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ROOFING |
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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.
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...
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:
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© 2006 Hinsperger Inspection Services Ltd |
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