How do you fight back when an appraiser — often from another city and working for a small fee on behalf of a big bank — wrecks your sale, purchase or refinancing with a low-ball valuation?

It’s a serious problem in markets across the country. For example:

●Homebuilder John Nolde of Richmond recently found a buyer for a new, green-certified house at $199,500, only to see an out-of-area appraiser cut the value to $169,000, a figure below Nolde’s combined construction and land costs. The low-ball valuation killed the deal.

●Southern Methodist University business school professor William Maxwell had his four-bedroom Dallas home appraised at $790,000 for a refinancing last year, but when he went to sell it this year, the appraisal came in at $730,000. Maxwell said the appraiser, who was not from the immediate area, “had never walked into a single house in this neighborhood” and knew little about local pricing trends. He pulled his house off the market.

●Gary Crabtree, an appraiser in Bakersfield, Calif., sought to sell his mother’s condo this summer for $155,000, a price he says was supported by extensive documentation of recent comparable sales. Within two days he got a full-price offer, but an appraiser assigned by the bank valued the condo at $147,000. When his buyer switched to a second lender, Crabtree says the assigned appraiser “came from 126 miles away.” Since Crabtree knew the appraiser was “geographically incompetent,” he “spoon-fed” the second appraiser the comparables he had found. Voila! The valuation came in at $155,000 and the sale closed in mid-October.

Disagreements over real estate values are nothing new, but agents, builders and sellers say current market conditions, plus recent changes in federal rules that effectively encourage banks to use in-house or affiliated appraisal management companies, are magnifying the problem.

In a recent survey of members, the Massachusetts Association of Realtors found that more than half of agents said sales had been hampered by appraisals that came in low. Polls by the National Association of Realtors also have documented widespread frustration over faulty valuations, and the association ranks them among the major causes of contract cancellations.

So what can you do to lessen the chances that a botched appraisal will torpedo your transaction? Here’s a quick guide.

Be proactive. Federal rules allow you to provide the appraiser your own comps — recently sold properties of similar size, condition and amenity levels in your immediate market area. Your realty agent can help you pull them together before the appraiser arrives. Or for a fee of $200 to $300, you can hire an experienced local appraiser to assist you.

Sara W. Stephens, president-elect of the Appraisal Institute, the largest group in the industry, says, “If you know there are comparable sales in the neighborhood” where the price was affected by a divorce, financial distress or heavy seller concessions to the buyer, “make sure you call the appraiser’s attention to” these factors. And give the appraiser a list of all the value-enhancing upgrades and improvements you’ve made, including dates and costs.

Accompany the appraiser during his or her inspection of the house. Ask questions crucial to competency: Where are you based? How long have you been in the business? What certifications and professional designations do you hold? Are you a member of the local multiple listing service (MLS), an essential trove of data for any accurate appraisal? Do you know local agents or brokers who can supply you with pending sales information and guide you on neighborhood price trends?

If the appraiser doesn’t have good answers, you are much more likely to end up with a poor appraisal. Alert the lender to your concerns as early as possible.

After the appraisal is completed, always ask for a copy to review; it’s your right under federal law. If the value comes in low, check everything in the report, from selection of comps to the accuracy of property measurements. If you find serious mistakes and the appraiser refuses to make corrections, appeal directly to the lender. Most have procedures to follow regarding “reconsiderations of value.” Ask for a second valuation by a locally competent appraiser, even if that costs you more money.

Finally, if the lender stonewalls you and the deal falls apart, consider filing a complaint with your state appraisal board. The boards don’t have the power to rewind your transaction, but they can discipline, fine, suspend or kick bad appraisers out of business.

Ken Harney’s e-mail address is