| In the discussion of metal roofing (see Metal | | | | depends on materials beneath the surface that |
| Roofing: A Buying Guide), the word "metal" covers | | | | could ignite in intense heat, so some metal roofs |
| a lot of ground. Several metals are used for | | | | applied over an old combustible roof--such as |
| roofing materials: steel, stainless steel, aluminum, | | | | wood shingles-- may be rated lower. |
| copper and zinc alloys. Each has different | | | | Heat conduction. Metal reflects radiant heat from |
| properties that affect durability, price, and | | | | the sun, minimizing midday heat gain. Though the |
| appearance. | | | | material itself is low in insulation R-value, many |
| Steel, used for most metal roofing, is heavier and | | | | systems utilize a dead-air space between the |
| sturdier than aluminum. Manufacturers have | | | | metal and roof deck to increase energy |
| settled on a number of durable coatings and | | | | efficiency. |
| finishes that protect steel from rust and corrosion. | | | | Minimal roof pitch. Most metal roofing materials |
| It's usually zinc-coated for corrosion protection, | | | | can be installed on gently pitched roofs without |
| then sealed. A coating of epoxy primer offers | | | | danger of leaking. Typical minimum roof pitch is |
| adhesion and a baked-on acrylic top coating adds | | | | 3-in-12 (the roof rises 3 inches for each horizontal |
| color and protection. Because sheet systems are | | | | foot). |
| designed for commercial applications, they | | | | Metal Roofing Drawbacks |
| generally are given highly durable paint finishes. | | | | Though metal roofing offers many pluses, there |
| One popular flurocarbon coating used on many | | | | are a few drawbacks or concerns worthy of |
| products is called Kynar(r). Stainless steel--a very | | | | consideration. For the most part, roofing |
| expensive roofing material--won't rust or corrode. | | | | manufacturers have faced these concerns and |
| Terne coating (see below) can give it a natural, | | | | improved their products to address or solve |
| matt-gray finish. | | | | many of them. |
| Aluminum, extremely lightweight, is the material | | | | Cost. The biggest drawback is initial cost. Metal |
| used in much residential metal roofing. It won't | | | | roofing is equivalent to other premium materials: |
| rust, but must be painted or coated for | | | | from about $150 to $600 per square (100 square |
| appearance. Coatings are similar to those used on | | | | feet). The secret is that you get it back if you |
| steel. Environmentalists express concerns about | | | | stay in the house for a long time. Of course, if |
| using this precious resource for purposes such as | | | | you plan to move in a couple of years, you |
| roofing. Copper metal shingles make a visually | | | | probably won't get the cost returned in value. |
| striking roof that may last as long as the house. | | | | Figure you can also save on engineering the |
| Copper, rooted in centuries of use, will not rust, | | | | supporting structure and maintenance. |
| has no "finish" to scratch or peel, is soft enough | | | | Noise. For some, the sound of rain tapping on the |
| to easily tool, and weathers naturally to a beautiful | | | | roof is romantic and homey; for others, it's like |
| verdigris patina. Unfortunately, it's very expensive. | | | | living inside a drum. In a rainstorm or hailstorm, |
| Alloys are formulated for strength, graceful | | | | living beneath thin sheets of metal is bound to be |
| weathering and durability. Cost depends on the | | | | noisier than beneath thick slate or tile. Noise can |
| specific material but, as a group, they are pricey. | | | | be controlled, however, both by using materials |
| The Benefits of Metal Roofing | | | | that have structural barriers to minimize the drum |
| Metal beats out conventional roofing materials on | | | | effect and by applying them over |
| a number of counts: | | | | sound-deadening insulation and solid plywood |
| Expected life. Properly installed, a metal roof | | | | sheathing. |
| should last as long as the house, completely | | | | Denting. Just as your car will dent if a golf ball hits |
| sealing out water, surviving high winds and easily | | | | it, a metal roof may dent if large hailstones fall on |
| shedding snow. Metal is resistant to fire, mildew, | | | | it. Aluminum and copper, much softer than steel, |
| insects and rot. Warranties vary widely but most | | | | are more prone to denting. Some are guaranteed |
| companies strongly back their products for from | | | | not to. |
| 20 to 50 years. | | | | Though you shouldn't have to walk on a roof that |
| Weight. Compared to tile at 750 pounds per | | | | doesn't leak, there may be occasions when a |
| square (an area equal to 100 square feet) or | | | | plumber needs to snake out a vent pipe or a |
| concrete tile at 900 pounds per square, metal | | | | chimney sweep will need access to the chimney |
| roofing is lightweight. Most are from 50 to 150 | | | | flue. You can walk on some metal roofs, but not |
| pounds per square. Some types of metal shingle | | | | all--depending on how the particular product is |
| systems may be applied over one or two existing | | | | made and the type of construction supporting it. |
| roofs without the need for tear-off or adding | | | | Also, metal is slippery when wet. |
| structural support. In fact, if you're building a | | | | Marring. Some painted finishes can peel, chip, fade, |
| house or an addition, you can often downsize or | | | | scratch or chalk, although nearly all are guaranteed |
| reduce the number of roof support members. | | | | for many years. Walking on some |
| Speed and ease of metal roofing installation. Most | | | | types--particularly those with a granulated-stone |
| metal roofing materials come in multi-shingle | | | | surface--may show wear. Installers must be |
| sections or in sheets. An accomplished contractor | | | | careful not to scratch or dent roofing during |
| can install these quickly. If your roof is stripped | | | | installation--panels must be treated with care. |
| off and a storm is on the way, shortening the | | | | Unlike conventional roofing, some metal shingle |
| process by a day or two may prove to be a | | | | systems are installed from the top down, |
| critical advantage. Note: You can also buy single | | | | eliminating the need to walk on them. Once |
| metal shingles that are relatively easy--but time | | | | installed, it may be necessary to hose-off roofing |
| intensive--to install. (Unlike three-tab asphalt | | | | now and then to keep it looking good. |
| shingles, each piece must be individually placed and | | | | Expansion and contraction. Because metal |
| nailed.) | | | | expands and contracts as it warms and cools, |
| Fire resistance. Because metal roofs are | | | | most new products have fastening systems that |
| noncombustible, they're given a Class A fire rating | | | | account for movement; otherwise, fasteners that |
| (the most resistant). Part of a roof's classification | | | | secure roofing tend to work loose. |