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What do you need to know before getting a new roof?

Q. I'm ready for a new roof. I'd like to know from you everything I should be aware of concerning roofs. Can you do that?

R.R., Sudbury

A. Years ago when I needed a new roof, I called Jack Clifford, who heads a roofing company in South Boston, and banged his ear for two hours, and did I get the information. He has done my roof twice, and we are mutually pleased.

So, R.R., here goes. There are many types of roof shingles, but we will deal with asphalt shingles. Two kinds: One is fiberglass, with a fiberglass core surfaced by asphalt on both sides and covered with a protective layer of gravel, tiny stones that protect and provide color. The other kind of shingle is called organic, with a saturated felt core.


All these shingles are graded for how long they are warranted to last: 20, 30, 40, and I think 50 years. Most look the same except for architectural shingles, designed to look better than the plain ones. Use them only if your roof is readily visible by you from the yard. If a shingle fails before its warranty is up, you will be compensated for the shingles only. The longer the warranty, the higher the cost. But the shingles themselves amount to maybe ¼ of the cost of the job. Some shingles are labeled as mold resistant.

How many layers of shingles are allowed? Two, in most areas of the country. A second layer is a good idea because it will save the expense of removing and disposing of old shingles.

Do I need a drip edge and an underlayment of an ice and water shield? Yes. A metal (usually aluminum) drip edge provides a neat, straight edge to the roof, and can be positioned so that roof water drips in the middle of gutters, along their full length. This is important because a mispositioned drip edge can cause overflowing of gutters, over front or back. Existing flashing around chimneys, in valleys and other parts of the roof, is usually left in place.


As for the underlayment, an ice and water shield is important to install, to prevent leaks from ice dams. Some roofers put 6 feet of ice and water shield, saying this is enough to prevent leaks from ice dams, also claiming that covering the entire roof will keep the roof from breathing. Other roofers suggest covering the whole roof with the shield, adding that proper ventilation will allow the roof to breathe.

And what is proper ventilation? Liberal use of vents: ridge vents, soffit vents (the soffit is the under part of the roof overhang), sometimes vents on the roof itself, all enough to vent out water vapor and sometimes heat, preventing mold growth.

Color? Black is best, because it goes well with any color house, keeps a tall house from visually soaring, and makes a low house snuggle into the earth, visually. Walk or drive around your neighborhood, and make a note of the houses that have black or dark shingles vs. light ones. Black roofs do absorb heat in summer, but with an attic well ventilated, this will make little or no difference. Light roofs are recommended in Southern climes because they reflect heat.

One final note: Reroofing is a good time to put in a ridge vent, and also to install zinc strips just below the ridge for its full length, with 3 inches showing, to allow rain water to flow down-roof, bringing bits of dissolved zinc over the shingles, helping to prevent the growth of mold, algae, and lichens.


Globe Handyman on Call Peter Hotton also appears in the Sunday Real Estate section. He's available 1-6 p.m. Tuesdays to answer questions. Call 617-929-2930. Hotton (photton@
globe.com) also chats online 2-3 p.m. Thursdays. Go to www.boston.com.