Which Metal Roof is Best For Your House? Understanding Metal Roofing

You may have to read this three times.  The first time just read the whole thing.  The second time in small sections.  Finally, a whole read again.   Browse through the blog for more information on each section with pictures also.

Metal roofing is not only steel, most metal roofs are actually made of other types of metal other then steel. Below is a summary of the different types of roofs, and how they differ from one another, and what benefits each one has, this will help you decide which metal roof is best for you.

Galvanized Steel

Carbon/Iron steel is prone to the elements, it gets rusted.  So galvanized steel has a coating, usually of zinc.  So the zinc acts as a barrier  The word Galvanic means barrier, by which the zinc coating keeps the weather from reaching the steel base.

Galvanized Steel is also works well with paint.

The thickness of the zinc is usually what determines the quality of the steel .  The standard is G-90, which means that .90 ounces of zinc is coated on one square of the steel.  Grades of G-30 and G-60 should be avoided from residential uses.

There is also the thickness of the steel itself.   Which is known by gauge, common gauges are 26 gauges, 24 gauges, etc.  The higher the number the thinner the metal is.

Another important aspect is “post-forming” coat which is help protect against corrosion
in areas where the metal had been refashioned during the manufacturing process. So some metal sheets will be re-coated and some manufacturing companies will not re-coated.

Because of its strength, galvanized steel is a good option for homeowners in hail prone
areas like Texas. Galvanized steel is not a good option for homeowners in coastal areas or areas with an
above average amount of corrosive elements in the air. Salt spray and these other elements can
speed up corrosion and shorten the life of galvanized steel.

Galvanized Steel Summary
Advantages: Strong, lower cost, comes in almost any look.
Disadvantages: Shorter life span than other metals, can rust prematurely if not used or installed
properly, can be more difficult to work with, must be cut with a shearing action rather than sawcut.
Thicknesses: 26-28 gauge (.018” - .014”) are most common for shake, shingle, tile and slate
profiles. 24 gauge (.024”) is most common for standing seam systems, with a good amount of 26
gauge as well.
Weight: Between 100 and 150 lbs. per square (100 sq. ft.).
Recycled Content: Usually around 35%.

Galvalume Steel

Carbon/Iron based Steel coated with an alloy of  zinc and aluminum.  When aluminum is added to zinc, it amplifies both the negatives and positives of aluminum.  Aluminum is very corrosive resistant, and so it makes a galvalume steel is also very corrosive resistant.  The negative aspect of aluminum in the alloy, though, is that Galvalume does not self-protect scratches or cut edges nearly as well as galvanized steel does.

Galvalume steel is also more susceptible to a process known as “Tension
Bend Staining.” When the steels are formed into the various metal roofing profiles, the
Galvalume zinc/aluminum and the galvanized zinc coatings are spread very thin over areas in the
metal where there are deep folds or tight bends – so thin, in fact, that the coating has a tendency
to form microscopic cracks. Because of galvanic action of zinc, galvanized steel is able to protect
these scratches with little harm. With Galvalume steel, however, the aluminum in the alloy
somewhat neutralizes zinc’s galvanic properties and therefore the Galvalume steel is not able to
self-protect the cracks, or other scratches in general. Tension Bend Staining occurs when moisture
or other corrosive elements permeate these cracks and facilitate rusting. The result is “stains” of
rust in areas with folds and bends in the metal.
For this reason, Galvalume steel is used most commonly in rather simple profiles, such as
standing seam, because there is not quite as much bending in the metal. Because Galvalume steel
is more corrosion-resistant than galvanized, it is sometimes installed unpainted. While this is most
often done in commercial applications, homeowners who like the bright, shiny metallic look have
selected unpainted Galvalume as well. Most Galvalume steel, though, like galvanized, is painted
for added durability and beauty.

Galvalume Steel Summary
Advantages: Very corrosion resistant, strong, relatively inexpensive (but often slightly more
expensive than galvanized).
Disadvantages: Susceptible to tension bend staining, limited profile availability (mostly standing
seam or simple shingle styles), must be cut with a shearing action rather than saw-cut.
Thicknesses: 24 gauge (.024”) is most common for standing seam systems
Weight: Between 100 and 150 lbs. per square (100 sq. ft.).
Recycles Content: Usually around 35%.

Aluminum

Lightweight, durable, and corrosion resistant, aluminum is a good option for almost any
residential metal roofing system, including standing seam, shake, shingle, tile, and slate profiles.
Aluminum will never rust, so it is an ideal metal for coastal applications and other areas where
steel might be in danger. Aluminum’s propensity to resist rust gives it an extremely long life span.

Nowadays, virtually all aluminum roofing is prepainted, and aluminum can be found in
just about any profile in which metal roofing is manufactured. In fact, more heavily formed
products lend themselves very well to aluminum due to its high malleability and the fact that
heavy forming adds additional structural strength. Aluminum roofing is usually manufactured
from a large percentage of recycled material, a majority of which is post-consumer material, such
as beverage cans. One square of aluminum roofing (.019” thick) can use as many as 1,152
aluminum beverage cans – closing the recycling loop for the consumer. Classic’s roofing systems
– Rustic Shingle, Oxford Shingle, Standing Seam, and Victorian Diamonite – are all
manufactured from aluminum, and aluminum roofing is easily one of the best choices a

homeowner could make when searching for a residential metal roof

Aluminum Summary
Advantages: Lightweight, rust free, attractive, energy efficient.
Disadvantages: More expensive than steel. Not as hail resistant, particularly in less-formed
profiles.
Thicknesses: .019” for shake, shingle and tile. Minimum .032” for standing seam. .032” for some
heavier tile profiles.
Weight: As low as 45 lbs. per square.
Recycled Content: Usually around 95% (mostly post-consumer)

Copper

Copper is generally recognized as one of the most attractive metal roofing options.
Unfortunately, it carries a pretty hefty price tag as well. Copper is the most expensive of the three
most popular roofing metals (steel, aluminum, copper – in increasing order of expense). Rarely
used over an entire residential roof, copper is mainly used for accents over bay windows, on
dormers, or other areas where a touch of elegance is desired. Copper is used often commercially
on older buildings, church steeples, cupolas, and the like. Copper is installed in short standing
seam panels or sheeting, but there are some copper shingles available as well. Classic Products’
Chateau Slate and Oxford Shingle are both available in copper, and are both ideal choices for the

applications mentioned above.

Sometimes, copper is used as a flashing material in conjunction with other roofing
materials, but that is not a recommended use with aluminum or steel roofing, not only because
most residential metal roof systems come with their own preformed flashings anyway, but also
because if copper is left in direct contact with a dissimilar metal, it will speed up the deterioration
of the other metal through galvanic action. Besides, as the copper patinates, the water runoff has a
tendency to stain other metals, brick, concrete, and almost anything else with which it comes in
contact. Therefore, it is important to understand where the water runoff over a copper portion of a
roof is being directed and how it is channeled off of the roof.  Lead-coated copper is sometimes used as a replacement for pure copper to prevent this problem. This is being done less often, though, due to the public outcry against anything lead-related in building products.

Copper is best known for its attractive blue-green, or verdigris patina that forms when left
exposed for 8-15 years. The actual length of time to completed patination depends on what is in
the air; salt spray in a coastal environment, for example, dramatically hastens the process. The
patina is like a barrier against corrosive elements and is part of the reason for copper’s extremely
long life. While copper can be treated to speed up or slow down the patination process, or even be
purchased pre-patinated, most homeowners elect to allow copper to weather naturally so as to
ensure the rich, luxurious verdigris look.

Because copper is relatively soft and malleable, it is fairly easy to work with and usually
solders well. Copper is extremely durable and has a very long life – sometimes more than 100
years.

Copper Summary
Advantages: Beautiful, extremely durable, easy to work with, easily to solder.
Disadvantages: Expensive, runoff can stain, natural patination takes some time.
Thicknesses: 12 oz. (.016”) and 16 oz. (.022”) are common for preformed shingles,
16 oz. (.022”) and 20 oz. (.027”) are common for vertical seam.
Copper is still measured by the ounce because it is considered a precious metal.
Weight: Between 150 and 200 lbs per square.
Recycled Content: Varies but is often very high

Terne (II) and TCS (II)

Manufactured by Follansbee Steel in West Virginia, Terne steel is a zinc-tin alloy (ZT
alloy) coating over base carbon steel. The original Terne metal was a lead-tin alloy coating over
base carbon steel. This original Terne had been used extensively in the 18th and 19th century as a
residential roofing material. Today, Terne II, as the new version of the metal is called, is often
selected residentially for historical retrofit projects. Terne II is initially a dull gray color and over
time, patinates into a weathered gray that achieves a certain historical charm. Terne is very
durable and corrosion resistant – it will last for centuries, but the cost is similar to that of copper.
TCS II, Terne Coated Stainless, is stainless steel coated with the ZT alloy. It looks very
similar to Terne, the dull gray color, only is more durable and a little more costly

Zinc

Like copper, zinc is very soft and malleable. It starts out as a dull gray, and patinates into an attractive charcoal color. Zinc is mostly commonly used in standing seam, but some companies are now offering pre-formed zinc shingles as well. These can be really stunning on residential projects but do come at substantial

cost.

There are other metals available for roofing as well, including stainless steel and titanium.
Generally, roofs made from these more exotic metals will be architect-specified and will be
custom-formed by a manufacturer for a particular application.  Contact us at 817 381 6855 for more specific information.

Terminology and Product Types

Architectural vs Structural Roofing

For residential roofing, you want Architectual Roofing not Structural Roofing.

Architectural metal roofing products are designed to shed water in an efficient manner, and also
to accentuate the other architectural elements of the home. What sets apart architectural metal
roofing products from structural products is that they are applied over solid decking and therefore
are manufactured from thinner metals than structural metal roofing products. In essence,
architectural products are designed to pass rooftop weight loads through to the roof decking
beneath them rather than support weight loads and pass them through to the building’s structural
members. Architectural metal roof systems allow for standard attic ventilation methods.

Structural metal roofing products are installed without a solid decking beneath them. That
is, they are generally used in applications where the metal roofing is installed over purlins, also
known as lathe boards.  Structural metal roofing is generally intended for commercial
applications such as university buildings, industrial facilities, strip malls, warehouses, and other
industrial applications. Rarely are structural metal roofing products used for residential
applications. Because of the potential for direct contact with the backside of the roofing panels
and warm, moist air inside the structure, special ventilation issues can exist with structural metal
roof systems especially on smaller buildings.

Steep vs. Low Slope

Roof pitch factors are stated in terms of rise over run. For example, 3:12 refers to a roof
that is framed such that, for every 12 feet the roof goes back horizontally (“run”), it will “rise” 3
feet vertically.

The industry defines “steep sloped roofing” as anything with a pitch of 3:12 or greater.
Virtually all metal roofing products are appropriate on steep sloped applications; however, 3:12 is
usually the minimum pitch for which shake, shingle, slate, and some tile profile are applicable. In
heavy snow load areas, some shake and shingle products are appropriate only on pitches of 4:12
and higher. Steep-slope roofing products are also referred to as “hydrokinetic,” because they are
designed to shed water.

Most standing seam profiles are applicable on certain low slope roofs, usually down to
2:12 pitch. Any roof with less than a 2:12 pitch requires a mechanically seamed profile to help
ensure water tightness. Typically used on commercial buildings, availability of these products for
residential use may be limited. Such very low-sloped roofing products are said to be
“hydrostatic,” because they allow for pooled water without allowing it to penetrate into the
structure.

It is not at all uncommon for homes with a combination of steep and low-sloped roof
sections to use a combination of metal roofing products to appropriately accent the different roof
configurations. For example, a homeowner may choose a metal shingle profile like Rustic Shingle
for the majority of the roof, but select a standing seam profile for a portion of the roof, an
overhang over a porch, for example, that is low-sloped.

Under absolutely no circumstances should a metal roofing product ever be used on a roof
of lower pitch than that recommended by the roofing manufacturer.

Through-Fastened vs. Clip-Fastened Systems (Snap Locks)

Through-fastened panels refer to metal roof systems in which the screw or nail that
secures the metal roofing to the deck, purlin, lathe, etc., actually penetrates through the panel
itself. Conversely, clip fastened panels utilize a specialized clip system that attaches to the panel
or shingle. The fasteners are then driven through the clips and therefore have no direct contact
with the metal panels themselves. In most cases, clip fastened panels are designed so that the clip
and fastener are concealed (concealed fastener system/snap locks or snap ons). The fastener can also be concealed on certain types of through fastened panels as well. Some products with concealed fasteners may use a combination of through fasteners and clips.

Through-fastened panels that utilize exposed fasteners are much more common. In many
cases, the exposed fastener is simply driven through an overlap in the panels’ courses as well as
through other strategic locations as specified by the roofing manufacturer. Exposed fastener
systems are usually lesser-quality systems and therefore are subject to lesser warranties than
concealed fastener systems. The reason for this is that exposed fasteners are subject to the
elements and tend to break down and fail much sooner than concealed-fastener panels. Exposed
fasteners are normally self-drilling screws with a hex-head drive. These screws will typically have
an oversized “cap” head, which protects a neoprene washer, which is in place for water tightness.
The screws will normally be painted to match he roof system. Although the screws are self drilling, most installers will predrill holes in the roofing from the backside to ensure proper placement.

Concealed-clip fastener systems are usually regarded as higher quality and more
functionally sound for another reason, too. Because metal expands and contracts when it is
subjected to temperature changes, sometimes panels have a tendency to “wrinkle” or “oilcan” as it
is called in the industry. The most common cause of oil canning is fasteners that are driven too
tight and are therefore not allowed to move when they expand and contract. If the panels are
secured with fasteners that are driven through a clip and not the panels themselves, the result is a
system “floats” over the deck and is much less susceptible to oil canning. This also creates far less
concern for what is called "fastener fatigue". With concealed fasteners, the fasteners are often screws for longer roofing panels and nails for smaller “modular” sized shingles. Other causes for oil canning can
include an uneven surface of the original roof deck, improper forming of the roofing and, quite
often, unavoidable stresses and chemical composition differences inherent to the metal itself.

Coatings

There are three main types of finishes used in the metal roofing industry: the first is the
water-based acrylic emulsions. In terms of the quality of coatings, the maxim “You get what you
pay for” holds true. Therefore, because the acrylic emulsions are the least costly, they are also
among the lowest quality of coatings and will carry a relatively weak warranty against fade and
chalk (if warranted at all). Acrylic emulsions are typically two-coat systems consisting of a primer
coat followed by a topcoat.

The second type is polyesters including a number of formulations such as siliconized
modified polyester (SMP). Polyesters are also lower cost and last only slightly longer than
acrylics before fade and chalk are noticeable. SMPs are higher quality than more generic
polyester paints, but still will not achieve the performance of the standard for today’s metal
roofing industry: polyvinylidene fluoride (PVDF).

PVDF coatings are usually sold and applied to metal as the trade names Kynar and Hylar.
These are two-coat systems with a primer coat followed by a topcoat. If the formulation is made
up of the standard 70% Kynar or Hylar resin, it can use the full Kynar 500 or Hylar 5000 trade
names. These trade names are used so that consumer, contractors, and architects can tell for sure
that the finish on the metal roof system they are selecting is of the highest quality possible. There
is no substantive difference between Kynar PVDF resin and Hylar PVDF resin, except that they
are manufactured by two different companies, and thus marketed under two separate trade names.
Kynar 500 / Hylar 5000 finishes usually carry a 30 year fade warranty up to five Delta E units. A
Delta E unit is the smallest recognizable color shade shift seen by the naked eye. PVDF represents
the highest quality coatings available for use on metal roof systems. Most metal roofing
manufacturers and contractors would never recommend selecting a residential product that uses
something other than a PVDF – Kynar 500 / Hylar 5000 finish.

In addition to these base coating options, many steel shake, shingle and tile profiles
include an extra layer of coating to add both beauty and functionality to the products. The two
coatings are applied “post-forming,” which means they are applied after the profile is fashioned
by the manufacturer. The advantage of these post-forming coats, in addition to creating a
gorgeous look, is that they can help seal off any cracks or fissures in the zinc or zinc/aluminum
coating over the steel that may have occurred during the fashioning of the profile.
The two main options here are stone-coatings and Kynar powder coatings.
Stone coated steel products (also called “aggregate” or “granular” coated) are used very
extensively for residential applications, primarily on the West Coast and in the Southwest. These
attractive coatings present a multi-hued, textured appearance and are primarily used on shake and
tile profiles. The coatings consist of ceramic-coated sand or stones, which are bonded to the base
steel and then covered with a clear acrylic coating. The other post-forming coating option, the Kynar powder coat, is so far a Classic Products exclusive. This coat is an electro-statically applied Kynar powder coat that is then baked into the base Kynar coat. The result is a beautiful, long-lasting, scratch-resistant, multi-hued coat that represents the pinnacle of modern coating technology--- called ThermoBond Textured Finish.

The newest development under the “coatings” headline is probably the most exciting due
to its potential impact on the entire roofing industry: reflective pigment technology. These
specially formulated pigments, which were first developed by the military in order to help
camouflage tanks against infrared detection, are able to reflect a much larger percentage of the
sun’s rays even in darker colors. This means that less heat is absorbed into the attic space, and
therefore less energy is required to keep the home at a comfortable temperature during the hot
summer months. The end result is a reduction in the home’s energy bills! Classic Products is the
first and only specialty residential roofing manufacturer to incorporate this technology into all its
product lines. Classic Products calls this technology Hi-R, for highly reflective. Other
manufacturers are marketing their versions under various names, and the stone coatings are
developing this technology as well.

Please note that all galvanized steel, Galvalume, and aluminum roofs should have some
sort of protective coating on the backside of the metal as well. It is acceptable for this to be a low
cost coating. In many cases, it might be colorless.

Underlayment


Most contractors, out of force of habit, use asphaltic-based 15-lb or 30-lb felt
underlayment on any type of project no matter the roofing type. While this is usually enough to
satisfy a building inspector, some metal roofing contractors, including Classic, now offer an
alternative to the traditional felt underlayments. These new polymer underlayments are beneficial
in that they are much lighter and easier to install for the contractor. Also, in the event of a
construction delay, they can be left exposed for up to twelve months with no ill effects. These
polymer underlayments also last much, much longer than asphalt-based 30-lb felt, and if you are
installing a “lifetime” metal roof on your home, do you not want an underlayment that will last at
least as long as the roof itself? Of course, if all goes well, the type of underlayment will not be a
factor at all. But in the unfortunate event of a breach in the roofing material or a flashing, it is
good to know that the roof’s second line of defense, the underlayment, is still intact enough to
handle the problem. This might not be the case if using the traditional 30-lb. felt, especially with
standing seam. In hot weather, the asphaltic-based 30-lb felt may stick to the backside of the
standing seam panels, and when the panels expand and contract, the underlayment can tear. Most
responsible contractors, if they do use 30-lb. felt with metal roofing applications, will use a “slip
sheet,” most commonly red rosin paper, between the 30-lb. felt and the backside of the panels.
With the use of the polymer underlayments, this slip-sheet is not necessary.

Additionally, many contractors will use specialized self-adhering ice and water barrier
underlayments near the eaves and down the length of all valleys. In colder climates with heavier
snow loads, these products may be used over the entire roof. Building codes in certain areas will
mandate the use of at least some of this type of underlayment material.

In all cases, the underlayment used beneath metal roofing should have a smooth, nongranulated surface. Granulated surfaces can cause damage to the back of the metal roofing panels over time.

Classic Products recommends the use of “Sharkskin” underlayment. Along with a
premium self-adhering ice and water barrier.

Profiles & Styles

There are literally dozens of different “looks” and “feels” that can be achieved with metal
roofing – from the traditional, sleek standing seam look, to the old-world tile look, to the more
agricultural corrugated look. The variety of attractive metal roofing profiles is one of the great
advantages of the industry. No matter what the style or look of your home, there is almost
certainly a metal roof system out there that will complement it perfectly! Unfortunately, the
variety of profiles is sometimes one of the industry’s detriments as well because it can lead to
improper products being used for less than ideal applications. The following section should help
you make an informed choice about the product that will work best, both aesthetically and
functionally, for your home.

Sheet Roofing

Sheet metal roofing is available in many different profiles, all going by different names.
“5V” Crimp, “R” Panel, corrugated roofing, face-fastened panels, through-fastened panels, or
screw down panels are some of the synonyms for the style of metal roofing that is encompassed
under the umbrella term “sheet.” Metal sheet roofing is manufactured primarily from galvalume
or galvanized steel in thicknesses that vary between 24 and 30 gauge. The defining characteristic
of all sheet roofing is large panels (or sheets) of varying widths and lengths that overlap and have
exposed fasteners. The fasteners are driven through the overlapping portions of the panels, as well
as in other strategic locations and into the roof decking, purlin, or spaced sheathing below. A
neoprene washer is located beneath the head of the fastener to ensure water tightness.

One common residential type of sheet roofing is the 5V Crimp pattern. It has five small V
crimps per panel. Other corrugated patterns of sheet roofing give a more “wavy” look. The look
of any of these products is sometimes construed as an agricultural or rural look. Sheet can also
give a historical look, particularly if used unpainted.

Sheet roofing can be installed painted or unpainted. Because sheet roofing is often chosen
as a more economical type of metal roofing, the paints used on sheet metal roofing are often
lesser quality. This saves even more money on the overall system. Generally, sheet-roofing
systems should be examined closely before being selected for residential projects looking for a
lifetime roof. While most sheet roofing is still higher quality than many traditional roofing
materials, it contrasts pretty sharply with some of the more technologically-advanced metal
roofing options available to homeowners who want to make lasting investments in their homes.
Sheet roofing is the most economical form of metal roofing. It is also one of the easier-toinstall types of metal roofing. The disadvantages of sheet roofing are that it is not as long lasting, both functionally and aesthetically, as some other types of metal roof systems.

Standing Seam

Standing seam is probably the most recognizable profile of metal roofing for both
commercial and residential projects. The popularity of standing seam has grown so much in
recent decades that many people automatically assume that standing seam is implied by the term
“metal roofing.” Standing seam provides a very contemporary, distinctive look, and is chosen to
complement homes of all styles. The key, though, to choosing the right standing seam depends on
the actual dimensions of the roof. More often than not, residential roofs are smaller, more
compact, and more complex than commercial roofs. For this reason, it is advisable to select a
standing seam roof with a relatively small panel width – usually around 12″. Wider panels will present a more commercial look to the roof, obviously a condition to be avoided when selecting metal roof for a home.

As mentioned in the section on through fastener vs. clip fastened systems above, standing
seams can be either through- or clip-fastened. Through-fastened standing seam systems are less
common and utilize a nailing “flange” that runs the length of the panels. The fasteners are driven
through this flange and then concealed by the subsequent panel. So, although the fastener is
concealed to the elements, it is still fastened directly through the panels themselves. These
systems are more cost effective options, but since most quality standing seams used residentially
are continuous panels – meaning the panels are custom formed to the length of the rafter – using
these through-fastened panels is not recommended on longer rafter lengths. The reason is that the
longer the panel, the more it will expand and contract, and the more likely to fatigue fasteners,
“wallow out” fastener holes and also to oilcan. These through-fastened panels are a good option,
however, for shorter runs such as porch accents or bay windows.

For longer runs, the better option is a standing seam system that utilizes a clip system. The
clip should be manufactured from a similar metal as the standing seam itself, or from a metal like
stainless steel that is not conducive to the galvanic action between dissimilar metals. The clip is
fastened to the roof deck so that the panels are allowed to “float.” This helps to ensure that the
system will maintain its water tightness much longer, and also its aesthetics, as oil canning will be
less of a concern. For longer runs, it is also recommended that a system with a higher rib is used.
The rib is the portion of the standing seam that gives it its dimension, and is also the joint of the
two adjacent panels. Higher ribs will give the panels more capability to carry water down the
entire length, and thus prevent water from spilling over the panels and possibly backing up under
an overwhelmed rib or other flashing.

Standing seam roofs are most commonly manufactured from galvanized or Galvalume
steel and range in gauge from 18 for the heavier structural products (rarely used residentially) to a
lighter 26 or even 28 gauge for simpler projects. Gauge 24 and 26 are the most common for
residential steel standing seams. Some high quality standing seams, like Classic’s Premium
Standing Seam are manufactured in heavy gauge aluminum ranging typically from .032” to .050”
with .032” common for residential applications.

Our Standing Seam Systems, come with an entire array of preformed flashings. These
flashings help reduce installer error and help ensure a watertight roof for many decades to come.
Flashings for true standing seam systems usually need to be custom-made for each job in order to
exactly meet the pitch and other geometry of each individual roof.

Shake, Shingle, Tile, and Slate

The growth in demand for standing seam in the residential roofing market over the past
few years may be exceeded only by the growth in popularity of the “new metal roofs” – the
shake, shingle, tile, and slate profiles. Many of these specialty profiles are designed almost
exclusively for residential use. Very early profiles of this type were designed for commercial
applications (Pizza Hut or Dairy Queen, for example) and, with updates in manufacturing and
coatings technology, have evolved into the beautiful residential systems that homeowners cannot
seem to get enough of. The four different types of “modular” panels can vary greatly in terms of
look and use. Following is a description of all four.
Metal shakes are designed to mimic the look of hand split cedar shakes. While many
homeowners select these shake systems because of their resemblance to wood shakes and also
because of the long-term performance metal provides, many other homeowners enjoy these
specialty metal shake systems for their own, unique and distinctive look. These modular panels
come in various sizes with common dimensions of 2’ x 1’ and 5’ x 1’ and are usually fastened to
the roof deck with a concealed clip system or a nailing flange formed into the top of the shingle.

Shake and shingle facsimile profiles are installed on the roof in a staggered pattern to avoid
vertical line repetition. The shake systems are usually more “high-profile” than shingle systems,
meaning that they are designed with a little more dimension and texture. Many times, this added
dimension to the shingle allows it to be installed directly over previous roof layers, even some
thin wood shingles. Metal shakes are usually manufactured from steel or aluminum, either 26 or
28 gauge steel, or .019” or .024”. Steel metal shakes are commonly coated with a post-forming
stone coat or Kynar powder coat. This helps seal the edges in areas where the zinc or
zinc/aluminum alloy coating has been spread thin over areas of tight bends. Some manufacturers,
including Classic Products, also offer aluminum shakes with the special post-forming coats, but in
the case of aluminum, these coats are selected more for aesthetic reasons than to ensure the
functional soundness of the system.
Most metal shake systems come with a complete line of preformed flashings, which
usually include hip caps, ridge caps, gable trim or flashing, sidewall flashing, eave starter strips,
and valley. These are typically universal flashings designed to work with any roof pitch. Higherquality metal shake systems utilize an open valley system to help ensure that leaves, ice, pine
straw, etc. do not block up the valley and cause water to back up under the panels or the valley
itself. It is usually a good idea to inquire with your contractor about the type of valley flashing
used with the metal roof system you are considering.
Metal shingles are similar to metal shakes except with a lower-profile design. Many
homeowners who are fed up with the short lives of the traditional machine split wood shingle
select metal shingles for their durability and beauty. Also since metal shingles look more like
dimensional standard shingles, some homeowners choose them for their ability to blend in with a
more modest neighborhood look. Like the shake profiles, the single metal roof systems are
modularized panels fastened to the roof deck most commonly with a clip system, or sometimes
with a nailing flange formed into the top of the shingle.
Metal tile profiles come in a wide variety of looks and feels, from the exotic
Mediterranean barrel tile look to the stately S-Serpentine look. Most tile profiles are through
fastened, and some utilize a batten grid attached to the roof deck to which the panels are attached.
Most metal tile systems are made in large sheets that typically stretch from eave to ridge. Fewer
seams and quicker installation are a plus, but waste can be dramatically increased with such
systems.

Metal slate profiles are manufactured in steel, aluminum, and copper to replicate the look
of natural slate. The advantage of metal facsimile slate profiles is that they are about ½ to 1/3 the
cost of real slate, and are also much, much lighter than traditional slate – which can help prolong
the life of older buildings.

Some other, more exotic profiles, such as diamond shapes, scalloped, and flat tiles are
available in metal roofing.

Common Issues & Concerns

Selecting and purchasing a new roof is a significant event for any homeowner. Those
homeowners who do their research and have complete information available to them are the ones
who end up making wise investment choices when it comes to roofing. Following are several
concerns which arise fairly frequently during the roofing decision making process. If you have
questions or concerns, which are not addressed here, please feel free to contact us direct using the
Contact Information at the end of this document.

Installing Over Existing Roofing Materials

Due to their very low weight, many metal roofs can be installed over existing roofing
materials. This is particularly the case when going over old composition shingles. Additionally,
the formation of many of the heavily profiled shake and tile profiles of metal roofing can even
permit installation over wood shingles or wood shakes.

Before deciding to install over an existing roof, the manufacturer or an experienced
contractor must be consulted, as weight is not the only issue. In many cases, building codes
prohibit more than two layers of roofing, although building inspectors have been known to waive
that restriction for metal roof layover installations. If there is an existing weight problem with the
structure or if there is question as to the integrity of the structure or roof decking, those issues
must be addressed before installing over the existing shingles.

In some cases, particularly with wood shingles and shakes, the old roofing can be removed
from the edge perimeter of the roof and even the lumber can be removed and replaced with fresh
lumber before proceeding with the roof installation.

Metal can also sometimes be installed over existing slate and asbestos slate roofs though,
again, the manufacturer or an experienced contractor should be consulted. Existing tile roofs and,
in most cases, existing metal roofs, need to be removed prior to installation of the new roof.

Lightning
It is common for homeowners to wonder whether a metal roof might attract lightning. Fact
is, metal conducts electricity but it does not “draw” it. There is no evidence that metal roofing
puts a home at greater risk of a lightning strike. Typically, lightning will hit the highest object
around and rarely is that the top of the house. Just the same, metal roofs can be grounded by a
lightning protection specialist if desired.

Fire Safety

Most metal roofs are approved for Class A, B, and C fire ratings. In some cases, a special
underlayment may be required to meet certain code and fire classification requirements. However,
metal roofing is widely recognized for its resistance to airborne sparks and burning debris.

Sound Transmission

Most residential metal roofs are installed over solid decking and, in most cases, there is an
attic space beneath that. These factors help to reduce noise transmission and avoid objectionable
noise from rain hitting the roof. Additionally, the more heavily profiled metal roof styles are very
good at breaking up any “sound board effect.” Whereas rain may create a slightly louder sound
hitting metal roofing than other products, it will not create a “tinny” sound. If your home has
areas where there is no attic space or insulation, talk to your metal roofing contractor about this
and see whether there is a way to add insulation for sound deadening as well as energy efficiency.

Ventilation

In most cases, metal roofing does not increase the need for attic ventilation. However, it
also does not decrease it. Fact is, homes are being built more airtight today than ever before. This
is resulting in moisture getting trapped inside the house. This moisture generally migrates to the
attic and needs to be exhausted out year-round, as does the excessive attic heat, which can build
during the summer months. The most proven method of venting is a combination of soffit vents
and a roof ridge vent. Most metal roof systems will offer some sort of ridge vent option. If
moisture is not vented from an attic, unhealthy and damaging conditions including mold and rot
can occur.

In the rare instances when structural metal roofing (i.e., metal roofing that is installed over
purlin or lathe rather than solid decking) is used on a residential-scale building, good ventilation
is critical to prevent the collection of condensation on the exposed bottom side of the roofing
panels.

Stress Skin “Sandwich” Panels

Increasingly, homes are being built from stress skin panels, which consist of foam
sandwiched between two layers of decking or outer decking and inner gypsum board. These
panels can pose potential condensation issues because they often do not have any venting. This
goes against the International Building Code, which requires a 1″ vented airspace in the United
States and 1½″ in Canada. Before proceeding with the installation of any roofing over stress skin
panels, consult with the panel manufacturer, roofing contractor, and building officials as
necessary to ensure that steps are being taken to avoid condensation issues. Because they will
occur over time.

Hail
Metal roofing is widely respected for its hail resistance. While there can certainly be
storms which no roofing material will escape unscathed, metal roofing offers good protection
from leaks even if aesthetic damages do occur. The most widely-accepted test of hail-resistance is
Underwriters Lab (U.L.) 2218, a steel-ball drop test that simulates the effect of hail impact on
roofing products. Metal roofs pass U.L. 2218 at Class IV, the highest rating. As a result,
homeowners in many hail-prone states can obtain discounts on their insurance premiums.

Additionally, unlike other roofing materials, metal roofing resists hail damage even as it ages.

Walk ability

Most metal roofs can be safely walked without damage. Inquire with the roofing
contractor as to the correct methods for foot traffic on the roof. Some of the shingles and shake
style metal roofing products have optional foam backers for even greater rigidity and walk ability.

Environmental Impact

Metal roofing is increasingly being recognized for its many “green” benefits. The
durability of metal roofing makes it a very sustainable product. Additionally, should it ever need
to be removed in the future, it is 100% recyclable. Most metals used in roofing have very high
initial recycled content. This is as high as 95% with aluminum. The production of metal from
recycled stock also has very low embodied energy in comparison to producing metal from
original ores.

With the onset of various “cool roofing” initiatives in the country, metal is being
recognized for its ability to keep buildings cooler in hot weather. This is done through a
combination of reflectivity and emissivity, often enhanced by coatings on metal roofing.
Additionally, shake, shingle, and tile profile metal roofing products have minimal contact with the
home’s structure, blocking heat transfer by conduction as well.
Finally, the ability to install metal roofing over old roofing materials means that landfills
are not being burdened with the old roofing.

Warranties

Metal roofing has a long history. Many metal roofs 100+ years old can be found in the
United States today. Those roofs did not have the benefit of today’s coating and manufacturing
technology either. Metal roofing manufacturers provide warranties covering such things as
manufacturer’s defects, product integrity, and coating integrity. The coating warranties may
include such things as fade and chalk.

Proper Installation

As is the case with any building material, metal roofing must be properly installed in order
to be successful. Homeowners are encouraged to fully investigate both the metal roofing materials
they are considering and the contractors they are considering for installing those materials. This
investigation should include looking at past jobs and talking with past customers. If the
manufacturer and/or the contractor are unwilling or unable to share information with you
concerning proper installation procedures, it might be best to find different suppliers.

Benefits of Metal Roofing
Metal roofing offers many benefits to homeowners. As you investigate various products, the
manufacturers and suppliers should be very happy to provide you with details as to the particular
benefits and attributes of their products. However, the benefits of metal roofing frequently
include:

Distinctive Beauty
Increased Home Value
Worry-Free Lasting Durability
Fire Safety
Low Weight
High Wind Resistance
Energy Efficiency
Recycled Content, and 100% Recyclable
Installation Over Existing Roof
Eliminates Ice Dams & Leaks
Does not Support Moss or Fungus Growth

Further Information

call 817 381 6855