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.
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 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.
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.
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.
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.
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
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.
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.
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.