Treehouses are hot right now. There’s a popular reality TV show (“Treehouse Masters” on the Animal Planet channel) devoted to their construction, and no shortage of “treehouse resorts” popping up that promise to let guests return to their childhoods, at least for a week. Really, though, many of the treehouses getting all of this attention have nothing to do with kids—they’re house-like structures full of amenities geared for adults.
“Treehouses are a trend right now, but it’s a long-lasting trend. They have been increasing in popularity since before I got involved with them; treehouses have always been popular in England and throughout Europe, and they seem to be just catching on in the U.S.,” says Dan Wright, who founded Tree Top Builders back in 2003 and has built more than 100 treehouses. His company is based in West Chester, Pennsylvania, but he travels the country—occasionally, even the world—to build treehouses for clients. There is a relatively limited number of companies that specialize in treehouse construction, and Wright is one of the few of those who also is a certified arborist.
Wright had experience in challenge course climbing and carpentry, and he figured there was no better way to combine those two passions than by constructing treehouses. “I became a certified arborist along the way; I learned tree climbing from another arborist who was building treehouses at the time,” he explains.
“There aren’t too many people doing this,” he notes.
It’s a specialized niche, and there aren’t necessarily textbooks explaining the intricacies of treehouse construction.
That means that those in this business need to be inventive and resourceful.
“I’ve learned a little bit from a lot of people, but a lot of the time it’s just been me figuring things out,” says Wright. Typically, the books about treehouses are glamorous profiles of treehouses rather than how-to guides. “And a lot of the guides that you do see at the bookstore [contain techniques that] are not good for trees – they’ll tell you to wrap cables around trees, which girdles them, or bolt boards directly to trees.”
Using improper techniques and materials can damage not only the tree, but also create serious safety problems.
For example, the swaying movement of trees can cause the treehouse structure to break. It’s difficult even to predict what impact the natural growth of the trees will have over time.
“If you bolt a board to a tree, the tree is going to try to grow around that board. At some point, its new tissues are going to support that board in place. But the other thing that can happen is that it can push a board right over a bolt head, and that could eventually make it fall down,” Wright says.
Sometimes things do work out (“I’ve seen some 30-year-old, homeowner-built treehouses that are still there,” he says), but, given the safety implications involved, the safer bet is to use specialized equipment and time-tested construction techniques.
For instance, instead of traditional bolts, Wright uses specialized large fasteners called TABs (treehouse attachment bolts) when connecting the structure to trees. (There are a number of treehouse product supply companies, such as TreeHouse Supplies, offering these types of specialty components, as well as how-to videos.)
“There is a trade-off,” he explains. “Because they are larger, you have to pre-drill a larger hole in the tree initially. So you’re interrupting the tree’s transport system in a bigger way by creating a bigger wound. However, you can also perch loads out away from the tree. So you can put a beam 3 inches away from the tree trunk, so you have 3 inches of growth before you have to do any maintenance. And a lot of times you can separate the beam from the joist and slide the beam out even farther later on. So, these systems offer extendable life spans.”
On the East Coast, trees might grow one-eighth- to one-half-inch per year (radius), so 3 inches of growth would mean somewhere between 6 and 24 years before maintenance is required.
The physical connection between the tree and the structure is what’s truly at the heart of constructing a safe, high-quality treehouse. “Our expertise, really, is attaching things to trees,” Wright says.
“That could be a little platform for kids to have a picnic on, or it could be a guest room, or even a room for a bed-and-breakfast that gives them another rentable unit.”
Taking stock of the trees
The first step in any project, Wright explains, is to talk with the client to find out what kind of project they’re interested in. “We then have to assess their trees and their budget, and make sure we have a good fit,” he adds. A combination of sketches and AutoCAD plans help to create a final design, and then work can begin.
For anyone building a treehouse, knowledge of trees can be very helpful. “It doesn’t always require that an arborist look at the trees, but it’s usually a good idea,” Wright says. “If I’m going to visit the site, I’m comfortable assessing the trees. Occasionally, if I see something I don’t recognize, I will call in a consulting arborist with more experience.”
Certain species of trees are better for treehouses than others, he says. Some compartmentalize poorly, though, and that would limit the type of project they would be suitable for. “If someone wanted to build a $100,000 guest room with a bathroom and a kitchen in it, I wouldn’t advise building it in something like red or silver maples, or cottonwoods, or things like that. But if it’s just a backyard kids’ treehouse, then, sure—you could build that in an apple tree.”
Generally, he likes to work with middle-aged trees that are free from structural defects. “I can live with a structural defect that’s up higher, especially if we’re talking about a branch that’s leaning away from the project,” he notes. “But I wouldn’t want to mount our main support beam above a structural defect.”
In cases of smaller, less-expensive projects, the client may only be looking for a lifespan of five or 10 years. The more- expensive projects that involve substantial financial investments might need to last 30 years. Wright says he listens to what the client wants and then makes sure that the trees he’s building it in will last that long.
In some cases, pruning work is required in the tree before construction starts. “I like to remove dead wood only, if possible, because we are putting holes in the tree as part of the construction process, so the tree really needs all of its available vitality to respond strongly to those wounds. We want a lot of wound wood formation around the bolts in the first few years,” Wright says. Removing the dead wood also eliminates hazards.
There are times when green branches are removed, as well. That’s often with branches that would pass through a wall and up through the roof. Sometimes that’s the desired effect, but other times a priority is placed on making the structure waterproof. Anytime a wall or roof is built around a branch, there will eventually be a leak as the tree grows and moves in the wind, Wright stresses. Plus, it takes more time during construction to build around branches, so the project will cost more.
“So, sometimes there’s a case to be made for removing live branches,” he states. “In those cases, you evaluate how important each branch is to the tree. If it’s smaller and not that important, and it’s going to be expensive to work around, and you’ll eventually have a leak, you cut it; if you’ve got a really important branch and it’s bigger, you might decide to leave it.”
Since the time that Wright first learned climbing from another arborist, he says, he’s seen some changes in the industry—like the use of the Blake’s hitch rather than the taut-line hitch—but the general principles of getting up and down the tree remain the same, whether you’re in treehouse construction or tree care. “We climb just like arborists do,” he says.
The first 5 to 10 percent of a project usually involves working in and around the trees. After that, ropes are typically used only as safety lines as construction can take place on the treehouse deck.
“At that point, we’re more like carpenters who are working at height, but we’re still using arborist ropes and we’re wearing tree-climbing saddles,” Wright says.
The ropes are also left in the trees throughout the entire project (although they’re sometimes moved higher after the platform is set) and are the last thing to be packed up when the job is done.
“You never know when, for example, you’re going to need to put some trim on a window and hang over the edge,” he says.
The most time-consuming part of treehouse construction is the carpentry, he explains: “On an average project, we might spend one day leveling between the trees, installing the bolts and hoisting the beams. And then you build a deck, and then railings and stairs and walls, siding, windows, roofing, accessories—it’s mostly carpentry.”
The average treehouse is only 8 to 12 feet off the ground. “But, occasionally, they do get pretty high—30 or 40 feet up,” he says. Whatever the height, all of the building materials need to be brought up. It’s possible to simply hand the materials up if the treehouse will only be 8 or 10 feet high, but higher structures require the use of block-and-tackle and lots of ropes to hoist things higher.
Most features are built in place rather than assembled on the ground, which would then require lifting a very heavy component rather than individual boards. Still, says Wright, “We’ve hoisted beams into the air that weigh 1,000 pounds.”
Twice each year, Wright conducts workshops to help educate others about the construction of treehouses. More than half of those who attend typically are tree care professionals interested in adding treehouse construction to their list of services, as well as carpenters looking to expand their capabilities, but there also are homeowners contemplating taking on their own project. The classes cover construction techniques, as well as the different specialty attachment bolts and brackets used in treehouse construction, and the various cables and hardware needed to construct tension bridges and zip lines.
For those in the tree care industry who are interested in expanding into treehouse construction, Wright says he has two pieces of good news:
First, most treehouses can be built with basic carpentry skills and supplies. “You have to do everything right, and fasten everything properly, but most of them use basic materials,” he explains.
Second, most tree care professionals probably already have most of the tools necessary and would only need to purchase a few items. For example, says Wright, “There’s a certain kind of drill that we use for pre-drilling for the TABs; we use an electric drill that works at a very low speed but high torque – I burned up some standard drills on my first year doing this.”
It’s also important to check to see if you’re covered from an insurance perspective.
“You have to ask your broker if you are covered for carpentry and construction, which most arborists are not,” Wright says. “A lot of times, they’ll let you build one if it’s not your main line of work, but you should definitely ask your agent.”