The era of extensions is now – light wood is the optimal building material

The natural qualities of wood – lightness and strength – bring multiple positive consequences for both individual constructors and societies undergoing heavy urbanisation. According to experts, one of the areas of wood construction with most potential is extension building. Wooden materials like Metsä Wood’s Kerto® LVL (laminated veneer lumber) make construction fast, light and green.
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Our existing built environment is going through an era of refurbishment. The need to renovate building service systems such as sewage and ventilation is a remarkable driver of residential refurbishments. To finance these operations, new storeys are in some cases being added on top of existing buildings.

“Adding new layers to the roofs of old buildings requires careful planning. Old structures may have been calculated in accordance with different standards than those applied today, or the materials may have been damaged during their service life,” Aalto University architect and researcher Matti Kuittinen points out.

Using lightweight building materials is one valid option for solving this problem.

Exceptional extension building near Paris – 33 apartments in 6 months

Image by Virtuel Architects

Wood is strong and relatively lightweight. This makes wood elements and modules made with Kerto LVL an excellent option when adding new storeys on top of an existing building.

In Poissy, near Paris in France, 33 new apartments were constructed on top of a group of existing residential buildings. Due to prefabrication and light wooden structures, it took only six months to complete.

“What’s interesting about the solution for vertical urban development is the prefabrication,” declares Laurent Pillaud, architect at Virtuel Architecture. "Each apartment consists of three or four modules and one roof; the production of the modules took one month. Then the modules were delivered, and each was installed directly on the rooftop in one day." 

No need for heavy foundations or a laborious logistical effort

One of the most essential advantages of building with wood is the lighter weight of the structure, which enables building on a lighter foundation.

“This in turn leads to cost savings, as less piling, construction material and time are needed,” architect and researcher Matti Kuittinen says. 

For constructors, the other benefits of using light wood elements include easier material handling at the building site and more efficient construction logistics. Again, time and money are saved during the construction project.

Learn more about light building with wood.

This article has been published as part of the Kerto LVL Fast, Light, Green series. All the articles are available at



 T. Konstantinou, Facade Refurbishment toolbox: Supporting the Design of Residential Energy Upgrades, TU Delft, Delft, 2014.

M. Langen, “Building additional floors with wood”, Metsä Wood articles, 2016.

H. Berger, Light Structures, Structures of light: The Art and Engineering of Tensile Architecture, Basel - Boston - Berlin: Birkhäuser Verlag, 1996.

For more information, please contact:

Viivi Kylämä, Marketing Manager, Metsä Wood, mobile: +358 40 820 9850,
Kirk Nichols, VP Sales, Americas, Metsä Wood USA, mobile: (404) 861-1098,

For press information in UK, please contact:
Matt Trace, Director, Defero Communications, tel. 07828663988,

Metsä Wood

Metsä Wood is one of the leading European producers of engineered wood products. We are committed to serving three segments: construction, industrial and distribution customers. Our primary products are Kerto® LVL, plywood and other wood products. We also sell Nordic timber produced by Metsä Fibre.

In 2018, Metsä Wood's sales were EUR 0.4 billion, and it employs approximately 1,500 people. Metsä Wood is part of Metsä Group.

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