Only the knowledge of real-life effects of exposure on a roof system can determine the life span of your roof.

Determining how much life there is remaining in a roofing system, whether it has just been installed or if you are looking at it after some years of abuse from the elements, is a difficult task.  There are various laboratory tests performed by manufacturers on their roofing membrane materials to determine things such as; cyclic fatigue, sun exposure, tensile strength, shrinkage, etc.   Although these tests are important toward producing quality and durable roofing materials, the only true test for roofing systems is actual time on the roof of a building, exposed to “real life” elements and abuse.

“Real Life” Exposure

When we refer to “real life” exposure, we are referring to what actually happens to a roof after it is installed on top of a building and is exposed to a variety of ongoing elements.  Some of these elements consist of the following:

-         sun

-         cold/ice

-         sudden temperature differences such as a cold rain on a warm day

-         ponding water

-         dirt

-         algae

-         pollution

-         differing expansion and contraction rates of all components used to make up the roofing system

It is very difficult to simulate these actual conditions within a confined, protected environment of a laboratory setting.  Manufacturers may claim their roofing membrane material passes extreme laboratory testing which simulates 20, 30 or more years of exposure.  However, what we really want to know is, what is their actual documented “real life” time of their roofing systems out on buildings.  Unfortunately, this information would be extremely difficult to come by from the manufacturers as they typically don’t make it a habit to document when all of their roofs fail.  It is more likely to find this type of information from a roof consultant that has a sophisticated database  which tracks actual failure time of roof system types and manufacturers.

A roof consulting firm is typically exposed to hundreds of existing roofs each year by performing inspections and condition analysis.  Thus, a consultant would have genuine knowledge of how roof system types are performing out in “real life”.

Some Determining Factors for Roof Longevity

Type of Surface Protection – The type of  surface protection will greatly determine the longevity of the roofing system.  It is extremely important, especially in asphalt-type products, to protect the roofing membrane from sun exposure.  Types of surfacing include gravel, coatings, granules, etc.

Deck Type – The structural deck’s expansion/contraction characteristics may affect the roof’s longevity.  A concrete, lightweight concrete, gypsum or tectum deck with lower coefficients of expansion and contraction seem to provide more stability for a roofing system resulting in longer life.

Type of System – There are various types of roofing systems to choose from and each type will provide various results.  For instance, a built-up roofing system may be installed with 2, 3, 4, or 5 felt plies.  The old rule of thumb is, life expectancy of a built-up roof system can be determined by multiplying the number of plies used in the system times 5 years, or 5 years per ply.

Building Structure – The type of construction used for the building may also determine how long a roof will last.  Structures made with tilt-up walls and large expansive support beams will create a substantial amount of movement that will affect roof membrane performance.

Drainage – Ponding water on a roof system is never a good thing.  Although some types of roofing products are more adapt at withstanding the degrading effects of standing water, such as coal-tar, ponding will shorten the life expectancy of any roofing system.  Proper design of slope should be a number one priority when installing a roof system.

Proper Design – The design of a roofing system for a particular building is as important to the roof’s longevity as the materials themselves.  The design of a roofing system is critical. The method of attachment, drainage, allowance for expansion/contraction, insulation type and surface protection to be used must be evaluated and decided on to achieve the intended results for longevity.

Workmanship – The best materials and best design of a roof will still not work effectively if the installation is poorly done.  Workmanship problems within a roof will typically show up as deficiencies within the first five years of roof life.

Insulation – Insulation that may be installed between the roof membrane and deck to provide a required “R-Value” can affect the longevity of the roof.  The insulation tends to absorb and retain the sun’s heat, which can elevate the roof membrane’s temperature during a sunny day.  Over time, these elevated temperatures will cause degradation to the membrane.  When insulation is not used within the roofing system, heat from the sun tends to pass through the roof membrane and the membrane stays cooler.

Flashing Details – Roof flashing details used at roof penetrations, walls and curbs are an integral part of the total roof system.  These flashing details are typically the first thing that troubles a roofing system.  It is critical to design and install detail flashings that are relatively maintenance-free and will accommodate movement within the building and roof system.

Environment – The type of geographical environment, as well as building usage, will have an affect on roof longevity.  A roof in Phoenix, Arizona will require a different roof design than one located in Chicago, Illinois due to the weather extremes each area is exposed to.  An industrial type of building will also require a different roof design than an office building due to the roof being subjected to possible chemicals and substantial foot traffic.

Regular Inspection and Maintenance – This is a must if roof longevity is to be achieved.  Many new roof owners believe that if they buy a roof warranty for 10 years, they never have to look at the roof or maintain it for at least 10 years.  This, unfortunately, is likely one of the main reasons that our national average for roof service life is at 12 years.  It is very important to catch any developing defects within a roofing system early on prior to the defect expanding like cancer within the system.  If a defect can be identified and repaired properly prior to it leaking, the roof system will have a much better chance at lasting well beyond the 12-year average.

Conclusion

As you can see by the above partial list of  factors, there are many things to consider when determining how long a roofing system actually lasts in a “real life” environment.  However, it can be guaranteed that if a roof system is not maintained readily and properly during its service life, it will fail much sooner than what it would with proper maintenance.

As mentioned earlier, it may be advantageous to contact a roofing consultant that has historical database tracking capabilities of actual roof system performances.  This will give you a better idea of how long roofs last in certain environments and what types of maintenance will be required to get the most life out of your roof asset.