I am about to replace a 3 panel (4.0 ft) each ) - 12 ft total 18 year old sliding door in a coastal rental property I recently purchased. One panel opens but the rest are frozen . The rollers and weather stripping are shot (& obsolete ) and it is time for new door unit . I measured the heights at various spots and there is about 5/8" sag in the middle . There is vinyl siding on the outside and drywall on the inside. I would like to maintain the opening for a new door unit . I wondered if could cut the sagged portion then remove some drywall and install a steel plate (flitch plate) or plywood to eliminate future sagging ? I would appreciate any suggestions on how to address this situation . - Thanks

We’re installing an Anderson frenchwood patio door. We are ready to install the frame in the rough opening and and are using Bituthene for the vapor barrier, but was wondering if it we can install the sill directly on the plywood, or if we should install aluminum flashing first. Can the Bituthene be used in lieu of the flashing? – i.e. can the Bituthene can be tacked all around the rough opening including the sill and can the sill of the frame be attached to the Bituthene with caulking. Thanks! Todd