Anneke Dekker plays in her treehouse designed by Frank Hyman. Photo by Lissa Gotwals

When little Katie Concannon asked for a "princess balcony" on the treehouse, where she could "cuddle with her blankie and animals," I outwardly kept taking notes, but inwardly her request caught me flat-footed. For two decades I had been filling my mind's eye with images of the built environment of a dozen cultures. Normally a client's request generated a mental gallery of arbors, pathways, gardens and more that I could improvise from. This wasn't my first treehouse, but the request for a "princess balcony" brought to my mind a vast, white, soundless, blank space and a rising fear that for the first time I might have to tell a client "I really just don't know how to do that." And that client was a trusting little 4-year-old girl. "Yeah, princess balcony," I said. "I'll see what I can do."

The other requests Katie and her 7-year-old brother Ian made for the treehouse were all doable: a place to play board games, eat snacks and read books. A tire swing and a flagpole. A ladder and a bucket on a rope and pulley. I had worked with their parents, Sue and Kevin Concannon, on their landscape before. Now Sue had called me in to help make the back yard into a thoroughgoing Romper Room for the kids' minds and bodies.

I never had a treehouse as a kid, but being military brats, my buds and I had built forts from branches and dug foxholes to hide in. We'd dammed up creeks with rocks and climbed trees to hang tire swings. What I remembered from those days was that our imaginations could transform nothing into something. Looking back, I've seen that any boredom we felt was largely a symptom of not engaging our imaginations.

Ian Concannon swings from his treehouse. Photo by Lissa Gotwals

Albert Einstein, who probably could have appreciated a good treehouse, said that imagination was more important than knowledge. Think about that. The guy who showed us that space was curved and who divined the recipe for energy obviously treasured knowledge, but calculated that imagination chalked up a higher place on the blackboard of human values. Something to think about in an age when many parents are over-scheduling their kids in the hopes they'll become little geniuses and Baby Mozarts.

I try to keep those thoughts in mind when putting treehouses together. Fortunately, the parents I've worked with had specific goals of getting their kids out of the house, away from the video screens and into their own imaginations.

Not surprisingly, some of those parents could imagine themselves getting a little use from that treehouse, too. One mom hoped the finished project would be suitable for her to have a friend over for "a beer and a burrito." Another parent uses the treehouse as a meditation space when the kids aren't around.

In order to save money, several parents showed me their troves of scrap lumber. Scrap plywood became a roof for one, spare 2x6 planks became a diagonal floor in another, and rough-sawn 1x12s became board and batten siding on a third. Some parts came from my own inventory of odd and ends. Two small cedar trunks--all that remained of a bit of "landscape by subtraction"--became posts for a front porch. Old brass spigots have been threaded into trees to tap imaginary water, maple syrup or "root" beer.

Katie Concannon steps out onto the ledge of her treehouse. Photo by Lissa Gotwals

As Katie and Ian's treehouse evolved on paper and in my head, it took on some of the character of a treeboat. Two straight trees that would support it could be masts (though one "mast" would have climbing rocks bolted to it leading to the quarterdeck). A bowsprit made from a 4x6 beam projecting from the front could support the tire swing. Above the bowsprit, every boat needs a forecastle ... that ... could ... double as a princess balcony!

OK, now I was getting somewhere. After asking around, one colleague suggested the style of balcony found on Swiss chalets with cutouts of tulips. Going that one better, I asked Katie to draw me some pictures of animals, which I transferred to the panels of the balcony and cut out with a jigsaw. The balcony/forecastle was now a step up from the main deck and enclosed on three sides by planks with cutouts of an owl, a butterfly, flowers and a cat with a curvy tail. The balcony also sported a plank in the floor that could be lifted to reveal a secret chamber for hiding jewels and coded messages.

To my eyes the results looked fabulous. But would they survive the acid test?

On the first day the treeboat was "launched," both kids scaled the Swiss Family Robinson-style ladder carved from a log and played there heartily with their friends. Katie stayed in it all day asking that her meals be brought to her and wanting to sleep in it overnight. The princess did get her meals catered, but that night she cuddled with her blankie and animals in her own bed.

Also in Casa Treehouse tips How to make a custom hideaway for the kids (or the grown-ups) By Frank Hyman Off the grid How a couple's nature-friendly dream home ran up against the law: Jesse Crossen and Hope Donny-Clark and the urban caravan By Katy Barron