The terms “sustainability,” “efficiency” and “green” (good for the environment) are very often used in our industry these days. The color of the roof can seem to be more important than how well it keeps water out or resists wind uplift and, just as importantly, how long it lasts. But please don’t confuse how long it lasts with how long the warranty is. But I digress.
Certainly the first question, when considering sustainability, should be how long something will last in the first place? Then, how can I extend the life and for how long?
Built up roofs (BUR) and their offspring, modified bitumen roofs, have been a staple of the roofing industry since before it was called an industry. Many roofing contractors and manufacturers still swear by these systems. Why is that? Some may say it’s because we’re old fashioned and don’t like change. In fairness, there is probably some truth to that. But like many things that endure, there is a reason. To put it quite simply: they work and work well.
But with all the new technology and the advent of single-ply systems in particular, are they still needed? At this point, there are simply not enough fair comparisons available to conclude that they are not. The most prevalently used single plies have not been around long enough to know. We do see extended life in many single-ply systems that have used the same composition or formula long enough to observe them fairly. But keep in mind, there are many built-up roofs in Florida that have been in service for not just 20 years but 30, 40 and more and there are a lot of them. These are primarily multi-ply, gravel-surfaced roofs. We also see some of the original APP (atactic polypropylene) modified bitumen systems that are more than 30 years old still in service. For these roofs to last this long, they required some degree of maintenance, but you might be surprised, in a few cases, just how little.
One of the reasons these systems last so long is the basic materials they are comprised of: asphalt and, in fewer cases, coal tar bitumens. Just as importantly, they are usually made up of multiple layers or plies and, in the best cases, multiple waterproofing
layers. In all cases, they are made up of bitumens and a reinforcing layer or layers. In Florida, with our brutal environmental conditions, it is great to have some portion of your waterproofing protected from not only the sun but also from our constant wet-dry cycle, both of which are very detrimental to any constantly exposed material. This is one of the reasons why properly installed gravel-surfaced BURs have proven to be so durable and thereby sustainable. They have a sacrificial layer of bitumen (flood coat) that helps to protect the waterproofing layers. The gravel in turn protects the sacrificial bitumen. Some disadvantages of gravel-surfaced roofs are that they are not good substrates for coatings and should only be used where the possibility of wind-borne debris from gravel has been considered.
Granule-surfaced modified bitumen membranes provide a very similar protection, just less of it. The granule surface on a BUR cap sheet is also similar, but with even less asphalt. These granule surfaces, when caught before extensive granule loss or other degradation has occurred, make excellent surfaces for ever-improving roof coating systems. That is, of course, as long as the surface is properly prepared. Properly prepared smooth surface APP-modified bitumen membranes are also good substrates for coating. These improved coatings give these systems new relevance when considering sustainability. A properly chosen and applied coating system may extend the life of a properly applied multi-ply roof system for several lifecycles. Single plies can pose some challenges when being used as a coating substrate. It is still unclear how long their lifecycle can be extended by doing so.
One thing that the granules can’t do as well as properly installed gravel surfacing is to help minimally sloped or nearly flat roofs dry within the code-required 48 hours. The gravel in a given depression displaces much of the water that would otherwise be there. A flood coat of asphalt needed to surface with gravel will tend to be deeper in the center of small depressions, thereby reducing their depth. Also, as the top surface of the gravel dries, the moisture below migrates to the surface as wet chases dry. Keep this in mind when replacing a minimally sloped gravel-surfaced BUR with any smooth or granule-surfaced roof system. You may not meet the code requirement for positive drainage. There is no exception in code for a “ponding water spec.” For existing buildings, if the roof isn’t dry within 48 hours after the last rain fall, it doesn’t meet the requirement.
Not all roofing contractors want to deal with the heating and handling of liquid bitumens. That is certainly understandable. There are other options that still give you the advantages that modified asphalt bitumens provide. There are torch-applied systems as well as improving self-adhering or peel and stick membranes. With self-adhering membranes, compatibility of the membranes (they have to stick) and cleanliness are critical since they are less adhesive than asphalt-applied systems whether they are mopped or torched.
I also want to point out that recovering (installing a second roof system over an existing one) does not save space in landfills nor is it somehow environmentally friendly. Code requires that no more than two roof systems are allowed. After that, all roofing materials must be removed down to the deck, which actually eliminates the ability to save any rigid insulation previously paid for, thereby possibly adding more debris. Sooner or later, that original roof will end up being disposed of, either during reroofing or when the building is demolished.
In my opinion, it is too soon to drop the mic on these time-tested roof systems. If we lose our ability to produce and install these roofs, our industry will have lost something very hard, if not impossible, to get back. Let’s keep improving the materials and installation techniques and they will be around for many more decades.
I have stated on many occasions, “there is no perfect roof system, only pros and cons for each.” The trick to being a good roofing professional is evaluating the structure that needs a roof as well as your customer’s needs and then selecting the proper roof system to minimize the cons and maximize the pros. Hmmm, that last part could apply to the industry in general, as well as to FRSA’s overall mission.
Mike Silvers, CPRC is owner of Silver Systems, Inc. and is consulting with FRSA as Director of Technical Services. Mike is an FRSA Past President, Life Member and Campanella Award recipient and brings over 40 years of industry knowledge and experience to FRSA’s team.
Previous Article
Next Article