I have about 1,800 sq. feet of roof here in Miami. 900 is well pitched and covered with barrel tile. The remaining 900 is more or less flat. this section was built in the 70s with 4"X10" cypress beams spaced at about 34" and covered with cypress tongue and groove. Above this wood aspect is about 9" of insulation covered with rolled bitumen (2 skylights sit on this flat roof area). I would like to recover my pitched roof with Galvalume or something similar but I am really stumped as to how to approach my flat roof area where I now have standing water. I have looked at tapered insulation products, the possibility of re-sloping the flat roof by building new trusses to connect to pitched roof, etc.
I'm also a bit confused by the many membrane choices: PVC, EPDM, Rolled Bitumen (again), or metal again if the flat roof is pitched to at least 2"/12". I don't want to confront standing water. Do you trust tapered insulation? My budget is about $25,000 for the roof. Any advice you could give would be appreciated.