One of the most common things a buyer wants to know about the house is, “How old is the roof.”  This is code for, “How much longer will the roof last.”

These questions are not all that easy to answer—especially the later one.

While I do my best to give some “general” guidance regarding these questions, I make it very clear that whatever I say should be considered a “guesstimate” at best.  There are many factors that can contribute to the condition of a roof:  color, type, style, installation methods, exposure, maintenance, factory defects etc.

For example take your typical “15-20 year,” three-tab, composition roof.  Exposed to full sun, a light colored roof will tend to last longer than a dark black roof.  Protected from full sun all colors will last longer but if this protection results in the roof staying covered with moss the roof can be damaged anyway.  Frequent pressure washing will take years off the life of a roof, as will installing it over other layers of shingles.  Shingles that are stapled as opposed to nailed are more vulnerable to wind damage.

Roofs can be subject to other forms of mechanical damage such as from overhanging trees, shoveling off snow in the winter, hail, water from upper roofs beating down on lower roofs, and downspouts from upper gutters flooding across lower roof surfaces.  Even pigeons and seagulls, hanging out on the ridge pecking at the roofing granules, can damage a roof.  Installing shingles when it is too hot can cause mechanical damage that will later result in a shortening of the life of the covering.

Of course using the roof for sunbathing and star gazing can cause damage to the roof—-as well as uncontrolled falls to the bather/gazer.

These indicators also have to be adjusted for different conditions in different parts of the country.

So when a buyer asks me how long is the roof going to last, these are the kinds of things I must consider in giving any kind of an answer.

A roof that has few visible signs of aging is the hardest to predict in some ways.  We often have sources of information to give us clues as to when the roof was installed and then we can use rough rules of thumbs to give an “approximate” idea of how much longer the roof might last. For example if the seller tells us that the roof was replaced when he bought it and we know he bought it ten years ago it is a “fairly” safe bet it is 10 years old.  That info, coupled with what it “actually” looks like at the time of inspection, one could reasonably expect to get another 5 years out of the roof—-assuming that it is a 15-year-roof—-and it looked like it might last another 5 years. Again, I always warn my buyers that these are “best guesses” and that there are many factors to take into account.

No home inspector is likely to “warrant” a roof and most are pretty careful to make their predictions “necessarily” vague.  The reality is, that predicting the life of a roof is very difficult and if one is accurate within 5 years one is probably pretty close.

On the other hand, some roofs speak very clearly when they are past their expected life, as the following picture will attest.

There are no maintenance questions here.

There are no questions as to how much longer the roof will last.

This roof was likely past its expected life 20 years ago—and the buckets in the attic agreed with me.

By Charles Buell, Real Estate Inspections in Seattle

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