Roof drain advice

Need advice on roof drain, Recently reroofed 700 Sf flat roof on building addition. The roofer provided a five-year workmanship warranty and received final payment. Less than three-months after payment, the owner was notified of water ponding due to uneven roofing reported by a structural engineer. Roofer offered to install a drain rather than pull back the single ply and correct the decking. I’m afraid a drain will just cause water leaks & icing. He provided 5 yr workmanship, says drain is all he will do. He provided cert of insurance, but insurance says workmanship not covered. Now not sure I want him back on my roof, since engineer and several roofers have stated the work is shoddy.

Probably wouldn’t ask him back. Ponding isn’t alway as bad as people think though- it depends entirely on the type of roofing, how much water is ponding, and how long it takes to dissipate. Slope is your friend, and even just 1/8" per ft. Can make a huge difference.