There are many different types of modified roofing systems. The original product came over from Germany in the late 70’s to early 80’s. The first roofs were so successful, that everyone wanted to jump on the band wagon.
One of the first major systems that went down was a TAMKO modified system that we installed on the Delta Airlines terminal in Tampa. This was a black roof that went down both terminal sides, and also covered the center which was higher and had a water cooled air conditioning system on it that kept 2 inches of water on at all times. They purchased a 10 year modified roofing system because they were planning on remodeling the terminal and wanted a cheap roof. They understood that the roof probably would not last the full 10 years because it was a roof over application that we installed over an asbestos roof. There was also the problem that by using a black roofing system the roof would exceed roof temperatures over 180 degrees, and since it was a roof over, the temperatures would be trapped at the roofing surface. The roof warranty was no different than all roof warranties did not cover a roof that had ponded water, so to say the least there were no high expectations on this roof.
When the roof reached 8 years old, I informed them that there roof was nearing the end of their warranty period, and I should inspect it to make sure there were no problems, which I did. Unfortunately for me there was no work needed.
When the roof was 10 years old, I inspected the roof, and reported the roof was in good shape, but we should consider coating the roof with a white or aluminum coating. Unfortunately for me, that decided to wait.
When the roof was 12 years old they reported a leak. Upon inspection we discovered a pitch pan needed to be resealed. But that was the only work needed.
I inspected the roof at 15, and then 20 years. Unfortunately for me they knocked the building down when the roof was 22 years old, and there were no additional leaks ever reported.
All roofing systems have little quirks that have to be designed are worked around. When installing modified bitumen in hot asphalt, there is a tendency for most rolls to have a bow in them from the factory. Most rolls will also shrink within a few days, after the asphalt cools. We also find that if the roll is pushed during application, the roll will look great, but when the roll cools, there will be a line from top to bottom or what in roofing teams is called a fish mouth. We have found that if you will chalk a line on the top side of the roof, and give the modified an extra 1″ of lap, you can allow the roll to bow above the line about the ½”, and not have to bother pushing back down to the lap line. When a roof is finished, you should be able to site from one end of the roof and see all of the rolls lining up together.
There are a lot of new systems that pop up every day. Some aren’t too bad, but a lot of them are. From what we have seen, there are only a couple of modified systems that we will install, but for Florida, they are the best systems we have available for most roofing surfaces.
It also possible to torch modified systems on however, we always do small test applications, and watch other people’s mistakes before we attempt to install or specify a system for any of our customers. To date we have never seen a torch on system that has performed to our standards, and will not install that system until the performance standards have improved.
We have installed peal and stick asphalt shingle applications, but are a little reluctant to install a modified peal and stick on a low sloped application. They have only been out a couple of years, and have not proven themselves yet. However, we are concerned from the problems we have had with the surface being perfectly clean on the underlayment applications that we would rather be in a wait and see on the peal and stick modifiers.
We have installed quite a few roofs not with the modified adhesives. We have a few quirks as always to make sure there are a proper seal and the modified lays down properly. However the roofs that we have installed have been beautiful.
There are only 2 draw backs that I am aware of. First you have to be careful with any other contractors that have to work on the roof. We have had a little difficulty with the mechanical contractors that step on the laps, and walk around the roof leaving feet prints all over the finished surface.
The other drawback is a little more serious. In some instances there has been an oder that can get trapped now and then. There really is no smell on the roof, but there can be an oder that stays for 2 to 3 days. After that it starts to disappear, but once you smell it, you imagine it for a week or so.
With the exception of the smell issue, it appears that this system may be the best of all of the systems, even though it is slightly more expensive on certain situations. There is not heat introduced to breakdown the modified, and the sealant used is very strong and is the same materials of the modified.