Concrete floor over concrete

[NUTTSGT]

I need a new floor in my garage, the old one is about 75 years old. I also want to raise the floor level, to help keep some excessive rain out.

I plan to bust out the old concrete at the door and pour a new footer and apron. The current floor is poured up against an existing foundation wall, which extends about 10 inches above the current floor. I plan on pouring the new floor up against that wall along with an expansion joint.

Some have told me to etch the old floor but it can't move side to side and at a depth of 3.5-5.5", it's not going to lift up. Does this sound okay? How would it be different than the original pour onto of stone or like my tought below of using foam ?

I was also thinking of laying down an layer of foam, whether it be 1/2 or 1" . Any thoughts of this ?

Thanks.


BTW, the garage is heated all winter, I have a wood burner out there and rarely gets below 50*.

 

[s_ontario]

I have floors like you want some add up to 9 - 12 " thick

First you have to make sure no voids are below the old concrete if its solid pour right on top if you have major cracks or old concrete has settled i would bust it up and just pour over top you can rent a 60# electric jack hammer that will bust your poor concrete areas up into small chucks for $50.oo a day

Hardest concrete i have ever tried to break out was poured in the 30's over top of field stone base was like breaking granite with a tooth pick

 

[NUTTSGT]

The old floor is pretty much solid. I did bust out one section a few years ago and replace it. This stuff was poured in '35 or 36 and pretty damn hard.

 

[Justanoldguy]

Pour straight over the top.
It's been there long enough that any settling will have occurred many years ago.
Go for it.

 

[NUTTSGT]

Pour straight over the top.
It's been there long enough that any settling will have occurred many years ago.
Go for it.

Kinda what I have been thinking. I wanted to see if anybody else thought the same or point out something I haven't noticed yet.

 

[jrj3rd]

I did the same thing with mine last year. Cleaned floor. Installed some rebar pins into the old floor attached to new rebar grid. Coated with a liquid binder and then poured 3.5 - 5 inches over the top to get a level floor. Old floor was almost 50 years old. No issues.

 

[Daniel Dudley]

I would go with at least three inches of concrete, four would be better. I wouldn't worry about bonding, and I would consider a plastic vapor barrier as a slipsheet to keep cracks from migrating, especially if you don't know if you have a vapor barrier. I would consider metal reinforcing mesh or rebar if I were doing it for myself.

You will not have any problems if the old floor is stable.

 

[NUTTSGT]

I would go with at least three inches of concrete, four would be better

I plan on making it 3.5" at the walls, but the center will be about 5.5" only because it slopes toward the original back wall. Then the addition that was put on about 30 years ago, tapers back up.

 

[BetterDays]

I just did something similar with a sidewalk, but used Tapcons instead.

 

[tncatadjuster]

Good call, vapor barrier is a must. I have glued them together on spec jobs with no call back. Shotblast and apply a bonding agent,it was on the 10th floor.