What is the proper method of flashing a metal hatch on a flat roof (touchdown). I had my roofer come back to look....there was not flashing on the hatch but a generous amount if roof cement. It has dried out since the and a leak was coming from the hatch

I did ask why it was't flashing applied with a sheet and he said due to contraction/expansion of the metal, it will still move and the sheet will crack just the same and his position was to apply new:additional cement and treat it as a 3-4 maintenance job to retop the cement when it dries out...to the point of water ingress.

Seeking input here, as while the roofer has the *paintbrush* in this application it's his painting ....as the analogy goes, but roof cement is like caulk to me. Inevitably it will dry and pull away, just a matter of when. He did state that flashing will still have the same issue since the *metal hatch* does have quite a bit of movement to it