cantelever support question - The Treehouse Guide

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cantelever support question

one tree, treehouse

joemendes

2009-07-26, 15:59 #1

since Jul 2009 · 2 posts
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Subject: cantelever support question

I am in the process of building. I have two 10 foot cantilevered beams made of 2 x 8 extending out from the tree. They start 24" apart and then fan out from each other to about 3 to 4 feet apart ( I have yet to attach the 2nd beam -- it cannot be parallel to the first beam because there is an branch below where I am attaching it that will run into the support part of the cantilever).

Here is my question:

1) Did I make these beams extend to far out for a safe cantilever? ( I did use 2 x 6 for the 45 degree angle that attached to the tree....and the 2 X 6 is 12' long)

2) If the beams are safe, what size structure can I place on them. Originally I was thinking 8' by 8'....but is this too big?

3) If either the cantilever span is too long, or the structure is too big to be supported to be safe...I do have ONE idea. I coud post posts under the 2 X 8's to safely support the structure.

Oh yeah, the structure is 17 feet off the ground...wanted it to exciting.....hmmmmm

Thanks for your comments. I am just a teacher...what did I get myself into!!!?????

The Treehouse Guide Administrator 2009-07-27, 16:05 #2

User title: The Treehouse Guide
since Aug 2006 · 67 posts
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A centilever is a beam with one end unsupported so your beams are simply supported beams rather than cantilevered beams. The floor joists you would put on top will extend out from the beams, so these parts are cantilevered.

These lengths of beams and braces are pushing the limits a little. While the span and size of the beams could withstand the load of a small, single level treehouse, you would need more of them radiating out to properly support the 8'x8' floor you mention, otherwise the treehouse could tip over either side of the 'V' formed by these two beams.

The braces may take the load, but could bend when loaded due to their length. Having a cantilevered floor could cause them to twist and buckle more easily. You could replace the braces with larger timber, add more braces and reinforce the braces with cross bracing. Extra beams would reduce the load on the braces that you do use and reduce the amount the floor needs to overhang. Another alternative is to support parts of the floor with cables, but depending on the house design you could have cables coming up through the floor.

Ultimately the size that the treehouse can be is determined by several factors - weight, height, local wind speed, support materials and type of tree. Calculating the size of supports can therefore be complicated so it's best to overbuild them as much as possible to add redundancy and use lightweight materials for the house structure to keep the load to a minimum.

Current time: 2010-01-04, 16:28:52 (UTC +00:00)