Wood construction


Wood has always been a traditional construction material in Finland. It has always been available and it’s easy to work. As an insulating material it has been excellent to keep the warmth inside and frost outside during cold winters. Commonly, traditional buildings are built of logs with many different kinds of log construction techniques and decorations. The trees used to build houses were selected carefully and cut down in the spring with snow on the ground when the tree was in it’s rest phase. The log house was also designed in a way that it was possible to take down and reconstruct it ,log by log, if needed. The surface was protected usually with red ocher and shingle was chosen as the roof material.

When thinking about a wooden house, almost all of us can imagine a picture of a Finnish Veteran House from 1940–1950 with its porch and central walls. Alvar Aalto, Aarne Ervi, Aulis Blomstedt and other notable architects of the time were designing the model houses. Here also the construction material was wood, although this time as a modern frame structure and with sawdust insulation. The roof material was already selected to be felt, sheet metal or some other more modern material.

Old traditions have formed a certain kind of relationship to wood houses. To many, wood houses bring into mind grandparents’ home during childhood with its yard, and to others rotten lower logs and burnt chimneyless cabins, or the mouldy air of a summer cottage instead. To many constructors a wood house means an eternal maintenance target and risk of moisture in the structure. You can hear the comment “No wood to other places than to a fireplace and parquet!” from the mouth of a builder still in 2020. There still lives a conception of a stone house as a value house and of a wood house as somehow poorer in quality. This is of course not the truth. Many precast concrete buildings from 1960–1970 are already at the end of their life. These were advertised during their time as maintenance-free. As heard already during architecture lessons in school, the repeated sentence “maintenance-free equals impossible to repair” seems to be correct. Of course a traditionally constructed fully bricked house is a really good structure, as well as log structure. It is still not about the material, but about a good structure.

The new coming of wood construction has been talked about as long as the coming of the information model, it is to say at least 25 years. So, the information model is now finally true, and soon the wood construction will be as well. Why? Because wood has excellent qualities that the world and Finland need at the moment. Responsibility, carbon neutrality, and energy saving are constantly growing phenomena, and their value in relation to the economy increases. Helsinki has a “Carbon neutral Helsinki 2035” program and Vantaa has an equivalent for the year 2030. Equally, the government starts to regulate the carbon footprint in the buildings probably already in 2025, when a person starting a project must point out the carbon footprint in the building permission just like is done with energy class today.

Big cities are facing a big challenge; how the production of energy is going to be changed to carbon neutral? A big part of the energy of the city is produced for district heating and it is going to be produced largely with fossil fuels. The buildings have to change themselves to energy producing units and at the same time transfer excess energy to a net or to save it. At the same time the energy consumption of the buildings must be able to be reduced even more from the current time. Because the energy efficiency of the buildings has improved for the new regulations and technology during the last decades a lot, the attention is next going to be in energy and carbon during the construction time. The energy consumption of contemporary houses during the construction time is estimated to be approximately one fifth of the consumption of the total age of the building.

Another big challenge is material efficiency and its carbon footprint. Here wood is totally superior compared, for example, to concrete. It has been stated in VTT’s research that the carbon footprint of a wood house is approximately half that of an equivalent concrete building (VTT 2017). Wood binds carbon to the structure and the rule of thumb is that a ton of wood binds approximately a ton of carbon. In the structure and the facade of the building it is therefore bound for 100–200 years. Equally, producing cement used as a binder of concrete consumes 5–8 percent of the greenhouse gas emissions of the whole world. Let alone that, sand used as a material of concrete threats to come to and end in the world. Concrete is an excellent material and it can not be totally replaced but the increasing use of wood from the environmental perspective is welcome. There aren’t yet totally exact indicators to calculate these because of many factors but as a directive fact it can surely be stated that wood is a responsible and environment-friendly choice.

The third remarkable factor is recyclability. As log houses before, also modern wood houses can for their materials easily be taken down and sorted, and their wood material can be partially used again. The recyclability of concrete is weak.

Other benefits of wood are the domesticity and locality of the material. The use of wood employs Finnish employees and companies. Large-scale use of wood in construction can increase total profit of gross national product by about 1 billion (PTT 2012). Wood is also a light material, its effects to foundations are remarkable, and also lifting of current buildings, as wood-structured, is often possible. Furthermore, the importance of the use of wood in the inner surfaces can be mentioned, a person experiences wooden surfaces on average more pleasant and healthy than non-organic materials.

AS&H invests in the development of wood construction together with other actors in the field. Wood structures and facades still require a lot of further research and clarification of official regulations. In a collaboration with the leading special designers, fire consultants, product-parts manufacturers and authorities we develop wood construction as a system to move to a more versatile and daily-life fitting way. An example of this is Keilaniemen Portti constructed by Varma, which is going to be the highest wood-structured office building in the world when finished. There are also some other wood construction projects on the design table.

As it was stated in the above mentioned VTT’s research, wood construction is an ecological act. At the same the article also took a strong stand when it comes to design:

“An architect is a guard because it is going to be decided on his or her table whether the building is going to be carbon efficient”

Sami Horto
Architect SAFA, Chairman of the board