TomKruger's blog

Roofing…Overlooked and underappreciated

A comment about the roof coverings and the effect of ventilation.  In the Grayslake, IL area, roof covering is usually asphalt shingles.  Two general statements that hold true are (a) three tab asphalt shingles are a lower grade than architectural multilayered asphalt shingles; and (b) the life of an asphalt shingle increases with the increased pitch of the roof.  In fact, shingles should never be used on a flat or nearly flat roof.  The average life of an asphalt shingle is between 20 and 30 years, depending on the quality of the shingle and the pitch of the roof.  A low quality shingle placed on a steep pitched roof might last 25 years plus while a quality shingle placed on a roof not as steeply pitched might last 25 years or less.

The condition of the asphalt shingle may give an indication of other problems with the roof system.  Asphalt shingles that are 25 to 30 years old have reached the end of their life expectancy and will have curled, cracked, or have buckled tabs, bare areas, loose granules in the gutters, nails that have popped, and may be missing tabs or shingles here and there.  This is to be expected with roofs that are 25 years old; they need to be replaced… soon!

However, the asphalt shingles above were installed only 16 years ago, something has gone wrong.  There are other underlying problems.  As the sun beats down on the roof, it heats the shingle.  Not only is the shingle heated but so is the wood material behind the shingle.  Eventually the air in the attic is heated.  In the summertime, temperatures can reach over 160F, thus cooking the shingle from both sides, causing early failure of the shingle.  To keep the asphalt shingle from cooking on both sides it is necessary to have air movement in the attic.  On the underside of the roof is the soffit.  In the soffit there should be vent holes to allow air to move up into the attic.  At the ridge there should be a ridge vent to allow hot air to escape.  If there are no ridge vents then there should be top mount vents to allow the hot air to escape from the attic.  In the picture above there are neither ridge or top vents.  Therefore there is no exchange or  no circulation of air.  As long as there is an exchange of hot air for air of a lower temperature, it is possible to keep the shingles from cooking.  In the picture above there are no roof vents present, that’s why the shingles (top right) probably failed.

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