I want to maintain the original thickness of my walls after tearing out the plaster and lath.

The thickness is 1 inch.

I'm thinking that I'll just double up on the drywall, dealing in 2 sheets 1/2 thick each.

However, I've read that 5/8 sheets are code for garages due to how it responds better in a fire.

I don't want to just assume that by doubling up I get better fire prevention properties... though it seems like a safe assumption.

Dealing with the 1/2 sheets is so much nicer than the 5/8 sheets (this much I know from prior experience).

So,
  • Is there any reason for me to achieve a 1 inch thickness any other way than just to double up the 1/2 inch sheets?
  • Should I bother taping and mudding the hidden layer (is there a fire safety benefit there)?
  • Is there a significant benefit to staggering the layers instead of just cutting them the same and putting them up at the same time?

Thanks!