# monolithic slab vs Block Slab



## The General

I would like to read some opinions about slab on grade vs footing, block, and slab. The foundation co. that is bidding on my project is pushing slab on grade. The dirt looks to be like clay with medium rocks but I am no expert. The grade of the lot would look to me to be a 3 or 4 block high job as the back of the lot is lower. Any ideas on which is better for making it last for ever. Also I live in Arkansas where the avg night temps are above 32 in the winter most of the time unless we get snow which never lasts longer than 2 or 3 days on the ground. I have some building knowledge but cost accounting by trade. My gut tells me to stick with the block slab.


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## TimWieneke

Hi General,
I personally have never had a problem with monolithic slabs where code allows it here. I've also lived in Springfield, MO for some time and had the pleaure of trying to dig a few sewer lines there. Where you've got dirt, you've got that red dirt there right? According to my old college science teacher, that's from bedrock being so close to the surface. Not having seen it, I'd be willing to guess you've got really solid ground there and a mono would probably be just fine (Is their bid price lower for the mono slab?).

Tim


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## pondman

By all means if you have the grade and soil you will save money and time by going with a mono slab. In less than 5 days you can have it graded formed, plumbed, inspected and poured.

We started mono slabs for all grades that allowed it over 10 years ago and for timing and costs you can't beat it. :Thumbs:


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## The General

TimWieneke said:


> Hi General,
> I personally have never had a problem with monolithic slabs where code allows it here. I've also lived in Springfield, MO for some time and had the pleaure of trying to dig a few sewer lines there. Where you've got dirt, you've got that red dirt there right? According to my old college science teacher, that's from bedrock being so close to the surface. Not having seen it, I'd be willing to guess you've got really solid ground there and a mono would probably be just fine (Is their bid price lower for the mono slab?).
> 
> Tim


Tim and Pondman thanks for responding. I have a few more questions. The foundation is the one thing I will spend what it takes to get the performance of a dream home foundation that will last. If I do go with the slab on grade would it be worth it to beef up the concrete. He is already going to put #4 steel in the footing but my question is go with a 6in slab over 4in. Or does concrete not work that way. Would it be better to put smaller square or more steel in the 4in slab. The grade is my biggest concern along settlement. The area would be roughly 72x58 then oversize that and bring it up 4 or 5 feet with good fill. Seems like even if it was compacted 95% there could still be a lot to settle. Also I am building over an area where 15 to 20 trees have been pushed with a dozer. Would it hold up to small tree roots left under the ground. I guess he will take it down then back fill. Oh well looks like I got a good list of questions for the sub before he starts. Any tips on building it well will be greatly appreciated. The General


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## pondman

General,

I'll make this quick and simple for you. I will assume this is your own home for this purpose. I always overbuild my own home. I'm anal that way. I also overbuild my other homes but not quite as extinsive.

As far as compacting the soil is concerned. I always hire a soil engineer company to bore and take samples. This way if anything goes wrong they are on the hook for settlement issues. They are the engineers. Around here that can cost $300 to $800 depending.

On monolithic slabs for a two and half story home a 4" slab will do fine. In the footers I run three rebars all around. I also put rebar in all point load footers. For the enterior slab I use a wire mesh.

Other that that it is vapor barrier and pea gravel. I have never had a problem.

The truly one thing I overkill is all foundations. I never want settlement.

Hope this helps. Best of Luck.

Mark


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## Teetorbilt

Monolithic is about all that I know and everything in this state is either beach or swamp.


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## Mike Finley

In my personal stuff, everything I pour is 6 inches instead of 4. Ask any woman and they will tell you 6 is better than 4. :cheesygri 

Out here we have expansive soils, nothing is going to stop a foundation from moving when bentonite gets wet, I heard somewhere that that stuff has something like 90,000 lbs of moving force or something. So only proper foundation techniques will overcome bentonite, not just adding inches.

But for slabs I see cracks all the time which to some degree would be avoided with a thicker slab. In your neck of the woods 6 inches might be over kill. 

Keep in mind just how much more expensive those extra 2 inches will be that is a lot of extra concrete.


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## The General

Thanks to all who replied and I will keep you posted. I used the ol brain and found my septic permit. The geology report says four pipes drilled and bedrock found at 72 to 75 feet. Still not sure if that means I have solid ground but Tim sounded like he has seen it before. Brown red clay with rocks the size of golf balls to fist size. I will let you know the two bids for the different foundations but I do expect the mono to be quite a bit lower.I should have them by friday. The General


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## pondman

Mono slab should always be lower. Are you asking what is the lower price or what you should go with??


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## CHADILLAC

*mono vs. footings?*

General, I would tend to agree with pondman's suggestion. Protect your investment! Get intouch with a reliable Geotechnical company to bore some holes and test the samples taken. Some clay can swell, which can lift foundation several inches. Every soil has a classification, your local company can tell you exactly was it's properties are for your area of concern and give you some suggestions on structual stability. In my opinion, being from colorado and have seen many different soil types, every situation can vary. So pay a little extra $ and give yourself the upper hand if things gone wrong in the future, liability is on the geo company and the contactor. Sounds like you may have decent soil to work with. good luck.


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## PipeGuy

Hi Chad, welcome.
I see you just joined and thought I'd let you know that, as a rule of thumb, posts as old as that you're responding to (it was written over 2 years ago) don't typically merit a response. While your certainly welcome to respond / comment on whatever you'd like, please don't feel slighted if your insight doesn't spark renewed interest in the topic.

See you around.

PS-I would have mentioned this to you through the private message system but I saw you have it turned off.


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## craft homes

*general,*

general,

In south central alaska general practice for a monoslab.

Dig 4 feet below grade or more to get below organics.
Fill and compact with 1.5"minus crushed and graded (nsf). compacting every 6 inches. 
24" deep footers 16" wide with 2- 5/8" rebar up 8" from bottom.and 1 at 4" down from top of slab 4" in from outside. 
If over 2 storys tall 24" w/ 3- 5/8
6-6 10-10 reinforcement mesh in slab 4"-5" thick.
2" blue board under slab. over vapor barrier, foam continueing out 2' past footers.
sometimes 2' grid of 1/2' rebar also used in slab. this doesnt add much cost. 
monoslab cost after excavation is about $7 a sq. ft.

I have seen no problems with monoslabs.


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## dakzaag

Crafty,
Welcome to CT. You might want to post an intro and include you location. 

Just a note to consider, the thread you replied to was started in 05 and the latest post was 07. 

No big deal, but probably not the most current topic to be responding to. 

Other than that, come on in the waters fine.:clap:


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## NannaWolf

PipeGuy said:


> Hi Chad, welcome.
> I see you just joined and thought I'd let you know that, as a rule of thumb, posts as old as that you're responding to (it was written over 2 years ago) don't typically merit a response. While your certainly welcome to respond / comment on whatever you'd like, please don't feel slighted if your insight doesn't spark renewed interest in the topic.
> 
> See you around.
> 
> PS-I would have mentioned this to you through the private message system but I saw you have it turned off.


I would like to add that even if the original poster may not see the comments, this post showed up in my search bar, so thank you to all who commented.


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