ChiefUserBigRob

24" MONO SLAB

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is anyone familiar with a 24" mono slab pour? typically they are 4" with footings. the builder for my client said it's cheaper to take out my stem walls and make it 24" slab. that sounds like a crap ton of concrete to me. anyone got a detail or pic of what he is talking about?

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That is a ton of concrete.  It only really makes sense if the soils report requires mat-slab or requires pier and grade beam foundation.  
With a mat-slab you use two layers of steel, one near the top one near the bottom.  Not cheap, but can be less than a lot of piers... again , really depends on the soils report.

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Must be talking about 4" mono slab and 24" thickened perimiter footing.

No reason to pour entire slab at 24" deep.

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Confusing...You said 24" slab, so I thought you were talking about a mat-slab.
Okay, I get it now. You must've shown a two-pour system... pour perimeter first then the slab.  
Yes, single pour is how you detailed it, unless you want the curb which your two-pour would have provided.  You can still form a curb with a mono-pour, but it's a little trickier to do.

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Also you may want to verify if L hooks will required from footing into slab 

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you know, the more i look at my detail, what are you really saving on money wise? essentially you are doing the same type of foundation as a stem wall just more meat in the chamfer. am i correct?

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Comes down to labor really-

if your excavator cuts the trench clean and you can run 1 form on the permimiter it sets up pretty quick.

 

Also you need to decide of you need the stemwall standing tall off the slab on the interior or if the framed wall can sit right on the slab.

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Also think about the extra excavation needed to set up footing and wall forms - concrete contractor will need room on both sides to work.

 

Trench footing eliminates that.

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Sometimes called a grade beam when they are that deep. May....M A Y...be better as a 2 pour grade beam, but would have to see a soil report and rebar requirements.

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1 hour ago, ChiefUserBigRob said:

essentially you are doing the same type of foundation as a stem wall just more meat in the chamfer. am i correct?

Not necessarily... looked to me like you put a bit too much meat in that chamfer.  As Rob L. said... it'll be mostly a labor cost difference... which can be quite a lot to bring a conc. crew out to the site a second time. 

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19 hours ago, ChiefUserBigRob said:

is anyone familiar with a 24" mono slab pour? typically they are 4" with footings. the builder for my client said it's cheaper to take out my stem walls and make it 24" slab. that sounds like a crap ton of concrete to me. anyone got a detail or pic of what he is talking about?

Rob, here in Houston, we mainly use monolithic slabs and pier and beam. If you like, send me an email (email below) and I'll send you details we use for mono slabs. Typically, the grade footing here is 24" to 27" depending on the engineer for a one story and 30" deep for a two story.

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1 hour ago, ACADuser said:

My take on the foundation.

An engineer has the final word.

24 POUR.pdf

thanks guys, i will let you know what i find out. i sent my sketch to the builder. i'm anxious to hear his reply on how this is done. i probably should have mentioned that this all started from the front porch being raised 20" and his suggestion of this type of slab. the 24" would create the 4" step up into the home.

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