WASHINGTON -- Zoning has often been described as a necessary evil. While it is meant to promote order, the strict application of ordinances can render a property practically useless.

Consequently, the need arose for variances: exceptions that allow property owners to use their land or build on it in a way that is otherwise prohibited. Most jurisdictions allow doctors to see patients in their home offices, for example, or permit additions that come close to property lines.

Getting a variance -- essentially, approval to violate local law -- isn't automatic. But generally, as long as you meet a few conditions, you shouldn't have too much difficulty.

No two jurisdictions do things exactly alike. Some places will be tough to work with; others, downright easy. Still, there is enough similarity among the thousands of local rules to give you a fairly good idea of what hoops you can expect to jump through.

Prior to starting construction on any remodeling or home improvement project, no matter how small, you should first determine whether or not you will need a building permit. Surprisingly, a permit is required for practically everything you might want to do around the house -- even replacing a garage door.

Depending on where you live, your permit application may have to be approved by more than one local or state agency. At the same time, many enlightened jurisdictions offer one-stop "walk-through" systems in which a permit for most alterations and additions to a single-family residence can be obtained within a few hours.

That still doesn't relieve the applicant of all the legwork: Among other things, you'll probably have to provide your land/tax number, lot and block number, subdivision name, estimated construction cost, estimated starting and completion dates, and the license number of your contractor. Depending on your project, you may also need several complete sets of building plans, as well as numerous copies or your site and/or landscaping plan. And that's on top of the required filing fee, which may or may not be refundable if you are turned down.

The zoning office will review your plans to be certain your project conforms to specific restrictions regarding setback, height, frontage, lot size, lot coverage, density, parking and use. If you fail to meet any requirement, your application will be rejected and you will have to appeal -- for another fee -- to a higher authority for a variance.

Generally, dimensional variances are granted if the parcel meets several conditions: It is unusually narrow, shallow, oddly shaped, or has exceptional topographic conditions; a strict application of the law will result in undue hardship; or the variance will not substantially impair the integrity of the general plan for your area.

When applying for an exception, you'll have to provide a list of the names and addresses of adjoining property owners so they can be notified that you want to change your property in way that could affect theirs. In some cases, you might even be required to identify local citizens' groups so they can be contacted, too.

It makes no sense to try to hide what you plan to do from your neighbors, especially if there is a possibility someone will object. It's far better to clue them in early and win their support. Perhaps you even can persuade one or two to be with you at the hearing so they can voice their approval.

Similarly, if you misrepresent what you intend to do to zoning officials, you could be denied a use-and-occupancy permit when a final inspection reveals that, say, the oversized garage you want to build is really for servicing other cars, not just your own. Even if you manage to pass that hurdle, the government will find out what's going on when your neighbors start to complain about traffic and parking difficulties. And when that happens, which it will, you can be ordered to tear down your addition.

There are any number of uses for which a special exception may be granted. Generally, home-based livelihoods are allowed if they are performed entirely within the dwelling, incidental to the home's primary use, do not change the character or appearance of the dwelling and do not include the storage of merchandise to be sold.

It's when the proposed use will alter the residential character of the neighborhood -- by generating unwanted traffic, taking scarce parking spaces or creating objectionable noise, odors or sights -- that you are likely to encounter tough sledding. That's why many people within the ever-growing work-at-home movement, as well as increasing numbers of land use experts, believe zoning laws should focus more on the impact of a home-based business on its neighborhood, and less on compiling a list of "acceptable" occupations.

Until that debate is settled, it is again in your best interest to be open and above-board when applying for a use variance. You'll need all the support you can get, and going behind your neighbors' backs is not the way to gain it. It's also a good idea to try to anticipate the building department's questions and possible objections, and have your responses ready.

If you think you might run into trouble, you may want to hire a zoning attorney, who will not only prepare and present your case but also help you determine whether you need such expert witnesses as engineers, planners and real estate brokers.

Whether you have counsel or not, it will help your case to use maps, photographs and other visuals. And while zoning cases are supposed to heard on their merits -- no one case should set a precedent for another -- it won't hurt to show examples of similar exceptions that have already been granted in your neighborhood.

New-home buyers usually don't concern themselves with footings, framing, wiring, ventilation and the various and sundry mundane structural items that go into a house. Those things are the province of the home's builder.

But when you're turning your carport into a garage, extending your kitchen another five feet or adding a second story to your 15-year-old rambler, you are the builder. And as such, you have to pay close attention to your local building codes.

Building codes are a set of minimum design and construction requirements set forth to protect the public health, safety and welfare, and they're rooted in ancient history. Back in the 18th century B.C., for example, the Code of Hammurabi mandated death to the son of a builder whose building collapses and kills the son of the owner.

Today's codes don't carry such weighty penalties, but they are somewhat more encompassing. Generally, they cover structural design, foundations, exits, fire protection, sanitation and roofing, plus the electrical, plumbing and mechanical systems. Some even cover energy conservation.

Only 30 states have mandatory statewide codes, 19 of which allow local jurisdictions to make them tougher. The other 20 states rely on the jurisdictions within their borders to enact their own construction regulations.

The bottom line? If you're modifying the structure in any way, chances are, you'll need a permit. Perhaps even several. Worse, securing permits is often a time-consuming process, and an expensive one.

For one thing, you'll probably have to provide detailed construction drawings, maybe even multiple sets, and they might have to be drawn by a licensed architect. For another, all permits are assessed a fee based on the value of the improvements you are making.

Because of the extra time and money involved, some contractors will suggest that you secure the permit instead of them. Others will exhort you to skip the permit process entirely and get right to work. Neither is a very good idea.

While no jurisdiction will refuse to grant a permit to an owner-occupant who can prove he owns the house and lives in it, it normally doesn't cost any more if the contractor applies, and he can usually get in and out of the local building department a lot faster than you can.

Just as important, if you apply and say you are doing the work yourself, all you have to do is show your local building officials a tax bill or deed. But if the contractor applies, your local building officials will probably check to make sure his license is up to date and his liability insurance is in place.

Applying for a permit is also your assurance that your project will be done right, or at least up to minimum standards. Besides going over the plans before work begins and suggesting ways the job might be done better -- or perhaps even cheaper -- the local authorities will make periodic inspections to make sure the contractor is following the rules.

Some contractors argue that none of this is necessary, that they've forgotten more about construction than anyone on the government dole will ever know, that they don't want to hassle with fees and inspections, that dealing with local building officials is a bureaucratic nightmare.

"If you can't trust me," is a familiar refrain, "then you'd better hire someone else."

To a certain degree, the contractor-client relationship is built on trust. And while the head of the building department in some locales is also the guy who gives out dog licenses, it's best not to allow non-permitted work done to your house, especially if you know little or nothing about construction.

Besides the off-chance that non-permitted -- and, therefore, illegal -- work could fall down around you, there's also the possibility that if the local authorities get wind of what's been done, you could be required to rip everything out and start over.

What's more likely, though, is that you may not be able to sell a house on which structural work was done without a permit. Most states today require you to disclose such a material fact. If you ignore that law, you're still liable to be caught if your buyer is savvy enough to hire an independent home inspector to give the place a once-over.

Even if your buyer wants to proceed -- and assuming he can get a loan on a place that's not up to code, which is problematic in and of itself -- he's sure to demand a major price concession. And if an unsuspecting buyer doesn't find out until later that work was done without a permit, he can demand that the sale be rescinded and sue for damages.

NEXT WEEK: Special exceptions.

Is your market hot?

Every once in a while, local media proclaim that the local market is "on fire." But is it really?

If the report is based solely on the fact that there have been more sales in the current period than in the previous one, then it could be terribly misleading. There's more to a hot market than simply a pickup in transactions.

"Just like a medical diagnosis can be wrong if you are looking at just one vital sign, so can a proclamation that the market is hot -- or cold, for that matter," says Thomas Hoff of Pro Teck Valuation Services in Waltham, Massachusetts.

I asked Hoff about the key factors Pro Teck looks at to produce its monthly Home Value Forecast. He says the company watches nine different data points, detailed below, along with tracking trends and using consistent methodology.

The relative "hotness" of a local market is key information for its buyers and sellers. Luckily, most of the data that Pro Teck evaluates is readily available from the local multiple listing service, so your agent should be able to look at the same info and come up with a reasonable list price for your house (or how much to offer, if you are buying).

But if he or she simply uses comparables -- previous sales of similar homes in your area -- you might want to go elsewhere, or even try to do it yourself.

Here's a quick rundown of Pro Teck's nine key statistics:

-- Sales. The number of sales in a given month is important, but you want to compare it to the same month a year ago. Actually, Hoff uses a three-month rolling average, and compares it to the previous same three months. So, if you are trying to determine whether sales are up in December, you'd look at the average number of sales in September, October and November, and compare it to the average in the period a year ago.

-- Active listings. Here, you want to know how many houses are on the market compared to a year ago and the percentage change. "This is simple supply and demand," says Hoff. "The fewer number of listings make it a hotter market; the more listings, the slower the market."

-- Months of remaining inventory. This is the average rate of absorption, or houses actually sold. It is determined by dividing the number of houses on the market at any time during the previous month by the past year's monthly sales rate. According to Hoff, an answer of five to six months suggests a balanced market. If it's less, buyers should probably expect to pay more than list price; if it's more, you can probably bargain. Vice versa for sellers.

-- Selling price. Determine the average selling price, again using the three-month rolling average as compared to the same period a year ago. Use a rolling average so your number is not impacted by a house that sold for an unusually high or low price. "You want to get rid of spikes so outliers don't impact your figures," Hoff says.

-- Days on market. Again, using the rolling average, compare how long it takes to sell houses now vs. a year ago. If it takes longer, the market is slower.

-- Active price. If the average is rising, supply and demand fundamentals "are at work," Hoff reports. But if it's going down, there's more supply than demand.

-- Active days on the market. Similarly, if the average is going down, it's indicative of a hot market.

-- Sales price vs. list price. Here, you'll want to know the ratio between what houses were listed for and what they sold for. Of course, the hotter the market, the higher the ratio. Anything above 98 is considered pretty good. But if it is trending lower, it's not so hot.

-- Foreclosures. Finally, but still very important, you want to determine the number of foreclosure sales as a percentage of all sales. Five percent is healthy. But once this number rises above 10 percent, it starts to negatively impact the market.

Miami is a good example. Based on the number of sales alone, it looks like a hot market. But 12 percent of its sales are foreclosures, so prices are still depressed. "It's like an anchor dragging down prices," says Hoff.