Shingles for Your Roof: What to Consider

A “dimensional” or “laminate” shingle has extra pieces of shingle laminated to it that give the appearance of thickness and texture, when seen from below. There is no discernible shingle pattern, so it can be installed more quickly than the 3-tab type. Besides the natural shadow line created by the added thickness of the extra pieces, most manufacturers embellish with artificial shadow lines created by artful placement of colored granules.

The thickest and most expensive dimensional shingles, which usually carry the designation “40 year shingles,” often have two artificial shadow lines plus an overall subtle texturing of the shingle. The “30 year” dimensional shingle generally has only one fake shadow line, less subtle blending of the granule colors, and the shingle is not as thick. The least expensive, “25 year” dimensional shingle, which many tract builders offer as standard, has a less pronounced shadow line, and its thinner shingle creates less of a three dimensional effect.

When viewed up close on a sample board, only the shingle manufacturer’s artifice will be apparent. To get an idea of what the shingles will look like when viewed from afar, you need to find a finished house with a roof that has a similar size and slope.

Consider performance differences among shingles the best shingles are all all very strong and resilient–the attributes that best allow any roof to stand up well year after year. For example, if you live in an extremely windy locale, you might favor one of the shingles that has a higher wind rating which gauges the propensity to lift in a gale. If temperature extremes are the norm where you live, consider a shingle that is designed for very hot weather. If your home is close to a lot of trees–or if hailstorms are a regular occurrence–impact resistance may be an especially important criterion. The other consideration when choosing an asphalt shingle is longevity — how many years can it shed water and keep the rest of your house dry? Assuming that the roof has an adequate slope and is installed properly, this will depend on the local climate and how much asphalt, the key waterproofing ingredient, is on the shingle. Many manufacturers are now offering algae resistant shingles. In our opinion that is a must have feature as most homeowners find themselves having to deal with algae or moss on a yearly basis.

Shingles were once differentiated by weight, which indicated the amount of asphalt in the shingle. Then, about 20 years ago, as more and more manufacturers switched to making shingles with fiberglass cores that did not require as much “black gold,” they began to categorize shingles by their projected years of useful life. Since there is no industry-wide standard for what constitutes “40 years,” “30 years” and so forth, this designation has been left to individual manufacturers to determine. As Peter Kelly, Managing Director of the Asphalt Roofing Manufacturers Association said, “it’s up to the manufacturer to define what ’25 years’ means.”

In the absence of manufacturing precision, some explanation of asphalt shingle mechanics may be helpful. The key factors are time and temperature. The hotter asphalt becomes on your roof and the longer it stays hot, the shorter its useful life will be. A shingle in Phoenix, Ariz., will not last as long as one in Detroit. Even seemingly benign weather will heat up a roof. When the air temperature is a mere 75 degrees, the roof surface can easily reach 140 to 160 degrees.

Heat causes the asphalt to expand; the hotter it gets and the longer it stays hot, the longer it will be in a “stretched” position. When the sun goes down, the asphalt contracts back into its original position.

The UV rays of the sun are problematic as well, attacking the asphalt and causing it to become brittle and cracked. The  granules — those pulverized stones or glazed ceramic pieces that give a shingle its color — function as a “UV umbrella” to shield the asphalt from the sun. Eventually after several thousand heating and cooling cycles, the asphalt loses its ability to contract back into its original shape, and the granules start to fall out, exposing the asphalt underneath to the sun. At this point, the roof will start to look fuzzy. It may be several years before the roof actually begins to leak, but “most people don’t replace a roof when it starts to leak, they replace it when it looks bad,” said Tom Bollnow, technical director for the National Roofing Contractors Association.

How many years does it take for a roof to look bad? Climate clearly affects how long a given manufacturer’s “25 year” shingle will really last; so will its color. Across the southern half of the U.S., with longer summers and more intense sun, dark colored shingles will absorb more heat and age faster than lighter ones. In the northern half of the U.S., color is less significant, said Greg Malarkey, senior vice president of Malarkey Roofing Company, an asphalt shingle manufacturer in Portland, Ore.

The staying power of the granules is a critical factor, and a quick but telling test, no matter where you live, is to run a quarter across the granules on a builder’s sample. If a lot come off, it’s not a great shingle and you should question the quality of the other materials the builder is using.

The core material in the shingle can affect its longevity. In the northern areas of the Midwest, New England and Canada, which experience extreme freeze-thaw conditions, some roofers prefer an older style asphalt shingle with an organic mat core instead of a fiberglass one. In the Pacific NW, less expensive fiberglass shingles are used almost exclusively.