Reroofing Over Asphalt Shingles – HomeAdvisor

Reroofing Over Asphalt Shingles

As a roofing contractor doing business in my hometown for more than 20years, I consider it my obligation to give customers the best value for theirmoney. When their asphalt shingle roof has reached the end of its life, mostpeople assume their only option is to strip the roof to bare sheathing before anew roof can be applied. But unless the sheathing is extensively damaged or thestructure can't support the weight of another layer of roofing, a bettersolution is to apply a new layer of shingles right over the old one. Donecorrectly, a reroof job will look as good and last as long as a "new" roof, fora lot less money and a lot less hassle.

Advantages of Reroofing Most building codes allow two layers of organic or fiberglass asphaltshingles on roofs with a 4/12 pitch or less, and three layers on steeper roofs.If the structure can support the added weight, a typical 20-square(2,000-square-foot) reroof will cost at least $1,000 less than a tear-off job.Labor savings go beyond demolition: Not having to lay down felt paper saves $10a square; and site and weather protection, as well as cleanup, are all reducedif not eliminated.

Disposal costs are lower, too, because we don't have to rent a dumpsterand we save the $65-per-ton dump fees. We also save by not having to separatethe recyclables. Here in central New York, asphalt, cardboard, and wood allhave to be tossed into different containers, and in some cases hauled todifferent transfer stations. The same is true of flashing, drip edge, tarbuckets, vents, and other scrap metal.

Less liability. As a contractor in ahighly competitive business, I can't claim that a reroof is a lot moreprofitable than a tear-off job, but I can say that it's much less risky.There is no chance of a dumpster carving up the lawn or scarring the driveway;there is less risk of property damage from falling debris or from nails thatfind their way into homeowners' car tires. And because bare sheathing isnever exposed to the elements, there is much less chance of weather damage orof an employee being injured while scrambling around in the rain trying to getan exposed roof under cover.

Equal quality. All shinglemanufacturers honor the warranty, whether their products are used for a reroofor a new roof. If the job is done correctly, with the new layer of shingleslaid flat over the existing shingles, the old roof cushions the new one andserves as a secondary barrier should wind or water ever break through the newshingles.

Evaluating the Job Because my company does both tear-off and reroof work, I evaluate eachjob to determine which procedure is best. Whenever I'm called to give aroofing estimate, I always ask the callers to tell me why they think they needa new roof. Have they noticed leaks and stains, or is it simply because theirneighbors are replacing their roofs? I also ask about the age and apparentcondition of the roof. If the roof is, say, eight years old, it probably justneeds a repair. If it's 15 years old and they've noticed loosegranules washing off the shingles or running out of the downspouts, it's areroof candidate. When they tell me what neighborhood they're in, I canalso make a good guess about how many layers of shingles are already on theroof.

When I arrive to inspect the site, the first thing I look at is not the roofbut the condition of the house and the quality of any recent work that mighthave been done to it. We do high quality work and we charge more than theaverage fly-by-nighter. If a house looks like no one cares, I want to find outwhat kind of work the owners are looking for before I invest a lot of mytime.

I always walk the roof. A contractor who only does tear-off work can figurea job standing on the ground with a tape measure and a pair of binoculars. Notme. I can't be sure that reroofing will work until I've thoroughlyinspected every inch of the roof. Sometimes it's an easy decision: If Ipeel the shingles back from the rake edge and count three or more layers, andif most of the shingles are badly curled, the permanent step flashing is badlydeteriorated, or the deck feels soft and spongy wherever I step, it needs atear-off.

Even if the structure can support the added weight, the new roof won'tlast unless it's laid flat over smooth shingles, intact flashing, andsound sheathing. Localized problems, like a few missing shingles or one or twosoft spots in the sheathing at the mouth of a valley, for example, oraround pipes or at the bottom of the chimney can be easily repaired, butbeyond that it's more efficient to do a complete tear-off. I also rule outreroofing if a careless prior reshingling has left the roof with a washboardsurface.

If reroofing is warranted, I measure the existing shingles to determinewhether they're standard (12x36 inches) or metric (13x39 inches). The newshingles must be the same size as the old ones or installation will be anightmare. While I'm on the roof, I also measure the exposure of theexisting shingle courses and eyeball their horizontal straightness. If the oldroofing is extremely wavy or if the exposure varies more than 1/4 inch from thestandard 5 inches (55/8 inches for metric shingles), I won't be able tofollow the existing lines, so I'll have to allow more labor time forsnapping chalk lines and using gauges to ensure a first-rate job.

Prep Work The best thing about beginning a reroof job is the sound sleep I getthe night before, because I don't have to worry about everything thatcould go wrong between tear-off and dry-in. Even if a freak thunderstorm shouldstrike without warning, there's no need to panic. We just calmly seekshelter until the storm passes, then get right back to work. Any rainwater thatgets between the new surface and the old will evaporate.

The average reroof requires at least two full pallets of shingles, which Ihave delivered a few days before the job starts. For a nominal additionalcharge, some of my suppliers will place the bundles on the roof and scatterthem according to my instructions. When I can't get rooftop delivery, Icoordinate with the homeowners and give my supplier specific instructions aboutwhere to place the load. I don't want the homeowner coming home from workto find 60 bundles of shingles blocking the garage.

I like to use a five-man crew for reroof jobs: a crew chief, two roofingmechanics, one laborer, and one laborer-trainee. While the other guys areunloading, setting up ladders, and stocking the roof, the crew chief will walkthe perimeter of the house looking for anything fragile that might need to bemoved or protected. He'll also be on the lookout for pre-existing damagethat the homeowners might not have noticed. If he finds a loose railing or acracked basement window, he'll let them know about it so we don'ttake the blame later on.

Because we're not doing major demolition, we don't have to takethe elaborate site-protection measures I insist on when we do tear-offs. Wewill, however, lay plywood over air conditioning units and over any flatstepping stones that might get scratched. We've also learned the hard wayto always protect expensive plants with a plywood tent, and to lay sheets ofcardboard under any of our vehicles parked in the driveway to catch oilleaks.

After the roof is stocked, the laborers pry up several layers of capshingles at a time and toss them into plastic trash bins (see Figure 1).

Figure 1. Theroofing crew uses a Red Ripper roofing demolition tool to pry up cap shingles,which are collected in a plastic bin, along with old boot flanges and any looseshingle tabs.

Sometimes they use a standard gardener's "potato fork," but the besttool for the job is a Red Ripper (Integrated Roofing Technologies, 2413Stevenage Dr., Unit 11, Ottawa, Ontario K1G 3W1 800/352-6147). They also pry upand discard the old vent flanges, and start new boot flanges over the tops ofthe pipes. At this point, the prep crew also cuts out and replaces any badsheathing, and fills in any missing shingles with scrap pieces to give the roofa sound, uniform surface. Finally, they'll use a hook blade to cut backthe bottom 2 inches from the third course of existing shingles (12 inches upfrom the drip edge). This will make starter course layout easier.

After the messy work is done and the trash bins have been emptied into theback of the company pickup truck, the roof is swept clean, then drip edge isscattered along the perimeter of the roof and nailed in place. We use a specialdrip edge, called Overhang Drip (model DE6, Caliber Metals, 23500 John GorsuchDr., Clinton Township, MI 48036; 810/465-7650), which is made to fit over theold drip edge and shingles (Figure 2).

We run the metal along the eaves first, then up the rake edges, alwayslapping a higher piece over a lower one for good drainage.

While this is happening, one of the laborers separates the bundles ofshingles into thirds and scatters them on the roof. This puts the shingleswithin easy reach of the shinglers, who won't lose time hunting andreaching for fresh material. The other laborer makes all the precut shingleswe'll need later: inverts, one- and two-tab shingles, and caps. An invertis the 5-inch-wide top half of a full shingle; caps are one-tab shingles withthe top corners tapered to ensure the exposed edges follow a straight line.

by John Curran

This article has been provided by http://www.jlconline.com. JLC-Online is produced by the editors and publishers of The Journal of Light Construction, a monthly magazine serving residential and light-commercial builders, remodelers, designers, and other trade professionals.

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Reroofing Over Asphalt Shingles - HomeAdvisor