Professional Construction of Tree Houses
Professional fasteners for tree houses are the key to building safe and long lasting tree houses. The most important part of constructing tree houses is how the tree houses are attached to the tree. While different builders have preferences on attachment methods, there are definitely dangerous and wrong ways to attach tree houses. You are well advised to make sure that you understand how your tree house will be attached to the tree before you hire anyone to build your tree house.
Quality fasteners for tree houses are created to meet two needs: 1) so strong that they will never fail until long after the wood of the tree fails under the load, if ever, and 2) they perch the tree houses main beams several inches from the trunk, which gives trees years or decades of space to increase in girth (growth rate is species dependent) before the interface of the treehouse and the tree needs to be altered.
Proper materials attaching tree houses:
1. Treehouse fasteners need to maximize strength and minimize tree growth interference. These tree house fasteners vary slightly in size of stock, overall length, length of the collars, threading, heat treating, and powder coating. Most are made of 4140 steel, and according to designs that were created through the input of many people but made available to the world by Charley Greenwood, P.E. of Oregon. Most professional treehouse builders now use Treehouse Attachment Bolts, also known as TABs. To see examples of TABs, please visit the treehouse bolts page to see versions that can support loads from 2,000 to 25,000 when properly installed and backed up as necessary, depending on various application details. The species of the tree also affects support load. Some of Charley Greenwood's HL models developed for extremely large loads have been designed for up to 44,000 on one tree house attachment point.
Treehouse fasteners are also known as Tree Anchor Bolts, Special Tree Fasteners, Attached Limb Systems, HLs and others. All such fasteners for tree houses are in the same class and based on the same theory. The concept is to spread tree houses' load over a larger surface area of tree tissue so that greater loads can be applied without crushing the tree tissue on the underside of the fastener, which is the universal definition of failure of any fastener for tree houses. We see a lot of home-built tree houses that have already "failed" by this definition. A failed tree house fastener can keep a tree would open, sag or warp, and/or eventually break.
2. We special order several sizes of large lag bolts for tree houses from 1" diameter and up, that are typically 12" long. These mount securely into the heartwood and are suitable for very small tree houses or platforms or where they are only carrying part of the total load of the tree house. You can usually only find lag bolts up to 1/2" at hardware stores, and a few places sell up to 3/4" over the internet, but it's really not enough for perching tree house beams even for small kids tree houses. We almost always have 1" and 1 1/4" bolts readymade.
3. Our welding shop produces the steel brackets that we need to attach beams to treehouse bolts and large lag bolts. There are several different varieties that depend on the type of treehouse attachment points and they often need to be custom made for tree houses. If you would like to order quality brackets for tree houses from us, we will consider each case separately. Please draw the bracket you need precisely, with reference to the trees and forces involved. If you don't know what kind or style of bracket you need, then chances are you are really asking us to help design your tree house platform. We do offer this service for an accompanying charge for design and consulting fees as well as hardware costs.
Here is how NOT to attach tree houses to a tree.
Be wary of these four practices:
1. Don't use threaded rod to support a shear load. Threaded rod is intended to support loads in tension, not shear. When a shear load is applied, especially at any leverage, the rod will bend or break causing the treehouse to fall. The question always arises whether using a larger or higher grade of rod is appropriate for tree houses, and the answer is typically "no." If the tree house is very small so that the attachment point is only going to carry a few hundred pounds, and the load is not applied at significant leverage, then using a large threaded rod (1" diameter absolute minimum) may actually be safe for a tree house. However, there is no situation where threaded rod is anywhere near as strong as a similar diameter lag bolt, and I would avoid any tree house builder who regularly uses it. Would you rather have a cheaper tree house or a safe tree house? Our objective is building quality tree houses - we do not compromise when it comes to the safety of our clients' tree houses or potentially dangerous tree house accessories like zip lines.
2. Don't use too many fasteners. Experienced builders of custom tree houses will understand the safest and least harmful methods of attaching tree house beams to host trees. Trees need to compartmentalize each penetration or wound that they experience. So if you put several nails or small lag bolts in a concentrated area, presumably because just one isn't strong enough to support the treehouse, then the tree may treat the whole area as a single wound and shut the area out from the rest of the tree's vascular system to prevent the spread of decay. Your tree house is likely to be safe and appear fine for several years. But behind that board you put 5-15 nails or screws in, the wood is decaying and eventually the whole treehouse may fall down unexpectedly, revealing a huge wound in the tree. For quality tree house construction the key here is to use one large fastener rather than several little ones. The 1/2" galvanized lag bolts you'll find readily available are not enough. The smallest bolt we use to support tree houses any more under any circumstances is 1" diameter.
3. Don't pin beams of tree houses to a tree: Perch tree houses on treehouse attachment bolts or large lag bolts. We have seen thousands of tree houses built by others over the years as part of our tree house consulting practice. The most common errors we find are tree houses fastened by nailing or lag bolting a main support beam to the trunk of a tree. Our experience tells us that either the tree will push the board out over time pulling the fasteners through the board until the tree house breaks or the tree will try to grow around the board. Typically, the tree will try to grow around the board, but will either fail or take decades to completely seal over the beam. For those decades, the beam will interrupt the flow of nutrients on that side of the tree, and probably create a moist, dark, entry place for disease and decay to start. "perch, don't pin," is a key tree house construction concept to remember. Perch your beam on top of a really large fastener, and allow for tree movement through the use of custom floating treehouse brackets made especially for tree houses using artificial limb fasteners. Don't pin tree houses to a tree, essentially creating a tourniquet and a disease magnet on that side of the tree.
4. Don't trust what you read in every tree house construction book. Some of them have great advice, and others are dangerous or harmful to your trees. Many books tell you to do what we just told you above not to do. They are treating a tree like it was a 6x6 post or a telephone pole; not like it is a living and growing organism. Basic tree biology is just as much a part of tree house building as carpentry is. If you want to have a safe and long lasting tree house, then don't believe everything you read out there. We really care about our craft and don't want the whole tree house building industry to get a black eye when someone gets hurt because of poorly designed tree houses or poorly attached tree houses. So if you are considering building your own tree house, please do it safely. Tree Top Builders offers consulting services for building tree houses and we also schedule tree house workshops where you can gain hands-on experience for tree house construction.
When you are ready to get help building your own custom tree house - please contact Tree Top Builders!