A Beginner’s Guide to Roofs and Roofing Materials

If you've ever been camping and tried to keep yourself and your stuff dry during a downpour, you can appreciate the job done by your home's roof and roofing materials. Water is insidious. It can creep around surfaces like a spider and find its way into any opening. It also soaks through all but the most impervious materials (unlike that "waterproof" tarp you brought on your camping trip).

Roofing materials are the first line of defense against water as well as wind, snow, ice, and hail, but they don't do their job alone. They're supported by underlying layers and lots of metal flashing, rubber boots, and caulks and sealants, all of which make up the weather-resistant lid we call a roof. In addition, there are critical air vents that help keep your roof — and to some degree, your home — healthy.

The downside of roofs is that they don't last forever, and they're painfully expensive to replace, as you probably already know if you're currently in the market for a new one. Choosing the best materials for your home and budget requires some research and careful decision-making, but this is always time well spent, especially when you consider how much money will be spent. Understanding the basics of roof systems and what makes a good roofing material goes a long way toward making the right decisions, including your choice of a roofing contractor.

A roof is made up of three primary layers: the structural deck, the underlayment, and the roofing material. The deck, also called decking or sheathing, was traditionally made from planks of solid lumber, but around the middle of the 20th century, builders quickly transitioned to plywood or OSB (oriented strandboard) sheets, although some roofing materials (slate, wood shingles, tile) still use lumber planks that are gapped at specific intervals (called skip sheathing) to promote airflow. The type of roof decking you have isn't terribly important, but the health of it is. Roof decking must be flat, rigid, and free of damage and rot to provide a solid foundation for the roofing material.

Roof underlayment covers the decking and acts as a secondary wind and moisture barrier — essentially a backup for the roofing material. Until recently, most roofs had tar paper (also known as roofing felt) underlayment, but various synthetic materials made of woven plastic fibers have become increasingly standard. Synthetic underlayments are generally more durable and lightweight and are easier to work with than roofing felt. Underlayment is installed in an overlapping pattern, much like roof shingles, to help shed any moisture that gets through the roofing material.

The roofing material is the tough, weather-resistant, and preferably attractive stuff that's exposed to the sky. It's designed for 10 to 50 or more years of trouble-free service and has a price tag to match. Roofing is generally a get-what-you-pay-for product, but there are plenty of options in the middle price range that offer the typical homeowner a good value. For those who demand nothing but the best, there's always natural slate, real clay tile, and even copper roofing, all of which can potentially last a century or more.

Finally, there are vents and flashing. Roof vents provide airflow to the attic space to help reduce moisture and lower temperatures year-round. In summer, a hot attic increases your air conditioning bill; in winter, a roof that's warmed by the house melts rooftop snow and leads to ice dams. Roofs typically stay ventilated with a combination of soffit vents (for air intake) and roof or ridge vents (for air exhaust).

Flashing is a general term for various metal strips, channels, L-shaped pieces, and other fittings as well as rubber boots that slip over plumbing pipes. Flashing is used to create a weather-tight joint anywhere the roof meets another material or element, such as a house wall, a chimney, gutters, vent pipes, or skylights. You might think that a big, thick bead of caulk would adequately seal such junctures, and indeed it might for a while, but flashing is far more reliable and long-lasting than a smear of synthetic goo.

The two biggest enemies of roofs are time and acts of nature, which helps explain why few homeowners escape roof replacement forever. Time translates to wear and tear and the gradually ravaging effects of sunlight, rain, snow, wind, debris, moss, critters, basketballs, and even foot traffic. Acts of nature are much swifter and more devastating: large hail, high winds, and falling trees or tree limbs. Roofs can also be destroyed by fire, of course, and most roofing materials carry a fire rating, but this is more about not catching on fire (from flying embers, etc.) than about surviving a house fire.

As roofs age, they lose their protective coatings (such as minerals on asphalt shingles) and become weaker and more vulnerable to damage. Eventually, they become a liability and must be replaced to maintain the integrity of the home and to prevent expensive problems, like water leaks. If a roof's life is cut short, it's usually due to storm damage, most commonly hail or high winds. This is why most roofing materials carry ratings for impact resistance and wind resistance.

There's good news, and there's bad news. The good news is that the roofing industry is constantly coming up with new and better materials that outperform (and sometimes look better than) their predecessors. The bad news is that roofs will always be expensive. Even a basic 15-year asphalt shingle roof costs about $6,000 for an average-size house. Prices can go up significantly from there. The best advice for dealing with the cost of new roofing is to save your sticker shock until you see what's out there, keeping in mind that the cheapest roof often isn't the least expensive in the long run.

Back to the good news of product innovation and advancement, here's a quick rundown of the most common options:

• ​Asphalt:​ Still the most common type of roofing in North America, asphalt (also known as composition) shingles come in standard (low-cost) three-tab styles as well as various grades of thicker, more deeply textured architectural, or dimensional, versions.
  
• ​Composite/synthetic:​ This new kid on the block is a high-quality shingle that often mimics other materials, like slate or wood, and boasts impressive performance ratings, typically with a high price tag to match.
  
• ​Metal:​ From classic standing seam panels to stone or wood lookalike shingles, metal roofing options have expanded in both products and popularity. Metal is generally a strong performer and can be a very good value, but it's certainly not a budget option.
  
• ​Wood:​ Traditional, beautiful, and natural, wood shingles and shakes offer indisputably good looks, and that's the primary reason for using them. Other types of roofing in the same price range (particularly metal) outperform wood in durability, impact resistance, wind resistance, and fire resistance.
  
• ​Slate:​ While it's obligatory to include natural slate on any roofing materials list, very few homes actually have it, but its appearance is nothing short of stunning, and its longevity is deservingly legendary. It's also quite expensive and so heavy that it requires a stronger-than-normal roof structure.
  
• ​Clay and concrete:​ Like slate, traditional clay roof tiles are beautiful, long-lived, and heavy, but they're not as rarified as slate. Tiles are actually quite common in the sunbaked regions of the United States and many other parts of the world. Concrete tiles and shingles can mimic clay, slate, and wood and offer similar longevity at a lower cost and in some cases, lower weight. Some types are fragile and are not suited to all climates.

For almost all homeowners, including handy ones, replacing a roof is not a DIY enterprise. It's hot, backbreaking, specialized work on a surface that slopes toward a potentially deadly drop-off. It also needs to happen quickly and in favorable weather, so it's not a good project for beginners to take their time cutting their teeth. On top of all that, many roofs are paid for by insurance claims, and insurers may require that the work is done by a licensed professional (i.e., not you).

So, how do you find that qualified professional? Ask friends, neighbors, community chat boards, etc. Personal referrals are still the best sources for finding good contractors. You can also check reviews of local contractors on referral sites like Angi.com. Use only local companies with a good record of quality work and service; do not use out-of-town companies or, even worse, itinerant roofers who breezed into town on the tailwinds of the latest storm. Any roofer you consider must be licensed (if required in your area) and fully insured.

When interviewing past customers, focus on finding a roofer who executes; that is, he starts early and finishes late each day and knocks out the project in a matter of two or three days (depending on the size of the project and the roofing material). The roofer also needs to take care of the loose ends in a timely manner. It's nice to have the bulk of the shingles replaced efficiently; it's not so nice when you have to wait weeks for the roofer's B crew to come back and finish the gutters or some flashing.

Speaking of gutters, here's a tip you won't find in many places: If you're having your gutters replaced along with the roof, ask the roofer about his gutter contractor, who will likely be a subcontractor. Gutters are important and must be hung skillfully. You don't want some cut-rate hack who shows up in an unmarked truck and is clearly there because he's saving your roofer money. It happens.

Your roofing project must include a detailed contract with everything in writing: cost breakdown, materials (including specific roofing product), installation details, damage liability, warranty, start and completion dates (approximate), and payment schedule. For more guidance on selecting a roofer and roofing material, visit the consumer website of the National Roofing Contractors Association.

With most roofing materials, a roof replacement is a "wham bam thank you ma'am" affair. Roofers start at the crack of dawn and work until sundown while your house is filled with the sounds of hammer blows, staple-gun chatter, and a blaring boom box that, given the general cacophony, fails to entertain anyone. The fun starts with the tear-off — removing the old roofing, underlayment, and flashing to get down to the bare roof deck. Next comes a speedy inspection and repair or replacement of rotted, weakened, or otherwise damaged roof decking. If roof vents will be added, the holes for the vents are then cut into the decking.

Underlayment comes next along with drip edge (metal flashing installed along the roof edges; not used with all roofing types) and valley flashing (as applicable). Then, it's time for the shingles or other roofing material. Along with the roofing, the crew interweaves step flashing where the roofing meets walls, chimneys, skylights, and other vertical features as well as boots for plumbing pipes and furnace and water heater vents.

New gutters go on last after the roofers are gone. Gutter replacement may include repairing or replacing some of the fascia — the wide trim boards running horizontally along the roof eaves. The gutters install over the fascia, and all that close contact with water and even the weight of the gutters is hard on the trim boards, often resulting in rotted areas and open joints. It's best to replace it now (including painting it) before the gutters are hung. This may delay the job for a few days, but healthy, attractive gutters (and fascia) are key to a finished look and a properly functioning roof.