Residents and advocates are raising red flags about a rash of new high-rise towers and skyscrapers planned for Downtown Crossing — an area with outdated building rules that the Boston Redevelopment Authority has no pressing plans to update even as the Hub undergoes its largest building boom in city history.

Five towers are already under construction or proposed for the Downtown Crossing area, including:

• the 60-story Millennium Tower under construction at 426 Washington St.;

• an 18-story Emerson College dorm for up to 400 students being built at Boylston Place;

• a 20-story luxury residential building proposed for 171 Tremont St.;

• a 30-story residential building with retail proposed at the former Felt nightclub at 533 Washington St.;

• and a 59-story, 419-unit proposed skyscraper known as One Bromfield Street — a project that has more than doubled in height since it was proposed in 2008.

“We’re seeing a lot of different developers trying to do these one-offs,” said Downtown Crossing resident Doug Fiebelkorn. “It feels like every time you turn around there’s another building being proposed. Right now the streets are pretty clogged. It makes sense to update the master plan for the entire Downtown Crossing area.”

BRA officials told the Herald other developers are interested in the area and the agency expects to see even more high-rise proposals there this year.

But BRA Director Brian Golden said his agency doesn’t intend to launch a new master plan for the area — even though building regulations in Downtown Crossing haven’t been updated since the late 1980s. The outdated rules cap building heights in that district at 155 feet — the proposed One Bromfield Street skyscraper is seeking a variance to go more than four times that height — and many of the district’s current zoning rules seem to date back more than 100 years, mentioning outdated businesses such as millinery shops, telegraph offices, typewriter stores and custom furrier shops.

Mayor Martin J. Walsh said existing regulations allow both official diligence on large projects and “a lot of community input.”

“We’re in a unique time,” Walsh said. “We’re seeing incredible growth, but all of this goes through the community process, through the BRA process, through the zoning process. … There’s a lot of checks and balances along the way.”

Golden pledged that the BRA will vet each project and get public input.

“Ideally we’d be doing advanced planning everywhere that development could be theoretically coming,” Golden said. “But what we have to do is fix the airplane engine while it’s in flight and apply sound planning principles to development where it’s being proposed even if we don’t have new planning and new zoning.”

The development push in Downtown Crossing comes amid what Golden says is the city’s largest ever building boom — 46 million square feet of development has been approved all across the city since the beginning of 2012 and the boom has created an average of 8,894 construction jobs per year, the BRA said.

Golden said he’s not ?under pressure to approve projects quickly. But he also acknowledged the city is likely closer to the end than the beginning of the building boom and that half of all new city revenue comes from new development.

The BRA approved 71 large-scale developments just last year alone and officials told the Herald it takes about four months on average for large projects to go through the approval process, which includes studies of the building’s impact on traffic, daylight, and its shadow and wind effect on pedestrians.

Golden argues against the calls he’s heard to slow ?development until neighborhood planning is done.

“I think most people realize you would cut off a really positive development climate that brings about buildings people need for work and for housing and that brings about tax revenue that people need to run a healthy, vibrant city,” Golden said. “If we shut this off, that would be a real problem for everybody.”

Greg Galer of the Boston Preservation Alliance warned that without a comprehensive master plan for Downtown Crossing, much of the historic character that draws businesses and residents to Boston could disappear.

“The one-off doesn’t really work for anyone,” Galer said. “It doesn’t work for developers because they spend a lot of time going around in circles and get very frustrated. It’s difficult for the community, particularly at the pace we’re seeing now. It becomes impossible to attend all these meetings and really engage on a useful level.”

Golden says the BRA is planning for Boston’s future with ongoing initiatives in South Boston, the Jamaica Plain-Roxbury border and Dudley Station, and through Imagine Boston 2030 — a conceptual vision for more affordable housing and inclusive neighborhoods in Boston over the next 14 years. But so far, the project has produced no concrete, long-range planning.

“The city is doing Boston 2030, but by the time they get done approving these things a lot of these neighborhoods — and it’s just not downtown — will have changed dramatically,” Galer said. “We’re hearing from developers that they’re getting signals and encouragement from the BRA and that’s not necessarily a bad thing, but the fact that’s where that comes from and there hasn’t necessarily been any input in that ?encouragement from the community is troublesome.”

Rishi Shukla, co-founder of the Midtown Cultural District Residents’ Association, which represents more than 400 residents of the Downtown Crossing area, said most of his members support development. But he said, “The concern is around the overall plans for the neighborhood. ?Obviously we don’t want to wait 14 years for a master plan for the neighborhood. Let’s get a plan in place that reflects 2016 and not 1989.”