How thick are second story floors?
 

I have a '72 So. Cal. tract home. What was typically used for second story flooring then--single 3/4, double 3/4, single 1/2, double 1/2? Thanks.

Hmmm
 

It all depends on the builder. No one knows until you take it apart somewhere. Do it in a closet if you have to drill a hole somewhere.