Deteriorating flat roof, seller to do SOME repair

[Frank L. Bartlo]

A commercial building I recently inspected had a flat roof that was noticeably deteriorating (alligatoring, a few soft spots, etc.), but with no evidence of leakage at the time of the inspection (no bubbles when soft spots in puddles were stepped on, no water stains or visible leaks below).

An area near one of the corners had been recently patched, which to me indicated other areas are likely to need such maintenance soon. Some of the corrugated steel in the work area ceiling below the patched section was noticeably corroded, and coming loose. Evidently that area had prolonged leakage. The roof structure had wood framing between the ceiling and the roof surface, which appeared to be sound throughout.

I reported the roof as likely to need resurfacing within the next few years, and mentioned that top-coating after a thorough cleaning and drying may prolong the life of the surface before more extensive repairs are needed. The fact that part of the roof had been essentially covered over suggested to me that the roof would not have to be completely torn off

This morning my client called, and told me the seller is agreeable to "repairing the worst areas" of the roof. I' like some advice as to how my client could get the most "bang for his buck" as far as partial repairs go, i.e., how to prioritize the work. Top-coating first? Patch the areas that are cracking the worst? What about the area of damaged corrugated steel under the patched area?

I've included a few pics of some of the bad spots, one of the patched area, and one of the corroded corrugated steel underneath.

Any suggestions would be much appreciated.

[Chuck Evans]

IR thermography would have been good to identify areas of moisture entrapment. Beyond that you're getting into specifying repairs. I try to stick to identifying defects and let the contractors spec repairs / methods.

[Frank L. Bartlo]

Can't afford that expensive equipment. I agree that it is beyond the scope of my job to do more than identify defects and possible issues.

It appears most sensible to recommend my client bring in one flat roof specialist to make recommendations (and tell them that's all they want them to do), then bring in another to do the work. I'm not inclined to trust recommendations from the contractor who would be doing the repairs.

[James E. Braun, CMI]

Most flat roofing material manufactures require at lease an one inch drop every foot. Thus this is why you have ponding on the roof. The hot tar and gravel roofs are the only roofs I have seen that seem to hold up okay on totally flat roofs. I have found flat roofs can look visibly fine but if you cannot get the water to drain off of them they can leak. Sad but true.

[Frank L. Bartlo]

Yeah, I did point out to the client that it had a sub-optimal pitch, and it may even be advisable to have a pitched roof built over the whole thing when it would need to be torn off.

[James E. Braun, CMI]

They make 1:1 angled sheets of foam that screw directly on top of the roof, then roofing material can be applied on top.