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Roofs play a
key role in protecting
building occupants and
interiors from outside
weather conditions,
primarily moisture. The
roof, insulation, and
ventilation must all work
together
to keep the building free of
moisture. Roofs also provide
protection from the sun. In
fact, if designed correctly,
roof overhangs can protect
the buildings exterior walls
from moisture and sun. The
concerns regarding moisture,
standing water, durability
and appearance are
different, reflected in the
choices of roofing
materials.
Maintaining Your Roof
Homeowner maintenance
includes cleaning the
leaves and debris from
the roof’s valleys and
gutters. Debris in the
valleys can cause water
to wick under the
shingles and cause
damage to the interior
of the roof. Clogged
rain gutters can cause
water to flow back under
the shingles on the
eaves and cause damage.
Whatever the roofing
material may be
including composition
shingle, wood shake,
tile or metal. The best
way to preserve your
roof is to stay off it.
Also, seasonal changes
in the weather are
usually the most
destructive forces.
There
are two types of
roofs—flat and
pitched (sloped).
Most commercial,
industrial, and
apartment buildings
have flat or
slightly sloping
roofs. Most houses
have pitched roofs.
Some roofers work on
both types; others
specialize. Most
flat roofs are
covered with several
layers of materials.
Roofers first put a
layer of insulation
on the roof deck.
Over the insulation,
they then spread a
coat of molten
bitumen, a tarlike
substance. Next,
they install
partially
overlapping layers
of roofing felt, a
fabric saturated in
bitumen, over the
surface. Roofers use
a mop to spread hot
bitumen over the
surface and under
the next layer. This
seals the seams and
makes the surface
watertight. Roofers
repeat these steps
to build up the
desired number of
layers, called
“plies”. The top
layer either is
glazed to make a
smooth finish or has
gravel embedded in
the hot bitumen to
create a rough
surface. An
increasing number of
flat roofs are
covered with a
single-ply membrane
of waterproof rubber
or thermoplastic
compounds. Roofers
roll these sheets
over the roof’s
insulation and seal
the seams. Adhesive,
mechanical
fasteners, or stone
ballast hold the
sheets in place. The
building must be of
sufficient strength
to hold the ballast.
Most
residential roofs are
covered with shingles.
To apply shingles,
roofers first lay, cut,
and tack 3-foot strips
of roofing felt
lengthwise over the
entire roof. Then,
starting from the bottom
edge, they staple or
nail overlapping rows of
shingles to the roof.
Workers measure and cut
the felt and shingles to
fit intersecting roof
surfaces and to fit
around vent pipes and
chimneys. Wherever two
roof surfaces intersect,
or shingles reach a vent
pipe or chimney, roofers
cement or nail
flashing-strips of metal
or shingle over the
joints to make them
watertight. Finally,
roofers cover exposed
nailheads with roofing
cement or caulking to
prevent water leakage.
Roofers who use tile,
metal shingles, or
shakes follow a similar
process. Some roofers
also waterproof and
dampproof masonry and
concrete walls and
floors. To prepare
surfaces for
waterproofing, they
hammer and chisel away
rough spots, or remove
them with a rubbing
brick, before applying a
coat of liquid
waterproofing compound.
They also may paint or
spray surfaces with a
waterproofing material,
or attach waterproofing
membrane to surfaces.
When dampproofing, they
usually spray a
bitumen-based coating on
interior or exterior
surfaces.
A
number of roofing
materials are
available...
Asphalt
Asphalt is the most
commonly used roofing
material. Asphalt
products include
shingles, roll-roofing,
built-up roofing, and
modified bitumen
membranes. Asphalt
shingles are typically
the most common and
economical choice for
residential roofing.
They come in a variety
of colors, shapes, and
textures. There are four
different types: strip,
laminated, interlocking,
and large individual
shingles. Laminated
shingles consist of more
than one layer of tabs
to provide extra
thickness. Interlocking
shingles are used to
provide greater wind
resistance. And large
individual shingles
generally come in
rectangular and
hexagonal shapes.
Roll-roofing products
are generally used in
residential
applications, mostly for
underlayments and
flashings. They come in
four different types of
material:
smooth-surfaced,
saturated felt,
specialty-eaves
flashings, and
mineral-surfaced. Only
mineral surfaced is used
alone as a primary roof
covering for small
buildings like sheds.
Smooth-surfaced products
are used primarily as
flashing to seal the
roof at intersections
and protrusions, and for
providing extra deck
protection at the roof's
eaves and valleys.
Saturated felt is used
as an underlayment
between the roof deck
and the roofing
material.
Specialty-eaves
flashings are typically
used in climates where
ice dams and water
backups are common.
Built-up roofing (or
BUR) is the most popular
choice of roofing used
on commercial,
industrial and
institutional buildings.
BUR is used on flat or
low-sloped roofs and
consists of multiple
layers of bitumen and
ply sheets. Components
of a BUR system include
the roof deck, a vapor
retarder, insulation,
membrane and surfacing
material. A modified
bitumen membrane
assembly consists of
continuous plies of
saturated felts, coated
felts, fabrics or mats
between which alternate
layers of bitumen are
applied, either surfaced
or unsurfaced. Factory
surfacing, if applied,
includes mineral
granules, slag, aluminum
or copper. The bitumen
determines the
membrane's physical
characteristics and
provides primary
waterproofing
protection, while the
reinforcement adds
strength, puncture
resistance and overall
system integrity.
Metal
Most metal roofing
products consist of
steel or aluminum,
although some consist of
copper and other metals.
Steel is invariably
galvanized by the
application of a zinc or
zinc/aluminum coating,
which greatly reduces
the rate of corrosion.
Metal roofing is
available as traditional
seam and batten, tiles,
shingles, and shakes.
Products also come in a
variety of styles and
colors. Metal roofs with
solid sheathing control
noise from rain, hail,
and bad weather just as
well as any other
roofing material. Metal
roofing can also help
eliminate ice damming at
the eves. And in
wildfire-prone areas,
metal roofing helps
protect buildings from
fire should burning
embers land on the roof.
Metal roofing costs more
than asphalt, but it
typically lasts 2 to 3
times longer than
asphalt or wood
shingles.
Wood
Wood shakes offer a
natural look with a lot
of character. Because of
variations like color,
width, thickness, or cut
of the wood, no two
shake roofs will ever be
the same. Wood offers
some energy benefits,
too. It helps to
insulate the attic, and
it allows the house to
breathe, circulating air
through the small
openings under the felt
rows on which wooden
shingles are laid. A
wood shake roof,
however, demands proper
maintenance and repair,
or it will not last as
long as other products.
Mold, rot, and insects
can be a problem. The
life cycle cost of a
shake roof may be high,
and old shakes can't be
recycled. Most wood
shakes are unrated by
fire safety codes. Many
use wipe or spray-on
fire retardants, which
offer less protection
and are only effective
for a few years. Some
pressure-treated shakes
are impregnated with
fire retardant and meet
national fire safety
standards. Installing
wood shakes is more
complicated than roofing
with composite shingles,
and the quality of the
finished roof depends on
the experience of the
contractor as well as
the caliber of the
shakes you use. The best
shakes come from the
heartwood of large old
cedar trees, which are
difficult to find. Some
contractors maintain
that shakes made from
the outer wood of
smaller cedars, the
usual source today, are
less uniform, more
subject to twisting and
warping, and don't last
as long.
Concrete and
Tile
Concrete tiles are made
of extruded concrete
that is colored.
Traditional roofing
tiles are made from
clay. Concrete and clay
tile roofing systems are
durable, aesthetically
appealing, and low in
maintenance. They also
provide energy savings
and are environmentally
friendly. Although
material and
installation costs are
higher for concrete and
clay tile roofs, when
evaluated on a price
versus performance
basis, they may out
perform other roofing
materials. Tile adorns
the roofs of many
historic buildings as
well as modern
structures. In fact,
because of its extreme
durability, longevity,
and safety, roof tile is
the most prevalent
roofing material in the
world. Tested over
centuries, roof tile can
successfully withstand
the most extreme weather
conditions including
hail, high wind,
earthquakes, scorching
heat, and harsh
freeze-thaw cycles.
Concrete and clay roof
tiles also have
unconditional Class A
fire ratings, which
means that, when
installed according to
building code, roof tile
is non-combustible and
maintains that quality
throughout its lifetime.
In recent years,
manufacturers have
developed new
water-shedding
techniques and, for
high-wind situations,
new adhesives and
mechanical fasteners.
Because the ultimate
longevity of a tile roof
also depends on the
quality of the sub-roof,
roof tile manufacturers
are also working to
improve flashings and
other aspects of the
underlayment system.
Under normal
circumstances, properly
installed tile roofs are
virtually maintenance
free. Unlike other
roofing materials, roof
tiles actually become
stronger over time.
Because of roof tile's
superior quality and
minimal maintenance
requirements, most roof
tile manufacturers offer
warranties that range
from 50 years to the
lifetime of the
structure.
Concrete
and clay tile roofing
systems are also energy
efficient, helping to
maintain livable
interior temperatures
(in both cold and warm
climates) at a lower
cost than other roofing
systems. Because of the
thermal capacity of roof
tiles and the ventilated
air space that their
placement on the roof
surface creates, a tile
roof can lower air
conditioning costs in
hotter climates and
produce more constant
temperatures in colder
regions, which reduces
potential ice
accumulation. Tile
roofing systems are made
from naturally occurring
materials and can be
easily recycled into new
tiles or other useful
products. They are
produced without the use
of chemical
preservatives, and do
not deplete limited
natural resources.
Single-Ply
Single-ply membranes are
flexible sheets of
compounded synthetic
materials that are
manufactured in a
factory. There are three
types of membranes:
thermosets,
thermoplastics, and
modified bitumens. These
materials provide
strength, flexibility,
and long-lasting
durability. The
advantages of
pre-fabricated sheets
are the consistency of
the product quality, the
versatility in their
attachment methods, and
therefore, their broader
applicability. They are
inherently flexible,
used in a variety of
attachment systems, and
compounded for long
lasting durability and
watertight integrity for
years of roof life.
Thermoset membranes are
compounded from rubber
polymers. The most
commonly used polymer is
EPDM (often referred to
as "rubber roofing").
Thermoset membranes make
successful roofing
materials because they
can withstand the
potentially damaging
effects of sunlight and
most common chemicals
generally found on
roofs. The easiest way
to identify a thermoset
membrane is by its
seams, it requires the
use of adhesive, either
liquid or tape, to form
a watertight seal at the
overlaps. Thermoplastic
membranes are based on
plastic polymers. The
most common
thermoplastic is PVC
(polyvinyl chloride)
which has been made
flexible through the
inclusion of certain
ingredients called
plasticizers.
Thermoplastic membranes
are identified by seams
that are formed using
either heat or chemical
welding. These seams are
as strong or stronger
than the membrane
itself. Most
thermoplastic membranes
are manufactured to
include a reinforcement
layer, usually polyester
or fiberglass, which
provides increased
strength and dimensional
stability. Modified
bitumen membranes are
hybrids that incorporate
the high tech
formulation and
prefabrication
advantages of single-ply
with some of the
traditional installation
techniques used in
built-up roofing. These
materials are
factory-fabricated
layers of asphalt,
"modified" using a
rubber or plastic
ingredient for increased
flexibility, and
combined with
reinforcement for added
strength and stability.
There are two primary
modifiers used today:
aPP (atactic
polypropylene) and SBS
(styrene butadiene
styrene). The type of
modifier used may
determine the method of
sheet installation. Some
are mopped down using
hot asphalt and some use
torches to melt the
asphalt so that it flows
onto the substrate. The
seams are sealed by the
same technique.
Are You at Risk?
If you
aren't sure whether your
house is at risk from
natural disasters, check
with your local fire
marshall, building
official, city engineer,
or planning and zoning
administrator. They can
tell you whether you are
in a hazard area. Also,
they usually can tell
you how to protect
yourself and your house
and property from
damage. Protection can
involve a variety of
changes to your house
and property, changes
that can vary in
complexity and cost. You
may be able to make some
types of changes
yourself. But
complicated or
large-scale changes and
those that affect the
structure of your house
or its electrical wiring
and plumbing should be
carried out only by a
professional contractor
licensed to work in your
state, county, or city.
One example is fire
protection, by replacing
flammable roofing
materials with
fire-resistant
materials. This is
something that most
homeowners would
probably hire a
contractor to do.
Replacing Your Roof
The age of
your roof is usually the
major factor in determining
when to replace it. Most
roofs last many years if
properly installed and often
can be repaired rather than
replaced. An isolated leak
usually can be repaired. The
average life expectancy of a
typical residential roof is
15 to 20 years. Water damage
to a home’s interior or
overhangs is commonly caused
by leaks from a single
weathered portion of the
roof, poorly installed
flashing, or from around
chimneys and skylights.
These problems do not
necessarily mean you need a
new roof.
Fire-Resistant Materials
Some
roofing materials,
including asphalt
shingles and especially
wood shakes, are less
resistant to fire than
others. When wildfires
and brush fires spread
to houses, it is often
because burning
branches, leaves, and
other debris buoyed by
the heated air and
carried by the wind fall
on roofs. If the roof of
your house is covered
with wood or asphalt
shingles, you should
consider replacing them
with fire-resistant
materials. You can
replace your existing
roofing materials with
slate, terra cotta or
other types of tile, or
standing-seam metal
roofing. Replacing
roofing materials is
difficult and dangerous
work. Unless you are
skilled in roofing and
have all the necessary
tools and equipment, you
will probably want to
hire a roofing
contractor to do the
work. Also a roofing
contractor can advise
you on the relative
advantages and
disadvantages of various
fire-resistant roofing
materials.
Hiring a Licensed Contractor
One of the
best ways to select a
roofing contractor is to ask
friends or relatives for
recommendations. You may
also contact a professional
roofers association for
referrals. Professional
associations have stringent
guidelines for their members
to follow. The roofers
association in your area
will provide you with a list
of available contractors.
Follow these guidlines when
selecting a contractor...
- Get three
references and review past
work
- Get at
least three bids.
- Get a
written contract and don’t
sign anything until you
completely understand the
terms.
- Pay 10
percent down or $1,000
whichever is less.
- Don’t let
payments get ahead of the
work.
- Don’t pay
cash.
- Don’t
make final payment until
you’re satisfied with the
job.
- Don’t
rush into repairs or be
pressured into making an
immediate decision
You’ve Chosen the
Contractor... What About the
Contract?
Make sure
everything is in writing.
The contract is one of the
best ways to prevent
problems before you begin.
The contract protects you
and the contractor by
including everything you
have both agreed upon. Get
all promises in writing and
spell out exactly what the
contractor will and will not
do.
...and Permits?
Your contract
should call for all work to
be performed in accordance
with all applicable building
codes. The building codes
set minimum safety standards
for construction. Generally,
a building permit is require
whenever structural work is
involved. The contractor
should obtain all necessary
building permits. If this is
not specified in the
contract, you may be held
legally responsible for
failure to obtain the
required permit. The
building department will
inspect your roof when the
project has reached a
certain stage and again whe
the roof is completed.
...and
Insurance?
Make sure the
contractor carries worker’s
compensation insurance and
general liability insurance
in case of accidents on the
job. Ask to have copies of
these policies for your job
file. You should protect
yourself from mechanics’
lien against your home in
the event the contractor
does no pay subcontractors
or material suppliers. You
may be able to protect
yourself by having a release
of lien clause in your
contract. A release of lien
clause requires the
contractor, subcontractors
and suppliers to furnish a
certificate of waiver of
lien. If you are financing
your project, the bank or
lending institution may
require that the contractor,
subcontractors and suppliers
verify that they have been
paid, before releasing funds
for subsequent phases of the
project. A leaky roof can
damage ceilings, walls, and
furnishings. To protect
buildings and their contents
from water damage, roofers
repair and install roofs
made of tar or asphalt and
gravel; rubber or
thermoplastic; metal; or
shingles made of asphalt,
slate, fiberglass, wood,
tile, or other material.
Roofers also may waterproof
foundation walls and floors.
Keep these
points in mind if you plan
to have your existing
roofing materials replaced:
- Tile,
metal, and slate are
more expensive roofing
materials, but if you
need to replace your
roofing anyway, it may
be worthwhile to pay a
little more for the
added protection these
materials provide.
- Slate
and tile can be much
heavier than asphalt
shingles or wood
shingles. If you are
considering switching to
one of these heavier
coverings, your roofing
contractor should
determine whether the
framing of your roof is
strong enough to support
them.
- If
you live in an area
where snow loads are a
problem, consider
switching to a modern
standing-seam metal
roof, which will usually
shed snow efficiently.
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