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Preach_2 07-09-2010 08:24 AM

Best Roofing Material for a flat roof?
I built a new porch with a flat roof that slopes 4" in 15 feet and am wondering the best type of roof to use on it? I am located in the midwest (Kansas City) and we do get our share of rain and snow. Every roofer I have talked with is promoting a different product and cutting down the other guys and the prices are ranging all over from $575.00 to $2,400.00. The $575.00 is for a torch down and the $2,400.00 is for an IB Roof System that consists of an 80 mil PVC Membrane. The roof is 11.5 feet wide by 17 feet long but that does not include the sidewall flashing or part that will run up onto the existing wood shingled roof that has a 6/12 pitch.

Any advice you can give me will really be appreciated.

Grumpy 07-09-2010 09:44 PM

There really are no "best" systems when it comes to flat roof since every system has its' place. Kind of short compared to my usual write-ups but there is some basic advice on choosing a low slope roof system.

To elaborate, what's more important that the roof type to be installed is the roofer installing it. Everyone has their favorites. I have a few favorites that depend on the situation and there are pros and cons to each.

I can tell you to be weary, very weary of the $500 price. That just doesn't seem like enough. 3 squares of materials for a 10 year modified bitumen roof are approximately $250, plus shingles for tie in maybe another $75. How much are you going to pay the workers? $5 an hour? C'mon. Be very careful with this contracotr, if he is even a legitimate contractor, and exercise your due dilligence with extreme caution.

Furthermore, more information about a torch down roof system and an IB roof system is needed. For example torch down can be installed to a 10 year spec or a 15 year spec or a 20 year spec? which one is it? IB, although I am not very familair, I believe has the same system ratings 10,15,20... what changes is the manner in which it is installed. A 10 year modified bitumen is a base sheet and a smooth cap sheet while a 20 year modified bitumen is a double base sheet, smooth mid ply and granulated cap. There's just too much gray area to compare apples to apples.

80 mil PVC single ply roof membrane will last a lifetime. The wood you just built will rott before the roof fails, if properly installed. I can say that while I do not install IB, I do install PVC and if I were to roof this porch with an 80 mill pvc membrane I would be in the same ball park as the other roofer, probaby slightly less but I don't know enough so am really just guessing.

I really like single ply roofing systems like PVC, but going back to my previous comments about every roof having its' place, I often opt for a color coordinated granulated modified bitumen roof system when it's visible on residential and especially when it ties in with a shingle roof. There is nothing wrong with a shingle to pvc tie in, but the granulated modified bitumen looks more natural when tieing in with shingles. You may consider a torch applied or a self adhering. CertainTeed makes a flintastic and a flintastic SA. Remember, how it's installed determines its' longevity. some basic advice on choosing a contractor for your roofing project(s).

OldNBroken 07-09-2010 10:29 PM

Grumpy, be mindful it's only a 1/4"/12 so it's not going to show. That aside as usual your info is very thorough and I pretty much agree.

Preach 2, if you are looking for quality and longevity, I would seriously consider the IB system. They are one mfr that actually stands behind their warranties. Also would like to add any roofing system is only as good as the contractor installing it. In this business it really is "You get what you pay for"

Good luck

Grumpy 07-10-2010 07:58 AM

One more thing is details details details. Any good roofer will pay attention to the details. For $500 I can't see that guy installing the proper edge metal flashings. You'd want some kind of perimiter flashing at the edges to not only protect the membrane, but to good a nice clean finished look. This is commonly called a gravel stop.

Furthermore, what about a gutter, I'd imagine at one side the water would drain and you'd want some kind of gutter. Is this included? If so how will they terminate the gutter edge? There are several ways of doing it, not all are correct.

stuart45 07-11-2010 12:06 PM

1 Attachment(s)
Lead roofs are long lived, but are not the cheapest.
Attachment 22435

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