Load Bearing Garage Floor over a Basement

[gerard]

<font color="blue"> Question - what happens if the PEX goes bad if it's imbedded in the concrete?
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Some else will probably chime in but I THINK you're kind of out of luck if it goes bad after installation. On the upside the cross linked pex has an aluminum oxygen barrier in it to stop any oxygen migration and estimates for a lifespan is in excess of 100 years. When they install they pressurize each loop with a guage to make sure it's holding pressure ie no leaks.

 

[DocHeb]

PEX in concrete is pretty well protected, so leaks after installation are infrequent. During the pour the system should be pressurized to allow for some expansion of the PEX and to help monitor real-time for leaks. Repairs are possible by chiselling out the concrete and splicing the tubing. Further generic radiant heating questions can be found at Radiant Engineering FAQ.

 

[yooperdave]

The 9/16" metal deck is also known as metal centering. The deck does not act compositly with the concrete slab. Its sole use is to act as a form for the concrete in a plastic state. Its maximum span is 30.000" as an absolute maximum. You could specify a composite metal deck, but it would not be appropriate for this application considering the rolling wheel loads. The composite metal deck has dimples in it which engages the concrete, and acts as the reinforcement for positive moments applied to the slab.

You still might want to consider a membrane with a wearing surface over it.

Equipment might track in salts which will get down into the reinforcement and the deck and dissolve them over time.

Good Luck,

Yooper Dave

 

[Anonymous Poster]

Yup, pictures are wonderful things, I'm on the right page too.
More or less standard wrinkle decking.
You still want to vibrate he!! out of the concrete when poured, and were it mine, I'd install rebar and use fibreglass instead of screne.

 

[Von]

I used the steel in my floor. It has a 2" height difference and the waves are about 6" apart. The whole floor is tack welded together and then welded to the beams to keep it from moving when doing the pour. Poured about 5 1/2"(on the high side) of concrete on it. Have steel "I" beams running across about every 6' and one running down the middle, with two post holding that one up. The floor weighs in at about 26000lbs and has mesh and rebar in it. Will hold what ever I can fit in the shop! /forums/images/graemlins/cool.gif The cost of all the steel was about $900.00, and I set and welded it myself. /forums/images/graemlins/grin.gif Shop has been up for 6 years now and have not had any problems at all! /forums/images/graemlins/smirk.gif

 

[Hoeman00]

This was for a basement safe 10'x14' and poured an 8"
cap over top.
The walls are 12" block 13 courses w/ top course 8"set to outside.
This gives a 4" lip to set deck steel on.
6" mesh & rebar at 1' spacing both directions and into 8" block, all the block are filled w/ rebar, carbide cutters and concrete.
I put a beam w/ posts in center on 10' span to hold concrete
during pour then removed after curing 2 weeks.
Browning makes an excellent safe door that I put in
costs $2000+ but found a gun shop w/ one and was tired of
tripping over it so $1350.

 

[boustany]

Make sure that you have a structural engineer go over your plans before you proceed, even if you building inspector doesn't need it. Structural concrete is tricky enough and a load bearing slab is even trickier. Its better to be safe than sorry, or squished. /forums/images/graemlins/tongue.gif

I rented a crane for some some and it was a good way to spend $200 cash. Those guys know what they are doing!

Keep us posted - I want to do the same thing, sort of. I figure if I plan it right I could put a 25 yard pistol range in the basement. Nice and quiet and safe. Of course, I'd only use air pistol, 'cause its illegal to have a handgun range up here in the snowy north. /forums/images/graemlins/smirk.gif

 

[Makers_Mark]

<font color="blue"> You still might want to consider a membrane with a wearing surface over it. </font>

I am concerned salts and moisture seeping down to the decking. I asked the steel people and they just said to use a chemical penetrating sealer. What is this membrane you mentioned?

Thanks for all your advice guys. I will in fact set some rebar in the slab. What diameter rebar and what should my spacing be?

 

[Anonymous Poster]

The membrane concept involves using a waterproof membrane between the wear layer and the structural layer of concrete. Since you're in NJ, chances are you will bring a certain amount of road salt into the garage, and that salt + water will enter the concrete. Over time, the salt water will reach the rebar or mesh, and cause rust. Rust exerts tremendous force onto the concrete, and will eventually cause spalling of the concrete itself weakening the concrete.
Ways of countering this problem range from prevention of penetration via a wear layer + membrane to application of a DC charge to the floor itself.
Membranes range from silicone rubber sheets (similar to roofing) to mopping a hot tar coating onto the structural slab and up onto the walls, as is done in commercial bathrooms.
Spalling can also be minimized by using coated rebar, but as NY DOT is now learning, even zink chromate coated rebar rusts.

 

[Makers_Mark]

But wouldn't adding a membrane btwn the concrete reduce it's strength? Could I add somethng like EPDM or even a vapor barrier of sorts on top of the steel deck before I pour the concrete?