Simon Lancaster’s tree house in San Jose’s Cambrian Park neighborhood is a childhood dream come true, even though it was built long after he became an adult.

The tree house was custom-built out of pine and Douglas fir by Oakland-based O2 Treehouse for a tidy sum of $22,000. “I hired a professional to ensure the health of the tree and the safety of my children,” he said.

One side has a window that looks right into the canopy of his backyard oak tree, the other side has an opening that allows his children to grab a firefighter’s pole and slide down to the ground.

But the tree house may have to come down because it apparently has run afoul of city building codes.

It sits 10 feet off the ground above a fork in the tree trunk and stands a little more than eight feet tall, for a total height of 18 feet, 4 inches.

A city code enforcement officer who visited the Lancaster home Feb. 27 concluded the tree house is an accessory structure and as such cannot be taller than 12 feet. He followed up by sending a violation notice demanding compliance with the height requirement.

The inspector had responded to a next-door neighbor’s complaint to the city that the tree house was “way too big” and infringed on her privacy. The neighbor would not give her name for this story but said she and her husband “can’t sit in the backyard because the kids make a lot of noise when they go up.”

In his appeal of the city’s decision, Lancaster said he’ll argue that prior to construction, planners told him the tree house was not an accessory structure.

That’s why he didn’t think he needed to comply with accessory structure height limits or bother to tell city planners the tree house would be more than 18 feet from ground to roof.

“I tried to do my due diligence online and it was very confusing, so I called the city for clarification on Feb. 20 and 21,” Lancaster said. “My recollection is that for something to be a structure and covered by the code it would have to be underground or attached to the ground.”

He did ask if a ladder attached to the tree house would be considered a connection to the ground and said he was told no. The ladder hangs from the tree house and is not attached to the ground.

So, Lancaster went ahead with construction, saying he was only informed after the tree house was finished that it would need to comply with accessory structure codes. He was not required to get a building permit because one is only required for accessory structures that are 120 square feet or larger.

Lancaster’s tree house is approximately 100 square feet.

City code describes an accessory structure as a “separate and subordinate structure which is open in nature and the use of which is purely incidental to that of the main building.” Examples include, but are not limited to, fences up to seven feet tall, gazebos, arbors, trellises and pergolas.

“Not every possible structure, including tree houses, is specified in the existing Municipal Code,” planning, building and code enforcement spokeswoman Cheryl Wessling said in an email. “Tree houses have become more elaborate in recent years, some resembling small housing units in a tree. Over the last 20 years, we’ve had about 50 code complaints on tree houses; almost half of these have been in the last eight years.”

Wessling went on to say that the larger, more elaborate structures are often the ones that attract unwanted attention.

“We’ve seen tree houses larger than 120 square feet, with pitched roofs, finished siding and windows, and with staircases and electrical wiring,” Wessling said. “In (the Lancaster) case, the property owner is not being asked to tear down the structure but to make it conform to the height restrictions for accessory structures.”

Lowering the tree house isn’t a cheap option.

Dustin Feider, the founder of O2 Treehouse, said the structure could be lowered and rebuilt to comply with the height limit, but “it would barely be a tree house anymore.”

“We always put a tree house in the crown of the tree to allow for the most amount of interior space,” Feider said. “We chose the location for Simon’s tree house so it would be open and people could stand up inside.

“To have us come out and disassemble the existing tree house and rebuild it lower in the tree would cost nearly as much as the original tree house cost,” Feider added. “We’d have to take the entire structure apart and purchase new materials. We built the platform first and everything else was built around it to fit into the tree. So, we had to react to all the branch positions as we went along.”

To keep the same footprint for a lowered tree house, the “tree trunk would be in the interior and some branches would probably be inside,” Feider said.

Wessling noted that the city may consider developing tree house-specific code language.

But that doesn’t help Lancaster, who only wanted to build a fun play space for his kids.

“Looking back, of course I realize I should have built a stronger relationship with my neighbor,” he said. “When we talked in February, I tried to come up with reasonable solutions to his privacy concerns, which I understand. I rotated it 90 degrees so you can’t look into his yard and I offered to plant screen trees, but he declined.”

As for the noise, Lancaster says simply that “kids will be kids.”

“I love seeing the kids outside and they love climbing up and down, playing with toys up there and feeling the tree house sway in the wind,” he said. “We’ve camped up there and because the roof is clear Plexiglass, you can see the sky at night.”

Since a date hasn’t been set for Lancaster’s appeal, he and his children are continuing to play in the tree house.

The hearing officer can “uphold, modify or dismiss the code enforcement order,” Wessling said.

The city’s code enforcement staff will present evidence showing why they think Lancaster’s tree house violates municipal code and the hearing officer will consider that information, as well as Lancaster’s arguments.

If Lancaster disagrees with the hearing officer’s decision, he can appeal to the seven-member Appeals Hearing Board.