A worried dad and his son’s treehouse
Tribune Content Agency
WORKING on the treehouse and wait for a recording I would make to help him fix the errors. I also told the reader I would draw up a few simple sketches illustrating what he needed to do. I used to draw these years ago sitting at a dining room or kitchen table for customers as I explained how I was going to build something for them.
Let’s run down the list of errors made in the construction of the treehouse. The first one, in my opinion, was a lack of research before he got out his tools. I say this not knowing exactly what the reader did, but if he did do any, he either got very bad advice or, if he found great advice, he failed to follow it. The internet is overflowing with conflicting building advice, and if you don’t know what’s right and what’s wrong, it’s easy for you to go down the wrong path.
Allow me to describe what was built. For simplicity, the reader built a 12 foot by 12 foot deck in the air. The top of the platform is about 6 feet in the air and the entire structure is supported by eight 4x4 posts.
This is where all the problems started. I also frequently see professional carpenters make this mistake. The reader bolted the outer 2x6s to the 4x4 posts. He had two 3/8-inch diameter bolts at each post. Can you imagine how much weight is bearing on these bolts? The entire surface area of the top half of the two bolts at each post only adds up to 1.17 inches times the thickness of the 2x6. Realize the actual point loading is much more severe because the surface area of bolt contact through the 2x6 is a half-circle, not a flat spot like you might find on top of a post or column.
They should have used a notched 6x6 post so the outer 2x6 beam rests on solid wood. The weight would be directly transferred to the buried concrete piers in the ground. I suggested he fix this error by attaching a treated 2x4 to each 4x4 post. This new piece of lumber would extend from under the 2x6 down to the top of the concrete pier in the soil.
As I watched more of the video, I saw they had used what appeared to be galvanized drywall screws to attach the joist hangers to the outer beams. Drywall screws are not structural screws. You can buy special structural bolts made to fasten joist hangers to beams.