SI-Modular wood framing construction system offers precise timber assembly

Architect Hans-Ludwig Stell, based in Münster, Germany, has developed a modular timber construction system that relies entirely on interlocking components—eliminating the need for screws. The SI-Modular wood framing system, created under Stell’s firm Stellinnovation GmbH, is tailored for one and two-storey buildings and uses engineered wood I-beams and laminated veneer lumber (LVL) to create a fully timber-based structural solution. (main pic: SI-Modular wood framing construction system relies on interlocking components.)

The system was first developed for development aid applications and has since been expanded to meet European performance and energy efficiency standards. It combines simplicity, sustainability and structural performance in a building method that is largely self-explanatory, with the entire structure designed around a fixed grid and assembled using only a hammer.

Timber framing designed for precision and repeatability

The system’s foundation is Metsä Wood’s Finnjoist I-beams, and these beams are used throughout—forming the walls, floors and roof. Made from OSB webs and high-strength Kerto LVL flanges, the I-beams replicate the structural principles of steel double-T profiles, delivering rigidity with minimal material use.

Each structure is based on a fixed 1-metre grid. Building widths are set at either 5.10 m or 6.10 m internally, with the length extendable in one-metre increments. The largest width consists of five bays across five metres. The grid also allows optional intermediate studs to be inserted for applications such as plasterboard, without altering the frame logic.

The beams are mounted to horizontal rails fixed to the floor plate. These rails, along with connections and reinforcements, are made from load-bearing Kerto LVL S-beams or Q-panels. Transverse beams—called tongs—add further bracing. Once the structural frame is assembled, cladding, windows and other façade elements can be installed within the same grid framework.

Simple assembly using interlocking joints

One of the most distinctive features of the SI-Modular wood framing system is the use of precision-milled, interlocking timber joints. The components are slotted together by hand, and steel bolts are used only in selected areas for reinforcement. “Timber tends to move, but that’s not the case here,” notes Stell. The dimensional stability of the components ensures a tight, consistent fit throughout.

Each modular building is delivered as a kit of parts. This includes the I-beam frame, laminated timber elements, OSB bracing panels, DWD roofing sheets, and tension fasteners. Assembly instructions and structural analysis documentation are also included. The system’s light weight and compact packaging enable easy manual handling and reduced transport costs.

Modular kit homes and extensions from a standardised system

The SI-Modular wood framing system supports a range of building types, including standalone homes, extensions and linked modules. Roof options include flat, single-pitched and duo-pitched designs. Its flexibility and ease of assembly allow it to be used in both residential and commercial settings.

Compared to conventional timber frame construction, the SI-Modular system uses significantly less material, reducing embodied energy and thermal bridging. The result is a modular timber framing system that is both ecologically efficient and adaptable to varied architectural contexts.

Source: Metsa