Why Do Asphalt Roof Shingles Curl and get brittle?

I know you are going to have a hard time with this one, but would you believe that your roof, that bastion of protection from the elements (okay, maybe not so much against tornadoes and softball sized hail) actually has to breathe? It needs air circulation to perform properly and sometimes that can be a problem. Older homes with slate, tile, cement and well cared for cedar roofs can last for decades if not a century with proper routine maintenance. They are stiff, have plenty of air gaps and actually allow heat to escape. Most are installed over spaced roof decking to allow more air to move.

So why do some asphalt shingle which say they should last for 30 or more years look as if someone baked them in much less time? It’s very simple. When you have layers of asphalt covered paper and then a layer of self sealing shingles (self sealing is when the shingles essentially glue themselves to one another), an almost impenetrable barrier is formed that is effective in preventing water from penetrating the roof, but is equally effective in preventing air from escaping from underneath. This isn’t a problem in newer homes or where there is an unfinished attic space and proper ventilation.

The issue is in homes where the soffit vents have been blocked or where a former owner decided to pack insulation into the spaces between the rafters and then sheet rock the surface. Now where does all that heat go in the middle of the summer – especially on south-facing roofs? You’re right. It goes nowhere and as a result, it literally bakes the shingles and before long, causes the tabs of the shingles (the visible part) to begin to curl inward and occasionally bubble, turning brittle (not to mention, ugly) years before the roof’s official life expectancy. 

When looking at a home for sale, always check how the roof is insulated. If it is, make certain the underside of the roof deck has venting to allow cool air to enter at the bottom edge (soffit) and escape at the top through a ridge or gable vent, turbine or other device. Well ventilated roofs should last no less than their manufacturer’s rating unless damaged by hail or other force. It is not beyond reason that the life expectancy of a roof with no ventilation can be reduced significantly and most manufacturers warranties are voided by improper ventilation. 

To further compound the issue, more ventilation is not necessarily better ventilation. Improper ventilation can actually pull moisture into your attic space and create other problems. The key is to find a qualified contractor who knows how to do the job right. The cheapest guy is rarely the best deal and may actually cost you far more in the long run. Many issues are the result of contractors unwilling to spend a few more bucks to do the job right or contractors who are just ignorant. If you are looking to hire a qualified remodeling contractor, go to your local Better Business Bureau, Home Builders Association, or Building Department to find out who in your area is licensed and has been in business long enough to have a reputation for the quality of their work. Sticking with true professionals will get you a professional job. This website has some great information on questions to ask and things to consider when looking for a contractor.