to Select a Residential Metal Roof
Today’s residential metal roofing comes in a wide variety of styles and
designs. When choosing a roof for your home, make sure that the product’s
design is appropriate for your home’s construction. Most metal roofs will
require solid decking (or, frequently, an existing shingle roof) and some
can be installed over lathe boards or over wood shingles on lathe. Some of
the more textured designs can even be installed over slate and asbestos
roofs. Next, choose a product with an appropriate appearance for your home
and neighborhood. You can find quality metal roofing with about any
appearance, whether it is standing seam or a facsimile of shake, slate,
tile, or standard shingles.
Metal roofing is made from a wide variety of metals including galvanized
steel (which is zinc coating on carbon steel); galvalume steel (aluminum
and zinc coating on carbon steel); exotic steels such as terne and
stainless; aluminum; copper; and rolled zinc. Each metal has its own
properties and the type of metal used is sometimes dictated by the design
of the roofing panel. When making a wise investment in metal roofing,
consider all the available options. Many consumers assume that all metal
roofing is steel. However, most consumers would choose a permanently
rust-free aluminum car over a steel car of similar cost; it makes sense to
consider non-steel options for roofing as well.
While residential metal roofing is enjoying ever-increasing popularity,
some products are fairly new. As you evaluate various products, find out
how proven they are. Inquire about the systems’ flashings and accessories.
Look for proven, pre-formed accessories from the manufacturer. It is
particularly important to investigate how the valleys are installed. Look
for an “open” valley system which carries water on top of the metal panels
rather than a “closed” valley which carries water on hidden channels
beneath the panels. The hidden channels on “closed” valleys have been
known to clog with ice, snow, tree leaves, pine needles, and other debris,
causing water to spill over the channels and infiltrate the roof system.
Metal roofing should be installed without dependence on the underlayment
beneath it. However, metal roofing can develop condensation on its
bottomside during certain climatic conditions. Therefore, it is
jeopardizing the durability of your roof system to use a product which
does not specify a quality underlayment such as 30-pound felt or one of
the new polyethylene-based underlayments. If you are in an area prone to
high humidity or salt air and fog, give special consideration to rust-free
metals such as aluminum, copper, and zinc. Weather conditions can create
the retention of condensation between the panels and the underlayment.
Particularly with steel products which rest on or near the substrate such
as standing seam, 5-V crimp, and low profile steel shingles, this
condensation can cause them to rust from underneath. Keep in mind that
failures with steel roofing occur from cut edges on the back side of the
metal and rarely from the front weather side.
Because quality metal roof systems have panels which actively interlock
with each other, most metal roofs are known for their wind resistance. Be
sure to inquire what wind and uplift tests the systems you are considering
have undergone and passed. The better products have passed 150+ mph
wind-driven rain testing and/or UL 580 uplift testing exceeding 90 psf.
Some insurance companies in select states are now offering premium
discounts to homeowners who choose roofs which have passed U.L. 2218
Impact Resistance testing. This test is done in four levels, with Class IV
being the most severe level. Particularly if you are in a hail-prone area,
it makes sense to find a product which has passed this test. Additionally,
some shingle facsimile products offer backer boards to provide extra
rigidity for roof areas subject to heavy foot traffic, falling tree limbs,
etc. Also, look for products warranted to not loose impact resistance with
age and to not chip due to hail or leak due to hail indentation or
Metal roofing can help to reflect heat and keep homes naturally cooler in
warm weather. With steel, copper, and zinc roofing, energy efficiency is
achieved primarily when the metal is unpainted and treated to retain its
bright shininess, or when it is painted with a bright metallic or white
coating. Aluminum, however, inherently reflects radiant heat. Testing done
on aluminum roofing has shown it to be efficient even when painted in dark
colors. This makes aluminum desirable because most homeowners do not want
a white or metallic-looking roof.
Make sure that all fasteners (and other components) are of a metal which
is compatible with the roofing itself. Look for a system which has
concealed fasteners. Even with today’s neoprene washers and other methods
of keeping moisture out of exposed screw and nail holes, any exposed holes
through the panels are potential areas for water to enter the roofing
system. Any water which infiltrates can, with steel products, lead to
corrosion of the roofing and fasteners. Also, many metal roofing systems
use “clips” to fasten the panels rather than “through fasteners” which
attach the panels directly to the roof. The clips allow for expansion and
contraction of the metal. Otherwise, expansion and contraction might
“wallow-out” the fastener holes or cause the fasteners themselves to back
out of the roof. Clips are very important to standing seam panels which
sometimes have great length to them. They are also a factor with various
shingle and tile systems though some heavily textured products have an
inherent “accordion” effect which allows the metal to freely expand and
contract without trouble.
Metal roofing, especially steel, is dependent upon a good coating for long
term durability. Most product warranty lengths are determined by a
combination of the metal and the coating which is used to produce that
product. There are many types of finishes available and, hence, a wide
range of quality. Finishes such as acrylics and siliconized polyesters are
good for commercial applications where periodic re-coating for a different
“look” occurs. Other finishes such as PVDF Hylar and Kynar coatings have
longer lives, making them ideal for residential applications. These
coatings are widely specified by architects who respect them for their
long lives and color retention. Look for a finish which has proven the
test of time. Look also for a finish which is warranted against such
things as fading, chalking, coming loose from the base metal, and chipping
due to impact.
As with any building product, success of the overall project is dependent
upon proper installation. Look for products which have detailed
installation instructions from the manufacturer. Look for a contractor who
has substantial experience with the product you are choosing or has
undergone installation training from the manufacturer. Metal roofs do not
all install in the same manner. Be sure to check references of past jobs
done by your installers and make sure that they have the proper licensing
and insurance to work on your home.
Metal roofing is a wise investment in your home. Today’s numerous product
offerings provide homeowners with a wide choice of looks and qualities. By
making the proper product and contractor selection, you will substantially
increase your home’s value, beauty, and comfort.
Call NSS Exteriors for
a free on site quote to repair, replace or install a new residential metal
details on specific options, pricing and installation, please contact us
online or call 708-385-5815.
examples of our work:
Copper Roof Panels
Copper Panels on Chimney
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Types of Metal Roofing and Siding:
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General Metal Roofing Questions
What is the cost comparison between a
metal roof and an asphalt shingle roof?
The cost of a metal roof cannot be readily compared to asphalt for
various reasons. The condition and type of roof would have significant
bearing on the overall cost, as would the "profile" or style of metal
roofing you would choose. When considering metal vs. asphalt, you are
basically choosing between an investment (metal) over an expense
Will a metal roof increase the likelihood of a lightning strike?
The answer to this question is "absolutely not". Although metal conducts
electricity, lightning is not drawn to it. It's unusual for lightning to
hit buildings. Lightning typically strikes the highest object in an area.
That's why it often strikes trees, power poles, antennas, and towers.
But if your home were hit by lightning, your metal roof would disperse the
energy safely through the structure. Since metal roofing isn't combustible
or flammable, it's a low risk and desirable roofing option where severe
weather is concerned -- especially for lightning.
Are metal roofs loud?
This may surprise you -- metal roofing is often quieter than an asphalt
shingle roof. When installed with solid sheathing, a metal roof on your
home will actually silence noise from rain, hail and bad weather better
than other roofing materials.
Is a metal roof hot?
Metal reflects 70% of the sun's energy. This minimizes heat
retention and as a result less heat is transferred into the building's
structure. Further, 1985 research by the Florida Solar Energy
Center showed that metal experienced a 34% less heat gain than asphalt
shingles. Results indicate that metal roofing offers a similar effect on
R-11 insulation on top of the roof during sunny day conditions.
Will my metal roof rust?
Today's metal roofing systems are built to last. Steel metal
roofing has a "metallic coating" made of either zinc or a combination of
zinc and aluminum. This metallic coating prevents rust from forming and is
bonded to the steel at the factory. Paint is then applied over the
metallic coating to provide the long-lasting color homeowners desire.
Will hail dent my metal roof?
A metal roof can withstand decades of abuse from extreme weather
like hail, high winds, and heavy snow. In unusual cases, very large-sized
hail has been known to dent metal roofs during extremely heavy storms.
But, a typical hail storm will not dent your metal roof. Today's systems
also have a 120-mph wind rating (equal to an F2 tornado), meaning your
metal roof is also safe from wind gusts that can accompany hail storms.
Can I walk on my metal roof to clean gutters?
Many people think you can't walk on a metal roof -- but the truth
is that you can safely walk any metal roof without damaging it. Before you
walk your roof, however, we recommend you talk to your installer first.
They will have the details on how to walk the roof.
Do I need to remove my existing roofing
One of the benefits of metal roofing is that it is lightweight,
which allows it to be installed over existing roofing material. However,
the answer to this question ultimately depends on your local building code
requirements and the condition of your current roof's substructure.
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