An acquisitive real estate investment firm has locked down the purchase of its 13th storage business in South Carolina.

Ladera, Calif.-based Strategic Storage Trust Inc. said it has paid $6.6 million for Admiral Self Storage at 8550 Rivers Ave. in North Charleston.

The property is north of Ashley Phosphate Road. It has 630 units and about 97,000 square foot of space in two buildings. It also rentals parking spaces for owners of boats and recreational vehicles.

It was built as a retail center in 1974 and was converted to a self-storage business in 1999.

“This 10-acre Charleston site includes an expansion opportunity, which consists of additional RV/boat parking along with additional drive-up self storage,” said H. Michael Schwartz, chairman and CEO of Strategic Storage Trust.

It is the company’s seventh self-storage business in the Charleston region, where it has owns about 4,300 units. It acquired the other six last year, when it bought a portfolio of 16 properties in South Carolina, Florida and Georgia from Charleston-based Jupiter Holdings Inc. for $75 million.