Lightweight Concrete Garage Slab 3

[RM87]

Hello all,

Forgive me for not doing enough research before exploring solutions from all of you, but I could use some help and I thought my question may be something up someone's wheelhouse. I need a lightweight concrete slab mixture and reinforcement for a garage supporting vehicle loading. The thickness of the slab will be anywhere between 1-3/8" to 3-3/4" for sloping and general leveling issues, sitting on a slip sheet of visqueen over OSB subflooring. Anyone have any design recommendation to prevent cracking in the slab?

Thanks all,
R

 

[msquared48]

The slab will crack no matter what you do. You just have to define how much you can tolerate between the shrinkage and deflection cracking. I would use a minimum of 3" though and go up from there for any drainage.

Mike McCann, PE, SE (WA)

 

[RM87]

Thanks for the words of advice. I'll have to disclaim that there's no real solution I'd be comfortable with and to put in more frequent joints.

How would you reinforce a 3" lightweight concrete slab? Any preference on the f'c or mix suggestions?

 

[Ron]

Why are you placing a concrete slab over wood framing to support vehicles? Unless you have carefully designed the framing and subfloor, you are guaranteed to have cracking problems and structural issues. I hope the space below is not occupied. Further, 3 inches of concrete would be bare minimum as Mike noted.

 

[RM87]

Out of curiosity, how would you address having a garage over habitable space, in the context where all applicable structural elements are made of wood? What cover would you place over the plywood diaphragm?

 

[hokie66]

My first choice would be a compressed fibre cement sheet underlayment for a trafficable membrane.

 

[RM87]

@hokie66 - I haven't heard of that before, thank you. I'll check it out.

 

[hokie66]

It is a common solution in Australia, but I don't know about the US. James Hardie would be the most likely supplier of compressed fibre cement, I think.