The History and Benfits of Metal Roofing.
Metal roofing has been around in various forms for
centuries. It comes in hundreds of different sizes,
shapes, materials and colors.
There are architectural metal panels which are
made to go over roof sheathing and structural
panels that don’t need any sheathing at all. And
there are metal roofing products made to simulate
the look of tile and even wood shakes.
The minimum slope varies, but many metal roof
systems require at least 3:12 slope.
The benefits of metal roofing. Many people like
the look of certain types of metal roofing. In our
area for example, 5V metal panels are popular on
upscale beach homes. (They’re also popular on
barns… which makes more sense.)
Metal roofing has a long roof life, especially if it is
maintained properly. That gives it low life-cycle
costs.www.macgregorroofing.com
Metal roofing is lightweight and can go on
structures that can’t take tile.
And of course metal won’t burn, so it offers a Class
A fire rating. That alone could steer you in the
direction of metal roofing if you live in an area
prone to brush fires.
The problems with metal roofing. The biggest
disadvantage of most metal roofing systems is the
difficulty of walking on them safely. Just as you
should be able to walk across a roof without risk of
damaging the roofing, you should also be able to
walk on one without putting life and limb at risk.
That means having a moderate slope as discussed
in the design chapter. It also means having a roof
system that gives you good footing.
Have you every noticed how much a metal roof
panel looks like a playground slide? Did you ever
try to walk up one as a kid? Now think about doing
that with a hard fall waiting for you when you slip.
And when the metal is wet, like it might be when
you are having roof problems, it goes from
dangerous to treacherous. Remember what
happened to the roofer in the story that opened
this chapter? A little dew almost did him in.
There are some metal roofing systems that have
granules embedded in the face which offer better
footing, but that brings me to my second problem
with metal… exposed fasteners.
Many metal roof systems, including some of those
which are granule coated, are attached with
exposed fasteners.
It’s a curious thing that all other types of roofing try
to avoid any exposed fasteners whatsoever, yet
some metal roof systems have them all over the
place. Those 5-V panels on the upscale beach
homes for example, have an exposed screw every
12” over the entire roof.
Well, I guess that’s OK if you live in the desert or
some place like San
Diego that only gets nine
inches of rain per year. In Southwest
Florida where
I live, we can get that much rain from a single
tropical storm.www.macgregorroofing.com
The problem with all those exposed fasteners is
when they start leaking. It usually doesn’t happen
right away. But right about the time your warranty
expires, the grommets on the screws start falling
apart and/or the holes in the panels become
elongated from the constant expansion and
contraction of the metal.
The water gets under the roof panel at one or
more screws, which may or may not be the same
screws where the water penetrates the
underlayment.
Fixing this kind of leak is often a hit or miss affair
where you just caulk every fastener and seam in
the area, while hanging onto whatever you can for
dear life… Not my idea of fun. And caulk isn’t a
permanent solution, in spite of what it says on the
tube. The movement of the metal eventually tears
caulk joints loose and the leaks return.
There are some types of metal roofing with no
exposed fasteners. These are called “standing
seam” panels and have the fasteners hidden under
each seam. This is much better than all those
exposed fasteners, but standing seam panels have
a commercial appearance that looks out of place
on single family homes.
There’s another inherent problem with metal roof
systems you should know about….
Some systems can be damaged by walking on
them just like tile. It happens one of two ways…
In the first case, the metal is simply too thin and
will crush under foot. For example, a well-known
company used to make an aluminum roof panel
that simulated the look of wood shakes. You’ve
probably seen the ones that were painted red and
ended up on Dairy Queens across the country.
They were pretty, but wouldn’t stand up to high
winds and foot traffic.
The other situation is when architectural metal
panels are mounted on purloins or battens instead
of a solid roof surface such as plywood. This is
done to either avoid the cost of a solid wood roof
deck or to provide an air space under the panel to
minimize condensation.
But some architectural panels can bend under foot
traffic, wrecking both their water shedding
capabilities and their appearance.
Of course, if you know where to step, you can
avoid this damage.
But like walking on a tile roof,
you can’t expect everyone to know where the
”stepping stones” are.
Another problem is the life of a metal roof gets cut
short when the factory finish wears off. I’m sure
you’ve seen old barns and commercial buildings
with rusty metal roofs. They didn’t start out that
way. At one time they were painted or galvanized,
but that is only skin deep. When it wears off, it
doesn’t take long for rust to set in and start eating
the metal.
Some metal roofs are coated with a baked-on
finish that may last a long time… but the rust has a
place to start everywhere the metal is cut or
punctured by a fastener.
My opinion of metal roofing: Generally speaking,
I am not a fan, mainly due to the danger of walking
on it safely. YOU may not have to walk on your
roof, but somebody will… and THEY SHOULDN’T
HAVE TO RISK LIFE OR LIMB TO DO SO.
Metal roofing is perceived as a superior system,
but I call that a the crappy Myth”. I see it as a
second-rate system… better than tile and wood
shakes but not as good as asphalt shingles.
The perception that metal is a superior roof system
is perpetuated by people who either don’t know
much about metal or have a financial interest in
promoting it. www.macgregorroofing.com
You can do better… for less money.
If you choose metal anyway… Use a contractor
who specializes in metal roofing. This isn’t an
easy do-it-yourself project. Metal roofing requires
special tools and techniques to get a good job. The
guy who does it all the time should have the right
stuff.
If you go with metal panels, don’t use the 12-foot
lengths you get at the big home improvement
stores. Get seamless panels that are cut to the
length you need. It will reduce waste, save labor
and avoid unsightly laps in the middle of your roof.
Also, go with a system that is rigid enough for foot
traffic, regardless of where somebody steps.
Try to avoid systems that have exposed fasteners,
especially if you live in an area that gets a lot of
rain.
And consider a premium underlayment under the
roof panels for secondary protection. That will also
help to seal the screws from water that gets under
the metal. Check out Macgregor Roofing for yourself at www.macgregorroofing.com
