pouring over existing floor questions

[joe.striper]

I live in the Northeast. I have a 20x20 unheated detached garage that was built in 1949 with a poured cement floor and 3' apron. No cracks but EVERY Spring, for 25 years, I've had to deal with water backflowing into the garage as the built up ice and snow in my gravel driveway started to melt.

I've tried drains in the driveway but they don't work well because the snow and ice will build up and block the drain openings.

If I fix the driveway it will cost THOUSANDS to remove material and repitch it. The simpler solution will be to repour over my existing garage floor and pitch the garage apron so water runs the correct way and then add gravel near the garage door thereby insuring that its surface is pitched properly and will runoff into the road.

Sooo here's the question. what is the minimum thickness I can pour if I am repouring directly over my current floor and apron? I hoped I could get away with 3 inches. I plan to get a cement delivery and finish it myself. I know I will need to lay wire and raise it at least an inch above the existing floor. So where is my thinking flawed?

I'd like to keep it as thin as possible because much higher and I will be very close to my 7' 6" garage ceiling joists (I am 6'5" and my son is 6'10").

As we speak I have 1/2" of water across the entire front 1/2 of my shop. Please help me out. Thanks

 

[Denwood]

We did a 2" over pour, with 2" insulation and mesh. This floor sees floor jacks loaded with pallets and has held up very well. The pour over existing slab was done more for efficiency (added insulation), however we also installed radiant. Total floor thickness increase was 4" including the insulation.

 

[joe.striper]

We did a 2" over pour, with 2" insulation and mesh. This floor sees floor jacks loaded with pallets and has held up very well. The pour over existing slab was done more for efficiency (added insulation), however we also installed radiant. Total floor thickness increase was 4" including the insulation.

Thanks. Did they use standard concrete do you know?

 

[Denwood]

Nothing fancy. We added pigment, likely was 3000psi.

 

[Bondo]

Ayuh,.... Have ya shot the grades,..??

Will 3" give ya enough fall, to work,..??

Regradin' a gravel driveway oughta be a day job, for a dozer,....

 

[bigman68]

You should have no problems, just be sure you use a bonding agent, some thing similar to this:

http://www.larsenproducts.com/weld-crete/weldcrete-specs

There are many similar products out their just call your local concrete supply company and they should have something in stock.