Q. I received three significantly different proposals. How should I decide which contractor to select?

A. If one estimate seems much lower than the others and it sounds too good to be true, it probably is. Many fly-by-night contractors' below-cost bids seem attractive, but these contractors often are uninsured and perform substandard work. If an estimate is confusing, ask the contractor to break down the estimate into items/terms you can understand.

Clearly written proposals that are detailed and broken down into separate line items are a good sign that the contractor is being thorough and has prepared an accurate estimate. The following is a partial list of items your estimate or proposal should include:

• The type of roof covering, manufacturer and color
• Materials to be included in the work, e.g., underlayment, ice dam protection membrane
• Scope of work to be done
• Removal or replacement of existing roof
• Flashing work, e.g., existing flashings to be replaced or re-used, adding new flashing, flashing metal type
• Ventilation work, e.g., adding new vents
• Who is responsible for repairing/replacing exterior landscape or interior finishes that are damaged during the course of the work
• Payment procedures
• Length of warranty and what is covered, e.g., workmanship, water leakage

Q. One contractor's bid includes No. 15 underlayment and another contractor says he only uses No. 30 because it's the best. Who is right?

A. For asphalt shingles, NRCA recommends a single layer of No. 15 asphalt-saturated underlayment be used with roofs having slopes of 4:12 (18 degrees) or greater. For roof slopes between 3:12 (14 degrees) to 4:12 (18 degrees), NRCA recommends a minimum of two layers of No. 15 underlayment.

Q. Is it okay to use staples instead of nails to install my asphalt shingles?

A. NRCA recommends galvanized steel or the equivalent corrosion-resistant roofing nails for asphalt shingle installation. Also, verify the governing building code requirements and what the shingle manufacturer recommends.

Q. Is installing a ridge vent needed when I already have two single vents?

A. Roofing manufacturers suggest the amount of attic ventilation be balanced between the eaves and ridge. The intent of a balanced ventilation system is to provide nearly equivalent amounts of ventilation area at the eave/soffit and at or near the ridge. For a balanced ventilation system to function properly, approximately one-half of the ventilation area must be at or near the ridge. Proper attic ventilation is one of the least understood concepts in residential roofing.

Q. My house has a roof with a 2 1/2:12 (11 degrees) slope. The manufacturer says it's okay to use asphalt shingles, but my contractor says it isn't. Who's right?

A. There are some manufacturers (and even model building codes) that will allow the application of asphalt shingle roof having that slope; however, NRCA does not recommend shingles on slopes less than 4:12 (18 degrees). Asphalt shingle roof systems are watershedding and rely on gravity and roof slope to effectively drain water off the roof.

Q. My house has a flat roof. What is the best roof system for a flat roof?

A. There is no one roof system that is best for all applications. Keep in mind that even if you are using the best materials, your roof system still can be installed improperly and you could end up with a leaky roof. Good workmanship and proper attention to detail (e.g., flashing and drainage issues) are just as important as material selection. Also, maintenance plays an important role in roof system integrity and service life.

Also, keep in mind low-slope roofing materials manufacturers may not offer material warranties to homeowners. The only warranty you most likely will be able to obtain is from the contractor. So it is critical you work with a professional roofing contractor and get a detailed, thorough proposal.

Q. How do I clean algae and moss from my asphalt shingle roof?

A. Use a mild solution of chlorine bleach and water or mild detergent gently applied with a sponge or hand-held sprayer and rinse thoroughly. A power washer on a low pressure setting is acceptable but do not scrub the shingle surface.

Q. Do I Need To Be Home To Obtain An Estimate?

A. Yes, it's usually a good idea. Meeting with each estimator allows an opportunity to discuss your specific goals in obtaining a new roof and you may find each estimator will have slightly different recommendations in terms of materials and suggested options. This is also an opportunity to get a feel for a company's professionalism, knowledge and thoroughness.

Q. My Roof Has Only One Layer. Can I put another layer on top or Is It Better To Have Them Removed?

A. A number of factors come into play in making this decision. Older shingles tend to cup as they dry out and age. The new layer will follow the contour of the existing shingles which may cause your new roof to look bumpy or uneven. Also, the existing rows of shingles must have been run straight when installed. Again, the new layer will follow the old pattern and may lead to a visually unacceptable appearance.

Of greater concern is the inability to inspect the roof deck for heat damage, rot or loose decking. While the wood can be inspected from inside the attic space for broken boards or water damage, loose decking can not be determined without removing the shingles and existing felt paper.

Q. When are the roofing materials delivered and will they block access to my driveway or garage?

A. Generally, we schedule the materials to be delivered by our supplier a day before your planned start date. We do request that you keep the driveway area clear of vehicles on the day your delivery is scheduled unless someone will be home to move the vehicles when the supplier arrives.

Q. Do I need to be home while the work is in progress?

A. No. In fact many people prefer not to be home when the hammering starts! We do not need access inside the home providing there is an outside electrical outlet we can use in the case of bad wood. However, if we have noted the possibility of damaged plywood, some homeowners like to be home to inspect the decking.

Q. Will there be any accumulated dust or debris in my attic area?

A. Yes. In all roofing jobs, some of the finer grit will fall between the cracks of the plywood or plank board decking. In cases where you have an old cedar shingle roof underneath your existing roof shingles, quite a bit of debris will get into the attic. We suggest removing or covering any items stored in the attic space if dust or debris accumulation is a concern.

Q. Do I need to protect items inside my house from possible damage?

A. Yes. On all roofing jobs there is a degree of vibration which comes down through the framework of the home. While it is not necessary to panic, it is recommended you safeguard fragile items such as glass globes on chandeliers, pictures which are not securely mounted to the wall, or the "old family heirloom". Items in the kitchen cabinets should not be affected, nor should there be a need to empty the china cabinet. If in doubt, take a few minutes to protect any non-replaceable items.

Q. My Children Play In The Yard. Will Discarded Nails Be A Safety Concern?

A. We remove all roofing debris, clean out the gutter system and do a thorough cleaning of the grounds and landscaping. Included in this is the use of a magnet to pick up any nails that have reached the ground level. The perimeter of the home including lawn, landscaped areas and driveway are cleaned to the best of our ability. However, a few nails may surface later because we typically remove over 20,000 nails on an average size roof.

Q. What if something is damaged by one of the crews working doing my work?

A. Remain calm and call the office. Usually the foreman will be able to take care of the problem. If a ladder falls over and breaks a window, or knocks a light off a wall, don't panic. We'll take care of it. Remember, this is going to be a construction site and things happen. We will return your home back to you just the way we found it.