Architectural lightness

Lightweight wood enables ultimate architectural freedom

​The natural qualities of wood, especially its lightweight and strength, are much-needed features in building today’s urban environments. Using wooden elements in architecture has proven to be economical, structurally efficient and visually attractive.

“The composite structure that gives trees their lightness and specific strength is the same that makes wooden elements strong and lightweight,” Matti Kuittinen, architect and researcher from Aalto University, points out.

Indeed, the engineered wooden beams compare well in strength to concrete and steel alternatives. For example, the span to depth ratio of Kerto® LVL (laminated veneer lumber) beams is in the range of 20:1. Alternative steel beams reach figures from 15:1 to 25:1 and different concrete beams range from 7:1 to 26:1.

Wood is lightweight but strong

Design professionals appreciate wood’s special strength figure

It is the lightweight of wooden structural parts in comparison to concrete and steel alternatives that particularly deserve to be noted. The special strength figure, also known as strength-to-weight-ratio, is calculated by dividing the tensile strength with the density. For concrete the number is typically 5.22 kNm/kg, as for 3 meters long Kerto beam the figure is 68,6 kNm/kg.

No wonder that among design professionals wood is appreciated especially for its strength-to-weight ratio in comparison to other construction materials.

“All this considered, much less wood is needed for achieving the same strength as with, for example, concrete beams,” Kuittinen outlines.

Unique roof construction made possible with Kerto LVL

In Clamart sports center located in France, architects used Kerto LVL (laminated veneer lumber) that enabled a wide-open space that has astonished visitors and structural design professionals.

“In this project, the complex geometry, double-curved with long spans, presented interesting technical challenges. Kerto® LVL enabled long spans and complex curves for which the sports center is now famous for,” project manager-architect Gaétan Morales from Gaëtan Le Penhuel Architects explains.

In the Clamart project, the technical solution connects the façade and roof together with a continuous structure. This enabled greater architectural liberty, allowing wide spans, and optimizing the wooden structure itself. Use of engineered wood frame also proved to be economical, structurally efficient and visually attractive.

Lightweight material enables efficient design and construction process

The high specific strength of engineered wood products is an important feature in resource efficient construction. The lighter the building parts are, the less there is need to spend energy on their transportation and erection. This, in turn, leads to saving time and money.

A recent example of using wood innovatively and utilizing its best features was in Stockholm, where a temporary wooden building was built next to the old market hall as part of the refurbishment project.

Lightweight Kerto® LVL offered high degree of prefabrication and therefore suited well for the construction project. The concept for the temporary building was based on a modular system, which is easy and fast to erect and demount. It took only five weeks from the start for the external envelope to be erected.

“In this respect, utilizing lightweight engineered wood products streamlines and speeds up both the design and execution process without endangering quality,” Kuittinen states.

See some of the reference cases that show how wood elements and modules can help to tackle technical challenges and enable architectural freedom for structural designers.