The average life expectancy of an asphalt-shingled roof is usually between 15 to 25 years. Factors like harsh weather, improper installation, or a south sloping orientation can shave years off the life span of any type of roof. How can you tell if your roof measures up? A few ways to check includes counting the number of nails per single, measuring the shingle tabs and slot width, checking for cracks, and checking the ventilation. Let us explain.
Six Nails Per Shingle
In the early mid-1960s, it became common practice to use four nails per shingle instead of six. Also around that same time frame, self-sealing strips became more common.
In the late 1970s or early 1980s, metric shingles became common in certain areas. To identify if your shingles are metric, get out your tape measure—the tabs will be a little over 13 inches wide versus the 12 inch wide imperial tabs.
Cracks, Cupping, or Clawing
Other tell-tale signs of worn shingles includes broken shingles, loss of granules, moss or algae growth, cracks, curling, and buckling. As shingles age, they become more brittle causing them to tear from the roof more easily. Below is an example of cracked shingles. We estimated 3-4 years of life expectancy for this particular roof.
When shingles are new, the width between slots is about a quarter of an inch. As the shingles age, they'll shrink causing the slot width to grow to an inch or more wide at the end of the shingle life.
Proper ventilation can help prevent moisture from becoming trapped in insulation, structural wood, and shingles during cold weather months. And in the summer, heat build up can cause premature aging and cracking in shingles.
How are your shingles looking? Your roof may the the last thing on your mind, but it's as important as any other part of your home. It can cost between $10,000 to $15,000 to replace a roof. Doing a self-inspection once a year is the best way to prevent any problems from starting or getting worse (visually inspect your roof from the ground with binoculars), and doing so can help you predict and plan for future expenses.