(Koren Shadmi for The Washington Post)

Wet basement? Thinking about calling a basement waterproofing contractor? Stop.

Many contractors will propose the installation of expensive interior drainage systems — even if you don’t need one — when most moisture problems can be solved through less expensive means. You’re more likely to get good results and save a lot of money by exploring other solutions and hiring a basement waterproofing contractor only if absolutely needed. If your home was built within the past few years, check the builder’s warranty for clauses on seepage.

Most basements get wet when rainwater runs toward the walls of houses from roofs, yards and driveways. So your first step is to force it to run away from your home.

Start by cleaning your gutters, repairing holes, and making sure they slope toward downspouts and have not come loose from the house, allowing water to fall directly from the roof to the ground. Test downspouts to make sure they spill water at least four feet away from the house.

You can extend downspouts for less than $15 each; gutter repairs are more expensive. But these improvements are worth the price, even if they do not fully solve your water problem.

The next step is to inspect the soil around your house and regrade it if necessary. This is a job you can do yourself or by calling in a landscaper. The earth around your house should slope at least one inch per foot going away from your house for about six to eight feet. The grading should consist of fill soil with a clay content of 20 to 30 percent. Don’t use sandy soil or soil containing a lot of organic matter; it will not shed water adequately.

Before adding dirt around your foundation, rake out all old mulch, leaves and ground cover. If they are filled over, they will create a shelf that catches water.

A grading solution obviously has important advantages. It costs little — dirt, after all, is cheap — requires no great skill and should move enough water away from your house to prevent serious harm.

If portions of your yard slope toward your house, you may have to cut a swale to divert water before it reaches the house. A swale is a shallow, U-shaped ditch dug perpendicular to the water flow. Like regrading, it’s a fairly simple job.

Regrading or diverting surface water will solve most basement moisture problems, but it may not always be the best approach. It may cost more than other solutions — for instance, if you have to rebuild an elaborate patio that slants toward your house or if you have to redo extensive landscaping in the problem area. Furthermore, grading is not a sure cure for leakage problems; water may be penetrating your basement from places that originate well away from your house. Finally, sometimes regrading is a relatively frail solution; a little careless digging in your garden may produce a new source of leakage just after you have installed a home theater in your basement.

If regrading and other surface drainage improvements don’t solve the problem, more drastic and expensive solutions await.

For most homes, the next best approach is to waterproof walls from the outside. For this, a trench is dug to the depth of the footings of affected walls. Drainage pipe is installed at the bottom of the trench to collect water that seeps from above and carries it to a part of your yard away from your home or into a drainage pit. The exterior walls are re-parged and a vapor barrier added. The trench is filled with soil that is tamped down, and the surface area is regraded to improve surface drainage.

Excavating and waterproofing from the outside might be more expensive than installing an interior drainage system. But Checkbook’s view is that, unlike interior systems, this will actually solve the underlying problem by diverting water away from walls, rather than simply managing water that enters the home.

If you need to hire a contractor, meet with and obtain proposals from several. Many landscaping companies specialize in drainage work. You can get some insight into a company’s performance by checking the ratings and comments posted by area consumers in the “Basement Waterproofers” and “Landscapers” sections at Checkbook.org. Through a special arrangement with The Washington Post, you can access ratings in these categories free of charge until Feb. 25 at checkbook.org/washingtonpost/wetbasement.

Among basement waterproofing contractors, big differences exist in the quality of advice provided. Checkbook found that different companies may propose drastically different — and in some cases costly and unnecessary — solutions. Don’t let them pressure you into a decision. Avoid companies that use aggressive sales tactics.

Check any contractor’s schedule of payments. A payment schedule that allows you to pay most or all of the cost of a job after completion gives you leverage to make sure it’s completed promptly and neatly. The best arrangement is to hold final payment until after the first heavy rain, when you can find out how well the job holds up.

Compare the guarantees offered by companies that bid on the work. Of course, a guarantee should protect you if the system doesn’t work — but you still have to enforce it. In this field, don’t be too impressed with long guarantees. If a company goes under, its guarantee won’t do you much good — and waterproofing companies go under all the time.

Also, beware of technicalities in guarantees. Some impose an annual fee to keep the guarantee in force, an easy-to-overlook requirement. In addition, warranty coverage of sump pumps varies. Some warranties cover the pump for as long as they cover the underground system — perhaps five years or more; some cover it for a year or less.

Washington Consumers’ Checkbook is a nonprofit organization with a mission to help consumers get the best service and lowest prices. It is supported by consumers and takes no money from the service providers it evaluates. You can access all of Checkbook’s ratings of area basement waterproofers free of charge until Feb. 25 at checkbook.org/washingtonpost/wetbasement.