Everything about the steel around us


Metal Roofing Materials

In the discussion of metal roofing (seefire rating (the most resistant). Part
Metal Roofing: A Buying Guide), the wordof a roof's classification depends on
"metal" covers a lot of ground. Severalmaterials beneath the surface that could
metals are used for roofing materials:ignite in intense heat, so some metal
steel, stainless steel, aluminum, copperroofs applied over an old combustible
and zinc alloys. Each has differentroof--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, isheat from the sun, minimizing midday
heavier and sturdier than aluminum.heat gain. Though the material itself is
Manufacturers have settled on a numberlow in insulation R-value, many systems
of durable coatings and finishes thatutilize 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 corrosionefficiency.
protection, then sealed. A coating ofMinimal roof pitch. Most metal roofing
epoxy primer offers adhesion and amaterials can be installed on gently
baked-on acrylic top coating adds colorpitched roofs without danger of leaking.
and protection. Because sheet systemsTypical minimum roof pitch is 3-in-12
are designed for commercial(the roof rises 3 inches for each
applications, they generally are givenhorizontal foot).
highly durable paint finishes. OneMetal Roofing Drawbacks
popular flurocarbon coating used on manyThough metal roofing offers many pluses,
products is called Kynar(r). Stainlessthere are a few drawbacks or concerns
steel--a very expensive roofingworthy of consideration. For the most
material--won't rust or corrode. Ternepart, roofing manufacturers have faced
coating (see below) can give it athese concerns and improved their
natural, matt-gray finish.products to address or solve many of
Aluminum, extremely lightweight, is thethem.
material used in much residential metalCost. The biggest drawback is initial
roofing. It won't rust, but must becost. Metal roofing is equivalent to
painted or coated for appearance.other premium materials: from about $150
Coatings are similar to those used onto $600 per square (100 square feet).
steel. Environmentalists expressThe secret is that you get it back if
concerns about using this preciousyou 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 visuallycouple of years, you probably won't get
striking roof that may last as long asthe cost returned in value. Figure you
the house.can also save on engineering the
Copper, rooted in centuries of use, willsupporting structure and maintenance.
not rust, has no "finish" to scratch orNoise. For some, the sound of rain
peel, is soft enough to easily tool, andtapping on the roof is romantic and
weathers naturally to a beautifulhomey; for others, it's like living
verdigris patina. Unfortunately, it'sinside a drum. In a rainstorm or
very expensive. Alloys are formulatedhailstorm, living beneath thin sheets of
for strength, graceful weathering andmetal is bound to be noisier than
durability. Cost depends on the specificbeneath thick slate or tile. Noise can
material but, as a group, they arebe controlled, however, both by using
pricey.materials that have structural barriers
The Benefits of Metal Roofingto minimize the drum effect and by
Metal beats out conventional roofingapplying them over sound-deadening
materials on a number of counts:insulation and solid plywood sheathing.
Expected life. Properly installed, aDenting. Just as your car will dent if a
metal roof should last as long as thegolf 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 sheddingand copper, much softer than steel, are
snow. Metal is resistant to fire,more prone to denting. Some are
mildew, insects and rot. Warranties varyguaranteed not to.
widely but most companies strongly backThough 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 poundsoccasions when a plumber needs to snake
per square (an area equal to 100 squareout a vent pipe or a chimney sweep will
feet) or concrete tile at 900 pounds perneed 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 perall--depending on how the particular
square. Some types of metal shingleproduct is made and the type of
systems may be applied over one or twoconstruction supporting it. Also, metal
existing roofs without the need foris slippery when wet.
tear-off or adding structural support.Marring. Some painted finishes can peel,
In fact, if you're building a house orchip, fade, scratch or chalk, although
an addition, you can often downsize ornearly all are guaranteed for many
reduce the number of roof supportyears. Walking on some
members.types--particularly those with a
Speed and ease of metal roofinggranulated-stone surface--may show wear.
installation. Most metal roofingInstallers must be careful not to
materials come in multi-shingle sectionsscratch or dent roofing during
or in sheets. An accomplished contractorinstallation--panels must be treated
can install these quickly. If your roofwith care. Unlike conventional roofing,
is stripped off and a storm is on thesome metal shingle systems are installed
way, shortening the process by a day orfrom the top down, eliminating the need
two may prove to be a criticalto walk on them. Once installed, it may
advantage. Note: You can also buy singlebe necessary to hose-off roofing now and
metal shingles that are relativelythen to keep it looking good.
easy--but time intensive--to install.Expansion and contraction. Because metal
(Unlike three-tab asphalt shingles, eachexpands and contracts as it warms and
piece must be individually placed andcools, most new products have fastening
nailed.)systems that account for movement;
Fire resistance. Because metal roofs areotherwise, fasteners that secure roofing
noncombustible, they're given a Class Atend to work loose.



1 A B C D E F 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138