NEW YORK (This Old House) - In the small community of Quincy, Massachusetts, the zoning manual runs nearly 80 pages of single-spaced type and contains upward of 200 separate rules.

That's not unusual: In just about every town, zoning regulations fill a volume as thick as the local phone book. Some deal with the broad land-use ordinances establishing commercial, industrial, and residential zones. Others dictate the size or type of house that can be built on a lot.

But most cover matters of minute detail, from how steep a driveway can be to the number of kitchens a house is permitted to have.

There are good reasons for the vast number and specificity of zoning regulations.

A carefully crafted set of rules can prevent urban sprawl and over-development. It can also maintain the character of a community or ensure that historic homes survive in their original state.

In some cases, zoning regulations are designed to attract new industry, more retail outlets, and a larger tax base. But the welter of zoning rules can easily trip up unsuspecting homeowners.

"More than a few people have been surprised by a zoning law that they didn't know existed," says John Mixon, author of Texas Municipal Zoning Law. "And often that's an expensive surprise."

Claire Edwards learned how expensive zoning violations can be when she fixed up a 1920s cottage in Colleyville, Texas, last year.

At $115,000, the two-bedroom place was a bargain. Edwards immediately invested another $75,000 in improvements, including repairing the porch, updating the kitchen, and remodeling rooms she planned to use as the headquarters for her accounting business.

But just as she was about to advertise her services, she learned that local zoning codes restricted the square footage that she could devote to her business and prohibited her from employing administrative staff at home.

As a result, Edwards scaled back her home office to a small space that she uses for client meetings and was forced to rent a second office for her assistants, at a cost of $1,000 a month -- not to mention the $5,000 she spent to equip it with phones, fax, and computers. "This went from being a really great deal to a financial nightmare," she says.

More commonly, homeowners run afoul of zoning rules when they try to change the look of their house or the way they use the property. Sometimes the illegal alteration is made unintentionally, as when a homeowner erects a too-tall fence (in San Mateo, California, for instance, street-facing fences can be only 3 feet high).

Other times, people may try to hide less visible zoning violations, such as adding an apartment in the basement, by not obtaining the necessary construction permits. Or they may alter an approved project — say, extending an addition a few feet over the setback line, or building boundary — and hope that the town inspector does not notice.

Such moves can be risky because there are any number of ways that local zoning authorities can find out. A neighbor may report the infraction, an assessor could hit on it during a visit to update tax records, or it might be noticed during a routine inspection when the house is sold. But however a disallowed improvement is discovered, it may have to be demolished, and a fine may be imposed every day until the work is completed.

And take note: Even if a previous owner made the change, you bear the consequences if it is discovered after you bought the property. "When you add the cost of the improvement you're losing, the cost of demolition, and the fines, you can easily be out many thousands of dollars," says Edward Ziegler, professor at the University of Denver College of Law.

The only legal way for homeowners to undertake a renovation that breaks with zoning codes is to get a variance, or waiver of the rules. Generally, homeowners can do this by filing an application with the local zoning board, which will set a hearing on the request.

Neighbors will also have to be notified and invited to present their views on the renovation, in writing or at a public meeting. Most of the time homeowners can handle this without the help of their architect or contractor, but they must be prepared to respond persuasively to any challenges to the project. Objections can be raised for a variety of reasons.

Common complaints are that granting the variance will alter the character of the neighborhood, have a negative effect on property values, or pose a threat to the safety of local children.

Even if a project seems innocuous — for example, widening a driveway by a few feet, or changing the driveway surface from asphalt to gravel — exceptions don't come easily. "Unless the owner can prove a hardship that prevents him or her from complying with zoning rules, a variance is certainly far from being a sure thing," says Walter White, Quincy's zoning enforcement officer.

Most zoning boards will grant one only if the homeowner can demonstrate that not being able to make the alteration would cause significant personal or financial difficulty.

For example, if someone purchases a lot intending to build a house on it, and soon afterward the town changes frontage requirements in a way that makes the project in violation by a few feet, the zoning board would likely award a variance. On the other hand, a homeowner who wants to build a second floor on a street zoned for single-story homes because the house is too small for his growing family isn't likely to win over local officials.

Even when homeowners are in strict compliance with zoning rules, they can sometimes suffer if neighborhood or town regulations change unexpectedly. That?s what happened to Linda Morris, who moved to The Colony, Texas, three years ago to be near her daughter and son-in-law.

She bought a brand-new house in a development bordered by woodland. The real estate agent told her that the town planned to turn the surrounding property into a park. Even if that didn?t happen, the tract was zoned for business use, so Morris figured at worst she might have a small shopping center or professional complex for a neighbor.

She ended up getting a neighbor — but not the type she wanted.

Last December, The Colony city council approved a zoning change for the land bordering Morris's street that will allow a developer to construct 15 buildings for light industrial manufacturing and warehouse use. Soon, the roads will be busier, the neighborhood will be noisier, and, what's worse, Morris says, "the value of my house will drop. This house was supposed to be my retirement vehicle."

Nothing can be done before buying a house to completely protect against zoning changes to adjacent property, but there are a few places prospective buyers can look for hints about the future direction of an area.

For starters, while checking the zoning rules for the property they're looking at, homeowners should also examine the ordinances that cover neighboring areas. Just because a tract of land is being used as a horse farm doesn't mean it can't legally hold, say, a shopping plaza. In addition, home buyers should read the municipality's comprehensive plan, if it has one.

It may show that the town eventually intends to approve high-density, low-income housing in an area that is currently zoned agricultural, or to turn the edge of a neighborhood into an area of mixed industrial and retail use.

"The vast majority of the time, the town's future is communicated in the master plan — whether it's leaning toward industrial development, historic or agricultural preservation, or residential development," says Quincy enforcement office White.

If after taking these precautions homeowners still find than an unanticipated zoning change will cost them money or headaches, there's one more thing they can do: "Get as many people together as you can and yell as loud as you can," says David Callies, professor at the University of Hawaii's Richardson School of Law.

Even if the rezoning can't be stopped, concessions can be won. For example, Morris's neighborhood organization was able to get the developer to agree to leave 250 feet of woods as a buffer between the homes and the warehouses and not to disrupt a stand of trees along a nearby creek. The developer also promised to plant hedges and trees to screen the roads entering the industrial complex.

If there is one recurring theme in all zoing issues it is that being prepared — is the most effective strategy for preserving a property's comfort and value. Ignorance, experts say, is the worst excuse for making a mistake. "When it comes to zoning, homeowners do have rights," says Callies, "but they have to take positive action to know them."

Prospective purchasers can take any of these simple steps to protect themselves from zoning-related problems.

• Ask the sellers to add a clause to the sales agreement that guarantees they obtained the necessary permits before making any improvements to the property — and that they are responsible for any future fines having to do with these improvements.
• Hire a lawyer to investigate all permissible uses of the property and the legality of any specific changes you have in mind. This can cost around $500, but if you're planning to keep reptiles, say, or build a separate apartment over the garage, at least you?ll know ahead of time whether you?re allowed to.
• Conduct your own search. At the town's building department and zoning office, you can examine prior construction permits and permissible uses of the property. One caveat, though: You can't always trust what town officials tell you. And the fact that they may have given you incorrect information is no defense should you get in trouble with the zoning commission. Make sure that you are receiving the most up-to-date information — not all towns are diligent about updating the zoning codebook. New amendments may be sitting in an inbox somewhere waiting to be filed. There is no foolproof way to protect against lackadaisical filing clerks. But at the very least, check the date on the map and codebook and if they are more than a year old, call a member of the zoning commission to see if there have been any recent revisions.