Re pour basement floor?


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Old 11-04-09, 12:16 PM
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Re pour basement floor?

The house is old, 1919. The floor was probably just dirt back then. Seems like the floor there now was "poured in place" at a later date. It is very thin un even concrete. The old guy next door calls it "dry tamp" concrete. Maybe that is an old term for ready mix??

Anyway, I thought about tearing up the floor (we want to do a basement bath room also) and pouring a new one. I would like to put down a plastic vapor barrier (I'm sure there isn't one now, lots of moisture...) and then new concrete.

Does the plastic go under the gravel base? Does it seem pratical to do this job? I would probably rent a mixer and pour a section at a time. The base ment isn't that big....
 
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Old 11-04-09, 07:30 PM
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Well - Dry Tamped was probably a method where the cement (Redi Mix) was poured on the floor dry and then some water was added, but no stone of any significant amount and the cement was mixed just enough to make it set up.

More then likely there is no PSI in the cement and you can break it up with a sledge hammer and not even need a jack hammer.

A lot of things were done back then that are not done today.

Yes you dig deeper then you figure you need the basement to be and then you add 3 to 4 inches of gravel and then you lay down your plastic and pour your cement on top of that.

The gravel will allow any water that gets under the cement to drain and the plastic will allow the cement to stay on top of the gravel and act like a vapor barrier. But you will probably need some type of rebar in the floor and some wire and you will end up poking holes in the plastic. Some masons use pins in the floor so they know how high to pour and finish the cement to make it level.

I would just make sure that you have all your plumbing laid out properly before you do any cement work.
 
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Old 11-05-09, 09:46 AM
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From what I have read, I was under the impression that the plastic went under some gravel and the cement went directly on top of the gravel... Is the plastic sheet supposed to be in direct contact with the concrete?
 
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Old 11-15-09, 10:44 AM
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Originally Posted by Milemaker13 View Post
From what I have read, I was under the impression that the plastic went under some gravel and the cement went directly on top of the gravel... Is the plastic sheet supposed to be in direct contact with the concrete?
It absolutely is correct to have gravel THEN vapor barrier, and concrete directly on top of plastic in contact with the concrete. That is how my four year old house was done and is how it is recommended by building science. Apparently in California they do gravel, plastic, some sand, then concrete, but buildingscience.com has nothing good to say about this approach.
 
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Old 11-16-09, 07:30 AM
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OK, sounds good. I think we will tackle the basement plumbing this winter. We will be replacing the main line and add stubs for a basement bathroom. I want to pour this slab myself, but am I better off getting the plumbing finished and then hiring a concrete guy to pour and finish the whole basement floor at one time?? I don't know how smooth and even the floor would be if I did it myself...
 
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Old 11-16-09, 09:32 AM
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A nice feature even if it is a dry basement is to slope it to a drain/sump. Some will slope to the perimeter and that drains around to the sump. Others taper the outside all towards the sump. The perimeter drain can get in the way of walls so plan what you want.

While you are adding gravel and possibly a sump, you might as well read up on Radon. Not sure how much of an issue it is in your area, but a whole lot easier to prep for while the slab is going in. In fact it is almost done for you with the new gravel layer and you don't have to install the system, just have the ground prep included in what you are doing.

Here is that building science link to read. In between the ca bashing it does have some good information: BSI-003: Concrete Floor Problems —

Bud
 
 

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