Although building a tree-house is not something small it can be a fun thing to do if you use the right playhouse plans for the job. It's a great way to involve the whole family and there are loads of different designs to choose from. Whichever you ultimately settle on there are a few general rules to consider.
What you will require:
A ladder, A hammer and/or electric drill, A saw, At least seven 2x6x8 boards, galvanized nails or rope, exterior plywood sheets, 2x2x8 boards, a waterproof tarp, a staple gun, wood waterproofing treatment
1. Prior to doing anything else you need to choose the tree for your tree-house. An ideal tree is one that is mature and healthy with a minimum 16" diameter. Ideally the tree-house should not be higher than about 10-14 feet off the ground which means that the branches at that height need to be sturdy enough to support the weight of the tree-house deck. The tree needs to be of a hardwood variety such as maple or oak. Soft wood trees like pines are not suitable.
2. Using four 2x6 beams you will need to build the platform. This is a very important part of any successful tree-house construction. It should be build close to the trunk itself and should ideally make use of any available branches. Using diagonal bracing for additional support is always advisable and essential if there are no available branches. The purpose of this is to minimize movement of the branches as well as keeping the platform both balanced and level. Try not to cause too much damage to the tree when fixing the platform in place. Using rope or galvanized nails is a good idea. Un-galvanized nails will corrode and speed up rot in the tree which can and does lead to its demise.
3. Once the platform is securely in place the floor can be added and exterior plywood should be used for this purpose. The remaining 2x6 boards need to be placed 16" apart and parallel to the frame. Nail them in place from without to form your floor joists. Cut the boards to the desired length and lay them perpendicular to the joists. Cut the curves necessary in the floorboards for the tree limbs to come through.
4. Next comes the roof of the tree-house. Using 2x2 boards attach them vertically to each corner. Join with 4 horizontal 2x2 boards to form a frame that is rectangular. A gable is formed at each end by attaching 2 more 2x2 boards at an angle to each other. The 2 gables can be joined by attaching a vertical 2x2 board between them. The frame should then be covered with the waterproof tarp and stapled in place.
5. Once that is done it is time to add the doors, walls, and windows. Use your imagination in this regard but think "light". Opt for Plexiglass, plastic, or mesh screening rather than glass. You also need to consider how the tree-house should be accessed. Ladders are good provided they cannot be removed or knocked over by the wind.
6. Once the project is done it is time to waterproof the wood.
Useful Tips and Advice
Prior to beginning make certain that there aren't any restrictions where you live when it comes to building tree-houses.
Always ensure that the ladder is securely fixed to the tree while you are working on the tree-house and that you have a first-aid kit on hand in the event of injury.