How do I build a 4 hour burn wall, or were can I get drawings and specs?
I suggest that you refer to the Underwriters Laboratory for info on the designing/building of a 4 hour burn wall.
1. Masonry walls have a Fire rated construction design.
2. Is the wall load bearing?
3. Is the wall between two (2) living areas such as in a duplex (common wall between living spaces)?
I would examine Type X fiberglas reinforced drywall. Your local building department will have their specifications.
Drywall 5/8" x 4' x 8' or longer sheets are available. Wood framing may be superior to sheet studs because it will carry more weight. The drywall paper opposite the fire must ignite first, the wood may char but will last a long time until ignition and a flame is propagated.
One municipality requires two (2) sheets of 5/8" Type X
DW layered on 2x4 frame construction. Also see Pyro-Guard plywood where a fire retardant is pressure-treated into the wood.
Commercial construction specification books show cross-sectional wall construction methods. See your librarian.