Tree Top Builders, the custom builder based in Exton, is reaping the benefits of a surge in the popularity of treehouses, writes Monica Buchanan Pitrelli for CNBC.

The structures aren’t just for kids anymore

Over the past decade, nature-loving homeowners transformed these structures — once cobbled together from scrap wood and bent nails found in the garage — into showpiece homes for full-time living. A luxury home nestled into a tree can cost six figures when constructed by professionals.

“A fully appointed treehouse with kitchen, bathroom, heat and air conditioning … we’re building those around $200,000,” said Pete Nelson, the star of Animal Planet’s TV show Treehouse Masters.

Even the scaled-down version for children have changed.

Professional builders are constructing them, complete with safety measures to protect the children and adults who spend time there.

According to Tree Top Builders, children’s treehouses should be 6-12 feet tall with railings that are at least 36 inches high. Additionally, mulch or woodchips have to be placed below the treehouse to help soften potential falls.

Treehouses built for adults, however, are not constrained by the same standards. Some have open-design levels with only minimal railing but a lot of style — which makes them popular as rentals.

Read more about Tree Top Builders at CNBC.