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In Mark Twain's classic "The Adventures of Tom Sawyer," Tom tricks his friends into painting his aunt's fence. You probably won't get that lucky, but there are good reasons many homeowners keep their painting in-house. No building codes apply to interior decoration; if you do something dumb, you don't risk life and property as you would if you were, say, tackling a rewiring job; and because labor typically accounts for 80 to 85 percent of the price of a paint job, you'll save a ton by doing the work yourself.

If you choose to hire a professional instead, use Checkbook's ratings of local contractors. For the next month, Checkbook is offering free access to its ratings of local painters to Washington Post readers at checkbook.org/washingtonpost/painters.

Should you go with a pro or no? Before taking the painting plunge, consider the following:

Inside or outside? Inside, there are solid floors, reachable ceilings and uniformly bright working light. Outside, uneven ground makes it difficult to set ladders and reach roof overhangs. Nature isn't your friend here, either: Dew can cause paint-adhesion problems, and rain can ruin still-wet paint.

One room or the whole house? Applying one coat in one room is a reasonable DIY Saturday project (especially if you have help and beer). Multiply the time spent moving furniture, prepping walls and sanding old trim by the number of rooms in the house, and you might want to hire real help. It's the same outside. You can probably tackle one shady garage wall that needs a little scraping and sanding plus a coat of paint, but covering all surfaces of the house is usually best left to a pro.

One or two stories? Painting one story may be within the scope of an ambitious homeowner. Two stories means extension ladders and scaffolding — probably contractor territory.

New work or repair? If a remodeling contractor leaves smoothly finished drywall, prep work is eliminated, and the painting can begin. Where walls or siding need a lot of scraping, spackling and sanding, the same-size project can take twice as long.

Same color or stark change? Repainting with a similar color rarely requires more than spot priming and one finish coat. Dramatically changing the color usually requires at least two coats, doubling the painting work.

Mostly walls or woodwork? A roller makes quick work of unobstructed walls. Rooms with wide baseboards, elaborate window casings and cornice molding at the ceiling demand more time and effort. A lot of trim means a lot of brushwork — even more so if the job includes cabinets and shelves — and edges into the realm of professionals.

First-rate or second-best? Take a look at painting projects you've tackled in the past. Is the trim as smooth as you would like it to be for the new project? Are the walls uniform and free of lap marks? If you want results that may be difficult and time-consuming to achieve by yourself, hire a good contractor.

House built before the 1978 lead paint ban? If so, you'll probably want a lead-paint-certified pro to properly seal off rooms and do required testing and cleanup to minimize exposure. (These may sound like expensive tasks, but they're usually not.)

If you decide to hire help, have several contractors inspect the job and provide proposals. You'll probably find huge price differences for the same job. A Checkbook undercover shopper got quotes from nine Washington-area contractors to repaint the walls, ceiling and trim for a living room, dining room, family room, bathroom and kitchen. Including paint and supplies, prices ranged from $2,650 or less to more than $6,500.

Don't assume that low prices signify lousy work: Checkbook finds that companies that perform top-quality work are just as likely to quote low prices as companies that do shoddy jobs.

Ask companies to include all details in writing. Although that sounds simple enough, too many contractors submit offers such as "paint house for $5,000." A friendly contractor may offer a reassuring handshake and promise that the crew will take care of all the details — starting on time, working every day, cleaning up, etc. That's great, but why not include each point in the proposal? If it's a challenge to get a written description of labor, materials and other details, things will probably get worse when the work starts.

Good contracts include descriptions of prep work and repairs; paint specs by brand name, type, color and product number; the number of coats; and a full description of the work, including frequently omitted items such as cabinet interiors and shutters. Minimize delays by specifying that, weather permitting, work will be continuous. Get a payment schedule that minimizes the down payment — the more payment you can withhold until the end, the more leverage you'll have to get the job done well and per your specifications. Insist that contractors provide proof that they carry both general liability and workers' compensation coverage.

Specify whether the contractor or you will supply the paint. Check Consumer Reports' paint ratings: In its tests, some relatively inexpensive paints performed better than more expensive paints and cost $10 to $20 less per gallon. But keep in mind that most paints will resist cracking, peeling, mold and mildew. Who does the painting — and how well they do it — is more important than what's in the bucket.

Before work starts, do your part by clearing the area. It's okay to ask workers for help moving a large bookcase, but first pack up all the books — and all your knickknacks in the room. Move cars from the garage, driveway or in front of the house so the painter can park a van full of supplies near the house.

Once work begins, hold brief daily meetings to discuss the job and schedule and quash any misunderstandings. If there are surprises, seek middle ground. No contract can anticipate every possibility. Materials may be unavailable. Large chunks of rotten siding may crumble along with the old paint. Exterior jobs may be stopped cold by a week of steady rain. But know that you'll pay extra if you change your mind about a color after the trim is already painted or otherwise add tasks to the project.

The nonprofit Washington Consumers' Checkbook magazine and Checkbook.org help consumers get the best service and lowest prices. We are supported by consumers and take no money from the service providers we evaluate. See ratings of Washington-area painters free of charge until Sept. 30 at checkbook.org/washingtonpost/painters .