When considering replacing the roof, many people would be faced with different versions of the roof service life which ranges from 25 to 35 years. The service life of roof is closely associated with the quality of asphalt roof shingles which is determined by their own weight.  Asphalt shingles we may see in the market range in weight from 210 to 320 pounds per 100 square feet. The most common type that contractors usually opt for is 210 pounds per 100 square feet. In accordance with the construction code, the 210 pounds per 100 square feet is considered a minimum standard for asphalt shingle roof.

When roof begins its aging process, the gravels will fall from the asphalt shingles, which encourages the sunlight to melt the asphalt more easily, thus causing the bending and deformation of the asphalt shingles. Such asphalt shingle roof usually has a life expectancy of 12 to 15 years.

320’s (three hundred and twenty pounds per square) are usually provided with a 20-year warranty by the manufacturer. But few people use them; therefore they are rare in the market.

Finally, the layers of asphalt shingles are also the factors that influence the cost. Some people will shingle a new roof to an old roof, which will reduce the service life of the new one. However, tearing off the old shingles will increase the cost by 10 - 15%.