3. . INTRODUCTION
Metal. roofing. is. manufactured. from. a
variety. of. metals. and. alloys. These. same
materials. are. often. coated
in. the. factory
with. a
. high. performance. paint
. system
. . An
installer. must. be. familiar. with. some. of. the
characteristics. of. these. various. materials
and. finishes
,. and. how. they. aff
ect. working
with each material
Product. selection. is. not. the. i
nstaller's. job
(although it may be in some cases)
, except it is
important
to. understand. that. not. every. job
requires
the
same
material. or. coatings
Even when a job appears similar to another
job,. there. may. be. other. factors. that. will
require. different. fasteners,. materials,. or
methods
The installer must make sure that
the. correct. product
s. are
being. used
for. the
job,
. and
not. accidently. mix. products
. with
different gauges, materials
, or coatings
Understanding. the
material
. in. this. chapter
is. . necessary
; not only for
new construction,
but
for
any. reroofing. and. repair
. work. that
involves only portions of a roof, or interfacing
with another
roof
Using. the. wrong. fasteners,. materials,. or
method. for. the. job. will. cause. any. roofing
system. . to. . fa
ll. . short. . of. . it is. . expected
performance
Gauge
indicates
the. thickness. of. the. sheet
material
. It. is. often. stat
ed. as. a. number
Common gauges for metal roof panels vary
from. 2
0. to. 29. gauge. The. lower. the. gauge
number, the thicker the material
. The exact
thickness will depend on the type
of
material
such. as. stainless. steel,. or
. aluminum. In
most cases
, the lower gauge, thicker material
is
a. stronger,. more. durable. product
. within
the same type of material. A material with a
lower. gauge
number
. will. weigh. more
,. and
may
also
be more difficult for the installer to
work with
The. gauge. table. below
,. Table. 3
-1,. lists. the
gauge. and. sheet. thickness. in. inches. of. the
more. common. aluminum. and. steel. roofing
materials
Common. to. every. roofing. material. are
characteristics. like. g
rades,
alloys,. and
tempers. These "basics" will help determine
how. a. material. cuts,. bends
,. and. reacts. to
an
installer's
handling
3 1 1
Grades
Grades. refer. to. the. chemical. make-
up. of. the
material
,. such. as. l
ow. or. high. carbon. steel

Grade
number
may. . also. . affect
other
characteristic
s. of. the. material
. such
as. yield
strength
,. or. workability
. The. installer. may
notice
differences in cutting, bending, drilling
,
and fastening the material. Tool life may also
be affected by the grade of the material
being
used
3 1 2
Alloys
Often. terms. like
aluminum,. copper,. and
zinc
are. used
to. describe. the. make
-up. of. a
product
. In reality
, the product isn't made of
a. pure. form. of. the. metal
, except. an. alloy. of. that
metal. Rarely. is. the. pure. form. of. a. metal
suitable. for. the. purpose. it. may. be. used
Aluminum,. for. example,. in. it is. pure. form
,. is
very. soft. and. lightweight
,. except. tears. easily
Using. . an. . aluminum
alloy,. . a. . blend. . of
aluminum and one
or more
other
metals,
the
good. . qualities. . of. . aluminum. . can. . be
maintained
while improving it is weaknesses
An. installer. uses
a. variety. of. materials
identif
ied
only as aluminum, steel, or copper
Remember. that,. in. reality,. these. may. be
several. different. alloys. Each. alloy. will
have
different. characteristics
,. and. may. present
some. of. the. same. issues. mentioned. in. the
grading. . section. . above
. . Various. . alloys,
especially copper alloys
, will
age and weather
differently
. . They
. will. show
very. different
colors as they age
3 1 3
Tempers
Temper. refers. to. the. state. of. metal. in. terms
of. hardness
. or. strength
. . Metal. is. tempered
by. the. application. of. heat
ing. and. cooling
cycles at the time of manufacture
In manufacturing, metal is often tem
pered
, or
annealed,
. to. make. it. easier. to. form. and
shape. . Depending. on. the. part
. and. its
intended use,
this process
may also be used
to. harden. it. where. additional. strength. and
support is needed
Tempering,. or. annealing,. may. affect. other
characteristics of the material. Installers will
notice. the. temper. of. a. material. when
. it. is
necessary to cut, drill
, or bend the material

. they
oxidize. and. provide. a
natural protection from weathering. T
he roof
develops. a. beautiful. natural. finish. called. a
patina
. (Figure. 3-
1)
This. patina. varies. and
can
be uneven
Repairs
on such older roofs
can. be. challenging. and. impossible. to
visually. match. There. may. be,. however,
methods. available. to. "
pre-
weather
". newer
material
in. order. to. give. it. the. appearance
of an older, aged roof
Figure 3-
1
Aged Copper Roof Showing Blue-
Green Patina
Steel,. the. most. commonly. used. roofing
material,. requires. some. sort. of. covering. to
protect. it. from. the. weather
. and. corrosion
Instead. of. paint,. steel. is. often. coated. with
another metal, usually zinc or
a zinc
-aluminum
alloy
.