German Treehouse Screw ‘GTS’
Fixing treehouses – gently, safely, durably!
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Whether it’s a large treehouse, a small platform, a hunter stand or a swing beam – if you want to attach something heavy directly to a living tree, Tree Screws are the best solution!
1. What is a Tree Screw?
Without Tree or Treehouse Screws, modern treehouse construction as we know it today would not exist. The technology was developed more than 20 years ago by the American treehouse pioneers Charles Greenwood, Michael Garnier (Garnier Limb – „GL“) und Pete Nelson (Treehouse Attachment Bolt – „TAB“). Based on these American bolts, we have further optimised our Tree Screws and adapted them to the European market – we proudly present:
Example of a “German Treehouse Screw GTS” (also known as “Tree Attachment Bolt TAB”, “Garnier Limb”, “Treehouse Fastener”, “Treehouse Bolt” or “WorldTreehouseOrganisation Bolt”)
2. What makes Tree Screws so special?
Tree Screws are oversized screws designed to be mounted in a living tree. They can carry extreme loads of up to 8 tonnes.
The advantage over other fixing methods is that the wooden beams keep their distance from the bark. The tree is not pinched (see picture). Thus, the tree can continue to grow unhindered and wrap the Screw more tightly year after year – a kind of artificial branch is created.
The area of application is wherever heavy objects are to be permanently and securely fastened to the tree trunk: Treehouses, platforms and installations in climbing forests, high ropes courses, forest rope parks and treetop trails.
Example pictures of modern Tree Screws
3. Why shouldn’t you use normal wood screws?
Attention:
Ordinary wood screws and threaded rods with a ø < 40 mm (1,6 in) should not be used for fixing in the living tree – this is for the following reasons:
- The material is not designed for the load: In contrast to normal timber construction, large swinging and twisting loads occur in the living tree (storms). This continuous alternating stress can lead to fatigue fractures in normal screws.
- The tree grows with great force in width: wooden beams that are screwed directly to the trunk can rot and break; screws can bend and break off.
- If the trunk is pinched over a large area and prevented from growing (clamp mountings), predetermined breaking points can develop there.
Advantages and disadvantages of the different fixing methods.
4. How exactly do Treehouse Screws work?
The GTS Allstar consists of three segments
- A: Tree Thread
- B: Cylinder
- C: Shaft ø 40 mm (+ Support + wooden beam)
The shaft (C) is located outside the tree and the Supports with the platform beams are mounted on it.
First, a precise hole is pre-drilled
- Tree Thread ø 36 mm (yellow borehole)
- Cylinder ø 74 mm (green borehole)
- this creates the “contact surface” (red)
The GTS is screwed into the pre-drilled hole until the cylinder is tight against the contact surface.
Vertical load on the screw
The Screw transfers the load from the treehouse (red arrow) into the trunk. When overloaded, the Screw rotates around its pivot point, which is directly behind the cylinder, into the tree.
A GTS Allstar 2.0 alone has a load capacity of at least 2.0 tonnes (4400 lbs) in hardwood and 1.5 tonnes in softer softwood. With Accessories, the load capacity can easily be doubled!
Example: GTS Allstar + Dynamic Supports in the tree
When the Screw is ready mounted in the tree, the Accessories are pushed onto the shaft of the Screw. The support beams of the tree house construction are then attached to these “supports / connectors”.
And how does it continue?
Around the Screw, the tree forms resistant wound and reaction wood. Over the years, the screw continues to grow in and becomes an integral part of the tree.
Tree covers screw with extra hard wound and reaction wood.
The Screw remains at the same height in the tree throughout its life, like an incised heart; only at the buds does the tree grow upwards. The question of whether Screws harm the tree is answered here.
5. Load-bearing capacity of our GTS Tree Screws
Die Tragfähigkeit / Belastbarkeit der Schrauben hängt im Wesentlichen von 3 Faktoren ab:
a) Strength of the wood at the point where the Screw is installed
The load-bearing capacity of our Tree Screws strongly depends on the wood properties of the respective tree. In general, it can be said that the Screw is significantly more resilient in hardwoods (oak, beech, maple, …) than in softwoods (spruce, fir, pine, …). See here: Is my tree hardwood, medium hardwood or softwood?
The following diagram gives an overview of the load-bearing capacity of GTS Screws, the values were determined in load tests. For healthy trees you can safely calculate with the minimum values from the diagram!
b) Lever arm with which the load engages
The load-bearing capacity also depends on the lever arm, i.e. the point at which the load engages or the support rests on the shaft. The pivot point of the Tree Screw GTS Allstar is approx. 11 cm inside the tree.
The closer the construction is to the tree, the higher the load capacity: half the lever arm = double the load capacity!
For normal loads, we recommend a distance of approx. 10 cm between the beam and the bark, which is a perfect compromise between load-bearing capacity and enough space for the tree to grow in width. With Accessories, the load-bearing capacity can be doubled!
Load capacity of the GTS Allstar depending on lever arm and pivot point (e.g. 4–2 tons; 8800–4400 lbs in hard hardwood)
c) Direction in which the load attacks
The angle at which the load is applied also has an effect on the load-bearing capacity of the bolt:
FIG 1 – Good: Normal load on the GTS, vertical load in the middle of the shaft.
FIG. 2 – Very good: If the vertical load acts in the direction of the tree, the load-bearing capacity is greatly increased (e.g. strut with 45° angle)
FIG. 3 – Solala: If, on the other hand, a load pulls the screw out of the tree, the load-bearing capacity decreases, this should be avoided (e.g. tilting triangular construction).
FIG. 4 – Avoid: Lateral, horizontal loads should always be avoided, as the load-bearing capacity is only about 1/3 compared longitudinally to the grain (e.g. single strut pressing laterally on the screw or triangular construction heavily loaded on one side).
Load capacity of the GTS Allstar depending on the load application angle
6. Advantages of our “German Treehouse Screw”
- Proven fastening technology for over 20 years!
- Extremely high load capacity (with reinforcement up to 8 tons vertical load).
- High safety & lasting stability
- Free thickness growth for the tree
- Very low maintenance
- 100 % Made in Germany – Bavaria!
- Lifetime warranty on all GTS Screws!
- We sell 6 different GTS models – there is a suitable Tree Screw for every situation.
- Infinite design freedom due to extensive accessories.
- Low tool requirement due to perfectly coordinated products.
- Cordless working: Thanks to advanced screw geometry and sharp tool cutting edges, pre-drilling is effortless with a powerful cordless drill. Disturbing cables are now a thing of the past.
- European dimensions: Screw and Accessories were developed for the European market, i.e. metric dimensions, time-saving tool and spare parts procurement, no expensive special tools.
The latest model of our Tree Screw “GTS Allstar 2.0”
Technical details – Version 2.0Â
- NEW – Tree Thread 2.0: The two-thread coarse thread was specially developed for the living tree. The optimised thread form has an even higher load transmission and saves a lot of strength and time during assembly.
- NEW – Quick Start Pin: The smoothed pin at the beginning of the screw can be inserted directly into the drill hole – this makes assembly in the tree much easier!
- NEW – Cylinder HL: The massive “Heavy Load” cylinder (ø 74 mm) transfers even the largest loads safely into the trunk. 4 fine grooves mark the installation depth.
- NEW – Seal +: The expanding cylinder seals the drill hole, the screw fits snugly and tightly. The deep grooves make it easier for the tree to seal the wound when it grows in width.
- Natural Transition: Over the years, the tree overgrows the screw. This process is facilitated by the parabolic transition. The flowing transition makes the overall appearance more aesthetic – like a natural branch.
- Shaft ø40: With a diameter of ø 40 mm, the shaft can withstand even the highest alternating loads – peaceful sleep is guaranteed.
- Seamless: We do not use welded seams on our Screws – our new steel alloy makes the GTS Screws indestructible!
- Black KTL Coating: The environmentally friendly coating process ensures optimum corrosion protection and excellent sliding properties. Thanks to the black appearance, the screw disappears inconspicuously in the tree.
7. Assembly
Check out our Service Area and our assembly videos on YouTube!
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