Rooftop Knowledge: All About Asphalt Shingles

The roof -- the home's primary defense against the elements -- is one of the biggest investments a homeowner can make. The majority of residential roofs are covered with asphalt shingles, which are relatively inexpensive and easy to DIY. According to the Asphalt Roofing Manufacturers Association, enough asphalt shingles are produced each year to cover more than 5 million homes. Needless to say, the demand is great.

As we gear up for fall and start thinking more about air-sealing our homes, we decided to weigh the pros and cons of asphalt shingles and give you the lowdown on buying, installing, and maintaining this popular roofing product.

What Are Asphalt Shingles Made Of?
Asphalt shingles are made of tar-like hydrocarbon and speckled with small colored ceramic granules. The mineral granules offer protection from the sun's ultraviolet (UV) light, which deteriorates asphalt over time.

Pros of Asphalt Shingles
The ubiquity of these shingles speaks for itself, but here are some concrete reasons to stick with asphalt:

- Asphalt is the most affordable roofing material. At about $1 to $4 per square foot, asphalt shingles can't be beat in the price department, and that's a major part of their appeal. Other, more upmarket options, like architectural shingles, may run twice the cost of asphalt, while stylish cedar shingles can run six or seven times that amount.

- Asphalt repels water. Made from a combination of tar-like hydrocarbon and crushed stone, sand and gravel, the material is naturally water-repellent.

- Today's asphalt shingles are less susceptible to the growth of moss and mold on your roof than some other roofing materials, like cedar shake roofs.

- Asphalt shingles are relatively simple to install. Even a novice DIYer can save money by taking on the project, which involves putting down an underlayment of felt or fiberglass, laying out the shingles in a staggered pattern and securing the shingles in place with a nail gun. Trimming and capping the shingles is also a pretty easy process. The trickiest part? Installing the flashing -- the strips of metal along the edges of the roof that prevent water from seeping in.

Cons of Asphalt Shingles
No material is perfect, so of course there are a few reasons you may not want to choose asphalt shingles.

- Poorly installed flashing can lead to leaks. Asphalt gets a bad rep for causing roof leaks and dripping water, even though it's water-repellent. Why is this the case? The leak is often connected to poor workmanship in installing the flashing, as mentioned above. "In reality, about 90 percent of all roof leaks have nothing to do with shingles and everything to do with flashing," notes Lou Manfredini, Ace's Home Expert, in Mr. Fix-It Introduces You To Your Home.

- Asphalt shingles account for at least 5% waste when you buy the materials, especially if your roof is not made up of two perfectly sloped rectangular surfaces. If your roof has a few lifts and valleys, you're going to need some extra asphalt shingles.

- Asphalt is not a green building material. It's made from a byproduct of refining crude oil.

- Traditional asphalt shingles are not the most beautiful option out there. Consider architectural shingles if you're looking for a material that has a richer texture and more color options.

- Asphalt shingles will eventually need replacement. By comparison, slate and clay tile roofs can last a lifetime.

Buying Asphalt Shingles
You get what you pay for, so don't be lured into buying the bargain shingles. The cheapest shingles on the market just won't hold up. Often, bigger and heavier is best. Manfredini suggests spending the most you can afford, as higher quality shingles will simply last longer and are less likely to leak. He suggests looking into some of the better brands on the market, including GAF, Tamko, Certainteed, and Elk.

Installing Asphalt Shingles
Opting for asphalt? Keep these tips top of mind:

- Make sure to tear down the old roof first, if you're completely re-roofing.

- Lay down felt paper as an underlayment.

- Install a waterproof membrane just above the gutter -- before you lay the shingles down on the roof -- to help prevent big leaks from ice dams. This membrane goes over the felt or fiberglass underlayment.

- Allow overhang. If you're installing 3-tab asphalt shingles, you'll see the vertical ones from the ground. Allow for a 1" overhang on the sides. Check the alignment of the shingles with the ridge of your roof periodically as you move up so you're sure they're parallel.

- Be careful with the flashing. Metal flashing marks the transition points in your roof, and that's where leaks likely form. You may want to call in a professional or seek out some literature to guide you with flashing.

- Replace the shingles and the foundation. Each time you put a new roof on your house, be sure to lay down new underlayment and a waterproof membrane.

- If you're not DIYing the job, at least supervise it. Make sure a professional contractor doesn't take any shortcuts. Skipping steps in the installation instructions can void the warranty on your shingles.

Replacing Asphalt Shingles
Asphalt shingles will eventually come loose here and there, and you'll need to fix them. Work on a warm day; it's easier to replace the shingles when they're flexible. Use a pry bar to remove any damaged shingles. Then hammer any remaining nails flush with the sheathing. Use roofing cement to patch any holes or tears in the felt underlayment. Click here for full instructions on how to replace an asphalt shingle.

So how will you know when the time has come to replace the roof? An asphalt shingle roof has a lifetime of about 15 years. If your roof is 20 years old, you're probably due for an whole-roof revamp. Some telltale signs of an overdue roof replacement are shingles that curl at the edges and are severely discolored. Also, if the granules on your shingles are worn away, it's time to replace. One more clear sign? When you find yourself putting out pots and pans to protect your floors from leaks!