8/5/15
First day back to tree-housing after vacation! Decided on a lite load today. Just ran to the HD and grabbed enough 10' decking boards to cover the front deck portion of the total platform. I'm doing this section as a component, as this is the only section of decking I intend to screw down. The rest of the decking will fall below the actual shed structure, will ultimately be covered up with some type of sub-floor and/or finished flooring, and will thus only be secured with my fast, framing nailer.
Nine 10' decking boards stacked and ready for the next build day:
Nine 10' decking boards stacked and ready for the next build day:
Now I warned early on that I have a penchant for over-engineering! The following scheme is born of a paranoid delusion I have that the whole tree house is going to fall over! Let me explain. As you know, the platform is essentially a freestanding deck, supported by 4 6X6 posts, with an extension of the platform riding freely over another support beam anchored between the two trees. My irrational fear is that a tornadic wind will rip down through the ravine and overcome the vertical, upright strength of all 4 support beams and simply push the whole tree house over! The shed would act like a big sail, and the "floating" side of the platform would do nothing in the traditional sense of a deck, in that it doesn't represent a secure attachment to a fixed structure, e.g. like the ledger board of a deck fixed to a house. If all 4 beams broke in one direction, the floating end of the deck would simply slide off that beam and all would come crashing down. NOW, I seriously doubt anything like this would ever happen! The build thus far is SOLID as a rock, and only growing more secure as weight is added. HOWEVER, if I can spend $30-$40 on piece of mind, I'll buy it! Here's what I did:
Using chains, trailer tabs & carabiners, all rated close to 5,000 Lbs, I insured that the deck could only drift so far in either direction, relative to the underlying support beam (which is fixed between the trees). It's loose enough to allow for the anticipated movement between deck and beam, but not so loose as to give in to a horizontal, directional failure of the whole freestanding deck. Anyway, I hope this all makes sense! It does to me, and I now intend to sleep much better!
Hi there, great treehouse you've constructed! I've followed your blog and it's helped me a great deal with constructing my own. I have a comment/question though...do you need the chains to prevent movement?
ReplyDeleteDon't the treehouse bolts allow the trees to move on their own and not transfer that movement to the treehouse beam anyway? The reason I ask is because my treehouse has some slight movement and I think it would benefit from rafter/hurricane ties between the joists the beam between the trees. Maybe I'm not understanding how the treehouse bolts work with the tree movement. Any advice since yours was built a few years ago? Thanks!
I'm glad my blog has been helpful to you. To your question, you'll see that the "deck" comprised of the joists, outer rim boards, etc. is sitting (floating) on top of the beam crossing between the trees. The beam crossing between the trees has a fixed bolt connection to the tree and a floating bolt connection. This design allows the supporting beam to move freely between its two connections to the tree. If it were fixed on both ends, and the trees moved, the beam would be ripped from the tree. Now, the "deck" is in no way attached to this beam. It sits on the beam upon low friction pads, allowing to the beam / tree movement to slip and slide around underneath it, WHILE simultaneously supporting the deck. NOW, the chains you see are honestly overkill engineering. The theory behind them is that IF a massive wind got the whole deck + treehouse moving in one direction, i.e. being blown over by a tornado, there would at least be one "stop" when the chain connection ran out of slack in either direction. I hope this makes sense. The concern comes from knowing that traditional decks are not simply free standing. They are customarily "tied" into the house via a ledger board secured to the house. My treehouse design, with its reliance on the posts, looks a lot like a fress standing deck. That is why you see this fail safe chain apparatus and all the cross members running at a diagonal between my support posts. All of these components are added to kill sway / movement and/or avoid a paranoid's catastrophe! :) Let me know if you need me to elaborate more. Thx!
DeleteThanks for explaining, I totally get your train of thought. I actually am thinking that way too and is the way I've designed my treehouse. I have two posts and two trees with my structure and use a sliding Treehouse Attachment Bolt (TAB) and a fixed TAB. However, I asked the company I bought my bolts from (treehouses.com) and they said that normally you attach the joists to the beams. So now I don't think the treehouse moves on the bolts as you or I thought. Based on their recommendation of attaching the joists to the beam, I'm thinking the TABS absorb the tree movement without affecting the beam. I'm not totally sure how though. The slider I get, but the fixed one would move the entire structure and put stress on the posts I would think. Anyway, what do I know as a DIYer :-) Have you noticed much movement in your structure after a few seasons or is the beam pretty much in the same place on the joists that you started at? Yours might be stronger because you have four posts that are fixed instead of just two and that might limit movement quite a bit perhaps. You've been a great resource for me so thanks!
DeleteI agree with your suspicion. I look at it this way: Think about the side of your deck frame that is affixed to the FIXED TAB. Forget about the fact that the plane shared between the fixed and the floating TAB has freedom of movement; that is not your problem. Focus on the plane shared between the fixed point and the nearest, FIXED, adjacent post. If that tree moves vigorously away from said post, there is no give! NOW, some references will say that if the treehouse is less than 8' up the tree, AND you don't take extra measures to reduce the sway / flex of the fixed posts, e.g. knee braces, extra ties, etc., then the posts themselves can absorb this movement adequately. As for me, I say "Uh, uh, no thanks!" ;). So, if I were you, I'd explore more complex 4 tree arrangements, possibly including 'floating' decks, just to make sure you aren't putting your investment and occupants at risk. All this said, you would see much less over-engineering in my design if I was simply building an 8X8 for dude beer drinking during football season! As you can see, mine was built for the whole family, i.e. many children, to enjoy...Hence all efforts were made to secure / make safe the structure.I'm going to post some more references here for you as well.
ReplyDeletehttps://peacemakertreehouses.wordpress.com/2008/10/05/oct-3-2008-%E2%80%93-so-you-want-to-install-a-gl/
ReplyDeletehttp://www.thetreehouseguide.com/building.htm
http://www.instructables.com/id/Treehouse-Hardware-Series-Tree-Attachment-Bolt-TAB/
One last thing: The guys out at THC are great! Michael IS the GL, as you've probably already figured. So I in know way question their judgement. Their recommendation prob comes with a bit more knowledge of your project than what I've discerned here. Look at me this way: I'm just a bit paranoid when it comes to over-securing AND this was my first treehouse project! :) Good Luck!
ReplyDeleteThanks for your advice. I just wanted to wrap up this discussion in case it helps someone else looking for the correct answer. I've done some further research and Pete Nelson's book Be In a Treehouse confirms what you suggested. In essence it says that the beam should not be connected to the tree side as you've designed yours. I'll follow that advice and leave my treehouse the same. I'll just tighten up the sway by installing some block bracing between the joists. Thanks again for your advice!
ReplyDeleteCool, thanks for the follow-up! The single greatest reducer of movement in my build came after I applied the cross braces between the 4 fixed beams. Now, it takes a couple of adults intentionally jumping up and down to feel the slightest of wobble. As for the floating deck, I've gone out and HIGH wind storms to see what I can see. I've never been able to discern any visible movement at the GLs or between floating deck and support beam. I imagine the overall weight of the project has settled things down nicely. At the most, you'll hear a creak every once and a while, like an old ship noise ( I imagine). Best of luck to you!
ReplyDeleteI must not have documented the cross braces. However, they first show up in 10/11-10/12 post for reference.
ReplyDelete