Garnier Limbs

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• Cost Of Garnier Limbs
• Can I do it Myself?

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Engineering of Treehouse Fasteners

Before delving into how these treehouse fasteners are made, a paragraph of caution is due. Garnier limbs and other fasteners for tree houses have been designed by engineers, but no engineer could say that they are appropriate for the particular tree house that you are planning to build. Garnier Limbs have no weight rating. The actual load that each specific treehouse fastener will withstand before failing depends on many variables. Here are a few of the more important variables:

• Whether or not the treehouse fastener has been properly installed
• The distance from the bearing surface of the tree to the spot on the perch where the load rests.
• The size of the collar on the garnier limb and how far it is recessed into the tree.
• The species of tree, since trees all have specific densities.
• Whether or not the garnier limb has been hardened.
• Whether or not the garnier limb is part of a system - meaning, the end of the perch is backed up to a higher point in the tree.

If you have any doubts about what size of fasteners you need for your tree houses, please consult with a qualified engineer or professional tree house construction company. Safety should always come first.

This garnier limb design has been published on the web for anyone's review and use. It is not guaranteed in any way or specified for your tree house. But this is the main design that the pros use for the smaller garnier limb type anchor bolts. When you shop for garnier limbs, you will have to specify what, if any, modifications you require. Tree house building pros regularly modify these designs in minor ways. Professional tree house builders nor GarnierLimb.com assume any liability for what styles or modifications you choose to make. To get that kind of professional guarantee, you really need to have an engineer design your tree house. That being said, here are some of the variations that we have found in use and/or for sale from various places:

• The "perch" or the outer part of the GL is sometimes extended, up to 18" from the collar instead of 6". When extending the perch, it is strongly recommended (mandatory, if you ask us) to back up the end of the perch due to the increased leverage. Due to the backup suspender system being in place, these garnier limbs are sometimes not required to be heat treated.
• The "collar" is anywhere from 1/2" to 6" long. Anywhere from half to all of the collar is set inside the tree.
• The powder coating is often omitted. Arborists generally do not think the tree cares one way or the other. If a pipe wrench is used for installation, the powder coating on the perch may get chipped up anyway. But it does look nice, prevent rust, and it helps to identify where the fasteners were made.
• The heat treating is sometimes omitted. GLs that aren't heat treated are more likely to fail, all else being equal. The one exception to this is if the metal is heat treated improperly, then it can become brittle and weaker than an untreated garnier limb. But some argue that this level of hardness is not required when the perch is going to be suspended anyway.
• For especially heavy loads, larger studs with larger collars have been used. These are always custom made pieces because they need to be made to fit a specific tree house application.
• Some GLs have been produced with different threads/inch counts on both sides. This kind of fine tuning is what you do when you install hundreds of garnier limbs per year.

These garnier limb type treehouse fasteners are meeting the current demands of most serious treehouse builders. But if you can't tell from the disclaimers above, there is a lot of uncertainty over exactly how much weight garnier limbs can support. That is why we don't even suggest a weight rating, or even a range. Some tree house builders have suggested that depending on all the variables listed above, an appropriate load rating for a garnier limb type anchor bolt should be between 2000 lbs and 12,000 lbs. That's not very helpful to somebody trying to decide which size GLs to buy. GarnierLimb.com suggests to the tree house building community that perhaps some rigorous third party testing should take place to determine how much weight can safely be placed on them. This would make it easier to get building permits for tree houses, and make it easier for treehouse engineers and do-it-yourselfers to use garnier limbs to design and build their own tree houses. We realize that this is expensive, and the cost is hard to pass on to consumers because the people paying for the testing do not have a patent to protect their investment. That, in itself, is part of why such testing has not already been done. The other reason is that the market for the very best in treehouse fasteners is relatively small, making it harder to justify the great expense of such testing.