(..click on photos to enlarge..)
The idea sounds simple enough... a tree house!
And not surprisingly, everyone we talk to loves the idea and shows a big smile on their face. I had been harboring the idea for years, ...decades actually..., and now the time is right: our children can make it theirs, our backyard has the ideal trees, and we have saved a modest budget to pay for the lumber and supplies. Finding the time to work on it is still a challenge, but - heck - we can't wait
till retirement to start the project or it won't be ready until we have
grandchildren!
This blog entry will present progress on Panama (the name we gave the tree house) as progress is made. We will post photos and descriptions, but do not expect this posting to become a blueprint for your own treehouse project. We found, after reading about a dozen books on how to design and build a treehouse, that no two tree houses are the same, just like no two trees are the same. There are dozens of different techniques, e.g., how to secure a platform in a tree - we utilize only three of them. We do hope, however, that this post helps inspire you to build your own. Check out the reference section below for some excellent books on everything you may need to know when engaging in a tree house project.
Why is it called "Panama"?
The name came from one of our favorite children books by Janosch, entitled "Oh, wie schön ist Panama: Die Geschichte, wie der kleine Tiger und der kleine Bär nach Panama reisen." The English translation by Anthea Bell is entitled "The trip to Panama."
Tiger and Bär find a wooden crate that deliciously smells like bananas. They are immediately convinced that the place where this amazing box came from must be wonderful. 
When they find the word Panama printed on the side of the box, they decide to set out and find their promised land, leaving their little house behind. But in which direction should they go?
They post the board with the word Panama as a signpost and set out in the random direction it is pointing. On the road they experience all kinds of difficulties, are taxed, then robbed (same thing really) and repeatedly sent in the wrong direction. They also make new friends and find a red sofa they love to sit in. Unknowingly, for a long time they are wandering in a circle, only to return back to their original home without recognizing it. The signpost has long since disintegrated, yet as they recover the sign, they decide they have arrived in Panama at last and make their former house their home.
Getting Started
First things first: building a tree house is not a trivial task. Make sure you have the knowledge and skill, the right tools, including safety equipment, the right help when you need it, and pick the right trees! Over a period of about three months we read probably about a dozen books on deck and tree house design and building and it took us the better part of that time to select which tree we wanted to host Panama. All this happened before we bought the first piece of lumber or touched the first tool!
We cannot emphasize enough how important safety considerations are. In spite of being very cautious, alert, and safety conscious, we already had our share of small accidents, one of which caused me to spend a couple of hours in urgent care getting a head wound stitched up. I'll spare you the details - suffice it to say the lesson was to at least wear a helmet when working underneath a 16 foot 2"x10" that's only provisionally attached... better yet, to not stand there at all. Most books start with a section on how to work safely. Heed their advice to the fullest!
We found different opinions in the literature of what kind of building permits are required to build a tree house. Regulations differ widely across states and even cities. So rather than guessing or altogether ignoring the issue, we decided to pay a visit to Mountain View's building department. We were told that in Mountain View tree houses and their deck are structures that do not require a building permit as long as they are not greater than 120 square feet in size! Yay! Have I mentioned yet the deck will be 120 ft²?
Then you get to select the tree(s). Our backyard features a number of heritage trees and it was a difficult decision which one to choose. We settled on a group of two trees that stand closely together, near our patio. They are easy to reach, stable, mature trees and surrounded by soft mulch but hardly any other plants. We also figured that sharing the load of a tree house among two trees would reduce the burden of support on each individual tree. It also reduced the number of support beams we would have to use.
When we talked to the neighbors, we received enthusiastic endorsement of the project. Two of them had played in a tree fort their dad had built for them and they immediately offered help! In fact, one of our neighbors was surprised no construction had started within the month after we had talked to him, asking what we were waiting for!
The reason for the delay in starting construction was our desire and struggle to draw detailed plans before starting. We spent countless hours drawing up detailed platform and building plans with Google's SketchUp. But you know what - complete plans are not necessary for a tree house! A clear vision of what you want to accomplish and the knowlege of the major constraints to consider are enough to get started. Of course, the danger with planning along the way is always that decisions you have made earlier come back to haunt you, but part of the charm of building a tree house is to conquer these types of challenges as you go.
The Support Frame
Construction started
September 13, 2008, right after a trip to the lumber yard. A word here
about lumber and supplies: unless you are already an expert shopper,
expect to spend significant amounts of time shopping! 
This advice includes
comparing prices at different stores (at least in the Bay Area it is not uncommon that prices for the same type of lumber vary by a factor of 2½ between
cheapest and most expensive!) Also, always consider that this is an outdoor
project, i.e., use wood, paints, and hardware
that are weather-resistant. In the case of hardware that would imply galvanized, if not stainless steel lag screws, bolts, washers, and cables. Prices
for those also vary significantly from store to store for identical
products. We always buy a few extra and keep our receipts to be able
to return what we do not need. That's better than running out of
screws part way through your afternoon (and according to Murphy's law
that's probably about 5 pm on a Saturday, just about when your favorite hardware
store closes for the day, leaving you high and dry...)
There are many important rules to know when attaching support beams to trees. Tree and branches should be at least 6" in diameter, lag screws and bolts need to be the right size (at least ½" diameter and at least 4" into the tree.) Do not attach bolts directly above each other or you risk the part in between dying and disintegrating, eventually refusing to hold your platform... Individual lag screws or bolts hurt trees only in a minor way. While arborists use the analogy of a mosquito bite and unanimously say not to worry about it, we use the philosophy to get by with as few insect bites as possible! 
Attach your support frame boards in a way that allows the trees to sway in the wind without putting too much stress onto the boards. We solved this problem by allowing the lag screw to slide in the board.
Boards should be attached on edge because they can hold significantly more weight that way. Obviously you need to make sure they are level and remain in that position. 
That's simple enough for the first board, but tricky for the second and third, because all boards need to be not only level by themselves, but with respect to each other! You can accomplish that goal by placing an additional 2"x4" with a level attached diagonal across the two boards you want leveled. There are many more rules to be found in the references, depending on how you attach your platform.
The support platform for the deck is triangular in shape, held up by the two trees with one lag screw each and one vertical 6"x6" post, cemented into the ground. 
We dug the hole the old-fashioned way, throwing into the wind John's recommendation to rent a power auger. Wish we hadn't ignored his good advice. The soil in our area has a large clay content and it was quite a job to dig a hole for the post 2½ ft deep. Not only that - our hole dug by hand was necessarily wider than a hole dug by an auger, so we required 3 bags of cement, rather than one. However, chances are the additional cement keeps the post more stable, too. Trade-offs everywhere. We inched our way forward into the ground and started appreciating the work bank robbers go through when they dig a tunnel under buildings in order to crack the vault. While our reward was not quite as handsome, we did feel very accomplished after moving about 8 ft³ of soil ...and we did feel very sore the next morning.
Before placing the post into the hole we had stained and painted it, as well as covered the bottom 4 ft with roofing tar to minimize the amount of moisture that could attack the wooden post near its base in the ground. It was fun to apply the roofing tar - a funky, sticky, gooey substance. Make sure to wear disposable gloves and use a brush or plastic spatula you do not need anymore. We had an old ice scraper from our time in Sweden that we put to good use here, followed by its final resting place in the garbage bag.
Furthermore, we built a small wooden frame for the top few exposed inches of the cement foundation to make it look pretty, and to shape its surface to help rain water run off, away from the post. 
To keep the post from moving vertically in the dried cement base we screwed a few large lag screws (½"x6") partially into the base of the post, about one foot away from the end. Another way to accomplish the same is to place a rock at the bottom of the hole for the post to rest on. Call it German engineering, we did both. Once the post was braced in plumb position (all sides vertical) we mixed and poured cement - another job where you want to invite your friends to help. Even while pouring cement we repeatedly measured how plumb the post was and readjusted as needed.
After letting the cement cure, we attached the remaining two support beams. 
One of them rests partially on the support post, inside a section that we cut out of the post. We also cut the top of the post flush with the top of the support beams with a circular saw.
The result was reaching our First Milestone: a support frame for the deck!
The Deck Frame
The next step was to create the (mostly) rectangular deck frame that rests on top of the support frame and that holds the boards one can walk on. We call it the deck frame. There is a sketch on the left without the joists.
It consists of 2x6 redwood boards that we stained with DB1902 Duback Red Cedar stain & seal. The stain gave the redwood a happy orange-like color that blends well with its surroundings. Yet, as always with colors, beauty is in the eye of the beholder. We had used the same stain on the pressure treated redwood fir that was used for the support frame, which resulted in a much darker hue, as you can tell from the photos above. If you are unsure about how a color will look on the wood you are using, the best way to find out is to create a sample.
The frame measures about 16'x8', with one 4'x4' triangular corner cut out. That resulted in a surface area of about 120 ft² - as mentioned before, the limit for building without a permit in Mountain View. 
The frame members and joists were attached using joist hangers made out of galvanized steel rather than toe nailing or simply screwing everything together. The steel hangers provide much stronger support.
We started putting the frame together on the ground, but could not finish it there, because part of the frame surrounds one of the two supporting trees! So instead, we finished as much as we could on the ground, then lifted the largest piece into the trees onto the support frame before completing the rest of the deck frame.
Once the partial deck frame was lifted into the tree, we tied it with ropes to the support frame, preventing it from being able to topple over and fall down by itself! That was especially important as the front right corner was overhanging quite a bit. We then finished the deck frame by attaching the final boards.
The result was reaching our Second Milestone: the deck frame! 
The Deck
References
- Laurens, Alain and Dufour, Daniel and André, Ghislain and Perchée, La Cabane. Tree House Living 50 Innovative Designs. Abrams Inc. New York, NY. 2006.
- Nelson, Peter and Hadden, Gerry. Home Tree Home: Principles of Treehouse Construction and Other Tall Tales. ISBN-13: 978-0140259988. Penguin (Non-Classics). August 1997.
- Schmidt, Philip. Build your Kids a Treehouse. Black & Decker. Creative Publishing International. Chanhassen, MN. 2007.
-
Self, Charlie. The Black & Decker Complete Guide: Build Your Kids a Treehouse (Black & Decker Complete Guide). ISBN-13: 978-1589232877. Creative Publishing international. February 2007.
- Spence, William. Windows & Skylights. Sterling Publishing Co., Inc. New York. 2001.
- Stanley. Interior Walls. Meredith Books, Des Moines, IA. 2003.
- Stiles, David. How to Build Treehouses, Huts & Forts. ISBN-13: 978-1592281923. The Lyons Press. First edition. November 2003.
- Stiles, David and Stiles, Jeanie. Treehouses and Playhouses You Can Build. ISBN-13: 978-1586857806. Gibbs Smith, Publisher. First Edition. August 2006.
- Sunset. Backyards for Kids. Sunset Books, Menlo Park, CA. January 2008.
- Sunset. Children's Pay Areas. Sunset Books, Menlo Park, CA. January 1998.
- Sunset. Sheds & Garages. Sunset Books, Menlo Park, CA. January 2008.
- Time-Life Books. Windows and Doors. Time-Life Books, Alexandria, VA. 1996.
This page will be work in progress for a while.
Did you finish the treehouse? How is it doing now? I'd love to see more pictures of the process and finished product. I am a professional treehouse builder. I've got a website: www.treetopbuilders.net if you want to check it out. I'm always curious to keep up with what other people are building. Good luck!
Posted by Dan Wright on March 27, 2009 at 07:00 PM PDT #