Roofing System 13


Determining the factors that will cause the roof system to deteriorate is necessary in system selection. For example: 1) Is the project located in an area that experiences frequent and damaging hailstorms? 2) Does the roof have numerous HVAC units, the service of which will generate perpetual abusive foot traffic? 3) Will the roof be exposed to intense solar radiation throughout most of its life? 4) Is the roof accessible for repair? 5) Is there a kitchen hood that can damage the roof membrane? 6) Are there industrial uses or labs that exhaust acidic vapors? 7) Are there other toxic exhausts? 8) Etc.

In some cases, one factor will likely cause accelerated deterioration. In other cases, perhaps two or three factors may be nearly equally as likely to end the roof’s life. After identifying the likely cause(s) of deterioration, it is necessary for the roof designer to select a system with characteristics that can combat the destructive force(s).


Proper application is crucial to the long-term success of a roof. During the system selection process, the following should be considered:

  • Are contractors in the vicinity of the project site familiar with the system being considered? If not, either a system should be selected that the local contractors are familiar with, or a contractor should be brought in from outside of the project vicinity. It is important to avoid having a contractor install a system that he or she is not extremely familiar with.
  • It is preferable to select a system that can be installed by contractors who have an office relatively close to the project site. By doing so, the contractor will be familiar with local conditions such as historical weather conditions during the projected application period and logistics.


    Often there are regional requirements where the new building will be constructed, it is recommended that the roof designer request information on the type of roofs in the region, number of roofs within each system type, and the experience that the industry has had with the various types. If a specific system has been a good performer, it is probably best to use that system on the upcoming project, unless the new project has unique characteristics that another system would be better able to accommodate. Also, if the Owner has periodic inspection, maintenance, and minor repairs performed by in-house maintenance personnel, one advantage of keeping with the same type of system is that they will not have to become familiar with another system type.


    Most of the topics discussed in this chapter are technical in nature. Many of those considerations strongly influence the system selection. The considerations that influence system selection vary from job to job, depending upon the project location and requirements. When selecting a system it is important for the roof designer to determine whether the proposed system should more than just meet the minimum requirements. For example, if external fire resistance is particularly important for a project due to a strong threat from wildfires, then rather than just specify a system that meets Class A fire resistance, a better choice would be a system that has enhanced fire resistance, such as a paver-surfaced system. In northern climates consideration should be given to the potential for falling ice and snow. See the Resource Page Considerations for Building Design in Cold Climates.