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The hat for most homes: asphalt shingles

Posted by Rona Fischman June 4, 2009 03:20 PM

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Inspectors tell me to look at the individual rectangle of the roof shingle. If the edge is clear and discrete to the eye, then the shingle is newer. The fuzzier the line, the older the roof. This rule of thumb seems to work. Now, let’s hear from someone who can tell you more. Inspector Steve Roberts joins us again. Today, he is starting at the top.


Asphalt shingles are the most commonly used type of roof covering for pitched roofs on homes. The overlapping design of the installed shingles provides a double layer of protection as the water flows down the roof slope to the roof edge. Asphalt shingles, also known as composition shingles, are so widely used because of their moderate cost, light weight (compared to many other roofing products), durability, and ease of installation. Asphalt shingles are surfaced on the top side with mineral granules to provide protection from the elements and a level of fire resistance.

Asphalt shingles are available in a variety of colors, weights and patterns. Regular weight asphalt shingles generally have an economic life span of 16-20 years; heavyweight shingles are sold as 30-50 year shingles. Exposure to the sun will tend to shorten the lifespan.

The installation of an asphalt roof involves more than just the roofing itself. A water-resistant saturated felt underlayment is typically rolled out over the sheathing before the shingles are applied. In New England, a special rubberized membrane is installed along the eave to provide extra protection from ice dams and water backup. Eave or gable edge flashing is also used.

An integral part of any roof is its flashing. Flashings are used at all roof penetrations. Poorly applied flashings open and allow water to penetrate the roof surface. If valley flashings are too narrow, backed-up water can find its way under the roofing materials. Most reported roof leaks are in fact flashing leaks.

To obtain maximum life from your asphalt shingle roof:
• Keep trees trimmed to prevent damage to the roof surface from branches or falling limbs.
• Check the roof surface annually for obvious damage, lifted or worn shingles. Pay particular attention to valley areas and flashings.
• Have missing or damaged shingles promptly replaced.
• Periodically check the underside of the roof for signs of leakage or damage, especially around vent pipes and chimneys. Also look for any signs of mildew or mold, which may be associated with roof leakage or ventilation problems.
• Maintain good ventilation in the attic even in winter months. Poor attic ventilation can cause damage to a roof structure. Additional vents or an automatic vent fan may be required.
• Be alert for ice dams which form along the eaves. Ice dams can cause water damage to the interior ceilings and walls.

Regardless of the type of materials used, all roofing will require replacement. If it is badly worn or just suffering from old age, limited repairs won't add much to the roofs life. It may be possible to lay the new shingles over the old one. Most roof framing is designed to withstand the weight of two layers of shingles. By laying over the old roof, you will avoid the associated costs of disposing of the old roof, but eventually both layers will need to go.

This blog is not written or edited by Boston.com or the Boston Globe.
The author is solely responsible for the content.

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Scott Van Voorhis is a freelance writer who specializes in real estate and business issues.

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