Aug. 14, 2006
 
New Roofing Requires Answering Several Questions
 
By Dwight Barnett
Scripps Howard News Service
 
Q: I have a question about roofs. Our home is due for a new roof soon and we are getting different bids for the project.
 
The least expensive of the bids involves installing new shingles over the existing shingles. One roofer said I already have two layers of older shingles and a third layer would place too much weight on the roof.
 
He wants to remove the first layer of shingles before adding new ones. His price is significantly higher than the others. I'm concerned with his remarks that the extra weight could cause the roof to fall.
 
Is he just trying to frighten me into a more costly repair? Please respond soon.
 
A: I will try to help you but you did not give me enough information to make a definite determination.
 
With that said, most roofs should not have more than two layers of asphalt shingles. I have seen steep-pitched roofs with three layers, but the home's roof system had extra bracing in the attic to support the added weight of all the shingles.
 
In most cases, the costs of adding extra bracing might be more than the costs for the removal of the two layers of shingles, but the roof system would always be braced against strong winds and deep snow cover. On average, a common asphalt shingle weighs 240 pounds per 100 square feet. A small, single-story home measuring 24 feet by 40 feet has 960 square feet of floor space.
 
If the roof were a simple gable style with a moderate pitch of 5-inch in 12-inch (5/12) and a one-foot overhang front, back and ends, there would be about 12 squares of shingles weighing in at 2,880 pounds, close to 1 1/2 tons of weight on the roof.
 
Adding a second layer doubles that weight and a third layer could cripple the roof.
 
Also consider this: As you add layers of shingles, the life expectancy of that layer decreases and the manufacturer's warranty will be void. If the home has only one layer, you might consider one of the new steel roof panels which weighs much less than an asphalt shingle, has a 40- to 50-year warranty and is 19 percent cooler than a common asphalt shingle.
 
According to the Florida Solar Energy Center, a steel shingle will reflect anywhere from 66 to 77 percent of the sun's energy, making the attic space much cooler. Steel panels also have a class 4 rating, which is the highest rating available against hale impact damage. When the panels are screwed in place rather than nailed, they can resist winds up to 120 miles per hour.
 
Make sure the roofer is experienced in installing steel panels and that a felt paper is applied to the old asphalt shingles prior to installing the steel panels. The felt paper protects the zinc coating on the underside of the steel panels from being scratched by the sandy granules on the old shingles. If the zinc is scratched, the panel could start to rust from the backside.
 
Steel roof panels come in a variety of sizes, shapes and colors. Most makers claim the colors do not change or fade with time, but only time will tell. Dwight Barnett is a certified master inspector with the American Society of Home Inspectors. Write to him with home improvement questions at C. Dwight Barnett, Evansville Courier & Press, P.O. Box 286, Evansville, Ind. 47702.