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