I have a four unit apartment building with a flat roof in Washington
DC. It's two stories with two units on each floor. The top two units
have experienced leaks in the ceilings, to the point where the dry wall
in one of the units is actually sagging. The leaking only occurs when
it rains hard I'm in the process of getting quotes from different
roofers, and so far I'm recieving very different estimates. When I
bought the building 18 months ago, it passed the roofing inspection.
The roof was installed around 5 years ago.

The first roofer actually went on top of the roof, and looked for
possible problem areas. He said the roof was pretty good(made of
ruberoid bitumen?) and that he could tell it was pretty new. However,
he said the flashing was done in an inferior manner. He recommended
rdoing the front flashing wall, and around the vent pipes, skylght and
where ever it's needed. For this he'd charge $3500

The second roofer, didn't go on top of the building(the receptionist
told him it was an estimate for aluminum siding so he didn't have a
ladder with him). I showed him the leaks from inside the two units,
and he said I needed to replace the whole roof. He said he could do it
for $6200.

I'm still taking estimates, but it seems strange that the second roofer
could redo my entire roof for less than twice what the first roofer
would charge me. Any insights, or thoughts would be appreciated.