We have a submarine in our house. The lower-deck quarters—two connected rooms with a wood central ceiling where you have to be careful not to bump your head—link via caterpillar-tube passageway to ladders that lead to the upper deck.--- There are two ladders—sturdy child chairs upturned and rested on the cushion-less couch—because my children do not want to share. Also, Sylvia keeps climbing onto the roof sheet of the pilot house and collapsing it, much to her delight and Theo's horror.

At nearly 21 months, she gets some of the attraction of a fort, though, and when she’s not destroying one, she’s gleefully crawling inside its tiny spaces. Theo, four and a half, really gets forts.

He's the current inspiration and design mastermind: He occasionally draws a picture of his idea and presents it to me as a blueprint. Other times, we construct something collaboratively or he does his own pillow-propping. Completed, the forts generally fall into one of a few favorite categories: sea-going vessel, spaceship, knight's castle, dragon's lair, or happy baby-animal den.

I am happy that our couch is so often reappropriated for fort building, that boxes spend weeks in changing incarnations, that we had a cardboard rocket in our backyard for three months last summer. I love, too, that when Theo wanted a break from Sylvia's sabotaging of our couch construction, he hauled his camp chair to the observation deck of the more permanent wooden fort outside.

I love forts—love seeing them, creating them, remembering the delicious and giggly seclusion of sitting inside their perfectly little-me-scaled spaces. And I’m in good company—a New York Times essay exploring the art of pillow fort construction wound up among last Thursday’s most emailed Times articles.

The piece assumes an innate human inclination toward fort building and posits that's where architecture begins. It references an architect's blog that critically analyzes a series of box and cushion structures, the "basic building blocks of the design world." A commenter on this blog actually laments, "My couch doesn't have removable cushions. My kids are missing out on so much!"

But upholstery has no monopoly on fort-building components. Chairs, tables, desks, blankets, umbrellas, curtains, sticks, snow, trees, duct tape, scrap lumber, old culverts…material inspiration is everywhere. Design complexity and detailing vary.

Based on my experience and a crack survey of friends and relatives, key fort features incorporate essential coziness, privacy, kid scale and kid rules. There may be the atavistic affection for huddling in caves, but the main thing is imagining and then creating and then occupying your own little semi-secret-in-plain-sight place for a while.

“We all like space that fits us,” is the consensus of the architects quoted in the Times article. They address children’s joy and satisfaction in claiming personal places amid larger environments where kids have little control. So forts offer pint-sized refuge and a sense of authority; their invitation to fantasy and structural experimentation also includes a little sheet-shrouded laboratory for shaping their world, or at least their immediate habitat.

Considering this, I realize it's entirely possible that my current fascination with forts stems from a desire to create one for myself—a private retreat within a home environment over which I currently have little control, overrun as it is with toys, clothes, dishes, half-spawned and half-finished projects, dog hair and, yes, blanket forts.

I'd set up a little reading nook in there and a little lamp for my little desk and old typewriter. I'd rig a pillowcase skylight for my hideout/dominion. This makes such good sense! Forts for everyone! When Sylvia was born, insightful friends gave Theo a tent for when he needed some time to himself. I've been wondering lately why they didn't give me one, too.

Of course, from my perspective, much of the fun of fort building is in creating something together; it's a pleasure made of equal parts memory and observation, my childhood and my children's. This is a sweet fence to ride. My kids are little enough that I am still an important part of fort creation. And although I often don't fit, I'm invited inside.

But there will come a day when the thrill of Theo and Sylvia's forts will stem from their being beyond my jurisdiction—when their fort-only secrets will be only theirs, not the moist, breathy, preschooler stories exhaled into my ear.

This will be hard. Now, I just have to reign myself in from heavy-handed creative direction, to let Theo's precarious cushion balancing prevail. When my outright exclusion comes, it will be an emotional blow. It also will be just a huge bummer because I'll have to find another fort outlet.

One of the interviewees in the Times piece tears up remembering her days of fort-building glory with her sons. Another addresses the idea of impermanence—how forts teach the value of change (and maybe also of eventually having to clean up the living room). An architect friend of mine proclaims that when it comes to forts, the less stable the better because then you can keep rebuilding it.

The Times writer wonders whether this advice about letting things fall down is meant for the kids or the parents: “[M]aybe the experience isn’t about togetherness. Maybe it’s about letting go,” he writes.

I hope that I'll bring that sort of distance and maturity to my eventual expulsion from fort building. But I'm grateful I'm nowhere near that yet (and honestly, I'll probably try to hang onto fort inclusion far too long).

In keeping with the circumscription of the fort-world, I’m going to focus on the space I’m in now. Perhaps the fort-applied notion of creative destruction will one day expand to my adult sphere—maybe I’ll build one of those cool, modular, Dwell magazine office/lounge sheds. Today, though, I think Theo and I will just have Sylvia wreck our submarine so we can build another one.