If you thought Boston’s new convention center was big, just wait until you see the expansion.

The state authority that oversees the Boston Convention & Exhibition Center is starting to weigh a major addition to the $800 million meet-and-greet complex.

But if you think this means just slapping on a few meeting rooms onto the back of the Rafael Vinoly-designed hall, think again.

In the works are plans that could involve not just more meeting rooms, but also potentially a significant push beyond the hall’s 60-acre footprint to add some badly needed hotels.

Of course there is nothing official out yet.

But a draft report by a consulting firm hired to study a potential expansion – word of which is now filtering out after convention center board members were recently briefed – offers a few clues on where this is headed.

Not If But When

We are likely talking about some sort of public-private partnership to spur the development of hotels on some of the dusty, and yet to be developed tracts that still ring the sprawling, South Boston complex.

Really, the only question is not if there will be an expansion, but when. And let’s just hope it’s sooner rather than later, when construction prices are falling and the economy needs a boost.

Otherwise we are looking at a repeat of the woes that plagued the development of the center itself just a few years ago. That included a memorable construction freeze to head off a looming, $100 million cost overrun and a series of 11th-hour cuts to reduce the price tag.

“Any time prices are this low it is time to build,” said Dean Stratouly, a Hub tower builder and a long time member of the convention authority board, “except that prices are this low because no one is building, and they are not building because there is no credit and the state is in terrible financial condition.”

Despite the hedged endorsement, Stratouly, who oversaw the development of the new center a few years ago, has emerged as a bull on the convention authority’s board when it comes to expansion, including the construction of new hotels.

“My individual view is that right now we have one of the finest facilities in the country and … one of the worst hotel conditions in the country,” Stratouly said.

And without a plan to expand both the hall and the number of hotels around it, Boston’s new convention center “will lose market presence, and once we have lost market presence, that is very hard to regain.”

“It’s all about hotels, hotels, hotels,” he said.

Of course word of this is likely to get long-time convention business critics foaming at the mouth.

But the new center, after struggling with some real challenges early on during its development, has won over a number of skeptics since it opened its doors back in 2004.

If You Build It … Where Will They Stay?

The new center has pumped more than $1.7 billion into the local economy over the past five years, while helping to create 7,000 jobs, according to one estimate.

In fact, the new BCEC had so much success it is effectively booked out for several years. The only way to bring in more business is to build a bigger hall.

Yet a bigger hall won’t do much good without more hotel rooms nearby, of which there is already a dire shortage.

The Westin Waterfront Boston serves as the headquarters hotel, and there is a new Marriott a few blocks away as well as the Seaport Hotel. But that is far from sufficient to accommodate the tens of thousands of conventioneers who pour into town with the top shows.

That has forced companies and shows to bus attendees back and forth from the Back Bay, where most of the city’s hotels are clustered.

Sounds OK on paper, but there are big problems with this setup. The hotel rooms are pricier than what conventioneers often want to spring for. And the cost of bussing attendees is a budget breaker as well.

Throw in some nasty Boston traffic – bus trips back and forth to the convention hall on a bad day can take an hour – and you wind up with some very unhappy campers.

Nightmare Situation

With the new hall and the city’s hotels maxed out, convention center officials are now having to turn business – and badly needed spending – away.

That has resulted in lost business of that would have generated 250,000 additional hotel room bookings, noted James Rooney, chief executive of the Massachusetts Convention Center Authority, in a recent interview with New England Cable News.

While vague on the details, Rooney hinted at the need for a “comprehensive plan” for future expansion, one that would include hotels in the planning.

“You can’t have one without the other,” Rooney said of the symbiotic relationship between the convention and hotel business.

Behind the scenes, convention center officials are starting to look at expansion possibilities.

The easy part is to fill out the remaining 20 acres next door to the giant center with new meeting rooms, more exhibit space and an auditorium – all likely candidates.

But convention officials are also looking at hotel ideas as well.

Developers’ Dream

One possibility, raised in that recent draft consultants’ report, is the construction of new hotels around the South Boston center on some of the undeveloped tracts that now surround the center.

Back during the boom, a number of ambitious developers had big plans for condo complexes and retail shops on these sites.

John Drew, who built out the World Trade Center complex, put together plans for Waterside Place mall and residential complex just across the street from the convention center.

Meanwhile, real estate investor and developer Peter Palandjian had big plans for a new condo complex on another site next to the convention hall.

Given the down economy, both sites are now seen as potential candidates on which to build new hotels to service Boston’s bursting-at-the-seams convention center.

Other potential hotel development sites include the air-rights over nearby train tracks and a parking lot owned by the U.S. Postal Service in the nearby Fort Point district.

As important as figuring out potential development sites, though, is coming up with a model to finance their construction.

Simply relying on the private sector won’t cut it. New projects of all kinds are languishing on drawing boards across the country, with banks terrified of touching anything with even a faint scent of risk.

That means to get hotels built will require help from the public sector, though how much and by what means remains to be debated.

How other cities with big convention centers have tackled the hotel construction piece is also explored in the draft report:

Chicago financed hotel construction for its convention hall through a public-private partnership, where costs and profits were divided up.

San Antonio and San Diego had their local, industry and state supported convention and visitors’ bureaus build hotels, and then lease them to operators.

“In this market the only way you can get a hotel done is through a public process,” Stratoutly said.