How to Build a Treehouse in 15 Steps

Check Your Local Building Codes or HOA Regulations

With a project as big as a treehouse, chances are high that you’ll face some sort of local building codes or HOA regulations. Before you make any concrete plans, look up your local agency guidelines to ensure you can build the treehouse. In some cases, you’ll need to acquire a permit before you can get started.

Pick the Best Tree for Your Treehouse

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A strong foundation is a must, so—now that the paperwork is out of the way—pick the most suitable tree for building your treehouse. There are a few questions you’ll want to ask yourself while choosing a tree, including:

• Tree shape—Does the tree trunk grow into a “Y” shape to support the structure?

• Tree type—Is this type of tree strong enough to hold a treehouse? Oak and maple trees typically work the best, depending on what’s available in your region. 

• Integrity—Does this tree appear to be damaged or dying?

• Strong roots—Are the roots visible or are they mostly underground? Try to avoid trees with very shallow roots. 

• Strong Branches—Have any large branches broken off the tree over the last few years? Do the branches look sturdy? Try to find a tree that has two to three strong branches.

• Height—A tree that’s too short may not be structurally sound enough for a treehouse, but a tree that’s too tall may be unsafe for children. Try to find a tree that meets somewhere in the middle.

If you’re unsure of the tree in question, it’s a good idea to speak with an arborist near you and have your tree inspected before you invest in a project of such time, money, and labor. 

Draw Up Your Plans

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No matter how big or small, simple or complicated—every carpentry project needs a blueprint (or at least some sort of written plan) to keep you on track. Some homeowners opt for a premade treehouse plan to avoid all the complexities that come with designing and measuring the design from scratch. 

For those who do choose to build a treehouse design from scratch, try to plan your measurements as accurately as possible. This will help you gather the right amount of materials for the build.

It’s important to start by measuring how high up the tree you’d like the ground platform to be (remember, not too low to lose its whimsey, but not too high to be dangerous).

Once you’ve determined the height, ask yourself the following questions and draft up your blueprint accordingly:

• Platform measurements—How far from the tree trunk would you like the floor to expand? 

• Foundation plans—Will the foundation be in the ground or from a support beam on the tree? Or a combination of both? For safety, it’s recommended to support your treehouse using floor beams. This guide will reflect that design.

• Treehouse walls—How high up will the walls be? Will you be using planks or plywood sheathing for the walls?

• Doors—Where will the doorframe be? Will it just be an open-door frame or will you be installing an actual door?

• Windows—Are you including space for windows? Will they be framed?

• Stairs—Where will the stairs go? Will you be purchasing something premade or will you custom-build stairs or a ladder?

• Deck space and railings—Will there be “deck” space outside the actual treehouse? If so, railings are a must for safety. Include these elements in your blueprint.

Build the Support Beams and Floor Frame

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If your treehouse will be supported by floor beams, start by marking their locations using cinder blocks. You will need at least four support beams in most instances, but your design may call for more. 

It is possible to solely use the tree trunk to support your treehouse, but for safety purposes, this guide will follow the floor support design. 

• Raise the floor beams. Once all four (or more) cinder blocks are spaced according to plan (the tree should be in or close to the center), place a pre-measured and cut 4x4 wood post into each cinder block. When determining the height of your floor beams, consider whether you will add a handrail around the perimeter of the treehouse. If so, make sure the beams are tall enough to use as corner posts for the railing to attach to.

• Start the floor frame. Connect the four posts using 2x8 planks, a framing nailer, and 3-inch framing nails. This floor frame will support your treehouse floor, so measure the height accordingly before nailing.

• Keep it level. Use a level to ensure these posts are straight before nailing them to the floor posts. An uneven foundation will result in a slanted floor, posing a safety hazard.

Lay Out the Design of the Floor Platform

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Let’s continue building the floor platform of your treehouse. Before attaching the decking planks to the foundation, lay out the design on the ground first as a practice run. In this step, you will decide which direction you want the floorboards to point, as well as how wide you plan the deck to be. Though the deck’s dimensions should already be determined in your blueprint, laying out the planks will help you visualize the true size. Make adjustments to the blueprint in this step if you notice the deck looks too narrow or too large during the trial run.

Secure the Floor Joists

Floor joists are structural supports that run perpendicular to the floorboards. The direction of the floorboards will help you solidify where the floor joists will go. Search online for a floor joist calculator for an easy way to calculate how many floorboards you’ll need—but be sure to double-check your measurements before you tackle this step to ensure you have enough material! 

For the average treehouse project, two to four should be plenty, but larger, more elaborate treehouses may require more. Evenly space out the joists from the center. Consider drilling your center joists into the tree trunk itself for extra support. To do this, pre-drill both the lumber and the tree trunk to avoid damage.

Attach the Joist Hangers

Once all joists are in place, attach joist hangers to the corner of each joist, using 1-inchgalvanized nails and a hammer to secure them in place—not screws. Be sure to hammer in nails for every hole in the joist hanger to guarantee the platform can hold the max capacity.

Cut and Secure the Angle Braces

Though your structure may start to take shape at this point, without secure angle braces, the whole floor platform will be unstable and dangerous. That’s where angle braces come in. Secure the floor frame even further by using 4x4 posts as angle braces where the original four (or more) floor beams meet the floor frame. Use a circular miter saw to cut a 45-degree angle at the ends and secure them in place using a nail gun with 3-inch framing nails or a 10-inch lag screw.

Install the Floorboards

Once you’ve stabilized the floor platform, you can now start working on securing the floorboards (2x4 planks) to the floor frame using your nail gun and framing nails. Remember, the floorboards should be laid perpendicular to the direction of the floor joists. You may have to measure and cut planks as you go to fit around the tree trunk, so keep your tools on hand for quick, little changes as needed.

Build the Wall Frames

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With the deck boards in place, now it’s time to assemble the frames for the four walls. Do this by using 2x4 planks based on the dimensions of your blueprint. The wall frame should consist of one top, one bottom, and two side planks in the shape of a square or rectangle, depending on your design. 

Starting from the center of the plank, evenly install two to three stud planks, then secure them with framing nails. Do this with every wall frame, being sure to frame out space for the windows and door—if you’re including these in your design. Then secure the entire frame to the floorboard using a nail gun and framing nails.

Build and Attach the Roof Frame

Your structure now vaguely resembles an actual house, and with every house, you’ll need a roof! To build and attach the roof frame, follow these steps:

• Start with the ridge beam. Cut a ridge beam for the roof using 2x6 planks. The length of the ridge beam should measure the same as the width of your treehouse (this may differ depending on your specific design plans). You’ll have to use scrap planks to hold the ridge beam up while you secure the rafters. 

• Attach the rafters. Use 2x4 beams as your rafters, creating a gable roof. Attach each rafter from the top of the wall frame to the ridge beam at two feet on the center, or according to your blueprint. The edge of the beam touching the ridge beam will need to be cut at a 45-degree angle with a miter saw.

Install the Siding

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You should see the treehouse really taking shape at this point—all that’s really left is filling in the spaces of the frames. To complete the sides of your treehouse, be sure to do the following:

• Pick your siding material. Pick a siding material for your treehouse. Popular options include wood panel sheet siding and horizontal wood plank siding.  

• Gather the correct tools. You’ll need a standard saw, framing nailer, framing nails, and a reciprocating saw to do the job.

• Measure and cut your siding. Refer to your blueprint to measure and cut your siding to the correct sizes. 

• Install the siding. Secure the siding to the wall frames using a nail gun and framing nails. Keep in mind that you may have to use a reciprocating saw to fit the top of the siding underneath the gable roof.

• Cut out windows and doors. Use your reciprocating saw to cut out the areas between the window and door frames.

• Remove excess wood. If you see any extra pieces of wood around the perimeters of the structure, be sure to saw them off with the reciprocating saw for a finished look.

Install the Doors and Windows (Optional)

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If you want to add doors and windows to your treehouse, this is the time to install them. Of course, you don’t need to install an actual door or window to complete the treehouse. Instead, you can simply add trim around the door and window areas to give it a polished look. But for more elaborate designs—or treehouses designed for living or work spaces—doors and windows are a must.

Build the trimmings using 1x6 lumber to frame door and window openings. Secure the trim to the siding using your nail gun and framing nails.

Secure the Roofing

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Now that the walls are up, there’s only one thing left to do—finish the roof! Like previous steps, this task is best completed with an extra pair of hands to help you out. 

Start this step by measuring and cutting a sheet of plywood sheathing to the desired length for one side of the gable roof. Have your helper hold the plywood while you secure it over the rafters using your nail gun and framing nails. 

Repeat on the other side.

Tackle the Finishing Touches

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Voilà! You have a fully functioning treehouse. Now it’s time to add the final touches—railings, stairs, and a coat of paint. 

• Add railings for safety. If your treehouse design has a deck, you’ll want to install railings as a safety measure. Use two 2x8 wood planks for the top and bottom of the railing and connect them to two of the four 4x4 posts in the corners. Secure them using deck rail brackets.  Use vertical 2x2 wood planks between the two posts. The more of these planks you install, the more secure the railing will be. Use framing nails to attach everything together as you go.  Repeat this step for all sides of the deck. Be sure to leave an opening in the railing for ladder access. 

• Add a ladder or stairs. A secure ladder or stairs gives your kids safe access in and out of the treehouse. To build a simple ladder, install a 4x4 post next to one of the original base posts, leaving about two feet of space in between.  Use 2x4 planks as steps. Cut the desired amount and secure them to the posts using framing nails. Ideally, each step should be around 10 inches apart. 

• Add a fresh coat of paint or stain. This step is optional, but it creates a nice finishing touch. It also helps preserve the wood, keep pests out, and keep splinters at bay. Have your kids help with this part by choosing the colors and applying the paint themselves (with parental supervision, of course). Or, for a more cohesive look, opt for a natural-looking stain to compliment your house’s siding and surrounding nature.