Most homes have asphalt roofs which have a life expectancy of 15 years to 25 years. As the asphalt shingles dry out they curl, the surface becomes brittle and cracks allow water to get through the shingles. If the water gets through the shingles, it may rot the decking under the shingles and may even damage the rafters.
Most municipalities in the Milwaukee area allow two layers of shingles on a roof. If the roof leaks or has problems after the second layer of shingles wears out, all of the shingles must be torn off down to the rafters or the decking and a new layer of shingles must be installed. This is because roofs are not designed to handle the weight of multiple layers of shingles and heavy snow in the winter.
Roofs can be evaluated from the ground, but a better evaluation is made by walking on the roof. If the shingles are starting to curl and lose their sandy surface, the roof needs to be replaced. Replacing a roof early, in a timely matter prevents water damage to the interior of the house. A roof that has a steep angle typically lasts longer, but such roofs are difficult to repair, as workers are required to work on a steep incline.