A three-year effort to revise the city’s byzantine building code, a document largely untouched since 1968, could end up increasing New York’s already soaring construction costs, an expert on city real estate says.

The new code, drafted with the help of more than 400 industry figures — including architects, real estate developers, engineers, government officials, and union representatives — will be presented to the City Council later this month.

It is modeled on the International Building Code in use in cities across America, but it will contain provisions specific to New York City. Many experts consulted during the three-year revision process say it will finally bring the city into the 21st century when it comes to building and safety requirements.

A final draft has not yet been released, but Marolyn Davenport, the senior vice president of the city’s most powerful lobbying group representing the real estate industry, the Real Estate Board of New York, said the new code could lead to building cost increases, a perennial concern among developers.

“I think there will be some increases in costs,” Ms. Davenport, who has attended committee meetings on the new code over the past few years, said. “There are potentially new requirements that could cost more. I’m not saying it’s a bad thing, necessarily, if it’s something people should be doing” for safety reasons.

Skyrocketing construction costs, which by some estimates are rising more than 20% a year, have garnered the attention of the Bloomberg administration, which commissioned a study in October to find ways to ease the problem. The price of land in New York has been on the rise, as has the cost for construction materials, including steel and concrete.

The Department of Buildings commissioner, Patricia Lancaster, and others involved in drafting the new code said they do not anticipate it will increase building costs.

“The City’s long term growth and vitality depends on a building code that achieves a delicate mix of enhanced safety requirements, cost savings, and incentives for innovative and sustainable building,” Ms. Lancaster said in an e-mailed statement. “Cost analysis studies are under way and scheduled to be completed this month, however preliminary results show that the proposed code will offer significant opportunities for cost-effective building.”

Ms. Davenport said she is reserving final judgment of the new code until it is complete, but added that “there is a certain amount of concern.”

“The reason we want to look at it carefully, is to ensure we are not putting in unnecessary requirements,” she said. If new requirements are added on top of old ones, “then you raise the cost of construction prohibitively. That is a real danger.”

The executive director of American Institute of Architect’s New York chapter, Rick Bell, said he knows of no one who has examined the provisions of the new code who has said, ‘This is not going to work.’

“If anything, it will save money in the long run,” he said. Because the new code will be revised every three years, cost savings measures will be incorporated into the document more quickly than in the past, he added. He said the use of modern technology and new work practices will help cut expenses.

Mr. Bell also said he thinks the new code would be easier to read and understand. Since it is modeled off of the International Building Code, architects and engineers hailing from outside the city will have an easier time navigating construction requirements in New York.

However, unlike the International Building Code, a 664-page document that measures about one and a half inches thick, the city’s code is thousands of pages long and stuffed with memorandum, technical policy and procedure notices, rules, and local laws added over the past 39 years.

A managing director at Real Capital Analytics, Dan Fasulo, said remaking any city’s building code prompts a careful dance between safety concerns and cost constraints.

“You want the code to protect the quality of construction,” he said. “You want to make sure the code is up to modern standards. At the same time, you don’t want to make it too onerous, so it’s too expensive to build in the city.”

Building safety is a real and recurring concern in New York. Within the past week, two buildings collapsed in Manhattan. On Sunday, a vacant building on Mulberry Street fell and on March 28 a five-story building in East Harlem collapsed.

The entranceway to a Bronx apartment building collapsed on March 13, and on December 26 a building being renovated in Central Harlem partially collapsed, killing one and injuring two.

The president of the Building Trades Employers’ Association, which represents 1,200 union contractors, Louis Coletti, said safety has been the primary focus of his organization when it comes to the new building code.

He said the new code appears to go further than the old one when it comes to safety standards. Under the current code, for example, a safety manager is required to be on hand to protect public safety when a building 14 stories or more is under construction. The new code would extend that requirement to buildings 10 stories and up, he said.

A spokesman for the International Code Council, Steve Daggers, said it can cost more to build to code, but it should be considered an investment.

“For every dollar you spend to build safer and stronger, on average you are going to reduce your losses” by $4 to $7, he said. He likened new safety requirements to the introduction of seatbelts and air bags in automobiles. At first, the automobile industry balked at having to install extra safety measures. Now, having air bags in a car is a top selling point, he said.

A council member of Brooklyn, Erik Dilan, chairman of the Housing and Buildings Committee, said he expects the new code to make construction more economical. He said he has yet to hear vocal complaints from groups or individuals who stand to be more directly impacted by the new document, but he said he is certain he isn’t in the clear just yet.

“I think people are used to dealing with the current code,” he said. “People don’t deal with change too well.”