When hiring a contractor to install a new roof, take time to research the proper ways to install a roof, the best materials to use and the typical length of time and cost to do the job. (David Paul Morris/Bloomberg)

The high prices of many home improvement jobs are often tempered by the rewards they provide.

A room addition or finished basement provides more living space. A new kitchen may inspire you to cook and entertain. New carpet, flooring, furniture or a new coat of paint improves aesthetics. But unless you’ve let the old one deteriorate to the point where you have buckets strewn about the house, a new roof won’t make your life seem better.

Your wallet, however, will feel the difference. Roofing work is expensive, and, unless you purchase carefully, you may spend thousands of more-than-necessary dollars to get less-than-satisfactory results.

In our evaluations of area roofing companies, the nonprofit consumer group Washington Consumers’ Checkbook and Checkbook.org found big company-to-company differences in customer satisfaction. In our surveys of area homeowners, several of the companies Checkbook evaluated were rated “superior” overall by 90 percent or more of their surveyed customers. On the other hand, substantial numbers of some outfits’ customers regretted their choices: Several companies received favorable ratings from fewer than half of their surveyed customers.

Checkbook’s undercover shoppers also found huge price differences when they asked companies to bid on several different, carefully specified reroofing jobs. For one project, prices ranged from $10,720 to $18,690 — a difference of nearly $8,000. For another job, quotes ranged from $4,502 to $8,335 — a difference of more than $3,500. For the third, prices ranged from $12,600 to $19,752 — a difference of more than $7,000.

Although for each job the highest quote was thousands of dollars higher than the lowest quote, Checkbook found no price-quality relationship for roofing work, as highly rated companies were just as likely to quote low prices as companies that earned low marks for work quality.

Here are Checkbook’s rules for finding a reliable roofer:

  • To identify top outfits, use Checkbook’s ratings of local roofing contractors. For the next month, Checkbook is offering free access to its ratings of area roofers to The Washington Post readers via this link: Checkbook.org/washingtonpost/roofers.
  • Get several bids for your job. There is no hard-and-fast rule on how many bids to get, but, in general, the larger the job the more bids you should get. If there are large differences between the first two or three bids, you should seek more. And get more bids when labor — not materials — constitutes a large part of the cost. All contractors pay roughly the same amount for materials, but hourly labor rates and productivity may vary substantially.
  • If you can’t be present during the estimate, email your specifications in advance. Use estimators as your consultants, getting feedback from them to determine what needs to be done. Then go back to them with the final description of what you want and invite them to bid on the work.
  • Before deciding on any contractor, ask for proof that it is licensed and carries liability and workers’ compensation insurance.
  • Get a copy of the warranty from the manufacturer of whatever roofing materials are used. Also get a warranty on the roofer’s work, ideally for five years or more; have the roofer write into your contract: “In addition to all other warranties, if roof leaks within five years [or, better still, 10 years], except as a result of accidental damage, contractor will bear the cost of labor and materials to eliminate all leaks.”
  • Get a fixed-price contract. Specify exactly what roof areas are to be covered and other details, such as whether old shingles are to be removed, whether flashings are to be replaced, who is responsible for cleaning up and hauling away debris, and exactly what types and weights of materials are to be used. While you should be able to obtain a binding contract at the estimate price, most roofers will insist on provisions for extra charges if they will find damaged fascia, sheathing, or structural lumber. Most contracts state that required carpentry will be performed on a “per-foot” or “time-and-materials” basis. Make sure your contract states how charges will be computed, typically per-square-foot or per-linear-foot.
  • Avoid roofers that require big upfront payments. A 10 percent deposit to secure a spot on a company’s schedule is reasonable, but beware the home improvement scammers who demand a large deposit to buy materials. Reputable contractors have credit accounts with their suppliers that grant them at least 30 days to pay.
  • Arrange to pay for all or almost all of the job after the work is complete. Most roofers allow customers to withhold all payments until the job is complete. Try to arrange to withhold at least a portion of the price until your roof has been tested by stormy weather.
  • Report problems immediately. If you can’t arrive at a satisfactory resolution with the company, file a complaint with your state’s contractors licensing board.

Kevin Brasler is executive editor for Washington Consumers’ Checkbook and Checkbook.org. Washington Consumers’ Checkbook magazine and Checkbook.org is a nonprofit organization with a mission to help consumers get the best service and lowest prices. Checkbook is supported by consumers and takes no money from the service providers we evaluate. See ratings of area roofers free of charge until Aug. 10 at www.checkbook.org/washingtonpost/roofers.