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