[jyl]

Suppose you want to change a conventional 2x4 wood stud and lath/plaster wall to a non-combustible wall. For example, to install a commercial kitchen in a house.

Would you

1. Remove lath/plaster, remove wood stud, replace with metal stud, repeat until wall is all metal stud, then cement board? Seems you’d have to install the upper and lower channel in sections? Suppose it is a exterior wall with exterior sheathing nailed to the studs?

2. Build a second wall of metal channel and studs, inboard of the original wall with a 1” air gap, then cement board? Impossible to cement board the side facing the original wall. Might take a fraction of the time/effort of #1.