The expected lifespan of a 3-tab asphalt shingle roof, often called a 20-year shingle roof, is 16 to 22 years in Florida, with an average of 20 years. Why does a roof shingle with a 20-year or more manufacturer’s warranty typically last less than 20 years? Because the warranty is against “manufacturer’s defects” during the period of the warranty, not for the actual life of the roofing components used, of which the shingles are just one component. Poor workmanship by the roofing contractor is often determined to be the cause of early failure of a roof if a claim is made against a roofing material manufacturer.

    This graph compares average lifespan of a 3-tab shingle roof to other roof types:

   The 16 to 22 year average lifespan estimate is based on “average” conditions. Many factors contribute to a longer or shorter life of the roof; so a particular shingle roof’s life can vary—sometimes significantly—from the average. 

    Here’s a list of conditions that affect roof longevity:

• Color of roof - A dark roof absorbs more heat, which shortens the lifespan.

• Angle of roof slope - Higher pitch roofs tend to last longer.
• Orientation of roof surface - A roof slope facing south will get more sunlight, and have a shorter life.
• Multiple-layer roof - A roof installed over an existing roof will have a shorter life. Two layers of shingle roof are allowed by building codes, so it is possible to put a new shingle roof over an existing one—just once. While a homeowner saves the tear-off labor and dump fees for removal of the old roof, the shorter life of the new roof and double expense of the tear-off and dump fees when its time for a roof again make it a poor long-term choice. 
• Quality of roof material - “Economy” roof materials have a shorter life.
• Installation - Sloppy or improper installation shortens roof life. Manufacturers typically blame the roofing contractor for a roof that has a short life, and they are sometimes correct. Exposed fasteners, over-driven fasteners, and poor or missing flashing at valleys and edges will shorten the roof life.
• Attic ventilation - An unventilated or poorly ventilated attic reduces roof lifespan.
• Radiant Barrier - The foil sheet glued to the underside of roof sheathing to reflect the heat of the sun back out into the atmosphere—reducing the attic temperature in the summer—tends to also reduce shingle life because it makes the roof shingles hotter. 
• Trees near roof - Tree branches rubbing on a roof or the acidity from the accumulation of leaf debris on a roof shortens its life.
• Harsh climate - Severe weather, both harsh winters and hot summers, along with big temperature swings within a 24-hour period, also shorten lifespan because of the expansion and contraction of roof materials.

    Go to our blog post What is the average lifespan of the parts of a house? for rating of other house components. To understand the basis, potential use, and limitations of lifespan ratings, see our blog post How accurate are the average life expectancy ratings of home components? Are they actually useful?  

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Field Guide for Home Inspectors, a quick reference for finding the age of 154 brands of HVAC systems, water heaters, and electrical panels, plus 210 code standards for site-built and manufactured homes, and the life expectancy rating of 195 home components. Available at amazon.com for $19.95.
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  To learn more about roofs and attics, see these other blog posts:

• What are common problems of asphalt shingle roofs?

• Why is my roof sheathing sagging between the trusses?

• Why is granule loss a problem for an asphalt shingle roof? 

• What are the mistakes to avoid when doing attic improvements?

• What causes roof shingles to curl up at corners?  

• What causes shingles to buckle along a line on the roof?

• What causes leaks at a fake roof dormer? 

• What causes a sagging roof ridge line?

• What causes bubble-like blisters in a built-up and gravel roof?  

• Why does it cost so much more to replace a steep roof than a low slope roof? 

• What is "ponding" on a flat roof?

• Is an attic required to have a light by the building code? 

• How can I inspect my roof for hurricane damage?

• Why is premature curl of roof shingles a problem?

• How can I tell if a roof has more than one layer of shingles? 

• What are the common problems with attic insulation? 

• If my roof is not leaking, why does it need to be replaced?

• How can I be sure my roofing contractor got a permit?

• How many layers of roofing are allowed on a home? 

• What are the dark lines running parallel to shingles on my roof?

• How can I tell if the house needs a new roof?  

• Why does my homeowner's insurance want a roof inspection?

• What are the hazards to avoid when going into an attic? 

    Visit our ROOF AND ATTIC  and LIFE EXPECTANCY pages for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles. 

NOTE: These life expectancies are based on data provided by InterNACHI, NAHB, FannieMae, and our own professional experience. Because of the numerous variables that can affect a lifespan, they should be used as rough guidelines only, and not relied upon as a warranty or guarantee of future performance.