm that does both commercial and residential projects. They do inspections and construction monitoring as well. The plan is currently being reviewed by the county. If the drawing is stamped by an engineer and approved by the county, I would hope that it was designed properly, no? On top of that, the builder has a 10 year structural warranty.


Last edited by mossman; 10-10-17 at 06:52 PM.
 
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10-10-17, 10:03 PM   #13 (permalink)  
Mossman, this is just my opinion but I think you are asking questions that are pretty technical for a do it yourself website.
I remember seeing drawings of your foundation months ago, there was no reason for me to doubt anything the plans stated. The plans were obviously prepared by someone with knowledge and a CAD program.

I look at it this way:
You have done your research
The engineer that designed the slab signed off on the plans
The city engineers, usually fully qualified, signed off on the plans
The builder and concrete guys might have done this many times and it's not a problem for them

Slabs have been around for a long time and there is certain criteria. When I built my addition, I had about 2 questions.
Hope I don't offend, but I don't want you worrying yourself, just see how it goes. If you are unhappy, have them tear it out and redo it on their dime, that's your right.

 
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10-11-17, 03:44 AM   #14 (permalink)  
I hear ya. It's just frustrating to be uninformed, and I can't help but be concerned with this being executed properly based on the way things have been going. I'll leave it at that. Thanks for all the input!

 
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10-11-17, 11:16 PM   #15 (permalink)  
I think you are right to be concerned. Getting someone to tear something out after the fact is a helluva lot tougher than making sure the i's are dotted and t's are crossed beforehand. What do you have to lose by ensuring this? Nothing really, maybe you annoy some people. It wouldn't be a problem if you trusted them, but you said you saw with your own eyes how things were going.

So how does it make sense to let it go and hope for the best? Handyone has some good points, and its very possible you are just overthinking it. On the other hand, maybe not. He was obviously working with different guys, and he had faith they had a solid plan in place plus a good experience it sounds. Your situation sounds different.

Use your best judgment, and no, you're definitely not wrong to try and avoid the "just see how it goes" scenario beforehand. Ten year warranty may not wind up being worth a penny. One thing is for sure, if you can get a decent engineer at the job and to review things beforehand, a second opinion cannot hurt things.

 
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