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Building A Tree House

Building A Tree House

Ok so your kids are begging you to build a tree house.  If you are ready to finally start that big treehouse project, here’s a few things for you to consider when building a tree house.

the goal of this articles to give you some direction toward building a strong, lasting and safe treehouse.

Treehouses and Insurance

Before you even begin building a treehouse, it’s important to contact your insurance agency to see if it’ll be covered as a part of your home insurancepolicy. Many factors come into play with this, like potential injuries, and it also depends on your insurance company.

Building Code

Its important to check with your local building code department before building a tree house


Choose the Right Trees

Find a mature and healthy tree, that is structurally sound. The tree needs to be a hardwood, such as maple, oak, hemlock, or beech. Make sure that the tree has been pruned of dead leaders, branches and any falling hazards.

If you are unsure of a tree’s health (infestation and disease are not always immediately noticeable), or structural strength, you may want to consult an arborist in your area.

Build Low to the Ground

Obviously, most injuries result from falling out of the tree house. For this reason, a tree house that is more than 10 feet off the ground is probably too high.

Use the Right Materials

The framing of the treehouse needs to be treated the same as any exterior deck or structure. Use treated framing material, utilize structural plywood where you can and chose cladding that will keep water out and protect the structure from rot.

Support the Tree House

Prior to building your tree house frame and tree attachment, there are two things to consider with tree houses are:

  1. Tree grow
  2. Trees move in the wind [sway]

Trees Grow

The tree you are using will NOT stay the same forever. The trunks and branches will continue to grow.

Trees Move

Don’t bolt beams directly between thick trunks. Tree trunkscan generate immense pressure near the ground when the wind moves the branches higher up.  When a tree moves thousands of pounds of force is generated and can easily shear nails, screws or bolts.  If you bolt a treehouse support beam between two trees, you’ll run the risk of the bolts snapping in strong wind.

We were curious to see how much our trees moved in the wind. Prior to building we held a 16-foot straight edge and level at the base of the tree on a very windy day.

At 8-feet up the tree moved ½” and at 16-feet it swayed 1-inch plus.  The funny part was this movement was invisibly to the naked eye.

3 Important Treehouse Decisions

Armed with this information we made three decisions:

  1. Purchase and use a special floating bracket system that would allow us 3x the movement we recorded.
  2. Ensure that the roof edge would NOT exceed 12-feet in height and that it needed to be at least 3-inces from the trees edge, maybe more.
  3. Use Treehouse attachment bolts in two parallel tree and utilize two 6×6 pressure treated posts with 10” x 48” deep footings.

Tree House Attachment Bolt

The best fixture is a Treehouse Attachment Bolt, or TAB, which is specifically designed to support heavy loads in trees. We ordered ours online from, Treehouse Supplies, 1444 Phoenixville Pike, West Chester, PA 19380.

The MOST IMPORTANT thing to remember when starting to build your tree house is to reduce the risk of the trees growth or sway factor. These two factors can shear and damage your tree house frame.

Treehouse Attachment Bolts (TABs)

We decided to use two Treehouse Attachment Bolts (TABs) In today’s treehouse industry, the most efficient and practicable way to hold heavy loads in live trees are treehouse attachment bolts. TABs are engineered bolts designed specifically for supporting high loads in living trees.

One of the main features of TABs is their strength, requiring fewer tree penetrations for fastening your frame to. A typical TAB consists of a threaded metal bolt and a larger diameter collar. The collar is available in 1” 3” and 6” sizes and provides an extra bending strength by bearing upon the compression strength of the tree grain.

The stem of the TAB bracket is designed to support different tpes of cradle brackets. The cradle or “floating” bracket is what we secure to our treehouse frame.

Treehouses are subject to frequent load reversal produced by winds, as a result TABs are made of 4140 Carbon Steel.  TABs are able to support from 9,000 and 12,000 pounds (4,100 and 5,400 kg),and boast a greater strength load than conventional lag bolts.

Once the tab is installed the tree to grows around the TAB, making it stronger.

Installing the TABS

The TABs need to be installed according to the manufactures recommendations. Don’t install TABs in trees with a diameter las than 12”.

You’ll need the following tools to install this right:

To install our tabs we first drilled the larger 3-inch hole, then the smaller, deeper hole.  It’s important to drill your hole level into the tree.

Once the holes are drilled we hand screwed in the TAB as far as we could, then finished it with a large ratchet, socket, with the help of a cheater pipe for leverage.

We determined our height of our floor and subtracted to get the height of the TAB. Once we drilled the first TAB we used a straight 2xg and a 6-foot level to locate the second tree TAB.

Floating Bracket

A floating bracket is basically a platform support that can be used to span between two or more trees. We used two on our project.

The floating bracket slides onto the TAB and allows the tree to move freely and independently in any direction, while keeping the treehouse structure from moving.

We laminated two 2×10-14 pressure-treated boards to make a beam and mounted the brackets to the bottom. We would hang out floor josts off this beam.

Building the Platform

We used 2×10 pressure treated lumber for the treehouse floor system. The entire platform of the tree house is 8 x 14’ long. The treehouse is 8’x8’ and there are two 36” decks on either end.

The floor system consists of two outside double 2×10 beams with 2×10 joists installed between them, direct nailed and supported by galvanized hangers.

Opposite of the floating beam is a beam that is supported by two 6” x6” pressure treated posts connected post to beam, and post to footing galvanized connections.

Each post received three diagonal post to platform brackets.  The two concrete footings have 10” deep galvanized j-bolt, and is 10” in diameter and is 48” deep.

The Rest of the Treehouse

I just covered the most important part of building a treehouse. The structure on top is conventional framing – it’s basically a small shed or house on a deck platform.

I’ll briefly touch on the methods, and materials we used.


The decking of the treehouse is ¾” CDX glued and screwed to the joists. The exposed 3’ x 8’ decks have 5/4 x 6” pressure treated decking screwed and spaced 3/8” apart for drainage.

Wall and Roof Framing and Roofing

The treehouse walls are 2×4 and the rafters 2×6 reinforces with Simpson hurricane ties. We use a 2×8 pressure treated ridge because it extends out and over a deck. The idea here was to mound a pulley and rope to it later.

We flashed the top of the ridge beam with lead flashing.

For roofing we chose CertainTeed Carriage House Tile, Sherwood Forest color. These shingles had a scalloped shape and were a fun detail to add to the treehouse.

A Velux 30-1/16 in. x 37-7/8 skylight was added to one side for light and venting.

Wall Sheathing

For sheathing we used ½” T-111siding and oriented the lines horizontal to simulate a rustic clapboard or horizontal board look.

Windows and trim

We framed simple jambs and used 6 Bosco cellar window sash for the windows.  The windows have a simple lock and two hinges each. 3M safety tape was applied to both sides in case of glass breakage.

Exterior trim boards are ¾” Cedar.


The gable end on both sides was intentionally framed and left open for ventilation. We installed insect screening here.


4×4 pressure treated posts with top and bottom railings surround the open decks. We drilled a series of holed in the guard rails and the homeowner rigged roping for the balustrade.


We used IKEA Outdoor deck and patio interlocking floor tiles on the inside of the treehouse, installed in a herringbone fashion.


The door was designed by the future tenants. Days after we had a solar eclipse the kids decided that they wanted the door window to mimic an eclipse.

With a jigsaw we cut out a half moon and then used a burning tool to mark the outline the sun and sun rays on the door. Insect screening was then applied to the door opening.

Building a treehouse can be a fun project for you and a long “child-hood” memory for you kids. Just do it safely.

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