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The Sheltering Roof

How do you know when a roof needs replacing? Leaks through the ceiling, missing shingles, frayed or curling shingle edges, or erosion of the mineral granules on the asphalt layers are all signs that it’s time to repair or replace your roof.  

If you can see decay from the ground without climbing on top of the roof, it’s time to have your roof inspected by a reputable roofing contractor. The contractor can tell you if the roof was properly installed and maintained. If the damage is recent due to recent storm or hail damage, you can call your hazard insurance company to come out and do an inspection. You may get a new roof without paying much or anything out of pocket, unless the roof is past its useful life. Your insurer may calculate how much money they’ll put toward a new roof based on the age of the existing roof.  

Sometimes homeowners try to save money on reroofing by simply putting a new roof on top of the existing roof. But, if you want to sell your home, these “roof-over jobs” aren’t always a good idea. 

While many building codes allow for up to two layers of asphalt roofing, some manufacturers will not warranty a roof-over because the substrate may not be smooth, flat and clean enough. Insurers may also decline to either insure the roof-over or pay for roof damage if there are multiple layers. suggests that a typical asphalt shingle roof will last about 20 to 25 years, depending on variables such as the quality of the shingles, the professionalism of the installation, homeowner maintenance over the years, and, of course, the weather. 

Your roof should have several lines of defense or redundancies. If one part fails, such as when a shingle blows off, there should be other protective layers such as an underlying membrane, flashing around chimneys, and sealants that prevent the roof from leaking. Roof damage and missing shingles should be addressed as soon as possible, or they could place the redundancies could be at risk. 

Because 70 percent of U.S. homes have asphalt or composition shingle roofs, replacement roofs tend to be similar. According to, the average roof size in the U.S. is 1,700 square feet. Professional roofers calculate area by 100 square feet, so it would take 17 “squares” to reroof the average home. Materials and labor can run anywhere between $350 and $550 per square, or approximately $6000 to $9350 or more. 

If you’re selling your home, you may not be aware that the roof has any issues. In that case, the buyer’s home inspection should reveal any problems, and you’ll be informed and can make a decision about what to do.