Greetings Dave NH,
I live in N.H., and I hope that by your name that you do not live in N.H.
A 2" floor won't cut it up here. 4" is standard.
Because you have concerns about this, and your house is only 2 years old, I would go to the Building Inspector and ask to see the plans.
I do not know the formular for this but, I'm sure someone else on this site will.
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