Vapor Barrier?

[lrainh2o]

So planning out my new shop build, building will be 24x48 12 ft walls. I was curious to see opinions on the placement of the vapor barrier under the concrete slab.

Put in gravel, compact then lay vapor barrier and poor concrete, or lay vapor barrier and put gravel over it?

Have always heard that the plastic against concrete will change the way it cures, but I have seen some contractors put the concrete right on the vapor barrier.

Thanks

 

[TommyK]

Vapor barrier directly under concrete. Yes it changes the way the concrete cures but for the better. The finishers hate it because they have to wait longer for it to take a set. Wet cure it and cut control joints within 24 hours of placement.

 

[Daniel Dudley]

That would be the way. Water can get in the gravel, and concrete is porous.

 

[racerbob4]

The vapor barrier directly under the slab is right but dont forget some reinforcing steel. Most people use 6x6 10/10 woven wire fabric but we put real reinforcing bars for the slap sitting on chairs on the vapor barrier.

 

[lrainh2o]

Thanks for the info.

racerbob4 - I was planning on number 4 bar 16" oc.