The right treehouse tree
We show you what’s important when building a tree house!
Before you start planning and building your treehouse, you need a suitable tree.
For large treehouses, the tree must be able to support several tonnes of weight and withstand extreme weather situations. The house must be anchored securely and gently to the tree without overloading it. With a few exceptions, most trees with a trunk diameter > 30 cm (12 in) are suitable.
Here you can learn which tree species are best and least suitable for building a treehouse and what warning signs you should look out for:
Treehouse in healthy beech – example of the perfect symbiosis of tree and treehouse.
1. Table – The best treehouse trees
One thing first: there is no such thing as the “most suitable tree” for building a treehouse.
Every tree is unique!
Wood quality varies greatly, not only from species to species, but especially from site to site, from tree to tree, but also within the same tree. Influencing factors are climate, soil quality, age & exposure. Thus, it can happen that a Treehouse Bolt in a beech holds 4 tons (8800 lbs) in one place, but only 3 tons (6600 lbs) in a neighbouring place.
Nevertheless, there are of course tree species that are more suitable for building treehouses than others.
Good qualities are:
- High wood strength
- good wound sealing (when drilling holes)
- quick cultivation of reaction wood
- high average life span
- large expected trunk diameter
- robust bark (important for rope fastening)
As part of a bachelor’s thesis, we have researched numerous studies and compiled a list that shows us which trees are particularly suitable for treehouse construction:
Excellently suited: Deciduous trees such as beech, oak, lime, maple, ash, elm, sycamore, chestnut and many nut trees, as well as conifers such as larch, pine, Douglas fir and fir are excellently suited. These can be used without hesitation for the assembly of treehouses from a trunk diameter of >30 cm (12 in).
Less suitable (as sole support trees) are: Birch, elm, alder, cedar, spruce, horse chestnut and fruit trees. Here you should only build in mature and very healthy trees. Try to work with few fixings (few wounds from Tree Screws & Bolts). In the case of large and heavy houses, it makes sense to relieve the tree and place the treehouse partly on stilts.
Not suitable: Very soft tree species such as poplar, willow are not suitable for building treehouses; Sycamore trees < 100 years, cottonwood trees, palm trees and eucalyptus should also be avoided for tree house construction with bolts; Here it is better to build the house next to the tree on stilts.
2. How big and how high does my treehouse tree have to be?
A treehouse floats 5 m above the ground in the beech forest – here the trees must be fully grown and stable!
Of course, you don’t always have this huge dream tree in your garden, but that doesn’t matter, because you can also build great treehouses in 5 m high fruit trees, which are then usually a mixture of treehouse and stilt house. Trees below <5 m (16 ft) in height either suffer from the treehouse weight (too thin a trunk) or are “visually crushed” by the size of the treehouse.
If you are lucky enough to have several trees or a small forest, the rule is: “Look for the big, healthy trees first” for the following reasons:
- The tree is mature and has proven that it is resilient.
- It can withstand extreme situations (storms, dry periods, broken branches, hail damage, …).
- A solid tree trunk moves less during storms and the treehouse construction is less stressed.
- A mature tree requires less energy for height growth, it builds up safety reserves and uses these specifically for wound healing and the formation of reaction wood (ideal for Tree Bolt Fastening).
The decisive factor for building a treehouse is therefore not only the height of the tree, but above all its health and trunk diameter!
3. How thick must the trunk be at least?
Good for hugging, but too small to build a treehouse – Vitus and Tim at the not so “Giant Sequoias” in the USA.
IMPORTANT: The trunk diameter ø is measured at the height of the platform (mean value). It should be at least 30 cm (12 in), for the main tree (1-tree house) better 45 cm (17 in).
For tree house construction, a thicker trunk means:
- The treehouse may become larger and heavier.
- The house may cantilever out further to the side (tree swings less, less rotation).
- The house can be fixed higher in the tree.
- Many tree fixings can be installed in a healthy tree with a thick trunk.
- The larger the trunk diameter, the smaller the proportion of injured tissue when drilling.
In the following table, we show you how to calculate the minimum stem diameter MSD ø for our GTS Treehouse Screws:
These values serve as guidelines for our Screws, and should be adjusted individually depending on the situation on site. If you have any questions, please email us with photos of your trees so that we can evaluate them!
4. How to tell if the tree is healthy – warning signs?
Decades of professional treehouse building have shown that trees do not reject a treehouse, but rather integrate it into their lives as an integral part over time (more on this here). This is no problem for healthy, mature trees, as they have huge energy reserves. But how do I know if the tree is healthy?
For private and normal treehouse projects, a visual assessment of the tree is sufficient.
Treehouses should only be built in trees that have grown straight and are absolutely vital!
The good thing: You can see whether the tree is healthy or not.
Similar to humans (posture, skin appearance, hair, scars, …), there are also visible warning signs of poor health in trees:
- unhealthy crown (little and irregular foliage)
- many deadwood branches (without foliage)
- elongated cracks
- crooked, crooked trunk (bad statics for treehouse)
- unhealthy dying bark (pest infestation!)
- woodpecker (insect infestation!)
- excessive moss
- hollow sound (knocking test with hammer)
- many secondary shoots (new “panic shoots” in the middle of the trunk)
- Fungal fruiting bodies → do not build here under any circumstances!
In addition to the tree, it is essential to observe the location and the surroundings – look out for these warning signs!
- Excessively soft soil (roots can anchor badly)
- very wet soil or flooded area
- Tree on steep slope (tree can fall over)
- Tree on rocks (roots can anchor badly)
- Fungal or insect infestation on neighbouring trees
- Species-specific disease e.g. ash and elm dieback, chestnut (leaf miner) and spruce (bark beetle)!
If in doubt about the health of the chosen tree, always consult a tree biologist or tree expert for public or particularly large projects.
Always decide in favour of the tree, if necessary reduce the size of the treehouse or use stilts for anchoring.
5. How many trees do I need to build a treehouse?
You can build your treehouse in one tree or in several trees! The size and position of the trees in relation to each other are the basis for the construction of your platform. Of course, you can also support your platform with stilts; natural, round robinia trunks (also acacia) are particularly suitable for this.
A good distance between the trees is 2–6 m (6-20 ft), with even larger spans you will need very large beam dimensions and the beams will become incredibly heavy!
You can find out more about trees, timber and materials for building tree houses in our FAQs!