In the 1860 to 1890 era “Terned Tin” roofs gained in popularity in the Mid Atlantic region. The iron-coated tin roofs were inexpensive when compared to slate, wood and tile options available at the time and if properly maintained would exceed their 80 years expected lifespan. In the last 20 years, our company has replaced many of these roofs that are over 120 years old.

With tin roofs, longevity occurred with constant maintenance with proper painting being the most important. Keep in mind that almost all roofing paint until 1978 had lead so that the molecular adhesion sometimes helped the paint last 20 years between paintings.

Now the question is how long will modern metal roofs last? The most popular substrate available is Galvalume plated carbon steel. This plating was invented by Bethlehem Steel in the 1970’s. At that time they thought it would last 50 to 60 years.  In 2012, the Chicago-based Metal Construction Association (MCA) and Olympia, Wash.-based Zinc Aluminum Coaters Association (ZAC) commissioned a study to perform forensic tests at 14 existing Galvalume standing-seam metal roof sites throughout the country in varying climates and precipitation PH. The average age of these roofs was more than 30 years at the time of testing.

These sites were initially chosen for their varied temperature and humidity zones but it quickly became apparent the difference in PH levels was the factored that affected the lives of these Galvalume roofs. Here are the states these roofs were located: Massachusetts (2 sites), Ohio (3 sites), South Carolina (2 sites), Georgia (1 site), Colorado (1 site), New Mexico (1 site), Arizona (1 site), Oregon (1 site) and Wyoming (2 sites).

The conclusion was that the higher the PH levels the lower the acidity in the precipitation. The average panel life expectancy for 14 sites was 139 years. The lowest PH was 4.36 with a life expectancy of 66 years; the highest pH was 5.37 with a life expectancy of 375 years. After eliminating the highest and lowest, average life expectancy is 125 years. This average life expectancy is more than twice the 60-year life expectancy required by LEED v4.

When a coating is applied to the Galvalume metal roofs the life expectancy increases to over 180 years. At that time your great-grandchildren may want to discuss using one of their modern coatings to add another 100 years to this very long-lasting metal roofing system.

We can even add more years to these durable substrates if we include a roof ventilation system that, in some cases, can reduce attic air temperatures in the summer by as much as 50 degrees. For more information on our patented Therma Vent ventilation systems visit us at: AlphaRain.com

Written By: Brandy Dysart
Owner and Founder of Alpha Rain Metal Roofing