The Basics of Roofing Replacement

Cost, Materials, and Process

Construction workers on a roof of home

Steven Puetzer / Photographer's Choice RF / Getty Images

Of all major home repairs, installing new roofing is arguably one of the most important. You have many things to consider when replacing a roof, but you never want to let an old roof fail; water can destroy the inside of your home, from the attic insulation down through the painstakingly remodeled kitchen, right on through to the basement family room with a big-screen TV. Fewer home problems can be more disastrous than a failed roof.

Roof replacement is not something to take lightly, nor is it a repair you should delay. It's not too difficult to replace or repair a single shingle, but if one shingle fails, it's a good idea to have your roof inspected to check the rest of its integrity.

You might also need a permit in your state or locality to repair a roof, depending on the size of the area and the type of repairs. A permit may also be required when reroofing. When you sense that your roof is nearing the end of its useful life, brush up on these basics before soliciting bids from roofing contractors.

The Basic Roofing Materials

Your choice of roof replacement options often depends on your locality and your personal taste. For example, metal roofing is a standard selection in some regions due to its fire resistance. In contrast, the predominant home styles in other areas might call for a Spanish-influenced tile tool. Roof pitch (angle) also affects the roofing materials you can use. For example, wood shake shingles can be used for steeper-pitched roofs but are unsuitable for flatter, low-pitched roofs.

The most common choices for residential roofing include: 

  • Asphalt composition shingles:  These are cheap and easily obtainable, but they are less attractive than other options due to their flat appearance. This roofing type is by far the most popular roofing material.
  • Wood shakes or shingles: These are pricey but attractive shingles. They have excellent durability but aren't a good choice in regions with fire danger. 
  • Metal Roofing: Metal roofs made of steel or aluminum have become more prevalent in recent years due to their durability and fireproof durability. These expensive roofs require specialty contractors for installation, but they may be cost-effective over the long run due to their long life. Several types of metal roofing systems are available, including raised-seam panels and products that mimic the look of composite shingles. 
  • Slate roofing: This is a desirable, high-end roofing option, but it is expensive and heavy. Slate roofs are extremely slippery to walk on and difficult to repair when damaged. 
  • Composition slate: These synthetic tiles made from 95 percent recycled materials, including rubber, are gaining popularity. They closely resemble slate and other forms of stone tile but are much lighter and less susceptible to damage.  
  • Clay or ceramic tile: Long the most predominant image in Southern California and Florida, the so-called Spanish-style red tile roof is still common but is being gradually replaced by metal and composite materials that mimic the Spanish tile look. Other roofing materials are now available which meet ceramic tile's fire retardant ability, with much less weight put on the roof. This type of shingle is called the "half-barrel," because it is essentially a cylinder cut in half length-wise, roughly 16 inches long.

According to the National Association of Home Builders, costlier slate, copper, and tile roofs last more than 50 years. Wood shake roofs endure about 30 years, fiber cement shingles have a life of nearly 25 years, and asphalt shingle composition roofs last about 20 years.

Tear off or Second Layer?

It was once common to lay a new shingle roof over the preexisting layer at least once, or sometimes even twice. This roofing practice is no longer allowed in some jurisdictions, where complete tear-off of the previous roofing is now required. Even where layering is allowed, applying a new layer of shingles over the old should be carefully considered based on its pros and cons: 

  • Weight: The main argument against laying additional layers of asphalt shingles is that the roofing materials can get too heavy for the underlying roof framing. Excessive weight can cause structural problems, especially for older houses. A triple layer of asphalt shingles is often equal to a single layer of slate shingles—an exceedingly heavy type of material.
  • Telegraphing: Another problem with shingling over existing shingles is that you essentially repeat some surface irregularities that may already be present. If you're contemplating putting on a new roof, there's probably a good chance that you may have bubbles, bumps, and waves that should be remedied. Putting new shingles over existing problems can leave you with a rather unattractive new roof. One way to minimize this problem is to go over the old roof and correct as many issues as you can before re-roofing. It doesn't take much more than a hammer, some roofing nails, and a handful of shingles to correct bumps, gaps, and protruding nails.
  • Work and waste reduction: The primary advantage of layering is that it reduces the work involved. Stripping off the existing layer and then laying down a new layer adds more work to the process. Time isn't a problem if roofing professionals tackle the job because they can strip most roofs in the morning. But if you're doing the job yourself, it can be a strong argument for roofing over the old roof. 
  • Manufacturer's warranties: Some types of roofs and manufacturers require that roofs under warranty be stripped entirely to comply with the rules and restrictions of the warranty. If the roof is currently under warranty, check what the warranty requires.

Cost Considerations

How much it costs to replace a roof in your state depends on your choice of roofing materials (ranging from cheap three-tab asphalt shingles up to architectural shingles or even slate). The roofing contractor you choose, the pitch (steepness or your roof), and the square footage of your roof are other factors that affect the cost. 

Rock-bottom, a three-tab composite roof for a small home may cost as little as $7,000. Nationally, replacing a typical roof using architectural asphalt shingles costs between $3.50 and $5.50 per square foot—a cost that includes demolition, permit fees, waste disposal, and cleanup. 

Typical average costs of different roofing options: 

  • Three-tab asphalt shingles: $7,000 to $12,000
  • 30-year shingles: $9,000 to $15,000
  • 50-year shingles: $11,000 to $20,000
  • EPDM rubber: $8,000 to $14,000
  • TPO or PVC membrane: $10,000 to $15,000
  • Wood shingles: $14,000 to $25,000
  • Steel shingles: $14,000 to $25,000
  • Aluminum shingles: $15,000 to $28,000
  • Standing-seam steel roofing: $23,000 to $30,000
  • Natural slate: $25,000 to $50,000
  • Concrete tile: $20,000 to $40,000
  • Clay tiles: $25,000 to $50,000

Consider off-Season Roofing Work

A well-coordinated roofing team is an amazing thing to watch, which is why you pay them to do your roofs. While in most parts of the U.S., the optimal roofing season is from late spring to early fall, skilled crews can extend the work season, sometimes even roofing when snow flurries are threatening.

There is no reason, in other words, not to hire a skilled crew to roof your home during off-season periods. You may even enjoy lower prices at these times since the labor demand is low. The trick behind getting your roof job shoehorned into the offseason is having a large team of professional roofers who can knock out the work in hours instead of days, thus taking advantage of dry periods. 

Understand the Roofing Process

You'll be able to make advised decisions when hiring a roofing crew if you understand the steps to replacing a roof, as well as the jargon used in the roofing trade. 

A moderately-sized, professionally-installed roofing job might take only three or four days. The overall process followed by the roofing crew goes like this: 

  1. Remove all existing shingles; deposit them in a roll-off dumpster: Damaged or old valley flashing and drip edging is also removed at this time. A good crew will use tarps to protect foundation plantings and shrubs during tear-off and will use magnetic tools to pick up nails and metal objects from the lawn. 
  2. Make minor repairs on the roof if it is in good condition: If not, replace bad wood with new plywood sheathing or 1 x 6 sheathing boards. Whichever is applicable to your type of roof. 
  3. Install ice dam protection in regions that require it: The ice guard membrane is a synthetic waterproof barrier material designed to prevent melting ice from backing up under the shingles and penetrating through the sheathing, where the moisture can cause severe damage.
  4. Lay down asphalt roofing paper over the roof sheathing: The layer of roofing paper creates an inner barrier against water penetrating into the house. Rows of roofing paper are overlapped as they progress upward toward the peak and are normally tacked or stapled in place. 
  5. Apply metal drip edging around the edge of the roof, both the eave sides and gable sides: The metal drip edge is nailed in place over the roofing paper or ice guard. 
  6. Where necessary, apply a new valley flashing along with areas where two roof planes meet: The valley flashing is typically nailed to the roofing deck and sealed with roofing caulk.
  7. Apply the tab shingles, starting at the eaves and working upward toward the peak: Where roof vents are being installed, tab shingles are installed starting from the bottom, moving upwards.
  8. Apply the flashing around all areas where leaks might come into the house—against the chimney, around skylights and stack vents, etc.: Flashing installation may happen as part of the roofing installation, occurring as the rows of shingles progress upward on the roof deck. 
  9. Install the ridge vent: This continuous vent along the peak of the roof will help the air circulation in the attic space and can be integral in exhausting hot air and preventing winter ice dams. Ridge vents may not be included on older roofs, but installing them is a good idea whenever a house is re-roofed. If ridge vents are not practical, other types of roof or gable vents should be installed to provide air circulation in the attic space. 
  10. Complete the final cleanup and haul the debris away: Have the installation inspected and approved by a building inspector.

The roofing business uses some special terminology when estimating materials for a roofing job. 

  • The term "square," when used in the roofing business, is a unit of area. One square equals 100 square feet.
  • Shingles come in "bundles." Three or four bundles of shingles typically will cover a square of roofing area.