Treehouse Hardware Series - Tree Attachment Bolt (TAB)
Intro: Treehouse Hardware Series - Tree Attachment Bolt (TAB)
Treehouse ambitions still lingering since childhood? Not sure where or how to put that dream into action?
Look no further! I promise by the end of this instructable you will be fully learn-ed on one of the central unknowns in the world of treehouse building, how to properly attach a treehouse to a tree without barraging a box of your Dad's 12 penny nails into the trunk.
Contents:
Tools
Hardware
Bolt Locations
Drill Forstner Hole - Bushing
Drill Auger Hole - Theads
Attach TABs
Build Structure on TAB
Links Alternative Methods
Tree Health
STEP 1: Tree Health - Links
It would be impossible to cover even a portion of the tree health category sufficiently so I've provided a number of helpful links below to get your research . If you plan to invest quite a bit of money and time into your treehouse project I recommend contacting a local arborist as they will be most up to date and knowledgeable on local species, blights, harmful fungus, pests, and characteristics of the specific species for a specific region.
Tree Health links:
https://www.arborday.org/trees/health/
http://en.wikipedia.org/wiki/Tree_health
http://forestry.about.com/od/arboriculture/tp/Tree...
Live in CA? Have an Oak? Take a look at this first!
http://www.suddenoakdeath.org/diagnosis-and-manage...
Tree Diseases to be aware of.
STEP 2: Tools
Tools you will need include:
High Torque ( geared down drill ) - I prefer the Milwaukee brand Hole Hog Model
Auger Drill Bit ( appropriately sized to fit your tree bolt )
http://www.portlandbolt.com/technicalinformation/l... (use this link to understand the diameter of the pilot hole needed)
Self Feed Forstner Bit - I use also Milwaukee brand as they make them in all sizes
Burly 3/4" drive ratchet & breaker bar ( breaker bar is a essentially any tube that will slide over the handle of your ratchet )
Appropriately sized socket for your nut size/ all-thread size
Torpedo Level
Extension Cord
Sharp pocket knife/razor blade
Straw ( used to blow out debris from the tree hole )
STEP 3: Hardware
Tree Bolts or as they are referred to in the industry TAB ( Tree Attachment Bolts ) come in all shapes and sizes. They are based on a basic premise that load should be distributed into greater surface area at the moment or location where the bolt exits the tree.
The TAB consists of a boss or giant bushing affixed at the end of a bolt. Depending upon the context in which you plan to use the bolt you may have additional steel bar extending past the bushing on the outside of the tree. If you plan to use the TAB as a rigging point only then your bar needs to extend only a few inches past the pushing on the outside of the tree. I've pictured both types above.
Also pictured is a bracket that slips over the protruding end of the TAB. I call this a Bolt Hook. It is a simple laser cut bracket of 3/8" mild steel with a bit of a kink in it half way through. This hook is either used to rig directly off or can be used to rig a support cable that triangulates the cantilevered end of the TAB extension ( pictured ).
Here are a few resources for purchasing your tree hardware:
http://www.nelsontreehousesupply.com/
http://treehouses.com/joomla/index.php/constructio...
STEP 4: Bolt Locations
Now that all of the tools and proper hardware are gathered. It is now time to design the treehouse structure. I will not cover this process in this Instructable but will give you a few links to get started.
Treehouse Design
http://www.awc.org/calculators/
http://treehouseguides.com/faq.html
http://builtbykids.com/inspiring-treehouse-designs...
Brief on the Engineering
The tree connections need to be able to support the worst case loading scenario that could take place in the treehouse. I usually describe this as fully loaded to the Live Load Capacity, in an earth quake wind storm in the winter during a dance party.
This means that the total capacity of your connection points (if load and center of mass is distributed evenly) should be have a 5X safety factor. This means the capacity of your connections is 5 times greater than the total weight of the structure + the total weight of the people in the structure. Many of the tree bolts come with ratings. Since your installing this structure in a tree it is best to over engineer. My rule of thumb when rigging a structure with cabling is to base the capability of the structure on 3 rigging points although there are always more than 3 points distributing the load. This is to ensure that in a windy scenario should the structure swing onto only 3 points it is capable.
Wooooooood! Streeength!
Here are a few websites that will guide your engineering process if you will be performing any load simulations. Select your wood type and discover its properties so you can discover accurate results in your simulation.
The best one is www.matweb.com.
Enter the type of wood in the Text Search option in the middle of the page - try Oak and you'll see a bunch of options. Here are two links to a couple of the Oaks for example.. but generally pretty good cause they list for different moisture content, grain direction, etc.
http://www.matweb.com/search/DataSheet.aspx?MatGUI...
http://www.matweb.com/search/DataSheet.aspx?MatGUI...
Here's another one. A good long list of species, though not quite as much data on each one as MatWeb.
STEP 5: Drill Forstner Hole- Bushing
Bolt Installation
If the Treehouse will be resting on the TABs then it will most likely be necessary that the two bolts protrusions are directly parallel and level to each other. This requires extreme accuracy in locating the hole heights and the drilling of the holes to ensure a level resting platform for the beams.
#1 - A water level consists of a bendable clear tube filled with water. This simple tool will provide the ability to mark two hole locations on the tree either side of the tree or on two or more trees. Eyeing the water level on each side of the tube after waiting for the water to settle mark each hole location with a nail.
#2 - Install the Forstner Bit into the drill. Pull out the nail that was marking the location. Drill the depth of the hole shallow enough to ensure that the Boss on the TAB will protrude out of the tree enough to seal off any portion of the exposed interior of the tree. This is to ensure there is no space for infection or bugs to easily enter into and disturbe the critical nutrient flow layers just under the bark of the tree.
STEP 6: Drill Auger Hole - Threads
#1 - (Leveling drill holes to each other is only necessary when installing TABs where the beam will be seated resting directly on the TAB.)
Attach the Auger drill bit in the drill. Using a Torpedo Level and a friend or two to check your drill trajectory for accuracy begin drilling the hole for the TAB threads. Accurately locate the center pin hole left behind from the Forstner bit with the tip of the Auger bit. Raise drill to a level position using the Torpedo Level directly on the Auger drill bit. Also make sure that your horizontal trajectory is to the angle you wish. Begin drilling, use a friend who can keep an eye on your drill bit as you drill to ensure it stays level. Check often using the Torpedo Level during this process as well until the Auger is to deep. There are ways to create jigs specific to your drill to ensure that your drill trajectory is perfectly level as you plunge the drill into the tree. Many professionals use rigs like this during this process to ensure accuracy.
Once the hole is completed use a long straw to blow all of the wood chip debris from out of the hole. This will ensure a smoother installation of the bolt.
STEP 7: Attach TABs
Screwing the TAB can be an aerobic activity so make sure you have your money makers on.
#1 - Insert the back end of the TAB into the hole. Screw a nut onto the other end of the TAB. Use a hammer to knock the first couple threads in into the hole.
#2 - Hold the TAB level and start turning the bolt into the tree very slowly to ensure the first couple of threads catch the wood.
#3 - Continue screwing until the bolt is in the tree. It will probably become quite difficult once the bushing is up against the hole, at this point use the breaker bar ratchet handle extension to turn the bolt in the rest of the way.
* IMPORTANT - As the tree is a giant vascular system that pulls nutrients in water to its upper branches, there exists a small amount of pressure in the tree. This preassure causes the interior of the hole in the tree to swell a bit which starts immediately after drilling. Make sure to install the bolt directly after drilling the hole. There is about a two hour window to install the bolt, after this it will become progressively more difficult.
STEP 8: Build Structure on TAB
Once all of the bolts are completely installed, let the building begin! I've included two pictures which display different ways to triangulate the cantilevered end of your TAB should you be significantly loading the TAB. One of them reinforces the beam form the tip of the TAB and the other near the center with the beam loaded on the tip.
As my tabs are created from simple 1.25" all thread and a 4145 laithed bushing I needed to sheeth the treads where the beam would rest against the TAB all thread. I choose to do this because my bolting system allows for moement between the two bolts and there for the trees. The sheath that I used is a piece of pipe who's interior dimension ( ID ) matches nearly perfectly the outer dimension ( OD ) of my all thread. This sleeve sheath will protect the beam from digging into the all thread and allow for less friction in the system.
I was able to make this system dynamic and movable by fixing only one side of my beam to the bolt. This is illustrated in the pictures by the triangle plates. One plate has two holes where I've affixed the plate with bolts. The other side of the beam has a similar plate only on this side the plate has a long slot shaped hole. This long slot hole will allow this side of the beam to slide along the TAB and there fore allowing for movement in the system when the trees sway in the breeze.
STEP 9: Links and Alternative Methods
Rigging
http://en.wikipedia.org/wiki/Wire_rope
http://en.wikipedia.org/wiki/Turnbuckle
http://en.wikipedia.org/wiki/Eye_bolt
http://en.wikipedia.org/wiki/Swaging
http://www.sherrilltree.com/Professional-Gear/Tree...
Equipment
http://www2.vermeer.com/vermeer/NA/en/N/
http://www.wesspur.com/saddles/petzl-saddles-harne...
http://www.petzl.com/en/Professional/Harnesses#.VF...
Videos
46 Comments
bigrodent 6 years ago
Thanks for posting. I am having a real problem with how knee braces are attached in the YouTube video and the forces put on them. Bare with me while I explain, and please don't take this as a criticism, just trying to learn more about your technique.
The first question is that the knee brace produces and upward and outward vector force on the rim board. But there is nothing holding the rim board on but a joist hanger to the joists. This will help support the joists downward force but the force outward is only held by nails. I think a t-hanger on bottom of the rim joist would be a minimum here. Also, if the rim board is a supporting beam now, shouldn't that be a double?
Second question is the seat cut for the rim joist to sit on the knee brace. Didn't you just reduce your beam to a 2x by only having the support on the end? Again, if you went with a double you can widen your seat cut. Or reverse the cut to have the cut on the inside of the knee brace?
The third one was the picture you show for an angled support where you put a 2x board underneath the frame. I cannot see what this is supporting. It seems that it will directly hold one joist and limited support for 2 more since it is only a short 2x member. Also, in that picture is shows joist hangers on the rim board. If the support from the knee brace is now underneath the frame, the rim board is holding no weight, why the joist hangers?
Sorry for so many questions... it just seems to me that the forces are not being properly supported here.
The brackets look nice though, I am trying to find a good way to use them to truly support the cantilevered joists.
Thanks!
ntomdia 7 years ago
You my friend are a LEGEND! :) Thank you!
T0BY 7 years ago
ChadC15 7 years ago
If you spend a little time looking into these treehouse guys like Pete Nelson and Michael Garnier these people have dedicated their lives to trees and to people being IN nature. They have HUGE treehouses that have been around for 25 or more years and the trees are still growing strong. If you think a tree has feelings, ok, you have a point within that framework of that reality (in which case you should be posting on Psychiatry.org). Point is, there's nothing better for the world of compromise in which we live than the research of people who imagine more sustainable compromise. We are humans. It's in our nature to dominate. Dominate Sustainably. That's my thought.
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DerekS15 8 years ago
Did you make your own TAB using thread rod and a welded bushing? I am interested in making my own as I don't want to spend $250-$1,000 on purchased TABs. I was warned not to use thread rod but can't understand why if the steel and diameter meet load conditions.
itsjustmescotty 7 years ago
making your own TABs is not a difficult task as long as you have a healthy metal lathe that can turn and drill 3" stock for the roller and alsthread the round stock for the bolt. Problem lies in purchasing the steel. Looked them up on line and some weigh 20#s - that's going to be in the neighborhood of $20-30 each. Shop time is going to be $100 each to turn, drill and thread each TAB. Not much of a workaround unless you have your own lathe.
My thought on using prethreaded rod; most are zinc plated and I don't know if that's good or bad for the tree but it's NOT good for the roller as it will (depending on the weight of the structure) want to cut threads into the roller and/or peen the threads over on the rod and also the effective diameter of the bolt will be reduced by the thread depth.
Me, I have 10 acres of trees, a BIG metal lathe along a plethora of metal and woodworking tools, the ability to make my own TABs but no desire to construct a tree house.
HandiGirl 9 years ago
By drilling such a large hole in the "hopefully" alive tree, would the tree not begin to die due to stress, the movement of the tree by the wind, and exposure to parasites that could penetrate the xylem and the phloem........would the tree not begin to die and become a weak point for the treehouse? Would the tree not be ripped out of the ground by the excessive weight of the bulk of the treehouse? Would it not be better used as anchor point that is not pierced into the tree, itself?
starfoxx7 9 years ago
You're right on all counts. The tree will always move in the wind and loosen the nails and bolts in the tree house. I think this is a bad design. It should be on legs, free standing, allowing the tree to move a few inches inside the structure.
FlorinJ 7 years ago
Not really. The tree will regenerate around the holes. After a few years, you won't be able to pull the bolts out anymore. Trees don't die that easily.
You need to do some damage comparable to the tree's diameter to damage the tree to the point that it can't survive the wound.
As for parasites, just paint the trunk with lime up to where the treehouse starts. No more parasites - not even the naturally occuring ants. (The lime doesn't damage the tree at all, and as it washes into the ground provides useful nutrients for the tree).
Fly4aWhiteGuy 7 years ago
srilyk 7 years ago
I don't know if they do any kind of sealant around the bolt, like the kind I've seen painted on limbs that have been cut off due to storm damage, but that's pretty much the worst part of building a treehouse like this. By drilling holes, rather than driving nails into the tree, you eliminate splintering, so effectively what happens is that the area around the bolt dies and goes from living tree into... wood. Just plain ol' wood. Surrounded by living tree. And the wood is plugged up by the bolt. If you use nails, you're splitting the tree which provides a lot more room for parasites to enter the tree.
As for movement, I'm not a structural engineer, but just taking a gander at these photos it *looks* like what's actually going to happen is the treehouse structure will practically eliminate the movement in the lower part of the tree, due to the rigidity of the treehouse. The upper part of the tree will sway in the wind, but that's what trees do, I don't see anything to be worried about there. The only way that the tree would be ripped out of the ground is if the treehouse load is pulling from side to side - if you look at this one they're supporting the treehouse with multiple trees, which will definitely increase the stability. Also, another point to remember is that living trees are *heavy* - I think it's something like 150lbs per 16 inches with a 12 inch diameter. Depending on the size of your treehouse and your tree, you may not even be adding another half of the weight of the top of the tree.
All that being said, I'm still going to use pressure-treated lumber and just build a fort when I do (unless I had a bunch of woods on my property and I wasn't too worried about losing a couple of trees, worst case scenario),
wwestfall1 9 years ago
Ninzerbean 9 years ago
I had no idea that there was so much real knowledge about building a treehouse, this is great to know, now if I could just find trees that didn't have spiders...
srilyk 7 years ago
Spiders are your friends - they eat all the nasty bugs that you don't like. And unless you live in Australia, there are maybe two spiders with medically significant bites - the Black Widow (which prefers to be closer to the ground anyway) and the Brown Recluse (which, despite much lore, hasn't been proven to have a medically significant bite [any more than say, a bee sting, which can certainly kill people who are allergic to that sort of thing]). See /r/spiders on reddit for more information :)
Harly9 7 years ago
"Brown Recluse (which, despite much lore, hasn't been proven to have a medically significant bite" Seriously?" How uninformed are you? Try googling Brown Recluse bites and educate yourself.
srilyk 7 years ago
That's what I mean by lore.
https://en.wikipedia.org/wiki/Brown_recluse_spider...
"Around 49% of brown recluse bites do not result in necrosis or systemic effects"
Recluses are very disinterested in biting you. Most of the photos that you see on the internet blaming spiders are probably MRSA.
http://www.abqjournal.com/431736/documented-fatal-...
Google Images is not science.
Harly9 7 years ago
None of your links are viable. You still need to educate yourself on Brown Recluse bites. Stop propagating false information.
Ninzerbean 7 years ago
I just have an reasonable fear - I can't even look at photos of them, but thank you for your input.
steffelem 7 years ago