How to build a treehouse

There's something magical about treehouses. Perched amid the greenery, seemingly closer to the sky than the ground, these epicenters of endless adventures inspire whimsical visions in the young and the young at heart. Constructing one of the branchy bungalows is an exercise in pragmatism, requiring thoughtful planning, sturdy design and careful building. Don't worry, though. They’re easier to build than you might think.

"If somebody can build a deck and a shed, they can probably build a treehouse," says Dan Wright, founder of Tree Top Builders in Exton, Pa., a boutique treehouse construction firm.

Here are tips from three pros to help you get your treehouse-building plans off the ground.

If your neighborhood has a homeowners association, look at the bylaws, which may dictate the maximum square footage of the treehouse, its placement on the property and its height from the ground. You may also need to obtain permission from the township, city or county you reside in, so consult the department with jurisdiction over issuing building permits for your property. "The biggest thing is talking to your neighbors," says Conner Drummond, director of operations of Backyard Playground in Richmond, which has built more than 4,000 customized treehouses. "Just be courteous and make them aware it's going in."

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You’re looking for a healthy tree without mold or other damage, and it should be at least a foot in diameter at chest level, according to Wright. But it can't be too big, Drummond says, because if the tree is three or four feet in diameter, any deck built around it will be massive. "And we like the tree to be straight," Drummond adds. "If it's got a huge curve, it's going to take up a lot of deck space, reduce a lot of room up top, and make it all a little bit more challenging."

The average backyard treehouse will cost between $2,000 and $10,000 to build, depending on its size and the complexity of its design, according to Wright. "That includes all the materials and the beer you’re going to have to buy your friends to help you," he says. Christopher Richter, co-author of "How to Build a Treehouse," suggests sketching a design, either by hand or in a 3D drawing app, so you know exactly what materials you need and have a firm plan for your workflow.

Also keep safety in mind when planning the treehouse. If it's designed for children, it shouldn't be more than 6 to 10 feet from the ground and the deck should have a sturdy slatted railing surrounding it to prevent falls. Depending on your insurance provider and homeowner's policy, a treehouse may or may not be covered, so call your carrier before you start building to ask how your policy might address it.

To build a treehouse from just wood, Richter recommends having a cordless drill, handheld circular saw, hammer, measuring tape and pencil on hand. If you’re working with metal or plastic as well, perhaps for the roof or a slide, Wright suggests adding further specialized cutting equipment to your arsenal, such as angle grinders, band saws and jigsaws. You will also need a ladder, and a climbing harness can help ensure your safety when doing work high up in the tree.

"We almost always use pressure-treated pine," says Drummond. "It's cheap, widely available, extremely strong and lasts a long, long time." Other options include cedar, cypress and redwood, which are naturally rot resistant, but more expensive. No matter which wood you use for the exterior, Drummond recommends periodically applying stain or sealant to keep it looking fresh, protect it from mildew and reduce UV damage.

Stilt-like supports are the simplest method for supporting a treehouse. Drummond says to be careful when digging the holes to set them in concrete, to avoid damaging the tree's root system and degrading the health of the tree. Alternately, treehouse attachment bolts (referred to as TABs by the pros) are drilled into the tree to create artificial limbs to build on. These bolts are often complemented by steel cabling hung from the tree and connected to load-bearing beams in the platform of the treehouse. Richter recommends putting as few holes in the tree as possible, because even small ones made by nails create points where mold and other diseases can infect the tree.

For most of the treehouse roofs he constructs, Drummond relies on overlapping wood boards supported by strong rafters. This sturdy building technique is designed to withstand falling branches and battering from the elements. If shingles are a part of the roof design, he says, remember that they weigh more than wood; take the additional poundage into account when designing the support system for the treehouse. Also, don't build your roof around the tree, no matter how whimsical you think it looks. "Sealing the ceiling becomes impossible," says Richter. "It will leak, there will be airflow around it, and insects will be crawling up and down the trunk."

"I recommend as many ingress and egress points as possible," says Wright. "Kids like to go up and down in different ways." The possibilities are myriad: sloping ship's ladders, slides, rock walls, cargo nets, fireman's poles, spiral staircases, ziplines and ramps. If you install a rope ladder, Wright recommends staking it to the ground, because if a hanging ladder gets snagged while being raised, it can pull an unprepared child over the edge.

The sky is the limit when it comes to decorating. Add a wooden ship's wheel and a bird cage with a parrot doll perched inside to create a pirate ship. Attach a few futuristic looking dials and gauges to the walls for a time machine. Other fun design flourishes include skylights, portholes, a trapdoor or concealed cubbies for hiding treasures. "My favorite addition is a rope bridge out to another platform," says Wright "An overlook, a crow's nest you build higher in the tree or a little perch that doesn't have a roof on it."