1. Roof Age How old is your existing asphalt shingle roof? Most experts agree that a typical roof will last between 20 and 25 years. It also depends on whether the old roof was removed and you only have one layer of shingles, and if it is properly ventilated. If the roof was installed over another layer or several layers and it is older than 20 years, chances are you need a new roof.
2. Shingles curling and buckling Shingles that are curled or buckling are another sign that you may need a new roof. Look at the slopes of your home that get direct sunlight and if you notice the shingles are curling and losing granules, it could mean the shingles are past their life expectancy. There could also be a possibility that the roof is defective.
3. Roof valleys If your roof shingles are falling apart or missing in this area, it's a definite sign you need a new roof. Valleys are one of the most important areas of your roof. Snow and rain flow through valleys and into gutters. If the valley is compromised, you could be susceptible to roof leaks.
4. Missing shingles These are another sign your roof could be failing. Check to see if all of the shingle “tabs” are intact.
5. Chimney flashing This is another area to be concerned about. If your flashing consists of roof cement or tar, it may need to be replaced with a long-term, water-tight fitting, which would be a metal flashing system.
6. Shingle granules in the gutters Look in your gutters to see whether they are loaded up with shingle granules. Roofs tend to lose more granules toward the end of their life cycle. Inconsistant or darker color on some parts of the roof is another sign the granules have worn away.
7. Daylight through the roof boards You notice a spongy feel or trampoline bounce when walking on the roof, which means the underlying decking is weakened from moisture. Check your attic to see if there is any daylight coming through the roof boards. Also check for moisture in the insulation.