Hidrock Properties is converting one of its Garment District loft buildings into office condominiums.

The 12-story building at 35 W. 36th St. — built in 1911 — sits between Fifth and Sixth avenues in the Transit Triangle and has had numerous upgrades and improvements.

Office condo specialists Michael Rudder and Michael Heller of the Rudder Property Group are pre-marketing the units that range from roughly 3,300-square-foot half floors to 6,600-square-foot full floors.

Some are still occupied by office tenants under leases that expire over the next few years.

The decision to convert to ownership was made because the building’s central, two-door elevator opens directly onto each half floor. Hidrock Chief Executive Abie Hidary says, “There’s no hallway, and it feels like you have your own full floor.”

Some floors have already been renovated as pre-builts with whitewashed exposed brick, glass dividers and upscale pantries and bathrooms. There is 24-hour key-card access, a doorman, and individual HVAC units.

While exact pricing is yet to be determined through an approved offering plan, it is expected to range from $875 per square foot on the lower levels to $1,100 per square foot on upper half-floors that have three sides of windows.

“For $3.3 million you could have a large office in there and finance 90 percent or more of the purchase price with a Small Business Administration loan,” Rudder explained.

As common charges and property taxes total roughly $14.50 per square foot and comparable buildings cost about $20 per square foot, Rudder added, “Hidrock runs an excellent building at an excellent cost.”

Office ownership allows businesses to skip the costly commercial rent tax, while not-for-profits and foreign governments can apply to have the city property taxes waived.

The building has two stores, and the sale of those units — one of them a café — is also on the horizon.

HFF recently placed a $32 million three-year loan on Hidrock’s behalf through Ladder Capital Finance.