Dear James: There are leaks in our garage when it rains. The dark shingle roof is about 20 years old. Is it better to try to just fix the leaks or re-shingle the entire garage roof? —Jennifer T. Dear Jennifer: At 20 years, your roof is reaching the typical life of an asphalt shingle roof. Dark shingles also deteriorate faster than light ones because the dark color gets much hotter in the sun. High temperatures, in addition to mildew, leaves, moisture, etc., can shorten the shingle life span even further. With the lack of attic ventilation in garages, the heat buildup in the roof is even higher. What actually happens is the granules covering the shingles come loose in the high heat. One purpose of the granules is to reflect the damaging ultraviolet rays. When they are gone or thin, the shingle material underneath degrades quickly. Since your roof is …