Re-Roofing With Asphalt Shingles

To ensure a watertight job, don’t skimp on the underlayment

by Jim Bennette

I’m a second-generation roofing contractor, a certified installer of most common types of roofing. In this article, I’ll discuss what it takes to apply a guaranteed, watertight asphalt-shingle roof. While basic installation guidelines are printed on every shingle wrapper, there’s a lot more to know if you’re really interested in preventing callbacks. About 80 percent of our asphalt-shingle installations are replacement jobs working directly for the homeowner in which we use laminated “architectural” shingles — by far the most popular roofing choice here in New England.

No Go-Overs
Roofs age differently under different exposures and in different climates, but the roofs we replace are generally between 20 and 30 years old. Although shingling directly over an old roof eliminates the considerable effort and expense of stripping and disposing of the shingles (building codes permit a second layer only), we strongly discourage the practice, for several good reasons.

First, old step flashing can’t be inspected and replaced as needed. Second, adding another layer of shingles piles a lot of extra dead load on the roof structure — a particular concern in the case of older homes whose framing may not be up to snuff (see “Reroofing Over Asphalt Shingles,” Practical Engineering, 2/96). It’s a lot better to stick with what’s worked for that roof over time than to assume it’ll handle the extra weight.

Third, if you don’t strip the roof, you don’t know what you’re walking on. The sheathing may require repair in areas that can’t be reliably detected from the attic. Also, for homeowners looking to spruce the home up for sale, multiple layers of shingles on its roof are sure to prompt a lower assessment of value.

Finally, some roofers argue that a go-over has a shorter service life because the thicker the layer of shingles, the more solar heat is absorbed and held. When I explain these issues to the homeowner, it’s rare that they still insist on going over the old roof.

Tools for stripping. Stripping a go-over is particularly brutal work (yet another reason not to layer shingles). The tried-and-true dedicated shingle stripper, a spadelike tool with serrated teeth and a prying wedge on the underside, is our tool of choice (see Figure 1). We particularly like the Shingle Eater (508/248-7800, shingleeater.com). When stripping, the most comfortable and secure way to work on most slopes is in a seated position, working from the ridge down to the eaves. Two or three workers can typically clear a four-square area in about an hour.

Figure 1. Stripping the roof down to the sheathing exposes any hidden problems and provides the best conditions for reinstallation (top). The author strongly advises renailing afterward because stripping shingles can loosen sheathing nails. Workers carry a hammer along with the nail gun to whack down stray heads (bottom).

It’s important to protect foundation plantings and the face of the building from falling debris. We cover shrubs with tarps tacked up under the roof overhangs and keep one worker on the ground continually cleaning up and loading the truck. Tarps don’t last long around these loads. I like to recycle those big lift wraps from the lumberyard that are otherwise tossed in the dumpster. They’re almost as tough as standard poly tarps, and some of them will last through several jobs. But even if we get only one use out them, they’ll have done double-duty and saved me a little dough.

We generate a lot of disposable debris. As often as possible, I truck old asphalt shingles to a regional depot that charges $90 per ton and sends the material to be recycled into asphalt roadbed.

We strip only as much as we can cover again with underlayment that day. To define the strip area, we slit a line through the old shingles with a hook blade, straight up the roof, and tear off up to that line. Sheffield hook blades (516/746-5352, sheffield-tools.com) are by far the best, outlasting every other brand we’ve used by a wide margin. I buy them in bulk at a local lumberyard.

Renail the sheathing. It’s important to renail the roof sheathing before installing underlayment, because the violent action of stripping the roof can easily loosen the original sheathing nails. We use 8-penny galvanized ring-shank nails and hammer the old nail heads back down to prevent nail pops through the roofing. If any of the sheathing is in bad shape, now’s the time to replace it.

Underlayments and Flashing
An asphalt roof is not a waterproof barrier; it’s a durable water-shedding system that must be installed to strict standards in order not to leak. I’ve seen torn and poorly applied felt underlayment shingled over as if it were only a temporary dry-in measure. But properly installed underlayment is the last line of defense against leaks (Figure 2).

  
Figure 2. Carefully installed underlayment is the last best defense against ice dams and wind-driven rain (left). Plastic caps (right) provide superior holding power and prevent the roofing paper from tearing around fasteners. Slopes from 4/12 to 2/12 are covered with self-adhering membrane, which is also run up the rakes to protect the trim. 

Instead of 30-pound felt paper, we like to use CertainTeed’s Roofer’s Select, a fiberglass-reinforced asphalt-impregnated organic felt. It seems to have higher asphalt content than competing products. It goes down easily, resists tearing around fasteners in windy conditions, and provides a better grip underfoot than ordinary felt paper.

Although Roofer’s Select is less absorptive than ordinary felt — which readily absorbs atmospheric moisture, producing wrinkles that interfere with chalk lines and prevent shingles from lying flat — it too can hump up when wetted. As a quick and effective remedy, we dry wrinkled underlayment with a leaf blower that we carry with us as standard equipment. It works like a charm and is also great for clearing out gutters, a routine aspect of our work.

No staples. When it comes to securing the underlayment, I don’t find pneumatic cap tools to be worth the bother or expense. We hand-nail with plastic roofing caps. Since hammer-tackers and staples do more harm than good, they aren’t allowed on our jobs. Staples don’t have the holding power of the caps, and they set the underlayment up for tear-throughs and blowoffs. If an overlooked nail head pops through while we’re installing the underlayment, we pull the nail and repair the breach with a patch, making sure it sheds water. We never leave a hole or a void anywhere in the underlayment.

On slopes from 4/12 to 2/12, we use only self-adhering membranes. Actually, I prefer to treat a 2-in-12 slope as a flat roof and apply an impermeable EPDM membrane — but that’s not comfortable for every budget.

With self-adhering membranes, Grace Ice & Water Shield (617/498-4997, graceconstruction.com) is the one to beat. But it costs twice as much as CertainTeed’s WinterGuard — our standard waterproof membrane — so I use it only on high-budget jobs. I like WinterGuard because it makes a better sealed overlap than other granulated membranes (and I’ve tried them all).

We always install continuous water and ice membrane along eaves to a point 2 feet inside the exterior wall plane (Figure 3). Valleys receive full-length, 36-inch-wide membrane centered on the divide. We run membrane up the rakes, too, covering the top edge of the trim with a 12-inch strip. We also use self-adhering membrane around all penetrations like chimneys and roof vents. At chimneys and dormer cheeks (when accessible), we fold the membrane up the vertical face as a backup to conventional metal step flashing.

  
Figure 3. All shingle bundles are stocked on the roof weather-side up for fumble-free application (top). Self-adhering membrane covers eaves to a point measured horizontally 2 feet inside the exterior walls. Valleys are protected with full-width membrane folded up the center (bottom left). The material is less sticky in cooler temperatures, making solo installation easier (bottom right). 

Self-adhering membranes become exceptionally sticky in the heat of the sun and require careful handling to prevent frustration and wasted material. Never leave the rolls in the sun. Immediately store them in the shade or in the basement if possible, right up until use.

Applying the membrane is a two-person performance. First, cut it to length, roll it out, and position the edge accurately against a chalk line. Then, roll it back halfway along its length, carefully score the backing paper across the roll, and peel it away as you redistribute the roll. Repeat this process from the opposite end, and the membrane will end up right where it belongs.

Step Flashing
You can’t always inspect or predict the condition or quality of existing flashing along dormers and sidewall cheeks (Figure 4). After tearoff, we often find the typical paper-thin aluminum step flashing worn through from a couple of decades of acid rain. Depending on the type of siding and how tightly it was installed, worn-out step flashing can be difficult to replace. In some cases, I have to present the client with a change order to strip and replace the siding and trim before proceeding. Removal is certainly the best case, since it gives us the opportunity to run self-adhering membrane between the roof and the wall before installing new step flashing.

 
Figure 4. This copper step flashing around a cupola is still in good condition 25 years after installation. Thin aluminum flashing is less durable, and in many cases cheek siding must be removed to replace it.

It’s important to note that 5-inch-by- 7-inch aluminum steps aren’t suited to the wider coursing of metric-size shingles, now the prevalent size. However, most suppliers carry appropriately sized step flashing for metric shingles. Custom-bent flashing made of heavier aluminum or copper stock is best, but it can tax the average roofing budget.

We often find aluminum flashing folded around outside dormer corners in a tortured wrap that stands little chance of keeping water out. This is a common leak location. Here, we absolutely have to remove the corner trim and shape a piece of lead around the corner transition.

Quality Installation
Everyone pitches in to strip the roof, but after that the crew divides tasks. Two experienced roofers handle the shingle installation while the others focus on installing underlayment, stocking the roof with shingles, and keeping the job site cleaned up. It’s a team effort that keeps everyone moving at an efficient pace.

After installing aluminum drip edge on the eaves, we install starter strips both along the eaves and up the rakes (Figure 5). Proprietary starters are available, but we cut our own.

 
 
Figure 5. Aluminum drip edge is nailed over the self-adhering membrane (top left). The starter course is ripped so that the first full course installs at the same attitude as following courses and self-seals. Note the short piece of copper drip intended to mesh with copper valley flashing, preventing a galvanic reaction between dissimilar metals (top right). Rake starters provide a surface for the shingles to seal against (bottom).

Proper starters are about 7 inches wide. If you use a full shingle for a starter, the excess thickness of the first course will force the bottom edge of the second course to lift. This prevents the self-sealer from bonding properly and leaves the bottom edge of the roof vulnerable to blowoffs. Be sure to overhang the shingles beyond the metal drip edge by 1/2 to 3/4 inch; otherwise, water will follow the smooth metal surface and run down behind the gutter — a surefire callback. We always overhang the rake starters by 3/4 inch to help protect the trim.

Snap lines. With tab shingles, which produce a geometric roofing pattern, both horizontal and vertical chalk lines are a must, snapped at strict regular intervals. With laminated — or architectural — shingles, there is no vertical pattern, and we snap horizontal lines less frequently, about every 10 courses (Figure 6). Winding up with a wandering or tapering course against the ridge cap is the kiss of death.

  
Figure 6. Chalk lines are measured against the ridge line to ensure a parallel outcome. Here, the line guides the layout beyond a completed open valley and provides alignment for the opposite slope (left). Shingles are initially nailed high, then secured in the fastening zone to complete the infill (right).

Nails. While four nails per shingle is the minimum acceptable standard, a high-wind application calls for six per shingle. This is the only way we install shingles, regardless of wind considerations. We consider it cheap insurance. As a rule of thumb, it takes about one coil of nails to fasten one bundle of shingles, so we use a coil and a half per bundle.

Nailing by hand would deliver more regular results than using pneumatic nailers, but competition and sanity preclude that option. We deal with the occasional punch-through or angled head by immediately adding a good nail alongside it. Nail heads must be flat and flush with the surface of the shingle to ensure good adhesion of the sealer and prevent pop-throughs. The acceptable nailing area on a shingle is very narrow, only about 2 inches wide or less.

It’s critical to keep the nailing within the prescriptive zone in order to fasten through and secure both layers of a laminated shingle. Nailing higher than this area forces the upper lamination to the deck, distorting the shingle and creating lateral channels that can capture water and introduce leaks. Nailing lower, of course, exposes the nail to the elements. In either case, you need to tear the shingle off and start over. The same rule goes for those nails that happen to coincide with the butt joint between the next course of shingles. Pull the shingle and either replace nails at least 1 inch away from the joint or secure a piece of flashing under the joint.

In coastal areas, premium lifetime shingles are the rule to comply with high-wind requirements. But electroplated galvanized nails are not lifetime nails. I’ve inspected fairly new coastal roofs and found completely rusty nails holding them down — for the time being. Both double-dip galvanized and stainless steel roofing coils are available at an upcharge; they can cost up to three times more than a standard case. But a premium roof deserves a premium nail.

High-wind shingles. Nails alone, however, are no guarantee that the roof won’t fail in a high-wind event. For optimal performance, select a shingle specifically offered by the manufacturer as a high-wind product, with up to a 130-mph rating (Figure 7). These shingles are stiffer, to resist wind uplift.

 
Figure 7. The GAF/Elk laminated shingles installed on this roof are rated for 110-mph winds. Asphalt shingles are available with ratings up to 130 mph.

It’s just as important to make sure that the shingle courses self-seal to each other. In winter installations, self-sealing strips may not be activated until warmer temperatures arrive in the spring. In winter conditions, you may decide to apply roofing adhesive under every shingle. We don’t, and to this date haven’t had any problems. We do apply adhesive along the rake starters to reinforce this vulnerable edge against uplift.

Scuff protection. Warm weather actually presents greater installation obstacles than winter temperatures do. Protecting shingles from damage and shoe scuffs during hot-weather installation takes a little extra care. You can keep the shingles cool by hosing them down — but only installed shingles, never the underlayment. That precaution makes watering the least desired method.

We protect walkways and work areas with rubberized carpet pad or other foam rubber sheeting, which provides good traction on the roof while protecting the granules from smearing. Ordinarily, we use a minimum of roofing brackets and staging planks. On a 10-pitch or lower, we just set a plank at the eaves and work an open roof. In warm weather, though, we stage the entire roof to prevent wear and tear in the loading zones.

Last but not least, we wear sneakers, which are the most comfortable shoes to wear on a roof and the least likely to scuff.

Speed. There are a few roofers who just want to get the job over with as quickly as possible. Speed matters to me, too, but not at the expense of a good installation. Racking — or running the shingles up the roof in vertical columns — is a slightly faster method than cutting “books,” which is starting shingles at one edge of the roof in 6-inch staggers and extending them laterally in a pyramid pattern. Racking is the technique preferred by roofers who get paid by the square rather than by the hour. I pay my crew by the hour. Racking requires you to bend shingles back to nail those fed in underneath from the successive column. But with laminated shingles, this bending can crack the shingles and separate the laminations. Racking can also create an obvious patchwork appearance in the finished roof, since it concentrates shingles from a single bundle in one area. Shingle color typically varies slightly from one bundle to the next, so it’s best to blend shingles from different bundles. Poor color blending is a common complaint and it’s not covered by any warranty.

Valleys. While there are several accepted valley types — including woven, closed-cut, and open — we prefer the method illustrated on Tamko’s bundle wrappers. (Figure 8). It’s by far the fastest but is suitable for use only with laminated shingles, which effectively disguise the distinctive sawtooth pattern it produces.

   
Figure 8. The “Tamko” valley is a fast, watertight, manufacturer-approved method for completing a valley, but it’s best-suited to laminated shingles, where its sawtooth pattern remains inconspicuous. One slope — the shallower, if applicable — is completed first, with its courses running across the valley by at least 12 inches. To outline the valley, whole shingles are then nailed end-to-end along a chalk line. An optional bead of roofing mastic adds insurance against uplift (left). The opposite slope is completed from the valley line back, with square-cut corners toeing the valley line (center). A dab of mastic glues the sawtooth tips to the valley starter (right).

The technique is similar to that for a closed-cut valley, where one slope’s shingles are run across the valley and up the opposite slope by at least 12 inches. The opposite slope’s shingles overlap these and are cut to the valley line. The Tamko valley line is defined by butting whole shingles end-to-end up the divide, preferably along a chalk line. The opposite slope shingles are then started with their square bottom corner toeing the valley line, producing the sawtooth pattern.

Some roofers claim that woven valleys are the best for high-wind installations, but because both slopes must be worked simultaneously, they’re slow to install. Also, the weave is too bulky for thick, laminated shingles and doesn’t work in valleys of unequal pitch.

Shingle ManufacturersOrganic Based  Building Products of Canada Corp.  800/567-2726, bpcan.com CertainTeed Corp.  610/341-7000, certainteed.com Fiberglass Based  GAF-Elk Corp. 973/628-3000, gaf.com IKO  416/781-5545, iko.com Owens Corning  419/248-8000, owenscorning.com  Pacific Coast Building Products  www.pabcoroofing.com RGM Products  559/499-2222, ridglass.com Tamko  800/641-4691, tamko.com

Capping Off
I see lots of capped, vented ridges where the ridge-vent product stops about a foot short of the gable, forcing the cap to taper downward at the ends (Figure 9). It’s a bad look and a misinterpretation of prescriptive ridge-vent installation. For the best appearance, the venting slot should stop short by one foot and be covered by roofing material at gable ends and penetrations (such as chimneys), but the vent material should always run through.

 
Figure 9. Vented ridges look best when the shingle-over material runs all the way to the ends (top). Proper end closures are created by folding a shingle over the ridge opening underneath the vent material. The common method of stopping the vent shy of the end creates a pinched look and draws attention to the ridge (bottom). 

We fold the top course of shingles over the ridge for the first 12 inches at the ends and run the ridge vent full length, followed by cap shingles. The same method should be used at chimneys and cheek walls. Although exposed nails on a roof aren’t generally advisable, they’re unavoidable in the last cap shingle and in apron nailing. We like to use stainless steel box nails along with a dab of roofing cement to hold the shingles in place. The small heads don’t cause rust streaks and are nearly invisible in the roofing.

Jim Bennette owns J Bennette Roofing in Brewster, Mass. 

Preventing Wintertime Floods

Buying a new roof? Get your money’s worth!

Here’s a great resource for homeowners put out by the National Roofing Contractors Association. There’s a lot of great advice for homeowners so we wanted to be sure to highlight it below:

Roof system components

All steep-slope roof systems (i.e., roofs with slopes of 25 percent or more) have five basic components:

1. Roof covering: shingles, tile, slate or metal and underlayment that protect the sheathing from weather.
2. Sheathing: boards or sheet material that are fastened to roof rafters to cover a house or building.
3. Roof structure: rafters and trusses constructed to support the sheathing.
4. Flashing: sheet metal or other material installed into a roof system’s various joints and valleys to prevent water seepage.
5. Drainage: a roof system’s design features, such as shape, slope and layout that affect its ability to shed water.

Choosing a roof system

There are a number of things to consider when selecting a new roof system. Of course, cost and durability head the list, but aesthetics and architectural style are important, too. The right roof system for your home or building is one that balances these five considerations. The following roofing products commonly are used for steep-slope structures.

Asphalt shingles possess an overwhelming share of the U.S. steep-slope roofing market and can be reinforced with organic or fiberglass materials. Although asphalt shingles reinforced with organic felts have been around much longer, fiberglass-reinforced products now dominate the market.

• Organic shingles consist of a cellulose-fiber (i.e., wood) base that is saturated with asphalt and coated with colored mineral granules.
• Fiberglass shingles consist of a fiberglass mat, top-and-bottom layers of asphalt, and mineral granules.

Asphalt shingles’ fire resistances, like most other roofing materials, are categorized by Class A, B or C. Class A signifies the most fire-resistant; Classes B and C denote less fire resistance. Generally, most fiberglass shingles have Class A fire ratings, and most organic shingles have Class C ratings.

A shingle’s reinforcement has little effect on its appearance. Organic and fiberglass products are available in laminated (architectural) grades that offer a textured appearance. Zinc or copper-coated ceramic granules also can be applied to organic or fiberglass products to protect against algae attack, a common problem in warm, humid parts of the United States. Both types of shingles also are available in a variety of colors.

Regardless of their reinforcing type and appearance, asphalt shingles’ physical characteristics vary significantly. When installing asphalt shingles, NRCA recommends use of shingles that comply with American Society for Testing and Materials (ASTM) standards-ASTM D 225 for organic shingles and ASTM D 3462 for fiberglass shingles. These standards govern the composition and physical properties of asphalt shingles; not all asphalt shingles on the market comply with these standards. If a shingle product complies with one of these standards, it is typically noted in the manufacturer’s product literature and on the package wrapper.

Wood shingles and shakes are made from cedar, redwood, southern pine and other woods; their natural look is popular in California, the Northwest and parts of the Midwest. Wood shingles are machinesawn; shakes are handmade and rougher looking. A point to consider: Some local building codes limit the use of wood shingles and shakes because of concerns about fire resistance. Many wood shingles and shakes only have Class C fire ratings or no ratings at all. However, Class A fire ratings are available for certain wood shingle products that incorporate a factory-applied, fire-resistant treatment.

Tile—clay or concrete—is a durable roofing material. Mission and Spanish-style round-topped tiles are used widely in the Southwest and Florida, and flat styles also are available to create French and English looks. Tile is available in a variety of colors and finishes. Tile is heavy. If you are replacing another type of roof system with tile, you will need to verify that the structure can support the load.

Slate is quarried in the United States in Vermont, New York, Pennsylvania and Virginia. It is available in different colors and grades, depending on its origin. Considered virtually indestructible, it is, however, more expensive than other roofing materials. In addition, its application requires special skill and experience. Many old homes, especially in the Northeast, still are protected by this long-lasting roofing material.

Metal, primarily thought of as a low-slope roofing material, has been found to be a roofing alternative for home and building owners with steep-slope roofs. There are two types of metal roofing products: panels and shingles. Numerous metal panel shapes and configurations exist. Metal shingles typically are intended to simulate traditional roof coverings, such as wood shakes, shingles and tile. Apart from metal roofing’s longevity, metal shingles are relatively lightweight, have a greater resistance to adverse weather and can be aesthetically pleasing. Some have Class A fire ratings.

Synthetic roofing products simulate various traditional roof coverings, such as slate and wood shingles and shakes. However, they do not necessarily have the same properties.

Before making a buying decision, NRCA recommends that you look at full-size samples of a proposed product, as well as manufacturers’ brochures. It also is a good idea to visit a building that is roofed with a particular product.

Ventilation and insulation are key

One of the most critical factors in roof system durability is proper ventilation. Without it, heat and moisture build up in an attic area and combine to cause rafters and sheathing to rot, shingles to buckle, and insulation to lose its effectiveness.

Therefore, it is important never to block off sources of roof ventilation, such as louvers, ridge vents or soffit vents, even in winter. Proper attic ventilation will help prevent structural damage caused by moisture, increase roofing material life, reduce energy consumption and enhance the comfort level of the rooms below the attic.

In addition to the free flow of air, insulation plays a key role in proper attic ventilation. An ideal attic has:

• A gap-free layer of insulation on the attic floor to protect the house below from heat gain or loss.
• A vapor retarder under the insulation and next to the ceiling to stop moisture from rising into the attic.
• Enough open, vented spaces to allow air to pass in and out freely.
• A minimum of 1 inch between the insulation and roof sheathing.

The requirements for proper attic ventilation may vary greatly, depending on the part of the United States in which a home or building is located, as well as the structure’s conditions, such as exposure to the sun, shade and atmospheric humidity. Nevertheless, the general ventilation formula is based on the length and width of the attic. NRCA recommends a minimum of 1 square foot of free vent area for each 150 square feet of attic floor—with vents placed proportionately at the eaves (e.g., soffits) and at or near the ridge.

Even roofs have enemies

A roof system’s performance is affected by numerous factors. Knowing about the following will help you make informed roof system buying decisions:

• Sun: Heat and ultraviolet rays cause roofing materials to deteriorate over time. Deterioration can occur faster on the sides facing west or south.
• Rain: When water gets underneath shingles, shakes or other roofing materials, it can work its way to the roof deck and cause the roof structure to rot. Extra moisture encourages mildew and rot elsewhere in a house, including walls, ceilings, insulation and electrical systems.
• Wind: High winds can lift shingles’ edges (or other roofing materials) and force water and debris underneath them. Extremely high winds can cause extensive damage.
• Snow and ice: Melting snow often refreezes at a roof’s overhang where the surface is cooler, forming an ice dam. This blocks proper drainage into the gutter. Water backs up under the shingles (or other roofing materials) and seeps into the interior. During the early melt stages, gutters and downspouts can be the first to fill with ice and be damaged beyond repair or even torn off a house or building.
• Condensation: Condensation can result from the buildup of relatively warm, moisture-laden air. Moisture in a poorly ventilated attic promotes decay of wood sheathing and rafters, possibly destroying a roof structure. Sufficient attic ventilation can be achieved by installing larger or additional vents and will help alleviate problems because the attic air temperature will be closer to the outside air temperature.
• Moss and algae: Moss can grow on moist wood shingles and shakes. Once it grows, moss holds even more moisture to a roof system’s surface, causing rot. In addition, moss roots also can work their way into a wood deck and structure. Algae also grows in damp, shaded areas on wood or asphalt shingle roof systems. Besides creating a black-green stain, algae can retain moisture, causing rot and deterioration. Trees and bushes should be trimmed away from homes and buildings to eliminate damp, shaded areas, and gutters should be kept clean to ensure good drainage.
• Trees and leaves: Tree branches touching a roof will scratch and gouge roofing materials when the branches are blown by the wind. Falling branches from overhanging trees can damage, or even puncture, shingles and other roofing materials. Leaves on a roof system’s surface retain moisture and cause rot, and leaves in the gutters block drainage.
• Missing or torn shingles: The key to a roof system’s effectiveness is complete protection. When shingles are missing or torn off, a roof structure and home or building interior are vulnerable to water damage and rot. The problem is likely to spread-nearby shingles also are ripped easily or blown away. Missing or torn shingles should be replaced as soon as possible.
• Shingle deterioration: When shingles are old and worn out, they curl, split and lose their waterproofing effectiveness. Weakened shingles easily are blown off, torn or lifted by wind gusts. The end result is structural rot and interior damage. A deteriorated roof system only gets worse with time-it should be replaced as soon as possible.
• Flashing deterioration: Many apparent roof leaks really are flashing leaks. Without good, tight flashings around chimneys, vents, skylights and wall/roof junctions, water can enter a home or building and cause damage to walls, ceilings, insulation and electrical systems. Flashings should be checked as part of a biannual roof inspection and gutter cleaning.

Choosing a contractor

Buying a new roof system is an important investment. Before you spend your money, spend time learning how to evaluate roofing contractors. You should insist on working with a professional roofing contractor. NRCA wants to assist you in getting the kind of results you expect—a quality roof system at a fair price. All roofing contractors are not alike, and NRCA recommends that you prequalify roofing contractors to get the job done right the first time. The following guidelines will help you select a professional:

• Check for a permanent place of business, telephone number, tax identification number and, where applicable, a business license.
• Don’t hesitate to ask a roofing contractor for proof of insurance. In fact, insist on seeing copies of his liability coverage and workers’ compensation certificates. (U.S. workers’ compensation laws vary by state. Consult your state’s laws to determine workers’ compensation insurance requirements.) Make sure the coverages are in effect through the duration of the job. Many building and home owners have been dragged into litigation involving uninsured roofing contractors. Also, if a contractor is not properly insured, you may be liable for accidents that occur on your property.
• Check to see if the roofing contractor is properly licensed or bonded. Some states have specific licensing requirements, and others do not. Your state’s Department of Professional Regulation or Licensing Board will have this information.
• Make sure the contractor is financially stable. A professional roofing contractor can provide current financial information about his company.
• Look for a company with a proven track record that offers client references and a list of completed projects. Call these clients to find out whether they were satisfied.
• Insist on a detailed, written proposal and examine it for complete descriptions of the work and specifications, including approximate starting and completion dates and payment procedures.
• Have the contractor list the roofing manufacturers with which his firm is a licensed or approved applicator. Most roof systems require special application expertise to achieve lasting quality.
• Have the contractor explain his project supervision and quality-control procedures. Request the name of the person who will be in charge of your project, how many workers will be required and estimated completion time.
• Call your local Better Business Bureau or Department of Professional Regulation to check for possible complaints filed against the contractor.
• Carefully read and understand any roofing warranties offered, and watch for provisions that would void it.
• Choose a company committed to worker safety and education. Ask the contractor what type of safety training he provides for his workers and what industry education programs they have attended. The best roofing contractor is only as good as the workers who install the roof system.
• Keep a healthy skepticism about the lowest bid. If it sounds too good to be true, it probably is. Many fly-by-night contractors’ below-cost bids seem attractive, but these contractors often are uninsured and perform substandard work. Remember, price is only one of the criteria for selecting a roofing contractor. Professionalism, experience and quality workmanship also should weigh heavily in your decision.

Commonly asked questions

Q: How can a home owner recognize when a roof system has problems?
A: All too often, roof system problems are discovered after leaking or other serious damage occurs. Periodic (twice-a-year) inspections often can uncover cracked, warped or missing shingles; loose seams and deteriorated flashings; excessive surface granules accumulating in the gutters or downspouts; and other visible signs of roof system problems. Indoors, look for cracked paint, discolored plasterboard and peeling wallpaper as signs of damaged roof areas.

Q: What are my options if I decide to reroof?
A: You have two basic options: You can choose a complete replacement of the roof system, involving a tear-off of your existing roof system, or re-cover the existing roof system, involving only the installation of a new roof system. If you’ve already had one re-cover installed on your original roof system, check with a professional roofing contractor. In many instances, building code requirements allow no more than one roof system re-cover before a complete replacement is necessary.

Q: My roof leaks. Do I need to have it replaced completely?
A: Not necessarily. Leaks can result from flashings that have come loose or a section of the roof system being damaged. A complete roof system failure, however, generally is irreversible and a result of improper installation or choice of materials or the roof system installation is inappropriate for the home or building.

Q: Can I do the work myself?
A: Most work should not be done yourself. Professional roofing contractors are trained to safely and efficiently repair or replace roof systems. You can damage your roof system by using improper roofing techniques and severely injure yourself by falling off or through the roof.

Maintenance performed by home and building owners should be confined to inspecting roof systems during the fall and spring to check for cracked or curling shingles and cleaning gutters filled with dead leaves and other debris. If you must inspect your roof system yourself, use a firmly braced or tied-off ladder equipped with rubber safety feet. Wear rubber-soled shoes and stay on the ladder (and off the roof system), if possible.

Q: How long can I expect my roof system to last?
A: Most new roof systems are designed to provide useful service for about 20 years. Some roof system types, such as slate, clay tile and certain metal (e.g., copper) systems, can last longer.

Actual roof system life span is determined by a number of factors, including local climatic and environmental conditions, proper building and roof system design, material quality and suitability, proper application and adequate roof maintenance.

Roofing product manufacturers offer a variety of warranties on their products. Take a close look at those warranties to see what responsibilities and financial obligations manufacturers will assume if their products fail to reach their expected lives.

Q: What will a new roof system cost?
A: The price of a new roof system varies widely, depending on such things as the materials selected, contractor doing the work, home or building, location of the home or building, local labor rates and time of year. To get a good idea of price for your roof system, get three or four proposals from reputable contractors in your area. Keep in mind that price is only one factor, and it must be balanced with the quality of the materials and workmanship.

For each roofing material, there are different grades and corresponding prices. There also are a variety of styles and shapes. You need to look at the full product range and make a choice based on your budget and needs.

Within the roofing profession, there are different levels of expertise and craftsmanship. Insist on a contractor who is committed to quality work.

Q: How can I determine my annual roofing cost?
A: When considering your roofing options, the following formula may help:

Total Cost (Materials and Labor) ÷ Life Expectancy of Roof System (in years) = Annual Roofing Cost

Terms you should know

Deck/sheathing: The surface, usually plywood or oriented strand board (OSB), to which roofing materials are applied.

Dormer: A small structure projecting from a sloped roof, usually with a window.

Drip edge: An L-shaped strip (usually metal) installed along roof edges to allow water run off to drip clear of the deck, eaves and siding.

Eave: The horizontal lower edge of a sloped roof.

Fascia: A flat board, band or face located at a cornice’s outer edge.

Felt/underlayment: A sheet of asphalt-saturated material (often called tar paper) used as a secondary layer of protection for the roof deck.

Fire rating: System for classifying the fire resistances of various materials. Roofing materials are rated Class A, B or C, with Class A materials having the highest resistance to fire originating outside the structure.

Flashing: Pieces of metal used to prevent the seepage of water around any intersection or projection in a roof system, such as vent pipes, chimneys, valleys and joints at vertical walls.

Louvers: Slatted devices installed in a gable or soffit (the underside of eaves) to ventilate the space below a roof deck and equalize air temperature and moisture.

Oriented strand board (OSB): Roof deck panels (4 by 8 feet) made of narrow bits of wood, installed lengthwise and crosswise in layers, and held together with a resin glue. OSB often is used as a substitute for plywood sheets.

Penetrations: Vents, pipes, stacks, chimneys-anything that penetrates a roof deck.

Rafters: The supporting framing to which a roof deck is attached.

Rake: The inclined edge of a roof over a wall.

Ridge: The top edge of two intersecting sloping roof surfaces.

Sheathing: The boards or sheet materials that are fastened to rafters to cover a house or building.

Slope: Measured by rise in inches for each 12 inches of horizontal run: A roof with a 4-in-12 slope rises 4 inches for every foot of horizontal distance.

Square: The common measurement for roof area. One square is 100 square feet (10 by 10 feet).

Truss: Engineered components that supplement rafters in many newer homes and buildings. Trusses are designed for specific applications and cannot be cut or altered.

Valley: The angle formed at the intersection of two sloping roof surfaces.

Vapor retarder: A material designed to restrict the passage of water vapor through a roof system or wall.