A cascading U.S. credit crisis is not sinking the largest new housing development in Downtown history, according to Pittsburgh Cultural Trust boss Kevin McMahon.

It could, however, slow things down.

The original start date for the 700-unit, $460 million RiverParc project was summer 2007. But with no money borrowed or documents signed, the current plan is to begin in 2009.

"We're working methodically through the difficult issues in any development of this size," Mr. McMahon said, citing regular conversations with the Phoenix-based developer Concord-Eastridge and the complications involved with the project's environmentally friendly design, arts spaces and riverside park.

"We're sitting put until we're ready to jump."

Such caution may be the norm as real estate developers adjust to more stringent lending terms, a possible slowdown in corporate spending, uncertain consumer sentiment and the possibility of a recession.

All of that could slow the biggest local building boom since the late 1990s, when Heinz Field, PNC Park and the David L. Lawrence Convention Center went up at the same time. Last year, commercial construction in the Pittsburgh area totaled $3.55 billion, according to Ross-based Tall Timber Group, rising 20 percent as compared to 2006. Still in the pipeline are the $450 million Majestic Star Casino on the North Shore, a $290 million arena for the Pittsburgh Penguins and $1 billion in improvements to U.S. Steel Corp's Clairton Works.

Nowhere is the aggressive building more evident than in the Golden Triangle, where several hundred new housing units are under construction and more than 1,000 are still being planned, including the 700 from the Cultural Trust at Eighth Street and the Allegheny River.

The projects already under way or with financing in place should stay on schedule, real estate observers said, while those existing only in fanciful renderings could experience delays. Developers still chasing loans might be asked to commit more cash up front, pre-sell more units in the case of new residential units Downtown or guarantee higher cash flows to cover their mortgages.

"Anybody who hasn't started will be stalled," said Kevin Keane, executive vice president of Lincoln Property Co., which owns three major residential complexes Downtown, on the North Side and South Side.

"The winds are changing."

The same goes for office and retail projects across the region, noted Jeff Burd, president of Tall Timber Group and publisher of Breaking Ground magazine in Ross. A developer "may just say 'until this gets a little more clear, I am going to hold off for a while,' " he said.

At the least, "if you're going for a commercial loan, you will need more skin in the game than two or three years ago."

As recently as a year ago, Mr. Keane said, a developer could land a loan by paying as little as 10 to 20 percent down -- meaning a $40 million project would require only $4 million to $8 million up front. "Today, lenders are saying they want 30 to 40 percent down," Mr. Keane said. "That $4 million to $8 million turns into $12 million to $16 million. For any developer, that is a huge increase. ...will that stall or postpone development? My sense would be yes."

Despite such predictions, several developers said they foresee no changes in their plans this year. The Soffer Organization still plans to market the construction of two more office buildings at its SouthSide Works complex, and Columbus-based Continental Real Estate still plans another office building on the North Shore near PNC Park. Neither developer, however, plans to move forward without a major anchor tenant in hand. Both are pursuing Equitable Resources, currently in a new office building on the North Shore but looking for 250,000-300,000 square feet.

"We have been doing this for 30 years," said Continental Chairman Frank Kass, "paying back every penny every time."

Even in a good market, he said, Continental will not put up a building "on spec" -- with no tenants. "If tenants don't sign up because of their economic conditions we will not go ahead with the project.

"We are a low-risk borrower in a high-risk business."

Downtown, Holly Brubach said she sees no reason to alter her approach or timing on a condo makeover of a building at Sixth Avenue and Wood Street, despite the economic slowdown, the stricter lending standards and the abundance of competition for new tenants.

"It doesn't change my plans, and I am moving forward."

A former style editor for The New York Times, Ms. Brubach purchased The Granite building in late 2005. So far, she said, one of six planned residential units is under contract. She predicted that all six will be ready "for delivery" to buyers next fall.

But Scott Bergstein of Oxford Development Co. said the Downtown residential market is already tight. "The projects that are looking for financing are going to be challenged to find it and the debt is going to be more expensive," he said. "People will not be adding to that inventory until there is strong evidence that what exists now is being absorbed."

Oxford is the developer behind the new 23-story, $178 million Three PNC Plaza under construction along Fifth Avenue. That project includes 30 luxury condos that will be marketed for $500,000 or more, with some topping $1 million, according to past reports.

Mr. Bergstein, Oxford's vice president of realty services, would not confirm specific price ranges but acknowledged that the units will be for buyers who "are not so reliant on access to credit."

As a result, the current economic downturn "isn't affecting our approach to the 30 units at PNC. These are going to be the very top end of the condo residential market." With so many new projects competing for attention -- 1541 First Side, where prices range from $200,000 to $1.8 million; Piatt Place at the former Lazarus-Macy's building on Fifth Avenue; and the Carlyle at Wood Street and Fourth Avenue -- Mr. Bergstein believes the upscale units will continue to move. "I think the impact is going to be held at the lower end of the price scale rather than at the upper end," he said.

Mr. Keane, who in 2006 opened a 151-unit apartment tower Downtown called the Encore on 7th, disagrees with that assessment, arguing that there is not enough space Downtown for people making $30,000 to $45,000 a year.

"I certainly think the high end of the market has been satisfied," he said.

But Mr. Burd, publisher of Breaking Ground magazine, believes there is enough demand in the area to fill all the new Downtown residential projects and more. "You could have 10,000 people living Downtown," he said. In fact, he attributed the talk of overbuilding to competitive instincts. Mr. Keane's "attitude," Mr. Burd said, "is he built the last one people will want to rent or buy."