# Built Up Roof (BUR) vs Modified Bitumen Roof (Torch Down)



## RacerX (Jan 16, 2010)

I need some advice and/or opinions about these types of roofs. I have a flat section of roof on my house that needs to redone. I had this roof completely torn off and redone (BUR) approx 11 years ago. I spent a whole lot of money with a LICENSED contractor on this roof wanting not to have to deal with it again for a long time. Apparently it wasn't done correctly according to the roofers that have come out and bid the job. I was told that they didn't prime the edge metal correctly and this caused the edge to lift up/de-lam and water to wick in. It has destroyed all of the fascia on this part of the roof and some of the sheathing underneath. Other than the edges lifting up/ de-laming, the roof is still in relatively good shape. This is a FLAT roof with less than 1/4" per foot fall. Some of the guys bidding have suggested modified bitumen (torch down) as the way to go and some say that the BUR is the way to go. Which would provide me with the better roof? Which would last longer? Is it better to go with a 4ply (base, 2 11 lb. plys, granulated cap sheet) or a 5ply (base,3 11 lb. plys, granulated cap sheet)BUR?  What about a 2 ply modified bitumen vs. a 3ply modified bitumen? I live So Cal. and we don't get a ton of rain. I would like this roof to last at least 10-15 year min. Thanks in advance for any advice or suggestions!


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## oldognewtrick (Jan 16, 2010)

Racer, 1st off welcome to House Repair Talk, most membranes on a flat roof have a life expediency of anywhere from 10-15 years. Yours being installed incorrectly hasn't helped. What I see most often for premature roof failure is improper installation. Period. Not a failure of materials but a roofer who either didn't know how or care to follow the MFG REQUIREMENTS for installation. The quality of installation is only as good as the procedures followed to apply your new roof.

I would stay away from torch down if it were my house, Why? Because you have a very hot flame creating high temps to melt the asphalt adhesive backing. I've seen buildings burnt to the ground as a result of torch down. We quit using torch down 15 years ago. There are better, in my opinion, systems available. We use to install hot moped modified 2-ply with a granule cap sheet a lot, and have never had a call back from 20 years ago, great systems. We've found the liability of torch down and hot kettles just isn't worth the liability.

Newer generation systems available from Certainteed, "Flintlastic" or GAF "Liberty" are a better alternative and basically the same material, but a cleaner and safer installation. Both carry residential warranties and can be applied to low or no slope roof decks. 

Remember single ply (rubber) is NOT warrantied on residential applications.

Go to a MFG website and find an installer who is certified by that MFG to install their products. They will include all the components of the system as required to put you in compliance for warranty. If a product is not installed according to the install specs it will void any material warranties.

Good luck and let us know how it goes and what you decide to install.


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## oldognewtrick (Jan 16, 2010)

Another thing you might want to look into is the TPO roof system. The sheets are heat welded together to create one sheet, are white and might qualify for energy rebates.


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## inspectorD (Jan 16, 2010)

I like the TPO systems, another great commercial roof, available for residential.

Couple things, Old dog gives great advice, been at it long enough to know better.
First thing is to talk to your local Building Dept as to what is allowable in your area. These Cali folks have a whole different set O rules than the rest of us.
 You folks have Quakes, which should not matter on a roof, unless you are fixing structure.
The other thing is fire, rubber and vinyl roofs may have to be certified to withstand certain things. That is why rock ballast is on some older roofs.
Ask what they want to see before you get any estimates, then you can compare aples to apples ,, so to speak.


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## oldognewtrick (Jan 16, 2010)

Some municipalities have moved away from ballast systems from the stand point that, in the event of catastrophic winds, wind lifted debris becomes like a shot gun blast. Ballast systems are loose laid over a roof deck (roof membrane and a gravel ballast), usually a rubber roof membrane. When you have a major wind event, lifting will occur, and we've all seen 2X4's going thru a wall on the news from storm events. Negative pressure forms as wind transverses over a structure and creates lift, any material on a flat roof will become airborne projectiles and become, basically a shotgun. Ballast systems are the cheapest system you can install and are the most problematic. I personally dislike ballast systems.

Racer, i can not stress enough, get a "qualified" roofer for your install. Where do I find one? Call your local roofing supply house (listed in the yellow pages, not Lowe's or Home Depot) they will refer a couple of good people. Go to the mfg web sites and look for certified installers.


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