Hundreds of seniors are moving into the first phase of Stoneridge Creek, a 635-unit retirement community in Pleasanton.

The developer behind the 46-acre project, Continuing Life Communities LLC, completed 415 units that are offered at between $300,000 and $1 million. About 300 units were reserved before the project was completed.

“The demand was strong and continues to be strong,” said Troy Bourne, vice president of planning for Stoneridge Creek.

The developer, based in Carlsbad, bought the property and 5 acres for a park from the Alameda County Surplus Property Authority and started construction in 2011. The first phase cost more than $100 million to build.

Bourne said the average resident is in their 70s looking for an “all-inclusive” living situation and a community where they can live out their final years.

The way the community works is that residents pay a set amount upfront for a unit and services such as meals, house cleaning, utilities and amenities such as an onsite theater, gym, pool, spa and outdoor areas.

The units in the first phase range from small one-bedroom apartments to large penthouse apartments and single-level homes that are between 700 to 2,500 square feet. The maximum occupancy per unit is two people.

“Our residents are people who have a home they’ve lived in for a number of years and they’ve reached a time when maintaining the home is getting to be too much,” Bourne said.

Demand has been strong with residents coming from through out the East Bay and Peninsula cities, he said. Nationwide, demand for housing that caters to older generations has ballooned as Baby Boomers age and retire.

By 2030, about 18 percent of people in the United States will be age 65 or older, according to the Pew Research Center. Meanwhile, that figure was 13 percent in 2010.

Besides retirement communities, the change in demographics has pushed other trends like multiple-generation families living under one-roof and cooperative housing developments.

Continuing Life plans to build another 220 units at Stoneridge Creek and already has a waiting list of about 50 prospective residents. Those units could get underway in the next few years. Bourne said the developer wants to see which types of units sell best during the first phase.

Stoneridge Creek will also includes 68 assisted living apartments and a 73-bed skilled nursing facility that will be ready for residents in 2014.

The first phase, designed by Van Tilburg, was built by Palisades Builders, Segue Builders, Roberts Obayashi, Jensen Corporate Holdings and Top Grade Construction.