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How to Build with Wood

For Nordic Municipalities who want to explore the possibilities that wood offers in building greener, healthier and more liable urban areas, this How to Build with Wood guide will give you the introduction. The guide is divided into the different processes there will be in a municipality that consider or is already using wood. The different sections contain relevant links and resources at a national level, where you can learn more about the situation where you are.

Building regulation

Design considerations for wood buildings include fire protection strategies, requirements for acoustic performance and whether you want visible wood in the building envelope. Follow the links below to the national regulations within every Nordic country.

Use wood where it makes sense

Wood is a light material which gives opportunities for adding more stories on fragile terrain or adding stories to already existing buildings without compromising the existing foundations. Wood can be an excellent choice for cladding, but if exterior wood cladding is a barrier for your project, you can easily use another material for the building envelope of your wood building. Use wood where it makes sense in your project. You can find examples of using wood in Cases section on this webpage.

Wood based materials

Wood and wood based materials are all products covered by harmonized technical specifications under the umbrella of the Construction Product Regulations (CPR). Wood use as a construction material covers a large range of products produced in the Nordic countries, the most commonly used is to be found below.

Structural timber is to be used as a structural component as beams and/or columns. Structural timber is strength graded in European harmonized classes, e.g. C24 or C30 according to the European harmonized standard EN 14081-1.

Glued laminated timber (Glulam) is to be used as a structural component as beams and/or columns. Glulam is certified to European harmonized strength classes, e.g. GL28c or GL28h, according to the European harmonized standard EN 14080. An example of a glulam project is to be found at this link.

Laminated Veneer Lumber (LVL) is to be used as a structural component in the loadbearing structure as beams and/or columns, but also as full sized panels. LVL is covered by the harmonized specification EN 14374, but strength classes are individually declared by the manufacture.

I-joist is to be used as a structural component in the loadbearing structure as beams and/or columns. I-joist is not covered by a harmonized standard, but technical performances are declared on basis of European Assessment Documents EAD’s.

Cross Laminated Timber (CLT) is to be used as a structural component in the loadbearing structure normally as panels in walls and floors but also beams and/or columns. CLT is not covered by a harmonized standard, but technical performances are declared on basis of European Assessment Documents EAD’s. An example of CLT project is to be found at this link.

Non-structural Solid Wood could be used as paneling and cladding for interior as well as exterior purposes. Technical performances for Solid Wood paneling and cladding is covered by the harmonized standard EN 14915. An example of the use of non-structural solid wood is to be found at this link.

Wood based panels could be used as non-structural and structural in components as wall, floor and roof. Wood based panels are decided into different product types, e.g. Plywood, Oriented Strand Board (OSB), Particle Board and Medium Density Fiber Board (MDF) which all are covered by the harmonized technical specification EN 13986.

Wood Fiber insulation is used as an insulation material in external as well as internal walls. The technical performances for Wood Fiber Insulation is covered by the harmonized standard EN 13171 for mats and EAD 040138-00-1201.

Wood based materials are fit for digital design and off-site production. Therefore prefabricated elements and modular construction is widely used in the timber industry in the Nordic countries. Follow the links below to get more information about different wood based materials.

Design solutions

For inspiration regarding technical design solutions for different building parts with design descriptions and detail drawings, follow the links below.

Fire

Wood is a combustible material which requires safe implementation of fire protection measures in the building design. However, wood burns in a safe and predictable way which can be accounted for in the building design. Legislation regarding fire protection of wood buildings differ between the Nordic countries.

Simplified, there are two different fire protection strategies to choose from: active fire protection, in which a sprinkler system is installed in the building and passive fire protection, in which exposed wood surfaces are clad in non-combustible materials e.g. gypsum. To read more about fire protection, follow the links below.

Acoustics

Wood is a light material which needs to be considered when addressing impact sound and airborne sound insulation, particularly in residential settings. Often, additional weight is needed in order to fulfil acoustic requirements in floor constructions. Follow the links below to information about acoustics in wood buildings.

Visible wood

When designing a wood building you have to decide whether you want visible wood or not in both the interior and exterior of the building. Some stakeholders are of the opinion that a wood building should have visible wood in the exterior because they prefer the architectural expression. However, it is the structural skeleton of the building that defines whether a building is categorized as a wood building since a lot more material goes into the interior structure of a building than to the envelope cladding. If we want to use more wood in construction, it is important that we use more wood for structural purposes.

Your choice of material for the building envelope may be influenced by requirements given by aesthetics, maintenance, fire safety, sustainability, etc. If, for example you are in a Copenhagen neighborhood with brick-clad 5-storey buildings, it may not be aesthetically desirable to choose wood cladding for a new building in this area, but you can still construct a brick-clad wood building. Or if you have buildings in very close proximity, wood cladding may not be the best option in terms of risk of fire transfer from one building to another.

Visible wood in the exterior of a building typically adds maintenance costs compared to other materials, whereas visible wood in the interior of a building typically leads to less maintenance costs compared to other materials. Follow the links and read more about external cladding.

Building systems

Past and recent developments of modern engineered wood products have resulted in a range of different wood products being available on the market. Products like laminated veneer lumber (LVL) and cross-laminated timber (CLT) enables the construction of wood buildings up to 20 stories or higher. For the high volume 3-10 stories market, three main structural systems are available: post and beam systems, solid wood panel systems, and pre-fabricated wood elements/box modules.

Box module systems excel at the 2-5 storey level. They have a very high degree of pre-fabrication makes box module construction extremely fast, efficient and low-cost construction. Box module systems are limited in the degree of flexibility that the modules offer. They have typically found application in affordable housing projects.

Solid wood panel systems (CLT) and post and beam systems, provides opportunities to reach greater heights e.g. 5-10+ stories and they allow for greater flexibility in the internal building design, floor plan, and building use, especially the post and beam system. Together, the three building systems can cover all modern building requirements from affordable housing to high-end residential buildings as well as office buildings or even public buildings such as schools and hospitals.

For more information about different wood building systems, follow the links below.

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