Pros and Cons of Various Roof Systems

There are numerous roof systems available in today’s market, each with various strengths and weaknesses. Below I will describe each system briefly, and then list the good qualities and cons.

Thermoplastic and PVC- Single ply, could be mechanically attached, fully adhered or ballasted.

Pros- Superior performance in ponding water situations. Very lightweight roofs, in the neighborhood of 30lbs. per 100 sq . ft. Comes in white if a cool roof is desired, or in several different colors for aesthetic concerns. Yet another plus with these roofs is that large custom made field sheets can be ordered from the factory, minimizing seams sealed by the crew on the jobsite. Resistant to ozone, algae and field seams are 3-4 times stronger than EPDM filed seams. There is also a tremendous amount of flexibility in the material. And since seams may be welded with hot air, you will find no noxious fumes to manage. Both 15 and 20 year warranties available.

Cons- Being single ply, they have been vulnerable to discarded cigarettes, sharp objects dropped on the membrane, and broken glass from bottles thrown on roof (this happens a LOT) I generally discourage customers from installing these kind of systems if the roof has a lot of foot traffic or is easily accessible to unauthorized personnel. In the past, material shrinkage was at times a severe problem on Thermoplastic and PVC roofs, but changes in composition and manufacturing has ameliorated this matter. These roofs still shrink over time, though not to the purpose of failure as before.

Bottom line- Great roofs, especially on roofs that pond water heavily, provided that the roof is generally accessible only to authorized personnel.

Asphalt Modified Bitumen- This roof is what a lot of people call a rubber roof, when it is in fact composed mainly of asphalt. It is available in 3 ft. wide rolls and is usually torched down with an open flame, though they can be applied with hot air welders in certain conditions as well.

Pros- In my opinion, the greatest strength of these roofs is how well they resist outside stresses. They handle foot traffic better than any other membrane, and are difficult to puncture, especially if they’ve a granulated surface. These roofs are so tough in fact , that most insurance companies wont even recognize hail damage as they do on other roofs (I have personally seen modified roofs positively pummeled with hail and come out completely undamaged)

Cons- The most glaring disadvantage with your systems is that there is a seam every three feet, which makes for a LOT of seams. When you yourself have a diligent crew with a competent foreman who will make certain that every seam on the roof is triple checked, you’ll probably be fine with this system. If not, you can be pretty sure you can be with leaks fairly soon, well before the warranty expires in my experience. And large ponding areas of water on these systems will degrade the material prematurely.

Bottom line- With a good, experienced crew this can be a good roof on a building that does not pond water excessively. And if you have a building with a lot of rooftop foot traffic, this is probably the only way to go.

Foam roofs- This method is applied with a sizable spray unit, spraying two liquid components (isocyanate and resin) When the liquids are mixed together, they expand 20-30 times and will stick to concrete, wood, steel & most existing roof systems, but according to the manufacturers, NOT to modified bitumen.

Pros- When complete, the roof is monolithic with no seams, fully adhered and has insulating properties.

Image result for roofing

Cons- Full disclosure, I’ve limited experience with these roofs here in NE Illinois. We don’t install them, but I have been on 9-10 buildings with this system, and all them leaked badly, in a couple of cases within months of being installed. Leaks are extremely difficult to track down and difficult to fix even when found, as repair materials do not adhere to this surface well.