This article was posted on Tuesday, Oct 01, 2013

Property owners and managers who need a new flat roof on their building can have quite a dilemma on their hands. Many seasoned owners have had experience with flat roofs over the years and go with what has worked for them in the past. This is mostly hot-tar, either with a gravel or cap sheet finish. They know these roofs function for 10-20 years and are reliable. Newer owners or managers do not have the luxury of experience and so often research flat roofing options either on the internet or personal contacts. This method can be confusing and difficult, as there are several flat roofing options and many of the sources they find have their own agenda or they do not have all of the information about a changing industry. I have seen many well intentioned apartment owners and managers go down this road and come out being sold inferior roofing systems because of their lack of knowledge.

We are experienced in all of the flat roofing options available and will tell you the pros and cons of each of them, and show you which product will work best for you with your existing budget.

You must understand that the application of any system varies from installer to installer. I highly recommend in any choice you make that you choose a contractor who is an approved applicator of a major manufacturer to install that system. Simply ask if they are an approved applicator for the manufacturer of the material you will be installing. If they actually are, and you should check on this with the manufacturer, then you are more than likely in capable and honest hands. The reason for this is that manufacturers such as G.A.F. and “Versico” single ply systems, go through a rigorous acceptance process that includes all legal rudiments as well as experience and competence. They have done 90% of the work that you need done to choose a competent qualified contractor. There are unqualified people who present themselves otherwise that this process will eliminate.

Okay now for the roofing systems.

Built Up Hot Tar

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The most time honored and popular flat roofing system over the past hundred years or so is “built up hot tar.”  (“Built up” means more than one layer.) This system has layers of plies (sheets of felt usually with fiberglass infused in it) with hot tar between each layer topped with either gravel or a cap-sheet. Hot tar has been around for many decades and is completely reliable when installed properly. Hot tar systems last between twelve and twenty years depending on how many layers are used and the type of material. (There are different types of plies.)


Another flat roof method is called “torch-down”. This is a single layer of heavy duty cap sheet with tar embedded in the sheet. The sheet is heated with an open flame, or torch, which melts the tar allowing it to adhere to a base sheet below it and to another successive sheet forming a continual waterproof system. (Torch systems, although usually a single layer, are not to be confused with “single ply” roofing as they are completely different.) Torch-down roofing systems last between eight and twelve years usually, and depend greatly on the installer’s competence.

Foam Roofing

Another flat roofing system is “Foam roofing”. This system is sprayed onto the roof and boasts a thirty year longevity, and increased “R” value (insulation), however, there are drawbacks to foam roofing. Firstly, the system must be re-coated after several years and thoroughly maintained, which actually makes the claim of lasting thirty years false since it actually lasts ten or so years before needing to be re-coated. Also, the installation of foam roofing requires a higher degree of competence than other types of roofing. There is a procedure to create the mix, coupled with proper deck material and preparation that when incorrectly installed,SPFroofing systems exhibit inter-laminar blistering of theSPFlayers. Foam blisters most often occur by trying to stretch the application window, improper substrate preparation, or equipment problems. When installing anSPFroofing system, air-handling units must be turned off and covered if occupants are in the building. They should remain covered until theSPFis sprayed and the coating can cure.

Single Ply

The next type of roofing for flat roofs is called “single ply”.  Single ply (TPO or PVC it’s called) roofing is basically large rolls of different combinations of rubber, P.V.C., plastic, and other chemicals that are hard to pronounce. The material is “heat welded”, one sheet to another, to create a watertight system. The installers use what appears to be a small hair dryer to weld the material together, and a machine that resembles a lawn edger for larger projects. The material is estimated to last thirty years or more with no maintenance needed. There are two types of single ply T.P.O. and P.V.C. Both of these products carry 20 year warranties. The P.V.C. is more expensive, having the advantage of being more pliable than the T.P.O. and thus easier to work with. Both materials have a manufacturer applied white highly reflective coating that exceeds title 24 requirements. They are lightweight and in many cases can be installed over existing roof systems with no detrimental effects.

This type of roofing is being installed on most of the larger flat buildings acrossAmericasuch as Lowes, Wal-Mart, Home Depot, recently built Hotels inLas Vegas(Cosmopolitan, and the Vadera) Albertsons, and theL.A.Convention Center. The reason for this is that because of its longevity, moderate cost, reflective qualities and its environmental friendly nature, single ply is the best choice for flat roofing available.

So the moral of the story is this: As the propeller plan gave way to the jet, and dial phones gave way to push phones, so it will be with traditional hot tar roofing yielding to single ply. The reason for this is plain and simple; longevity, moderate cost, reflective qualities and an environmental friendly nature. It may take several years but the time is nearing when we will see hot tar kettles in the same junk yard as T.V. rabbit ears and old bulky computer monitors.

Tommy Scherer is the owner of T & G Roofing.  T & G Roofing is a Los Angeles based company serving the community for over 30 years. For more information or questions, call (818) 459-0702 or visit his web site at



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