According to the National Roofing Contractors Association, sales of metal roofing products have increased steadily over the past ten years, a clear sign that homeowners and builders are growing more and more aware of this product's benefits.
In fact, a whole new genre of metal roofing materials has hit the market. And these are a far cry from the corrugated "tin" barn roofs that leap to mind at the mention of metal.
They are high-tech answers to the need for durable, fire-resistant, lightweight roofing that looks at home on a house.
The case for metal
Metal beats out conventional roofing materials on a number of counts:
Expected life. Properly installed, a metal roof should last as long as the house, completely sealing out water, surviving high winds and easily shedding snow.
Metal is resistant to fire, mildew, insects and rot. Warranties vary widely but most companies strongly back their products for from 20 to 50 years.
Weight. Compared to tile at 750 pounds per square (an area equal to 100 square feet) or concrete tile at 900 pounds per square, metal roofing is lightweight. Most are from 50 to 150 pounds per square.
Some types of metal shingle systems may be applied over one or two existing roofs without the need for tear-off or adding structural support. In fact, if you're building a house or an addition, you can often downsize or reduce the number of roof support members.
Speed and ease of installation. Most metal roofings come in multi-shingle sections or in sheets. An accomplished contractor can install these quickly. If your roof is stripped off and a storm is on the way, shortening the process by a day or two may prove to be a critical advantage.
You can also buy single metal shingles that are relatively easy-- but time intensive-- to install. (Unlike three-tab asphalt shingles, each piece must be individually placed and nailed.)
Fire resistance. Because metal roofs are noncombustible, they're given a Class A fire rating (the most resistant). Part of a roof's classification depends on materials beneath the surface that could ignite in intense heat, so some metal roofs applied over an old combustible roof--such as wood shingles-- may be rated lower.
Heat conduction. Metal reflects radiant heat from the sun, minimizing midday heat gain. Though the material itself is low in insulative R-value, many systems utilize a dead-air space between the metal and roof deck to increase energy efficiency.
Because metal expands and contracts as it warms and cools, most new products have fastening systems that account for movement; otherwise, fasteners that secure roofing tend to work loose.
Minimal roof pitch. Most metal roofing materials can be installed on gently pitched roofs without danger of leaking. Typical minimum roof pitch is 3-in-12.
Find A Pre-Screened Metal Roofing Contractor in Your Area!
Common Concerns
Though metal roofing offers many pluses, there are a few drawbacks or concerns worthy of consideration. For the most part, roofing manufacturers have faced these concerns and improved their products to address or solve many of them.
Cost. The biggest drawback is initial cost. Metal roofing is pricey. It may cost as much as--or more than--other premium materials: from about $1.80 to $6.00 per square foot, plus labor. The secret is that you get it back if you stay in the house for a long time. When you amortize the cost over the long life of the roof, figure in savings on engineering, maintenance, and installation labor, metal becomes very affordable. Of course, if you plan to move in a couple of years, you probably won't get the cost returned in value.
Noise. For some people, the sound of rain tapping on the roof is romantic and homey; for others, it's like living inside a drum. In a rainstorm or hail storm, living beneath thin sheets of metal is bound to be noisier than beneath thick slate or tile. Noise can be controlled, however, both by using materials that have structural barriers to minimize the drum effect and by applying them over sound-deadening insulation and solid plywood sheathing.
Denting. Just as your car will dent if a golf ball hits it, a metal roof may dent if large hailstones fall on it. Aluminum and copper, much softer than steel, are more prone to denting. Some are guaranteed not to.
Though you shouldn't have to walk on a roof that doesn't leak, there may be occasions when a plumber needs to snake out a vent pipe or a chimney sweep will need access to the chimney flue. You can walk on some metal roofs, but not all--depending on how the particular product is made and the type of construction supporting it. Alcoa's aluminum shingles, for example, are installed over a foam insert. This foam, contoured to the shape of the shingles, minimizes noise, prevents denting, and makes the roof "walkable."
Marring. Some painted finishes can peel, chip, fade, scratch or chalk, although nearly all are guaranteed for many years. Walking on some types-- particularly those with a granulated-stone surface-- may show wear.
Installers must be careful not to scratch or dent roofing during installation-- panels must be treated with care. Unlike conventional roofing, some metal shingle systems are installed from the top down, eliminating the need to walk on them. Once installed, it may be necessary to hose-off roofing now and then to keep it looking good.
Modification. Roofing materials installed in large panels are more difficult to replace if damaged than individual shingles. Also, if you remodel or add-on to your home 10 or 20 years from now, it may be difficult to match the material. Then again, you may be ready for some marvelous new product by then.
Types of Metal
The word "metal" covers a lot of ground. Several metals are used for roofing materials: steel, stainless steel, aluminum, copper and zinc alloys. Each has different properties that affect durability, price and appearance.
Steel, used for most metal roofing, is heavier and sturdier than aluminum. Manufacturers have settled on a number of durable coatings and finishes that protect steel from rust and corrosion. It's usually zinc-coated for corrosion protection, then sealed. A coating of epoxy primer offers adhesion and a baked-on acrylic top coating adds color and protection.
Because sheet systems are designed for commercial applications, they generally are given highly durable paint finishes. One popular flurocarbon coating used on many products is called Kynar(r).
Stainless steel-- a very expensive material-- won't rust or corrode. Terne coating (see below) can give it a natural, matt-gray finish.
Aluminum, extremely lightweight, is the material used in much residential metal roofing. It won't rust either, but must be painted or coated for appearance. Coatings are similar to those used on steel. Environmentalists express concerns about using this precious resource for purposes such as roofing.
Copper, rooted in centuries of use, will not rust, has no "finish" to scratch or peel, is soft enough to easily tool, and weathers naturally to a beautiful verdigris. Unfortunately, it's very expensive.
Alloys are formulated for strength, graceful weathering and durability. Cost depends on the specific material but, as a group, they are pricey.
Two Main Types
Here's a closer look at the two main categories of metal roofings used on houses: shingle-type systems and larger sheet systems.
Shingle systems. Metal shingles are manufactured to resemble wood shakes, Spanish and mission tile, slate, and Victorian metal tiles. Most are made from painted or coated steel or aluminum that has been pressed or formed into realistic shapes.
Some are amazingly convincing in appearance. Producers of painted metal products reduce telltale sheen by texturing the metal and layering the finish. Those products given granulated-stone topcoats --typically tile or slate lookalikes-- are hard to distinguish from the real thing.
Metal shingle systems are made-up in large panels designed for quick installation (they're typically about 4 feet long) or as single shingles meant to be applied individually. Most panel types can be installed over one or two layers of existing roofing; the individual type require tear-off so they can be applied to a firm, flat roof deck.
Residential roofing contractors are the trades people who install metal shingle systems, though many who install wood, tile, asphalt and other more conventional products don't install metal. Because metal roofing requires slightly different techniques, some manufacturers or distributors require contractors to be accredited by taking a few factory-taught classes before they will allow the contractors to install their products.
Sheet-metal roofing systems. Sheet roofing begins as "flat stock"-- flat metal panels. Roofing manufacturers form it into roofing panels and components and--for some types-- apply a finish. Some flat stock is fabricated on the spot by contractors with the proper forming equipment. Problems with the latter method are 1) wide variations in the quality of the work, 2) limited possibilities for finishes, and 3) warranties are usually very limited-- one year or less. With site-formed roofing, you don't have the strength of a large manufacturer behind the product.
Manufactured sheet metal roofing is sold in large panels--normally 26-gauge coated steel that weighs about 1 pound per square foot. Other materials used include painted aluminum, solid copper, zinc alloys and terne-coated stainless steel. Because of the large panel sizes, this roofing works best on large, unbroken expanses where minimum cutting is required.
The two main systems are named after the method of joining panels together: "standing seam" has a self-sealing, raised seam and "batten" employs a wider cover cap (see illustration). Special matching metal parts are made for ridges, hips, edges, and connections.
These roof materials are typically priced by the square foot. Prices vary widely, depending upon the material and finish-- from a low of about $1.70 per square foot to about $6 per square foot (not including labor). Figures typically include panel, fastening clips, caps and all trims and flashings. If you ask for ballpark square-foot prices, be sure they're inclusive of all necessary parts.
To get bids, begin by calling the manufacturer (see Resources). They will usually put you in touch with a local representative or installer who will bid--or arrange for several roofers' bids--on your job. Be sure to clarify whether or not labor and freight are included in the price. Because freight can be expensive, it usually pays to choose a manufacturer in your region.
Here's a closer look at some popular brands. Actual prices vary significantly from those given here...the best way to get prices is to request bids.
Shingle Systems
* Gerard roofing is actually galvanized steel with a tile-colored finish of stone granules made in two patterns--facsimile shake and tile--and a variety of colors. The stone-finished shingles run from about $3 to $4 per square foot or more if tear-off is required.
* Decrabond(r), by Carter Holt Harvey is a tile facsimile with a granulated stone finish. Unusually shaped Colortile, by the same manufacturer, is galvanized steel with a baked-on acrylic finish (actually a series of seven coatings). Though available in only six standard colors, custom colors may be special ordered--subject to a minimum order size.
* Met-Tile, of painted 26-gauge galvanized steel, is a tile lookalike that ranges from $2 to $4.50 per square foot; most applications run about $3.
* Prestige Copper Shingles from Tegola U.S.A. are made up of real copper bonded to an asphalt shingle base. They offer the elegant look of a real copper roof at about one-third the price ($4 to $6 per square foot, installed).
* Zappone manufactures aluminum and copper shingles shaped to resemble wood shakes. About half of the shingles sold are owner installed--a relatively simple but time-intensive job. Material price runs from $1.25 to $3 per square foot for aluminum, $3 to $5 for copper, depending upon the roof's complexity (the number of accessories needed dramatically affects cost).
You can install copper accents without putting on an entire copper roof by ordering copper ridge caps, drip edges, valleys or other accent accessories and combining them with a different roof material such as wood shingles. Zappone also manufactures half-sized copper shingles for use on bay windows, cupolas, gazebos and the like. You can shingle a bay window with these for less than $300.
* Alcoa makes two varieties of aluminum shakes that resemble wood shakes and slate or tile. Both patterns may be applied over up to two layers of some existing roofing materials. Alcoa offers a lifetime, non-prorated limited warranty that's transferable when you sell the house.
Sheet Systems
* Microzinc Roofing System from W.P. Hickman is manufactured from a zinc-copper-titanium alloy in both standing seam and batten systems. This metal weathers naturally, developing a gray patina in 6 to 18 months. It's beautiful and very expensive: materials run from about $4 to $6 per square foot, depending on quantity and freight.
* Follansbee Steel terne-coats standing-seam roofing for ease of soldering during construction and excellent paint adhesion. On standard steel, this finish-- a mixture of 80% lead and 20% tin-- must be painted. But on stainless steel panels, it can be left to weather naturally (stainless steel won't rust). Stainless steel terne-coated roofing is both durable and beautiful--with oxidation, terne coating transforms from shiny metallic finish to a matt gray. This type of roofing material runs about $3 per square foot plus installation.
The lead content of the terne coating is a concern to some. Gloves are recommended for installers to protect against lead poisoning. During initial oxidation, some lead washes off the roof and traces may be detected in the soil around buildings.
* Of Berridge's wide variety of metal roofing and siding materials, their Victorian and classic shingles, prefinished or unfinished in Galvalume(r) are particularly interesting. These shapes are especially appropriate for older home restorations.
Choosing a Contractor
Because a new roof is a major investment and something you're likely to live with for a long time, choose your roofing contractor carefully. The best way to find a good one is through friends and neighbors who have done similar work. Unfortunately, because metal roofs are uncommon, this may not be possible.
Another route is to ask architects who have designed homes utilizing metal roofs for their suggestions. You can ask some of the manufacturers listed in the resource guide for referrals--or better, their local representatives or distributors. Or call the National Roofing Contractors Association contractor-referral hotline at 1-800-USA-ROOF. For sheet metal roofing systems, choose a contractor who has had at least 3 years of experience installing metal roofs.
Roofing Terms You Should Know
Butt-- The larger, exposed end of a shingle.
Deck--Plywood or oriented-strand board (OSB) sheathing used as a base for securing roofing materials.
Drip edge-- An L-shaped metal strip positioned along a roof's edges to allow water to run off roof without running down eaves or siding.
Eave-- On a sloped roof, the horizontal underside that projects out from house wall.
Exposure-- The part of a shingle that is exposed to the weather, usually less than half its actual length.
Felt or underlayment-- Asphalt-impregnated roofing paper that creates a secondary, watertight barrier between many roofing products and the roof deck.
Flashing-- Metal pieces that keep water from seeping into intersections such as valleys or joints at vertical walls, or around roof penetrations such as chimneys or vent pipes.
Pitch-- Roof slope expressed as the ratio of a roof's rise (vertical distance) to each foot of run (horizontal distance). A "4-in-12 pitch" means the roof rises 4 inches for every 12 inches of horizontal distance.
Rafters-- The framework that supports the roof deck and roofing. On a sloped roof, these are the angled timbers on the underside.
Rake--The sloped edge of a roof over a wall.
Ridge--The peak where two sloped roof sections meet.
Square-- A measurement of roof area that equals 100 square feet (an area 10' by 10').
Valley-- The angle formed where two sloping roof surfaces intersect.
