How to Build a Treehouse in Your Backyard for a Lifetime of Memories

Paul Pogue
Written by Paul Pogue
Updated January 24, 2022
A young family sitting in a backyard treehouse
Photo: Alina / Adobe Stock

A kid- and parent-approved backyard DIY

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A treehouse is a great addition to any backyard design. Learn how to build a treehouse in just a few steps and make family memories for years to come. 

Difficulty: Challenging (4/5)

This project is rated challenging for those without construction experience. However, that rating changes to intermediate (3/5) for those with carpentry experience. 

Project time: 2–3 days

Cost: $400–$11,000 

Prefabricated treehouse kits can cost anywhere from $400 to $2,000. Raw materials to build your own treehouse can range anywhere from $500 to $11,000 depending on the treehouse size, material choice, and location.

Tools

  • Framing nailer

  • Level

  • Hammer

  • Wrench

  • Nail gun

  • Reciprocating saw

Materials

  • Cinder blocks (one for each support beam)

  • (5) 4x4 wood posts for foundation and ladder support (you may need more posts  depending on your design)

  • 3-inch framing nails

  • 1-inch galvanized nails

  • Joist hangers

  • 2x8 lumber

  • 1x4 lumber 

  • 2x2 lumber

  • Plywood sheathing 

  • Deck rail brackets

How to Build a Treehouse in 9 Steps

Follow these steps to build a simple yet sturdy treehouse your family will cherish for a lifetime. 

1. Pick the Best Tree

The sun gleaming behind a large oak tree in the fall during golden hour
Photo: redtbird02 / Adobe Stock

First things first—pick the most suitable tree to build your treehouse on. 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. 

  • 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.

2. Draw Up a Blueprint

A father and son building a treehouse together
Photo: CarasaraGuru / Getty Images

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. Try to plan your measurements as accurately as possible. This will help you gather the right amount of materials for the build.

For this project, 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 custom building stairs or a ladder?

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

3. Start with the Foundation

A father and son building a treehouse together
Photo: yulkapopkova / Getty Images

If your treehouse will be supported by floor beams, start by marking their locations using cinder blocks. In most instances, you will need at least four support beams, 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.

4. Build the Floor Platform

A father and son building a treehouse together
Photo: yulkapopkova / Getty Images

Let’s continue building the floor platform of your treehouse.

  • Do a trial run. 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. The direction of the floorboards will also help you solidify where the floor joists will go. Floor joists are structural supports that run perpendicular to the floorboards.  Calculate how many you’ll need by searching online for a floor joist calculator. For a project this size, two to four should be plenty. Evenly space out the joists from the center.  Consider drilling your center joists to 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. You’ll want to use 1-inch galvanized nails and a hammer for this. 

  • Cut and secure the angle braces. Secure the floor frame even further by using 4x4 posts as angle braces where the original four floor beams meet the floor frame. Use a circular saw to cut a 45-degree angle at the ends and secure them in place using a nail gun with 3-inch framing nails.

  • Install the floorboards. Finally, secure 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. 

5. Build the Wall and Roof Frames

A father and son building the walls of a treehouse
Photo: Tiina & Geir / Getty Images

Now it’s time to assemble all four wall frames and the roof frame. 

  • Assemble the first wall frame. Using 2x4 planks, assemble the first wall frame according to the dimensions on your blueprint. The wall frame should consist of a top and bottom plank and two side planks that create a square or rectangle depending on your design. Install two to three stud planks within the frame, spaced out evenly from the center. Secure all of the framing planks together using framing nails. 

  • Build the other three walls. Repeat the above step three more times to complete all of the walls. Don’t forget to frame out space for a door and windows.

  • Secure the wall frames to the floorboard. Once you have built all four wall frames, secure them to the floorboard with a nail gun and framing nails. It’s best to have a helping hand for this step to hold the wall pieces upright.

  • 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. 

6. Install the Siding

A father and son installing siding to a treehouse
Photo: Tiina & Geir / Getty Images

You should see the treehouse taking shape at this point. Continue on to these last few steps to complete the project. 

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

  • 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.

7. Install the Doors and Windows (Optional)

A father and child looking out of a treehouse window
Photo: Cavan Images / Getty Images

If you will be adding 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. 

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

8. Secure the Roofing

A man building a treehouse in the woods
Photo: yulkapopkova / Getty Images

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.

9. Tackle the Finishing Touches

A man painting a treehouse exterior with white paint
Photo: AleksandarNakic / Getty Images

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. 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. 

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