Treehouse attachment bolt

Description

One of the main features of TABs is their strength, requiring fewer tree penetrations for robust fastening of a treehouse and hence less damage to a live tree. A typical TAB consists of a threaded metal bolt, a larger diameter collar, and a long perch terminated with a nut. The collar provides additional bending strength by bearing upon the compression strength of the tree grain. Since treehouses are subject to frequent load reversal produced by winds, TABs must be made of spring steel The bolts are able to support from between 9000 and, a much greater load than conventional lag bolts.

TABs are commonly used in conjunction with pipe brackets, allowing the treehouse structure to move independently with the tree. TABs are designed so a tree's added girth can further envelop it.

History

The concept of using a collar or large cylindrical object to increase shear strength in wood construction has been around for several centuries in the forms of split rings and shear plates. Shear plates provide a larger load-carrying capacity in shear than can be otherwise achieved by a bolt alone. Because this idea utilized less bolts for equal strength, it transferred well into the use of live trees, as they compartmentalize more efficiently with a single, larger cut than several, smaller cuts. Michael Garnier became involved in treehouse construction beginning in 1990 when he built his first treehouse in Josephine County, Oregon. Two years later, he was ordered by County official to close the treehouse to the public. He began developing what would become the Garnier limb, a high-strength alloy steel engineered bolt that can be screwed into a bore in the trunk of tree. In 1997 Garnier met Arborist Scott D. Baker who shared his knowledge of tree biology and tree structural responses. By 1998, Garnier had developed a commercial bolt product which he called Artificial Limbs. The Garnier limb was primarily developed to satisfy the safety requirements of the Josephine County Building and Safety building permit process.

Engineer Charley Greenwood, with the help of Michael Garnier and machinist Michael Birmingham, added a 3 in collar onto a 1.25 in hex cap screw to maximize the surface area and minimize compression in the contact area between the tree and the screw. Garnier was initially the sole producer of these bolts under the names, "Artificial Limbs" and "Garnier Limb".

References

References

1. """INTRODUCING THE XL SYSTEM ©- FINALLY, A TRUE TREE HOUSE MOUNTING SYSTEM"" (see the link to a brochure)".
2. Globe Pequot, "Knack Treehouses: A Step-by-Step Guide to Designing and Building a Safe and Sound Structure", 2010, {{ISBN
3. "https://treetopbuilders.net/pages/fasteners".
4. Van Rheenen, Erin. (2010). "Moon Living Abroad in Costa Rica". Avalon Travel Publishing.
5. "Interview with Pete Nelson of ''Animal Planet's'' "Treehouse Masters"".
6. "Pete Nelson – the Treehouse Expert". [[Animal Planet]].
7. "About Treehouse Masters". [[Animal Planet]].
8. Kurutz, Steven. (29 May 2013). "Houses for Dreamers (and Kids)". [[The New York Times]].
9. (6 July 2013). "Bird's eye brew: Treetop tasting room draws visitors". [[Akron Beacon Journal]].
10. (October 2013). "How to Build the Ultimate Treehouse".
11. "History of the TAB".
12. "Information regarding shear plates".
13. "Live tree reactions to TABs".
14. Goodnow, Cecilia. (23 August 2007). "Northwest Innovators Helped Revolutionize Construction". [[Seattle Post-Intelligencer]].
15. Kugel, Seth. (26 April 2003). "Refuge among the boughs". Marin Independent Journal.
16. Miskimon, Robert. (2008). "The Complete Guide to Building Your Own Tree House: For Parents and Adults Who Are Kids at Heart". Atlantic Publishing Company.
17. Garnier, Michael. "Official Garnier Limb Origin and Histree". Out'n'About Treesort, LLC.
18. "Creation of the TAB".