SI-modular wood framing system

SI-modular wood framing system

Location Germany
Architect (system provider) Hans-Ludwig Stell, Stellinnovation GmbH
Customer Private house end customer / Showroom Stellinnovation GmbH
Products Used Kerto LVL, Finnjoist ibeam

Sustainable framing concept with timber I-beams

The architect Hans-Ludwig Stell from Münster, Germany, has developed a sophisticated modular system aimed at the one and two-storey house construction. With this system, the houses are constructed in timber completely without screws, by simply using interlocking connections in the installation. The starting point for a sustainable concept with the idea of an easy, quick and self-explanatory timber construction was for Hans-Ludwig Stell the Metsä Wood's I-beams Finnjoist®.


Easy and quick assembly – at any place in the world

Unique challenge

Hans-Ludwig Stell was given the task of constructing a type of house within the framework of development aid that could be assembled as simple as possible, and almost self-explanatory in various regions of the world. “I was architecturally inspired by steel construction”, remembers Hans-Ludwig Stell, managing partner of the Stellinnovation GmbH, “nevertheless, our company, the architect team, excluded steel construction specifically for this application. While searching for a suitable solution, we encountered the timber I-beams by Metsä Wood.”

Originally used in development aid, Hans-Ludwig Stell further extended the type of house so that it complies with the European standards of today, for example regarding the EnEV. What remained was the simple construction which can be assembled easily and quickly by a few people. A good example is the one and a half storey home with duo pitched roof as a free-standing extension to an existing structure.

More information

Load bearing structures  with I-beams

Values guide Metsä Group's operations 

The key feature is that the construction of the entire house is created for the modular system with only one construction material, the I-beam Finnjoist®. Due to the high load capacity, the Metsä Wood I-beams are used for the walls, for the floors and for the roof. Because these are constructed analogous to the principle of a double-T steel profile: The OSB web in the middle separates the top and bottom flange that run parallel. The latter are made of high-strength Kerto LVL S-beams, in a single piece and can permanently carry enormous pressure and tensile loads. In short: The perfectly matched materials and the geometric optimization to the cross section make the timber I-beam Finnjoist® versatile and ideally fulfilled all required characteristics for the planned type of house.

Bracing using a fixed grid

Values guide Metsä Group's operations 

The SI-Innovation modular system is based on a fixed grid. The distances are exactly one metre. Five bays, i.e. Five meters, form the maximum width, the length may be any amount on the grid. For certain applications, such as plaster surfaces, the clear span can be halved by inserting an intermediate stud which is integrated in the system. The I-beams are fixed to the horizontal rails which are anchored to the floor plate. When erecting the walls, transversely running beams, the so called tongs, are visible. These, the rails, as well as connections and reinforcements are made of load-bearing and bracing Kerto LVL Q-panels or the dimensionally stable Kerto LVL S-beams.  

Interlocking connections without screws

Values guide Metsä Group's operations 

The individual timber components are connected using exact interlocking connections, that join into each other by themselves. Due to the dimensional stability of the I-beams and the precise milling, no assembly errors arise and, in addition, the construction is very stable. Only a hammer is necessary for the assembly. Steel bolts are hammered in selected places. “If you can generally say timber moves - this is not the case here!”, explains Hans-Ludwig Stell to sum it up.

Thus: Once the stable support structure made of Finnjoist® I-beams stands, façade elements such as windows and doors can in turn simply be mounted. All of this on the basis of connections joining into each other and of course in the grid of one by one meter. Further development can then be realized freely.


Interlocking connections without screws
Interlocking connections

​Components are connected using exact interlocking connections, that join into each other by themselves. Only a hammer is necessary for the assembly. Steel bolts are hammered in selected places.

Mounting the doors and windows
Mounting the windows and doors

​Once the stable support structure made of Finnjoist® I-beams stands, façade elements such as windows and doors can in turn simply be mounted.

Dimensional stability of the I-beams
Dimensional stability of the I-beams

The structure is based on dimensionally stable I-beams .​The I-beams are fixed to the horizontal rails which are anchored to the floor plate.

Values guide Metsä Group's operations 

Building construction kit made of I-beams - a special solution

The idea of modular construction has found a special solution with the construction kit system of the Stellinnovation GmbH. Since the modular construction kit system can be freely and as needed designed, it can also be implemented multifunctionally. The Stellinnovation GmbH has developed different types of housing, with a single-, duo-pitched or flat roof. The types of buildings can also be combined with each other using corridors.

The modular construction kit has applications both in the housing and commercial construction. The example of the extension with a duo-pitched roof with a size of five by five metres can be seen as basis. In comparison to traditional timber frame construction, relatively small amount of material is used due to the slim I-beam. This is not only ecological in the use of timber, but also resource-saving due to the optimized design of the I-beams. In addition, not only the volume but also the lesser weight has a positive impact during transport and assembly. In conclusion:

The construction kit system with the Finnjoist® I-beams has proven to be an extremely sustainable concept and offers rewards in different construction styles from the traditional residential building up to futuristic seeming office cubes.

Quick facts

 Overview of housing construction with wooden support beams in plug-in assembly:

  • One engineered wood product for the entire support structure: Wall, floor and roof
  • Dimensionally stable and load bearing
  • Exact interlocking connections
  • Lightweight and flexible

References related to building and construction

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  • Edinburgh Centre for Carbon Innovation

  • Metropol Parasol - one of the world’s largest wooden buildings

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  • Immanuel Kirche - wooden structure that impresses

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  • The Macallan Distillery

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  • Elementit-E modular wood construction

  • Harmet

  • Seagram Building redesigned

  • Aarch - Århus School of Architecture

  • Domaine de l'Hortus

  • Sustainable construction with lightweight roof elements

  • Dutch Stay Okay hostel

  • Cranleigh School

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