Phil,
Technically, Jerry's (dare I say it) wrong.
A true firewall is either designed by the architect or chosen out of a book (USG, etc). The design has to be tested in order to obtain a rating.
Attached
http://www.usg.com/USG_Marketing_Con...logs/SA100.pdf
find all different types of 'rated' assemblies (with steel & wood framing). Note most state "joints finished" which means just that.