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Yes, it is possible to have a perfectly installed "flat" (means very slightly pitched) roof that will not leak for a long time, if you know all about such roofs and you watch every aspect of the material selection and installation like a hawk.
That will not be the case when buying into existing condos.
There is also no reason for the entity responsible for installing the roof that's on there now (whether it's the original, installed by the builder, or a replacement, installed by a condo association) to have gone through the gyrations described above to make sure this is one of the rare perfectly installed "flat" roofs; and many reasons for them to cut corners.
Snow accumulation is not the only way "flat" roofs leak. If you have never spent time in a subtropical environment like Florida or Houston you will have no idea how much rain can fall in how short a time. It is literally like pouring water out of a bucket. I guarantee you that when this happens (many times a year) if there is any imperfection in your "flat" roof, water will come in. Pitched roofs are far far more tolerant of imperfection. Look at how traditional houses in all high rain environments are built, and you will see that 100% of them are built with high pitched roofs.
Don't forget, either, that in a condo situation you probably will, as a single member, have very little leverage over selecting or overseeing who does the inevitable repairs. Even something like walking on the roof to repair the AC units can cause damage, and you do not have the authority to say "boo" to the repair person, unlike your own house where you can tell him whatever you need to.
If you are willing to bet on the basis of essentially no information that the roofs on these condos are among the few that were perfectly installed and maintained, then go for it. Me, I would not even be bidding on a standalone house in a high rain environment with a flat roof, never mind a condo.
I have a small section of EPDM "rubber roof" on my house. It's pitched slightly so it won't ever have puddles that leak. It comes in several thicknesses that have different expected life. 45 mil is the thinnest commonly used. I have 90 mil on my roof which is rated to 30 years. I'm in the coastal northeast so I used black instead of white. I care about solar gain in the winter, not reflecting heat in the summer. My roof is small enough that it has no seams. The roof deck it sits on is brand new plywood and framing. An experienced roofer installed it, not some ex-convict. It has been shoveled once in an unusually snowy winter and wear from carelessly shoveling the roof is what causes failures. I'm 59. The roof will likely out-live me. If not, everything is new so I can glue a 45 mil rubber roof over that one for very little money.
Like anything else, the quality of the installation is what matters. I paid extra to get a sheet of EPDM that was wider than the standard 10' so I wouldn't have any seams. The original flat roof was a disaster. I had everything ripped out and started over from scratch with new framing, plywood, and insulation. The roof exceeds local new construction code for snow loading. You get what you pay for.
Here's a "before" photo when I was doing a first phase of remodeling. There were multiple layers of flat roof with a replacement roof framed over the original. Everything was cut out from underneath and re-framed.
Here's a photo of replacing the roof deck and rubber roof a couple of years later. The bald guy with no shirt is the "good" roofer in town. The other two guys did all the carpentry on my house. 90 mil EPDM. Ice & water shield underneath. "Lifetime" asphalt shingles. The "I want the roof to out-live me" way of doing things.
"New roof" in my universe was unfortunately a bit more involved than usual.
I did residential roofing in SE Michigan for 28 years. 95% of what I did was steep slope, mostly asphalt shingles. 5% was low slope (flat roofing is NOT a term in the Industry). In my area a low slope roof is more likely to be properly installed than a steep sloped roof because training of installers is more rigorous.
A few general thoughts..
* low slope roofing is a water proof concept:It can withstand slow drainage and some short term ponding
*steep slope roofing is a water shedding concept: It requires immediate drainage
*low slope roofing should not be flat. Industry standard is no ponding water 48 hours after the last rain.
* a low slope roof with drainage issues can be fixed with a tapered insulation system (and a new roof)
*flashing of anything that breaks up the roof plain is the biggest potential problem
*flashing details in general are a bit more problematic on a low slope roof...partly because there is a tendency for low slope roofs to have mechanicals on them (your issue with the AC)
In your case the AC on the roof would be my concern....that and rectifying "flat" if it doesn't meet the 48 hour rule.
Personally after 28 years in the residential roofing business I would rather have an EPDM "flat" roof with a 1/2-12 pitch than a shingled roof with a 4-12 pitch.
Oh my - these comments are scaring me away from this condo development. I've been leaning toward them because despite being about 40 years old, they have the best square footage I've seen in condos or townhomes for a 2 and 3 bedroom plus a large laundry room, not just a closet with a washer & dryer. Great storage, fenced in courtyard and low HOA fees. Saw very little damage or "blue tarps" on the roofs after Hurricane Charley passed by in 2004.
There aren't many options in this area that are VA approved and there are no single family homes in my price range that aren't in high crime neighborhoods or that don't have really high HOA fees. Still waiting to see from the reverse mortgage people regarding my late aunt's house. Decisions, decisions.
Flat roofs may develop a leak because of standing water which can cause the wood underneath to rot, but don't let that scare you away if that's the best home for your money. Get an estimate on an entire roof replacement just to get an idea of how much it would cost, and budget for that just in case it comes down to that. My son has a partial flat roof on his townhouse that was leaking but they caught it in time so that they only had to repair it and not replace any damaged wood.
We bought a house with a flat roof one time. We did have to replace the roof, but I think it's because it was about 30 years old. The house was mid-century. I always wanted to start singing the theme song to The Flintstones every time I pulled into the driveway, lol.
I did residential roofing in SE Michigan for 28 years. 95% of what I did was steep slope, mostly asphalt shingles. 5% was low slope (flat roofing is NOT a term in the Industry). In my area a low slope roof is more likely to be properly installed than a steep sloped roof because training of installers is more rigorous.
A few general thoughts..
* low slope roofing is a water proof concept:It can withstand slow drainage and some short term ponding
*steep slope roofing is a water shedding concept: It requires immediate drainage
*low slope roofing should not be flat. Industry standard is no ponding water 48 hours after the last rain.
* a low slope roof with drainage issues can be fixed with a tapered insulation system (and a new roof)
*flashing of anything that breaks up the roof plain is the biggest potential problem
*flashing details in general are a bit more problematic on a low slope roof...partly because there is a tendency for low slope roofs to have mechanicals on them (your issue with the AC)
In your case the AC on the roof would be my concern....that and rectifying "flat" if it doesn't meet the 48 hour rule.
Personally after 28 years in the residential roofing business I would rather have an EPDM "flat" roof with a 1/2-12 pitch than a shingled roof with a 4-12 pitch.
Is the A/C on the roof a problem because of leaks or because of inefficiency of operation there in the hot sun 24/7 in Florida?
Is the A/C on the roof a problem because of leaks or because of inefficiency of operation there in the hot sun 24/7 in Florida?
Leaks can be a problem, but compressor failure is the more common one. Some of those would happen anyway.
It took a while for me to get my head around this, but an AC unit in the hot sun is only about 11% less efficient than one in the shade. The head pressure is slightly reduced in the shade, but the cooling is minimally affected.
The shift from the refrigerant going from a gas to a liquid in the compressor or scroll is where the energy is put into the system. That energy heats the liquid tremendously, just like you can't put your hand on the bottom of a bicycle pump when inflating a tire. The outside coil then dissipates the bulk of that heat to the atmosphere. When the refrigerant hits the expansion valve and turns back into gas, it is STILL hot liquid. (If it isn't, that valve can freeze over.) The cooling comes from the change of state from liquid back to vapor, which occurs just a bit downstream of the valve in the other coil.
Compressor motors are designed to run fairly hot. The outside heat shortens their life a little, but other factors can be greater.
For those that think a flat roof isn't flat have probably never heard of Type II Dead Level Asphalt. With the summer sun it will seek a dead level just like water. It is the definition of a flat roof. When storing the open cardboard drums, you have to be careful that one is not tilted and be in the summer sun. Come back a few days later and you'll find it has run out of the drum. On the commercial jobs here that are flat, it is considered an unwalkable roof. At one time, we installed a product called Careytred that was laid in the Type II asphalt. It was an asphalt based product with roofing granules on the top side. The sheets were 3'x 6' x1/2" thick. These sheets gave you walkable access to the HVAC systems and in some of the older buildings, the water supply. But yes, there are 100% absolute dead level roofs out there.
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