A critical view on the use of wood in the structure of buildings.
Prof. Ir. Rob Nijsse
Why do I call the use of wood in big structures : A big mistake.
- Trees grow in the forest during a lot of years, taking their nutrients or ‘building materials” from the earth and atmosphere.
- If we remove a tree trunk from the forest, to make shelfs and beams from it, we take a way a lot of these “building materials”. The forest becomes poorer and the new (hopefully re-planted) trees will be weaker and less healthy.
- It is stealing from the forest without “paying” for what you take.
How many can we safely ( = without cracks) make wooden structural elements like floors and walls from a big tree trunk?
By cutting the tree trunk in little shelfs and glue them together in two perpendicular directions. This is called Cross Layered Timber. ( CLT ).
Attention! This requires a lot of sawing and glue!


Everybody says that building high rise buildings with wood as structural material is
“the Golden Road to a sustainable future”.
- Let’s look a a high rise appartement building of 50 meters height built with wooden walls and floors.
- We calculate how much trees are required for this building.

High Rise Building 50 m tall.
Four appartements of about 6 by 8 m on each floor. Total 16 floors.
CLT walls, thickness = 0.4 m.
CLT floors, thickness = 0.3 m.
Length walls = 4 X 12 + 3 X 18 = 102 m.
Volume walls = 102 X 50 X 0.4 = 2040 m3.
Volume floors = 12 X 18 X 0.3 X 16 = 1040 m3.
Total Volume Wood = 3080 m3.
(and we still need a lot of steel for connections!)
Okay, so we need 3080 m3 for our wooden high rise building. If we take 100 year old, 20 meter tall trees; how many trees do we need ?

- We need 3080 m3 of wood for our high rise building.
- Each 100 year old tree delivers usable 6.4 m3 wood.
- So we “use” for our building 3080 / 6.4 is
481 trees !!!
This is a forest on its own.
And the expected lifetime of this building?
50 years, if not rotted away before this time!
- Hence: be more reluctant to make big structures out of wood.
- Of course wood is a beautiful material to look at. So use it only on the outside of building elements! As a removable item.
- And use complete tree trunk as columns / beams for structure. Their fibres are not cut up and damaged. So they a large bearing capacity!

Dutch pavilion
EXPO 2000 Hannover
Architect MVRDV
stacked landscape.
- cellar for services
- concrete dunes
- flower layer
- flowerpot-layer
- a forest
- cinema, water curtain
- pond with island
- windmillls


Tree trunks return after 1000 years in our buildings, this time with a German certificate, issued by the German Prufingnieur.


A big crowd waits patiently till they are allowed in the pavilion.

Posbank restaurant (NL)
Architect : SeARCH
Truss with met
Tree trunks as
Compression diagonals

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