The cost of building a tree house can range from zero — free scrap wood and lots of personal elbow grease — all the way into professional construction and design firms creating a 6 figure arboreal mansion.
In my experience there are roughly three stages, and each costs more than the previous:
First, you’d want to get an evaluation of the trees you have available to build in and establish what exactly you want out of a treehouse. Hired help may take the form of an Arbourist to check the health of the trees and an initial consultation with a designer who can help you to define the functional parameters for the project. This often accounts for about 5% of the budget.
Second, you’ll need to come up with some design ideas that fit your needs and develop them into a carefully detailed plan that can be built from. At this stage, the designer / architect or builder can assist in creating a structurally safe yet stylish set of plans that work for your trees and intended use. It is also possible to create a materials list and an estimate of the cost of building the structure at this point. This costs about 15% of the budget.
Third, actually buy the wood and start making the structure. Professionals builders, carpenters, and labourers are hired at this stage to complete the plans. The input of a designer can be helpful here as it is often necessary to improvise around unforeseen challenges or to capture special characteristics that are only discovered partway into the build. Of the remaining 80% of the budget, materials usually account for around 1/4 of that and the rest is labour costs, overhead, and equipment.
The DIY inclined can do much of these stages themselves to save some money, and then call in the help for areas as needed. However, there can also be other variables that increase the costs in this formula depending on the complexity of the project and the level of fine finishing required.
There is an interesting article from the Washington Post that includes some comments from a contractor about the costs involved in building a treehouse:
“Treehouses are everywhere,” says Peter Nelson, author of four books about treehouses, most recently “Treehouses of the World,” and co-founder of TreeHouse Workshop, a treehouse-building company in Seattle. . . . “You take a walk in the woods, and nature has an incredibly soothing effect. It’s rejuvenating,” he says. “Treehouses are a part of that.”
Treehouses run the gamut from DIY affairs sketched out on a kitchen table to kits found online. Some people turn to local contractors or a handyman for the actual construction. Others call in a specialty treehouse design firm.
The costs escalate accordingly. Nelson’s no-frills (and no walls) models start at $85 a square foot, for just a platform. At the other extreme, a playhouse with walls, roof, ladders and a bridge can start at $20,000. The most expensive he has built cost an extraordinary $320,000 and included modern amenities such as fireplaces, stainless steel appliances, running water and plumbing. These projects, he admits, are actually more second homes than true treehouses. “When it has things like kitchens and bathrooms, it loses some of its spirit,” he says.