Is yours a typical flat roof where there is little or no space between the interior ceiling sheathing and the roof? If so, then the typical reason for using a roof-mounted blower for the range vent (eliminating noise from the kitchen) may not apply to you so much. Most of the time a remote blower like that is located an attic distance away from the kitchen. In yours, you would be gaining less than a foot of "remoteness". So a good quality range hood with an internal blower may be the answer for you. If you are tied to the external blower, consider checking around the area with roofing companies familiar with your type of roofing, or vendors who install skylights. I would think that the process of installing and sealing a skylight would be very similar to what you're envisioning. I'm not sure I'd DIY this.

Hi - My DH is a commercial roofer with 26 years experience. I'm typing this as he tells me what to pass along as his typing skills are ... First things first. Yes!! You absolutely need to have tapered polyiso insulation added. Without it you're opening yourself up to a lot of problems, not the least of which is the added weight of ponding water on the structure. As for you choice of products, much of it depends of the visibilty of the roof from the ground, upstairs windows etc. Most TPO roofs can look very nice, especially when there are no penetrations to have to flash. The draw back is it is not available to most contractors in less than full roll qty. It also requires the installer to have equipment/knowledge specific to this type of roof. If visibilty of the roof is not a factor, a black EPDM membrane will be very serviceable. EPDM is more readily available in smaller sizes and so should be less costly. Fully adhered would be the best choice. Torchdown, though effective, would be the least desirable IMHO. Playing with that amount of heat on an older structure is just not a good idea when other options are available. We just had an historical structure in our area burn to the ground from this very thing. Sorry this is so long winded. My DH sees a lot of mis-applied roofs and fixes poorly detailed ones all the time. Make sure you choose a reputable firm and insist that you have a Certificate of Insurance proving their insurance coverages.

I have an EPDM flat room on my garage - in MN. It lasted about 25 years. It does have a cedar deck over it - deck as in patio/deck - so it's protected from UV, etc. We had it replaced and the estimates varied widely - some were twice as much as others. I ended up having one of the less expensive people do the work and I think they did a good job - other than not being all that attentive to the details of putting the deck back on. I was just thankful to find someone who would do the whole thing - pull the deck off, replace the flat roof, put the deck back on.

millworkman: Proper installation is a necessity for a great many things. Poorly installed PVC trim can indeed mask other problems, but I have a hard time seeing that as a reason for not using it. Poorly installed wood trim can also mask problems as it rots in places hard to see from the outside. tlbean2004: Do not put PVC or anything else over wood. All that does is create a place for water to collect between two different materials. PVC is designed to be used alone as a replacement for wood. Will you ever have to replace it? Never is a very long time, but given correct installation, PVC trim will last much longer than wood. If your rot problems, however, were the result of improperly installed drip edge, etc., you may get good long life with wood once the problems are corrected. Rot resistant wood such as cedar or pressure treated is a good idea, but proper priming of all surfaces before installation is also very important.