A company that manufactures wooden play sets is set to expand its manufacturing complex in Rockland’s Industrial Park.

CedarWorks has filed plans with the Rockland Code Enforcement Office to expand its manufacturing plant at 12 Merrill Drive.

The proposed expansion would add 6,000 square feet to the company’s 51,625-square-foot building.

CedarWorks built the Rockland plant in 1987. The plant and property are assessed by the city at nearly $1.2 million.

CedarWorks was founded in 1981 in Rockport as a regional manufacturer of swing sets, play sets and other backyard wooden structures, according to the company’s Web site. Duncan Brown purchased the company in 1988 after gaining experience in manufacturing and sales in the woolen industry.

In 1989, the business became a family affair. While Duncan Brown worked to expand the company’s manufacturing and sales functions, his wife, Susan Brown, assisted in the marketing and general management of the business, according to the Web site. Their son Barrett Brown joined the business in 1997 and was named president in 2000.

CedarWorks’ product line has grown from two basic climbing structures to five play system product lines with 15 structures and numerous accessories. Sales have also expanded greatly and CedarWorks now sells swing sets and furniture to families in all 50 states and in 20 foreign countries.

Barrett Brown said the company entered 2009 with significant reservations but decided to keep going and to expedite its new line of indoor play sets. The sets are made of a combination of ash for the posts and Baltic birch instead of cedar.

He said it was soon clear that the demand surpassed not only the company’s projections, but also the capacity of the plant and the decision was made in November to expand.

The company employs 35 people. The administrative and sales offices are on Route 1 in Rockport.

The proposed expansion will be reviewed by Rockland’s code officer. City ordinance exempts projects in the Industrial Park from Planning Board review; instead the authority to approve rests with the code officer.