mmmarvel
MODERATOR
The mats need to be off-set from each other so that someone trying to drill in from the bottom will encounter rebar, followed by rebar, followed by rebar. It was the only vault that I did, but I found it very interesting.e hilton said:I build a lot of banks, and the spec for the slab under the vault is 18" of concrete with minimum 4 layers of #6 bar 6" OC both ways. The concrete sub has to be careful about using the vibrator propery to get the concrete to fill all the gaps between the rebar.