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Orillia Home Inspector Tips

Providing Valuable Home Owner Resources for Maintenance

Know Your Asphalt Roof

An asphalt shingle roof in good condition will keep your family protected from water penetration, while a roof in poor or failing condition can cause headaches and large bills due to damage and urgency. Asphalt shingled roofs are by far the most common type of roof covering found in homes today. They first came on the scene in the early part of this century and quickly became the roof covering of choice.

The condition of asphalt composition shingles is dictated by the condition of the granules in the joints between the tabs or cutouts in the shingles. Consider the following: *If the granules are intact in the cutouts or joints between the tabs, the shingles are acceptable and should have years of remaining life. *If the granules in the cutouts are worn and the asphalt matrix is visible, the shingles are marginal because of the obvious wear and limited remaining life expectancy, perhaps six months to two years. *If the granules and matrix in the cutouts are worn through and you can see the shingles or sheathing below, the shingles are no longer acceptable.

Curling or cupping shingles may be an indication of wear, age, or condensation problems. However, it does not indicate failed shingles. Remaining life expectancy could be two to five years. Even when shingles are in poor condition, roofs with multiple layers may not leak because of the layer of shingles below. These back-up layers can deflect water to the gutter system. The life expectancy of asphalt shingles is determined by the following: 1) The slope of the roof. Shingles will last longer on higher sloped roofs because water sheds quickly and more completely.
2) The color of the roof. Lighter-color roofs last longer than darker roofs because they reflect the sun better.
3) Exposure to the sun. North-facing shingles last longer than south-facing shingles because the sun causes as much damage as rain and associated weather.

High-slope, light-color, east-west facing roofs can last 25 years or more.
Low-slope, dark-color, south-facing roofs may fail within 15 years.

Roofs in the north tend to last longer than roofs in the warmer, southern climates. Careful attention should be given to flashings at all roof penetrations and valleys. Proper flashings and valleys should control and divert water away from the roof and walls of the house. The majority of roofing problems come from these areas.

How asphalt shingles are made: Asphalt shingles are made of asphalt flux, a material which is refined from petroleum in the distillation process. Asphalt flux is typically reinforced with glass fiber or cellulose fibers. Glass fiber reinforcement has evolved as the most desirable choice. The shingle matrix then receives a granular surface. Granules protect the shingle from the sun and the weather and increase the fire-resistance rating. Fiberglass-reinforced asphalt shingles typically have a fire rating. However, the primary materials in the shingles are cellulose and petroleum, which are flammable. Shingles come in different shapes and configurations. The most widely used shingles are self-sealing strip shingles. Asphalt shingles are normally installed on roof slopes of four inches per foot or more.

On slopes of less than four inches per foot or where the January mean temperature is 30 degrees F or less, the requirements are for specific materials that are designed for low slopes. Asphalt composition shingles were not designed for slopes of 4/12 or less.

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