How Long Is The Average Warranty On A Commercial Flat Roof?

by | Jun 20, 2024 | Featured, Planning and Budgeting

A flat roof warranty can protect you, your roof, and building contents from poor workmanship and defective materials. The best rooftop warranty affords you peace of mind because the roof has passed an independent third-party inspection, covers all parts and materials, and guarantees the workmanship of the installer.

Average Warranties

Most properly installed, current-generation single-ply membrane and modified bitumen (mod-bit) commercial flat roofing flat roof systems in the USA today come with a 20-year warranty. With proper care and maintenance, the roof life can be extended a few years past 20, but you should budget for a roof restoration (coating system) at around the 20 year mark.


A couple of caveats are in order when it comes to the type of flat roofing system. The 20-year benchmark refers to current generation single-ply membranes and modified bitumen (mod-bit) flat roofing systems only. Flat metal, built-up, and coal-tar rooftops are a different story altogether.

Air Conditioning Equipment on Commercial Flat Roof | Flat Roof Solutions

Flat metal rooftops can last much longer than their membrane and mod-bit counterparts, up to 50 years in fact. Metal is, however, more expensive to install and more cumbersome (and therefore expensive) to work with when repairs are needed and there is rooftop equipment.

Built-up and coal-tar pitch roofs have also been known to last a very long time (40 years plus), but have fallen out of favor in recent years because of environmental and health considerations.

Twenty years is still a good benchmark and touch point to keep in mind. When you hit the 20-year mark, you should budget for a roof restoration or a new roof system.

Longer Warranties

The trend in the last several years has been to roll out thicker roof membranes and more robust assembly specifications as a way of lengthening the rooftop warranty for up to 30 years. Bear in mind that if you have an existing building, you will have to do a full tear-off and replacement to get the 30-year warranty, even if you only have one roof layer.

To qualify for the 30-year warranty, manufacturers also require vapor barriers, high-density coverboards, thicker membranes and more enhanced wind uplift protection. All of these elements make for a wonderful assembly, but a costly one as well. Whether these upgrades merit the extra 10-years warranty coverage is a business decision. That said, I can tell you I am rarely asked to quote these longer systems because of the additional cost. My inclination is that if you go with a standard 20-year assembly and plan on doing a roof coating in year 21, you will be dollars ahead.

Shorter Warranties

Some manufacturers offer 5 and 10-year roof system warranties. These are usually thinner membranes that can be installed as a recover or second layer. In my opinion, a five-year roof system is probably not worth the money. It is certainly more expensive than a 20-year system when you divide the price by the years of warranty coverage.
Commercial Flat Roof Core Sample |

Five-year assemblies and warranties are sometimes the preferred option of building owners who are looking to sell their building in the near future. The buyer, however, might unknowingly be stuck with an inferior roof unless that information is disclosed up-front or a roof inspection is done prior to closing. During an inspection, core cuts are taken and the thickness of the roof measured. This allows for identification of the roof assembly and an estimate of the remaining roof service life.

So while most commercial flat roof systems in the USA come with a 20-year warranty, you can get one that is shorter or longer but they come with caveats.

Expert Advice

Whether you’re a beginner, need advanced information about flat roofing topics, or a refresher,  this is where you can learn everything you need to know about commercial and industrial flat roofing.

Contact us for more information or pricing.




Jared Van Vranken is Vice President and lead estimator at Flat Roof Solutions in Malvern, PA. Jared has directed the installation, repair, recovery, and replacement of commercial flat roofs for more than a decade at Flat Roof Solutions. He guides clients in selecting the best roofing materials for their needs and budget.

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