Frequently Asked Questions
Use a mild solution of chlorine bleach and water or mild detergent gently applied with a sponge or hand-held sprayer and rinse thoroughly. Do not use a power washer or high concentrations of bleach, and do not scrub the shingle surface. The Asphalt Roofing Manufacturers Association also offers cleaning recommendations.
Generally, chemical melting compounds do not reduce the overall expected service life span of asphalt shingles. Staining may occur until all the residue is washed away. Calcium or magnesium chloride pellets are less harsh and stain less than sodium chloride
Yes, and it is more probable for roofs with lower slopes, especially in valleys and upslope from curbs, chimneys and penetrations.
Remove as much snow as possible, but call a professional roofing contractor if your roof is steep, the snow is deep or the ice is thick. NRCA does not recommend using ice picks or shovels (or any tool with sharp edges) because there is a chance of damaging roof coverings and flashings. NRCA also does not recommend hosing down a roof with water or use of a hot air gun. Electric heat cables generally have limited effectiveness.
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.
To assist you in your decision-making, homeowners should be informed of what is available. Please refer to the Roof System Types page to learn about the different low-slope roof systems.
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. Be sure to read the recommendations listed in Buying a new roof and getting your money’s worth.
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.
NRCA suggests 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. To learn more, read “Principles of Attic Ventilation” an article by Mark Graham, NRCA Associate Executive Director of Technical Services, that appeared in NRCA’s magazine, Professional Roofing or see Technical Bulletin 98-2.
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.
No. Two layers of underlayment are referred to as a “double-layer of underlayment” and there is a 19-inch overlap between layers. One layer of underlayment is called a “single-layer of underlayment” and there is 2 inches of overlap between layers. NRCA recommends a double-layer of underlayment for roof decks having slopes of 3:12 (14 degrees) up to 4:12 (18 degrees).
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. If you are installing a heavier-weight shingle with a projected long service life, using No. 30 underlayment instead of No. 15 would be appropriate.
Asphalt shingle material performance depends of the quality, quantity and compatibility of asphalt fillers, reinforcements and surface granules. There are two kinds of asphalt shingles (based on the type of reinforcement mat used); fiberglass and organic. Fiberglass shingles are more fire- and moisture-resistant than organic shingles. Organic shingles have good wind resistance, high tear strength and can be installed in colder temperatures.
Asphalt shingles should be in compliance with American Society for Testing and Materials (ASTM) standards and applicable building codes. Fiberglass shingles should meet ASTM D 3462, “Standard Specification for Asphalt Shingles Made from Glass Felt and Surfaced with Mineral Granules,” and organic shingles should meet ASTM D 225, “Standard Specification for Asphalt Shingles (Organic Felt) and Surfaced with Mineral Granules.”
Consumers also should keep in mind a roofing warranty’s length should not be the primary criterion in the selection of a roofing product or roof system because the warranty does not necessarily provide assurance of satisfactory roof system performance. See NRCA’s consumer advisory bulletin addressing roofing warranties for more information.
If the contract didn’t specify the installation of new flashings, it wasn’t included in the original scope of work. Be sure that all items of work to be done are included in the contract before signing it.
Before signing a contract, make sure that it contains language addressing who is responsible for any damage that occurs as a result of the roofing work. All items of concern and work to be done should be included in the contract.
Time is not the critical issue; the condition of the underlayment is what’s important. Wrinkled or buckled underlayment should be replaced so the shingles lay flat.
If the wrinkling isn’t severe enough to affect the shingle installation (i.e., the wrinkling won’t telegraph through the shingles and they won’t appear buckled or wavy once installed), the underlayment probably can remain in place. The effects of wrinkling also will be minimized by using heavier weight shingles.
There are no specific temperature guidelines regarding when it is too cold to install asphalt shingles. Asphalt shingles do become brittle in cold temperatures, with fiberglass shingles more likely to break than organic shingles. Breakage can be minimized or eliminated if the shingles are stored in a warm area and loaded onto the roof a few bundles at a time. Another concern is that the self-sealing strips will not seal or bond sufficiently in cold temperatures. Hand-tabbing (the application of quarter-size dabs of adhesive to the underside of shingles) is recommended if the building is located in an area prone to high winds. This will help prevent the shingles from blowing off the roof until warmer weather arrives and the sealing strips can set properly.
Before answering the question, a clarification needs to be made about the different warranties you will come across during your roofing project. First, there will be the asphalt shingle manufacturer’s warranty. In general, this warranty covers defects in the manufacture of the shingle. The period of coverage can range from 20 years to a lifetime. Please read NRCA’s consumer advisory bulletin addressing roofing warranties for more information. Once the project is complete, be sure the contractor provides you with a certificate for your records.
Second, the roofing contractor will provide you with a warranty on his workmanship. Typically, this will cover installation and related issues. The warranty should contain what items are covered and what will void them. Many contractors offer one year to ten years of coverage; however, there is no industry standard.
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
- Installation method
- Approximate starting and completion dates
- Payment procedures
- Length of warranty and what is covered, e.g., workmanship, water leakage