Garage under Patio

[Wisconsinite]

Hello I have a L shaped house and in the inside the the L, I am going to be building a garage. I should also like to indicate the garage door side is exposed to the backyard. There is currently a patio with just a deck that will be raised. My plan is to have a stamped concrete slab above the garage. the garage will be 20' wide by 30" deep. The wife has placed these dimensional limitations. My original plans included a spancrete roof with rubber mat an concrete poured over. Upon contacting spancrete I was quoted a bill of around 7k just for the panels and setting them on my walls. I was also concerned about condensation in my garage weeping throught the spancrete. I am open to different methods of constuction and know how to weld. It just has to be able to support about 4 inches of concrete on it. I do not want any support poles in the garage. Any suggestions or advice would be appreciated.

 

[kbs2244]

Look into what I think they call "Aircrete."
It is lightweight concrete.
They use it in multi story buildings for the floors over corrugated steel floors.
Check how they do it.
I think Spancrete is over kill for what you are talking about.

 

[Wisconsinite]

Thanks, I will check out the aircrete. When I worked in the highrise apartment buildings in Chicago the floor levelers used a lightweight concrete they called acoustical concrete. Unfortunatly it was brittle and weak in comparison to conventional concrete. It also seemed porous.

 

[6768rogues]

You could use post tensioned concrete.

 

[Wisconsinite]

I have to say I'm unaquainted with post tensioning concrete. However after a little research it seems to be another alternative to spancrete. How much of a savings would it be vs. spancrete? I am also concerned with the possibility of condensation through the post tensioned concrete or the spancrete because its topside will be exposed to the elements. I mean of course I would put a rubber mat down and pour additional crete on top of the mat, but even so... I would hate a humid garage or a dripping cieling- that would be a disaster.

 

[thewelder]

Stain and seal the patio then you shouldn't have to worry plus the patio will look better

 

[kbs2244]

The highrise stuff you worked with was what I was thinking of.
I didn't think of the fact that it is a indoor only application.
I think it is time to talk to a concreat guy.
They may know of a color coat sealer that you can pattern and still have the loght weight stuff.
As a patio you are talking a pretty low stress surface.

 

[LongW8]

I have a very similar set up in the Milwaukee area. Mine was built back in 1969. Condensation is not to big a problem. The floor will get some on humid days but I have very poor air flow through the garage. The biggest problem is the leaking from rain and snow. Removing the patio slab and adding a PVC liner is on the to do list. The biggest problem is that the Spancrete expands and contracts. Because of this there needs to be some expansion joints in the patio slab above. Keeping these sealed, with or without a PVC liner may be difficult. I am sure that Spancrete has a solution for this, I just haven’t dug into it yet. The Spancrete tends to leak only at the joints between the sections. As a temporary solution (15 years now) I added some rain gutters under the joints to channel the water off to the sides.

 

[USMCvet]

Look into what I think they call "Aircrete."
It is lightweight concrete.
They use it in multi story buildings for the floors over corrugated steel floors.
Check how they do it.
I think Spancrete is over kill for what you are talking about.

Can I use that for the roof of my underground Fallout shelter?