TAMPA - Ken Stoltenberg saw the same presentation as hundreds of other real estate brokers, businesspeople and other boosters attending the annual Tampa Downtown Development Forum.

And he was just as startled.

David Traynor of Smith & Associates Real Estate presented figures showing three downtown apartments at least 98 percent leased and a fourth rental building at 94 percent occupancy.

"We knew the market was strong, we didn't know it was that strong,” said Stoltenberg, principal of Mercury Advisors, during an interview at his Bayshore Boulevard office, hours after the forum.

The strong occupancy has some downtown residential towers converting from apartments to condominiums, as originally planned in the early 2000s. With less than 10 units each available at Skypoint and Towers of Channelside, sales are fetching over $300 per square foot, or more than pre-construction prices, Traynor said.

"We are telling [renters] now is the time to buy your unit,” said Stoltenberg, who developed the 392-unit Grand Central at Kennedy. There, sale prices have climbed to more than $210 per square foot from $170 per square foot as availability has dipped below 100 units.

Nevertheless, current capitalization rates dictate that Stoltenberg's 314-unit Martin at Meridian, 1115 E. Twiggs St., will be developed as apartments rather than condos.

"Right now, it still doesn't make financial sense to build condos,” he said.

The Martin, on the drawing board since the mid-2000s, is expected to cost $60 million. Stoltenberg and his partners are still getting financing in place, but they expect to break ground by summertime.

Hardin Construction is tapped to build the 24-story tower.

The market is improving fast enough that the apartment/condo financing equation could change by the time Stoltenberg gets to another project waiting in the wings, the 32-story, 126-unit Delvillar at 858 Channelside.

"On that one we would finance it as apartments and see what the market tells us when we are done building,” Stoltenberg said.

He said the market also might see more condo financing that requires 50 percent down and the balance of payments on a schedule that satisfies the owner's obligation by the time the unit is ready to occupy.

"That type of financing is only available to a few people,” Stoltenberg said. "I think the next wave of ownership is still awhile off.”

Proximity to services attract residents

Changing attitudes and demographics are fueling interest in downtown living. Young people are waiting longer to get married and start families. Many want to live near work and avoid the hassle of commuting, especially in a community like Tampa with limited transit options.

Towards the other end of the population spectrum, empty nesters and other older residents want to be closer to medical services and amenities such as museums.

For the first time more than half of downtown Tampa workers said they are completely or somewhat interested in living in the central business district.

The 55.4 percent total is up from 36.9 percent in 2010 and 35.3 percent in 2008, according to the Tampa Downtown Partnership's latest Downtown Resident and Worker Survey.

About 7,000 people live in the downtown area, including Harbor Island. It's not difficult to imagine the number reaching 10,000 in a few years.

"Three years ago I was hoping for this day and this day is now here,” Traynor said during the March 8 forum.

Another 60,000 people work downtown.

It's all sparking new interest in office and retail activity.

Grand Central has filled its 72,000 square feet of office, with St. Leo University taking nearly a quarter of the space

Only about half of Grand Central's 108,000 square feet of retail space is occupied, but it appears that could be changing soon.

As first reported online by the Tampa Bay Business Journal on March 13, the Powerhouse Gym Downtown Tampa is planning to more than double its space to about 65,000 square feet in the coming year in a move from the west to the east side of Grand Central.

Stoltenberg's revised plans for the Martin, filed in late February, include a 36,840-square-foot, two-story retail space that has all the signs of becoming downtown's first grocery store.

Downtown boosters hope for a Publix. Stoltenberg declined to comment on negotiations with the prospective tenant.

He is confident of filling the retail space because both Grand Central and the Martin include more garage parking spaces than are required for the residences. "I've built in what I knew we needed for retail and office use,” he said.

Mark Holan's beats include commercial real estate and residential real estate.