Exact numbers on swing sets and play gyms are hard to come by. Market‑research firm NPD Group includes them in the $2.9 billion a year outdoor and sports gear category, whose sales have held steady over the past year.

Donald Hoffman, chief executive officer of specialty swing‑set maker Creative Playthings, said his sales are slightly down this year as the housing market stalls, but those who are buying are getting ever‑bigger playsets.

Like other specialty retailers, the Framingham, Mass., company sells its swing sets only through catalogues, its Web site and its own stores, not through mass retailers.

Toy retailer Toys “R” Us also reports greater demand for its readymade swing sets, especially those made of wood, as opposed to metal, said Juan Arrizabalaga, who directs the store’s team of buyers of swing sets and other outdoor items. He said parents want sets that look good in the backyard when friends and family come to visit.

While Toys “R” Us’ readymade sets are generally cheaper, running from around $119 to $1,119, installation is do‑it‑yourself and can take hours. The toy retailer doesn’t sell customized sets, although it sells accessories, like sandboxes, separately.

The U.S. government doesn’t regulate how residential swing sets are made, but many manufacturers follow voluntary guidelines set by the industry. About 50,000 children go to the emergency room every year because of injuries that occur while playing on backyard swing sets, and 80 percent of those injuries are caused by falls, according to the U.S. Consumer Product Safety Commission.

The commission recommends that people choose a level ground for the equipment and put shock‑absorbing material, like wood chips, under the set and at least six feet beyond its perimeter.

For parents who have already made big investments in home and backyard improvements, wooden swing sets are a natural addition.

“It’s like another room in the house,” said Jennifer Kroll of Yonkers, N.Y., who had Lapp build an $1,800 swing set for her new home last fall. “You’ll spend that much on a piece of furniture.”

Kroll’s set came with two swings, a slide and a wooden playhouse with green shingles on the roof. Her children love climbing up the rock wall and swinging on the trapeze.

“My son is like a monkey on it,” she said. “He flips.”

Kroll researched more‑established swing‑set makers, including Creative Playthings, Rainbow Play Systems and CedarWorks, but chose Lapp’s company, Green Tree Woodworks, mainly because of its prices.

At CedarWorks, where buyers and designers work together to create three‑dimensional models online, prices for a custom swing set start at $1,500 and “can go literally anywhere,” said CedarWorks President Barrett Brown. The Rockport, Maine, company uses only northern white cedar, a species of tree whose wood requires no annual maintenance, like staining, because it doesn’t splinter.

Brown said his company sold a swing set in May for $40,000 to a family in Fairmount, Ga. The playset, featured on the company’s Web site, has a total of eight castles, gazebos and towers, including a make‑believe crow’s nest, connected by a system of bridges and monkey bars that lead to an above‑ground “sky” tunnel, several sling swings and picnic tables.

CedarWorks’ online design system, a part of which is called “Cedar3D,” stands in sharp contrast to Green Tree Woodworks’ two‑room workshop in Quarryville, Pa., right outside Lancaster. Lapp doesn’t use electricity, answers his phone only between 9:30 a.m. and 10 a.m., and only recently created a Web site. “We don’t own a computer,” he said.

If people could find him on the Internet, Kroll noted when her swing set arrived last fall, “his business would triple I’m sure.”