Over the years we have gathered information and knowledge not found in the text books. One of the secrets to our longevity lies in our being selective. There should always be a good reason to specify a certain product. One cannot say that from today on we will only use X type of roof. Some owners insist on employing a specific roofing system or certain materials, and it takes all of our persuasive powers to point out that one should select from the total products market and choose the products more appropriately suited to the project.
Some building owners deal with a manufacturer's representative who will provide free specifications, consultation and inspection services. Products in this instance are selected from that manufacturer irrespective of the fact that there may be a product better suited to a specific project.
Manufacturers/suppliers also specialize in maintenance work, and many have a good range of products. You just keep applying the product every 2 or 3 years, etc. and it does a fine job! Our attitude is a little different. We believe in providing an independent assessment of all conditions with a view to eliminating maintenance work. If the perimeter roof edge is too low, raise it. If pipes project through the roof membrane too close to an opening, relocate the pipes in a manner that minimizes maintenance. Apply a roof system that has a good history of longevity. And so on.
When dealing with the roof, the building owner's usual rule of thumb is "out of sight and out of mind". The same could be said of preventative maintenance work.
Also, if a roof is subject to heavy pedestrian or other type traffic, roof system design must take that traffic into consideration. If a system is subject to oil or other type spillage or contamination, a membrane that can tolerate these influences is required. Incompatibility must also be considered. And the list goes on.
With respect to the infamous Toronto City Hall Podium restoration in 1980, it took six weeks to figure out what type of waterproofing system should be employed. The system as selected was not available on the open market. We just designed it. Very simply, we specified a 4 ply hot liquid applied rubberized waterproof membrane combined with 4 plies of polyester membrane. That was at least 25 years ago and it has never leaked. If and when it does leak, there will be no problem in locating the leak since the membrane is fully adhered to the deck and water cannot travel laterally within the system. Locating the point of water entry travelling within the system is a standard industry problem and a major headache. Leak detection is not generally easy. If leaks are not found immediately, substantial added damage to roofing materials will take place, not to mention damage to building contents and disruption to building operations.