# Monolithic slab replacement



## mtrel (Jun 9, 2009)

My house is a typical raised ranch in CT with a 46x22 foundation.  When I bought the house the garage floor had a large settlement crack and was pitched so that rain water would hit the slab beyond the garage doors and run into the garage.  The home inspector said it was really no problem since it probably happened 30 yrs ago and it could be easily removed and repoured since it's a floating slab.  Being the DIY'er I am I made a cut about 20 feet in, across the 22 foot width of the house and jack hammered out the floor myself.  When I was within a few inches of the wall on one side I decided to dig down to see how deep the footing was.  That's when I discovered what a monolithic slab is.  Now the slab is gone within 8-10 inches of the wall in most spots and within 4-5 inches in one part.  I called one concrete guy so far and he wants to cut the original slab 5 inches from each wall to make it even then put 24"rebar every 16 inches only in the 2 wall sides of the old slab. There will be no pinning to the original slab accoss the width of the house. He'll then pour a 5" slab with 4000 psi concrete with no other bar or wire mesh.  He says he'll skimcoat the existing 5" slab but it will probably break apart there eventually.  I am concerned that I have permanently damaged the structure of the house and would like to get some opinions on this and if this is the proper fix.  Talking to a few other concrete guys so far it seems like they all have a different opinion.


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## midunno (Jun 25, 2009)

oops..    anyways!    i woulda expected to see some bar or wire in the new slab too.    i would guess the main concern is tying the foundation together again. imho i would get an engineer to give you a plan...     might cost a few bucks but it is cheaper then a new home.    especially since the "concrete guys" have multiple opinions on how to go about it.   usually means they are not so sure about it.


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## spaz2965 (Jun 25, 2009)

A monolithic pour means that the footers and the floor have been poured as one, are you sure first off that is is a monolithic pour as the floor is normally poured 2-4" above the footer, 4" is better but sometimes not feasible. The re-bar drilled into the footer now, because that is what you have now, and you probably don't have the space to put 4" on top is fine, he is also correct in saying that he can skim coat the remaining footer but it will crack up unless he uses a concrete glue that makes it adhere to the concrete. The re-bar that he is going to put in keeps the floor from shifting and settling. You didn't hurt the integrity of your house by taking up the slab, cracks in concrete come from settling, and not having expansion joint at stress points. You will always get them in inside corners and will usually go to lolly columns or structural post. Hope that some of this is help full to you. Everyone may have a different solution and some will make you feel that you have a real problem and charge you more that what the job really is. 4000 psi is great and no you don't need wire mesh or re-bar if you feel more comfortable you may ask for it but not necessary, you may also get fiber in you concrete which makes it stronger. Do you have about 4" of stone in what you jackhammered out?, and is this all that you are repairing, what you have jackhammered out or are you doing the whole floor?


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## mtrel (Sep 9, 2009)

I haven't checked in a while.  Thanks for the replies.  I'm sure it's a monolithic pour.  The floor is 4" but thickens up to about 8" on the edges under the walls.  Another concern I have is that I replaced 2 lolly columns in the middle of the floor and placed them on footings which are 2x2x18" that are 4" below the floor.  The way the contractor explained the monolithic slab is that in the winter the slab will move somewhat because of the frost.  It moves as one unit.  I'm wondering now that the 2 lolly columns holding up the center joist of the house will stay stationary because they are on large footings unaffected by the freezing temps.  Will this crack the floor and even worse make the center of the house move independently of the walls?


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