In booming downtown Chicago new highrises seem to be sprouting on nearly every block. Many buyers in these buildings chose their units based largely on the promise of brilliant urban views. But with so much new construction, there are few guarantees that today's skyline vista won't be tomorrow's brick wall.

The issue is an important one for buyers not only as it affects the aesthetics of their new homes, but also, experts say, because of the very real impact a degraded view can have on homeowners' pocket books.

Condominiums are priced according to the views they afford. Identical units are priced higher if they are positioned on higher floors, or facing downtown's skyline instead of city neighborhoods or close buildings. Views have a concrete and often hefty value.

"We price views both in terms of height as well as direction," says Keith Giles, of Frankel & Giles Real Estate, developer of Dearborn Tower, 1530 S. State. "In Dearborn Tower, similar to our Filmworks project, which also had north skyline views, there is a big difference in pricing facing north as well as south. People will pay for the view."

In Dearborn Tower, unit 811, which has an unobstructed north-facing skyline view, is priced at $259,000. The same two-bedroom two-bath condo facing south is priced around $200,000. The value of the view is more than $50,000, or 20 to 25 percent of the unit cost, according to Giles.

John Jaeger, vice president of Appraisal Research Counselors, Ltd., says the value of premium views sometimes can account for up to half of a condominium's value.

"There are a couple of projects on South Michigan Avenue now, conversions at 332 S. Michigan and 910 S. Michigan, and the developers told us that on east-facing units, which have views of Grant Park and the lake, they found no restrictions to raising prices," Jaeger says. "They kept raising prices until they came to the point where they couldn't anymore because they ran out of those units."

Jaeger says some east-facing units in Michigan Avenue Lofts, 910 S. Michigan, were priced around $250 to $300 a square foot, while west-facing units were priced at $150 a square foot.

Buyers obviously can lose money or see lower appreciation - not to mention neighbors in their pajamas - if their view is later obstructed. What's a view-loving home buyer to do?

Becky Carroll, spokesperson for the city's department of planning and development, says the city cannot consider how new developments might impact existing views.

"The reality is that there are certain development rights associated with any given development," Carroll says. "An individual developer has a right to build up to a point designated by a given planned development. As long as they build within the parameters of that development, we can't stop them. There's no right we have."

That hasn't stopped some condominium owners and neighborhood groups from trying. In the South Loop, residents of the recently converted Transportation Building banded together to block D2 Realty from erecting a 17-story highrise that would have replaced their southern exposure with a close-up of a brick wall. Even with the added argument that the proposed building did not fit into historic Printers Row and its landmark status, neighbors ultimately could not keep the city's Commission on Landmarks from approving D2's plans.

In a similar battle over a planned highrise by Draper & Kramer at 1320 N. Lake Shore Drive, neighbors in pricey units with lake views that would have been ruined succeeded in passing an ordinance to block the building. Draper & Kramer, however, has challenged that maneuver in court, and experts say buyers should not count on clout coming to their rescue when their views are in danger.

Common sense is the key to finding protected views. Buyers should consider the following factors in shopping for a highrise with a perpetual view:

Avoid properties adjacent to vacant lots.

Given the heat in the city's real estate market, today's vacant lot is likely to be tomorrow's highrise. Do not count on a parking lot next door remaining a parking lot for very long. River Bend, a new highrise planned for 323 N. Canal, promises spectacular views and many of them will to be stunners. However, if a couple of office towers planned by the Prime Group get built next door, at least some River Bend views and light will be obstructed. Likewise, Michigan Avenue Lofts, 910 S. Michigan, offers some of the city's best views, overlooking Grant Park and the lake. However, some units on the side of the building overlook a parking lot that will almost certainly be developed down the road. These buyers should be aware that the view from their windows could be changing significantly during the next few years.

Do your homework.

Vacant adjacent parcels can be bad news for condo buyers, but so can lots across the street or dilapidated buildings next door. Check with the local alderman's office to find out what's planned, if anything, for nearby vacant or "tear down" parcels - older low-rise properties that could easily be torn down to make way for new development.

Carroll, of Planning and Development, recommends calling the city's new general help line, 311, to check on the zoning and plans for key parcels.

Don't rely on the developer to inform you about neighboring projects.

Jaeger, of Appraisal Research Counselors, says most builders do inform buyers if something is being built next door, but some may not. Also, plans change rapidly in the city and a developer might not know about a view-wrecking project until after you've bought your unit. Some buyers at Erie Centre, 375 W. Erie, could have saved themselves untold grief by doing a little research about the parcel behind their future home. Gallery 400, 400 W. Ontario, had been on the drawing boards for several years, according to developer Jeffrey Gelman, but buyers at Erie Centre say the developer never told them that some southern-facing units soon would be staring into a brick wall.

Make sure easements are long-term.

If a developer assures you that a view is protected because he or she has an easement granting air rights over an adjoining property, ask if the easement is permanent, or valid only for a certain number of years. One broker describes a situation in which buyers were paying many thousands of dollars extra for such an easement at the Park Shore condo conversion, only to discover that the air rights over a neighboring golf course were temporary. "If you're going to pay for an easement, it should be into perpetuity, not for 10 or 15 years," the broker says. "I couldn't believe it when I saw this was temporary, and a lot of buyers didn't know about it."

Perpetual Views

Probably the best strategy to ensure view security is to look for natural impediments to nearby building that will guarantee your vista. Consider the following:

Buy on a park.

Not only do the east-facing units at Michigan Avenue Lofts, 910 S. Michigan, have spectacular views of the lake and Grant Park, they will always have them. The building sits on the western side of Michigan Avenue and to the east is protected park land and then the lake - neither of which ever will be built on. Again, however, remember that the vacant lot next door could be trouble for the same building's southern views.

Buy on the river.

Two new projects, The Residences of River Bend, 323 N. Canal, and Kinzie Park, 500 W. Kinzie, are located along the Chicago River. Both projects enjoy sweeping vistas down the river and of the skyline across its meandering banks. Both sets of views are protected because the River obviously cannot be built on. Another recent project, Randolph Place, 165 N. Canal, also would seem to have views protected by the river. A closer look, however, reveals a small stretch of land, part of it covered by railroad tracks, between Randolph Place and the river. The tracks are no real protection, as anyone who looks at Randolph Place's sister building immediately south should know. On that site, a developer built a new highrise over the tracks abutting the building and destroying the river views.

Buy on a cemetery.

It may seem morbid, but the graveyard offers serious view protection. A new project at 1100 W. Montrose, the Views of Sheridan Park, touts its views of wooded acreage - Graceland Cemetery. From above the second floor, it's the trees, not the headstones, that stand out, and it's one stretch of open land not likely to be built on.

Buy next to new low-rise housing. Dearborn Tower, 1530 S. State, promises stunning skyline views from its South Loop location. Buyers can be reasonably assured these views will last because Dearborn Park II, a new low-rise housing development, sits immediately north, and Dearborn Village, a similar project is located to the south.

Buy in a building with long-term air rights.

Gallery 400, a loft and highrise development at 400 W. Ontario, sits next to Reza's Restaurant, a low-rise property that might have given buyers pause, except that the developer has purchased air rights over the building to protect views. Make sure to ask, however, about the duration of such an easement. If the air rights are for five years, your resale value could be in jeopardy.

Buy in a complex with abundant green space.