Anyone who has ever remodeled a house knows that a crucial moment comes when it's time to appy for a building permit. That little piece of paper entitles you to a series of safety inspections by experts from the local government to determine if the work is up to local building codes. It is also a message to the local tax assessor that your property may be worth more in his eyes at tax bill time.

Contrary to popular opinion, however, building permits may have little to do with how much your next tax bill goes up. Area tax assessors do use building permits as red flags, alerting them that a change is taking place in your house. However, they are also unlikely to use your estimate of what a remodeling job costs as a basis for reassessment. "We look at the value that a job is going to add to a property, not the estimate made by a homeowner or contractor," says George Altoft, a senior assessor for the District.

Some changes don't raise the assessment at all -- small cosmetic repairs, landscaping, new fencing or the addition of a decorative sidewalk. Sometimes even a swimming pool won't increase the value of the property. Altoft remembers one swimming pool jointly constructed by three Capitol Hill neighbors. In pooling their resources, the families got what they wanted. But in terms of adding a measurable amount to the value of the three properties, Altoft felt that a shared pool might diminish the marketability of any one of the houses.

Other so-called improvements can be done without adding much in terms of tax assessment even though they may be very costly. For example, skylights, cathedral ceilings, even central air conditioning in a small house, may end up costing more than they add in assessed value.

Getting a permit to make any alteration or repair can be troublesome. First one has to check zoning to be certain the change is in keeping with area regulations and set-back limits. If it's not, you could have a long wait.It takes anywhere from two to four months, for example, to get a zoning variance in Montgomery County. A similar variance in the District may take as long as six months to obtain. Any quest for a zoning variance means lengthy applications, big signs on your front lawn, lawyer's fees and a long wait. If you can find a way to add what you want without having to come up against a zoning problem, do it -- you'll save a lot of time and aggravation.

Assuming that you don't require a variance, you can go ahead and get your permit. The price depends on the jurisdiction in which you live and the kind of job you are doing. The fees quoted in the accompanying box are exclusively for remodeling and alterations as opposed to new construction.

Of all the area jurisdictions, the District government seems to have the reputation for taking the longest to issue a permit. One former District employe, commenting on the process, said, "I wouldn't build a dog house in the District."

One reason for the District permit department's unpopularity among architects and contractors is its insistance on the preparation of scale drawings for almost every remodeling proposal, followed by a tedious review of the drawings before the permit is issued. Other area permit offices usually ask only that you accurately indicate what you plan to do, how big the job is and how much you think it will cost.

Stories of permitless improvements are legion. Probably the best is the tale of the Fairfax County woman who dutifully called up the permits office and asked if she needed a permit for a tree house. Imagining a childlike structure with little boards tacked to a tree trunk, the fellow on the other end of the line kindly dismissed the lady with a word of caution about the steps leading up to the tree house. Then, as Fairfax County chief of permit applications Donnie Woodrow recalls, officials discovered: "The lady built an actual tree house, and was giving art lessons in it to about four or five people at a time . . . "

One Capitol Hill couple took an old garage and remodeled it into an exquisite guest house, complete with a full bath. Yet, from the alley, the garage had a tumbledown appearance with a sagging roof and a crude garage door. When the property was sold, the price may have raised a few eyebrows, but the owners who made the improvements were soon gone.

Bootleg remodeling jobs, though perhaps enhancing your lifestyle without having to pay the tax man, run the risk of work done that does not meet code standards and that may be hazardous.

One point often mentioned by people making improvements is that homeowner's insurance may not cover costs if a fire breaks out in an uninspected house after bootleg electrical work has been done. Talks with insurance agents and lawyers specializing in fire insurance cases failed to come up with a single such case. Most opinions are that the burden of proof would be on the insurance company to show that the fire was caused by faulty wiring that would have been caught in a proper inspection. The company probably would have to show that you were knowingly flouting local laws by not getting the work inspected.

But such risks are foolhardy. The inspections cost relatively little and bring peace of mind even if they do bring the assessor.

Some people consciously underestimate the cost of the work on building permit applications, not only to save a few dollars on the permit price itself but also hoping that this will lead to smaller increase in tax assessment. Most assessors contemplating an increase in valuation ask to look at the work that's been done. In many jurisdictions you can refuse to let the assessor in, but if you choose such a course of action, Altoft notes, "then we use our best guesstimate -- which is usually high."

You may think you are putting one over on the assessor, but remember that these people tour neighborhoods frequently, keep their eyes open and often have cultivated friendly neighborhood "eyes" who alert them to changes. Inspectors and assessors alike report that they often hear about improvements from neighbors rather than the houseowner making repairs. It's not big brother, it's the guy down the street.