The Life Cycle of Your Roof

The Hostile Roof Environment- How normal weathering affects your roof.

Consider the conditions your roof must endure. First, there is the intense heat of the sun, which scorches the surface of the roof and raises its temperature 50 to 75°F. The sun’s rays are relentless, especially during the early afternoon hours. In addition to heat, the sun is the source of ultraviolet radiation, which has been shown to degrade and accelerate aging of asphalt shingles. If not for the protective layer of colored granules, roof shingles would fail very quickly. Other factors such as moisture, pollution and physical stresses like hail, snow loads, or tree limbs all contribute to the aging and degradation of your roof.

Seasonal changes and day to day weather also play a role in the aging of you roof. For example, consider the common situation in which the roof is bathed in the intense summer heat. On such a day the rooftop may reach temperatures in excess of 160°F. Then suddenly a violent thunderstorm rolls in. Almost instantaneously, the rooftop temperature drops 60-100°F as it is flooded with rainwater. The expansion and contraction caused by these thermal shocks causes stress on the roof components. This cycle repeats over years and decades resulting in cyclic fatigue of the shingles. In addition to the climatic and physical elements which impact the lifecycle of your roof, also consider internal conditions that accelerate the need for roof replacement. Testing has confirmed that inhibited air movement due to an improperly ventilated attic space causes a variety of problems. Elevated temperature which can literally cook the shingles. Elevated humidity allows moisture to permeate the wood deck and framing which causes it to fail prematurely. As you can see, the roofing environment is a hostile one with many factors influencing the longevity of your roofing shingles. The natural aging process begins as soon as the shingles are installed on your roof. Day after day, the shingles are exposed to the elements-sun, rain, heat and cold.’ Your roof never has a “good” day.

Asphalt is one of the primary ingredients in roofing shingles. Its purpose is to provide the waterproofing integrity for the roof. Secondarily, the asphalt holds the colored granules in place and contributes to the overall strength of the shingle. Asphalt, which is derived from petroleum, contains the oils that provide ductility and pliability to the shingles. During the lifetime of the shingles these oils begin to rise to the surface, where they are washed away by rainwater. In an attempt to restore equilibrium, new oils surface and the washing process continues. Also, the intense heat of the roof oxidizes or hardens’ the asphalt over time. You may be asking yourself, “What can I expect my roof to look like as this aging process takes place?” One or more of the following conditions may occur over time:

Curling: As the asphalt hardens over time, the granules which were once securely embedded begin to break away. Occasionally you may have seen the colored granules in your gutters. Also, as this hardening advances, the asphalt layers begin to shrink. Of course, all of this is occurring at a microscopic level and is not something which will be noticeable on a daily basis. As the asphalt layer shrinks, it is being countered by the shingle reinforcement, which resists shrinking. We now have a situation in which the top and bottom coatings are shrinking and the reinforcement is remaining stable. As a result, the edges of the shingle may begin to curl over time. In addition, organic shingles may exhibit signs of curling which might be considered excessive, however, this is not a manufacturing defect and would be considered part of the normal weathering process of organic shingles.

Surface Cracking: Another manifestation of the normal aging process may be the development of surface cracks. For example, as the oils of the asphalt are depleted due to heat, the shingle becomes more brittle, to the point where surface cracking may appear. The stresses created by thermal shock and the movement of the roof deck also increase the likelihood of surface cracking.

Blisters: During the course of natural weathering, small bubble-like raised areas known as blisters may appear on the surface of the shingles. The blisters may be small and pea-sized or as large as a quarter. The blisters may be open, exposing the asphalt, or closed. Blisters frequently result when minimum ventilation requirements are not met.

Staining: Finally, over a period of time, shingles may develop dark brown or black streaks that are sometimes mistaken for soot, dirt, moss or tree droppings. In actuality, this discoloration may be caused by algae growth. Although most roofing systems are susceptible to algae discoloration, it is most readily visible on white or light-colored shingles.

When your new roof was installed, friends and neighbors may have remarked how it enhanced the beauty of your home. However, research indicates that aging begins soon after the shingles are installed and progresses rapidly during the initial curing phase of its life cycle. During this stage, granule loss may occur, small blisters may develop, or the shingles may curl slightly at their edges. You may even notice that this curling is more pronounced during cold weather and the shingles may lie flat as temperatures rise. The good news, however, is that after this curing stage the shingles enter a long period of slow aging; which lasts for the major portion of the shingle’s natural life.

During the “mid-life” period, aging continues at a much slower rate. The cracking or granule loss still occurs but does not increase at a noticeable rate. Only after this long period of mid-life does the aging process begin to accelerate once again as the shingles enter their declining years. It’s during this period that homeowners normally think about replacing their roofs.