I've recently come across a situation requiring remedial work in an attic
space adjacent to party walls separating condominiums. The original design
(almost 10 years old) called for FRT plywood sheathing on either side of the
wall, but this was apparently never installed. Unfortunately, the roof was
also just replaced without any attention paid to the sheathing, which
remains in good condition. Consequently, I am trying to recommend a remedial
treatment which will not disturb the roof and have consequently considered
requiring a UL-07 Design No. L505, which gives quite a high rating (2-hour).
I am asking this be also used to box out any included rafters and beams. Any
comments from anyone?