Re: Can you put sheathing over celotex fibreboard?
i can think of a couple things right off the bat,
by not stripping it off you wont be able to find out if the soft spots are do to leaks and if its causing rot to structure which needs to be attended to if so
your also going to require longer fasteners for the osb to go up and nail to the studs. and the same goes for installing the vinyl siding.
strip it down, start from scratch and makes sure its structurely sound and weather tight, from there the siding is just lipstick and mascara
fire up the saw and make some dust