Residential metal roofing is primarily made of steel or aluminum. Copper,
zinc and titanium are also used in specialized architectural applications for
Steel roofing for residential applications is very lightweight with the
heaviest product weighing about 1.5 pounds per square foot when installed. The
products are initially produced in giant rolls at the steel mills. They are
then coated with a metallic coating to prevent rust at the steel plant. The
rolls are then painted at a coil coating plant using high-speed paint lines
that bake on the coating. The painted coil is then shipped to a roofing
manufacturer where it is formed into long panels by a process called roll
forming or they are stamped into individual shingles using large presses.
Aluminum roofing follows the same process except that it does not require
the metallic coating step.
Steel residential roofing is made in thicknesses designated by gauge and is
generally 24 to 26 gauge, with the higher gauge being thinner than the lower.
These gauges are appropriate since most residential metal roofing applications
are over a solid substrate.
Decimal thickness and ranges from .023 to .040 thicknesses designate
aluminum residential metal roofing.
Granular coated steel shingles, shakes, tile are a special category and are
produced by stamping galvanized steel (26 gauge) then sprayed with an acrylic
coating embedding granular stone then baked in an oven at the factory.
All Steel Roofing has a protective
barrier on both sides of the sheet called a metallic coating, which protects
against rusting. This is underneath and separates from any paint, which imparts
color to the product. There are two types of metallic coatings used:
Galvanized: This is
100% Zinc in various thicknesses depending upon the product usage.
Galvalume or Zincalume:
A mixture of aluminum and zinc. (55 percent by volume aluminum)
Metallic coatings "sacrifice" themselves to protect the iron (Fe)
in steel from oxidation when exposed to the air and moisture is present. Zinc
is a more "active" metal than iron so it oxidizes first and forms a
protective barrier — zinc oxide, before the iron (Fe) in the steel can become
Ferric Oxide (rust). When zinc is combined with aluminum to form Galvalume
there is even more protection in most circumstances.
Different Levels of Protection
There are differing amounts of metallic coating used on sheet steel
depending upon its final product application. For agricultural applications,
galvanizing levels called G-40 or G-60 may be used quite successfully. For
houses, the MRA recommends a minimum of G-90 be used. This is in accordance
with the Guidelines for Residential Metal
Roofing published by the Metal Construction Association. The
greater the number, the longer the protection against rust will last.
The numbers G-40; G-60; and G-90 refer to the ounces of zinc per 100 square
feet of sheet steel coated (top and bottom). G-90 will have 90 ounces of Zinc-
45 ounces on each side per 100 square feet of roofing sheet steel.
Galvalume has a designation AZ-50 or AZ-55. These are equivalent levels to
G-90 galvanized product. However, in many years of exposure testing Galvalume
has proven to be up to three times more effective in preventing rust from
appearing on the sheet steel.
Aluminum sheet does not require a separate metallic coating barrier since
aluminum oxide, when it forms is not noticeable in most cases.
Aluminum is often preferred as a roofing material substrate in heavy salt
spray environments. This will occur where there is a lot of wave action in salt
water near the ocean. In many inland salt water situations steel with metallic
coatings performs very well if there is not a lot of wave action — intercostal
area of Florida and the Southeastern U.S., Puget Sound in Washington, etc.
Another factor to consider is how often the roof is rinsed with fresh water
In shoreline, non-saltwater environments both galvanized and Galvalume steel
will provide a long lifetime of protection.
Most residential metal roofing has a paint coating applied to the outside of
either the aluminum or steel plus metallic coating.
The paint finishes provide the aesthetic qualities that consumers want to
see on their roofs. They can also provide specific energy
Metal roofs that are painted use very sophisticated paint technology. The
roofing material is painted when it is in flat sheet form in giant coils. Yet,
the paint is flexible enough to be later stamped or roll formed into the final
roof shape-long panels, shingles, shakes, tiles or slate forms.
There are differing levels of paint quality for metal roofing-all affecting
the price of the finished product. The principal attribute that consumers are
concerned about is fading of the original color. When exposed to sunlight
(ultra-violet light) paints fade over time, some more than others. Generally,
in this situation you get what you pay for.
TAMCO's paint system processes have undergone
extensive field-testing in the most extreme conditions. In addition to
accelerated and detailed laboratory testing, actual painted panels have been
placed in field tests for extended time periods. These tests are usually
conducted in South Florida with the harshest exposure possible.
There are different levels of paint quality, which provide protection
against "chalk" and "fade." For residential usage it is
recommended that Standard qualified products be used. These paint systems will
provide years of great performance in most areas of the country.
TAMCO's Premium qualified products use the Akzo Noble Ceram-A-Star 1050 the Industry's best Silicon Modified Polyester coil coating system. have proven to add an
extra measure of performance against fading and chalking under the most extreme
sun, wind and rain conditions in accelerated field-testing. For those living in
high U.V. areas such as Florida and the southeastern United States one should consider Premium certified paint systems for your