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NILCO® Wood-Concrete Composite Slab Connector enables hybrid construction with even longer spans

A member of Peikko’s recently launched PUUCO® Timber Connections product family, NILCO® Wood-Concrete Composite Slab Connector, transmits forces between a CLT slab and topping concrete​. NILCO® is an innovative product that further enables open flexible spaces and long spans in hybrid construction, but what is the story behind it? Raimo Lehtinen, Peikko’s Business Director, tells what happened in a garage some two years ago, and where did it all lead to.

NILCO® Wood-Concrete Composite Slab Connector is pressed onto the CLT slab and it transfers forces through nails of the nail plate, both horizontally and vertically. NILCO® is a simple and tested innovation of transferring forces between CLT slab and concrete. It is both fast and easy to assemble on building site. Less NILCOs® obtain the same or even higher shear forces than the screws, which makes NILCO® a more cost-efficient solution too.


From an idea to a prototype

DELTABEAM® composite beam had been used for hybrid frame structures already since 2012, but the slab structure itself did not always utilize the composite effect. The CLT slabs did most of the load-bearing part, and the topping concrete was only used for sound isolation and for more stiff and stable flooring. The DELTABEAM® hybrid slab structure could reach its full potential as a composite structure only if the rest of the structure resonated it too.

The solution that we know today as NILCO®, combined perfectly Raimo Lehtinen’s experience as a Board Member at Ristek, a Finnish market leader of nail plates manufacturing, and the idea of Simo Hakkarainen, Peikko’s Business Director, DELTABEAM® Frame. Peikko had already previously brainstormed new solutions based on nail plates, but for one reason or another, those innovations never kick-started. Now it was the time.

In 2020, Peikko tested nail plates cast into concrete and load added to the shear force in parallel. “It worked. It really worked. This is when we knew that something remarkable was born”, remembered Lehtinen.


Tested and approved

After the core idea was born, started a thorough testing and refining the idea. In collaboration with Ristek, Peikko developed a U-shaped nail plate of 2mm thickness that was stiff enough to do the job, and easy to manufacture. Ristek manufactures NILCO® slab connectors on their highly automatized production line of nail plates, with an expertise and know-how of several years in business.

The initial testing was done at the garage of Hakkarainen during the COVID-19 isolation times. Lehtinen and Hakkarainen tried to find the best ways to attach NILCOs® to a CLT slab. The starting point was the construction site conditions; what could they easily use? First idea was a sledgehammer, which eventually resulted to be too manual and slow solution. The second attempt was a percussion drill with a special tool head, which worked well and made the assembly smooth and fast.

“NILCO was born as a COVID-19 times hobby”, laughed Lehtinen.

The first third party testing was made at Eurofins, and it only confirmed what Peikko already knew – NILCO® really did the job. Testing on a construction site was successful too – the assembly team gave positive feedback and found NILCO® as an easy-to-use solution and simple to assemble.


New possibilities for hybrid construction

The amount of NILCOs® assembled in a slab depends on the load-bearing requirements, the length of spans, and the thickness of the slab. For instance, only 6-8 NILCOs®/m2 already enable extremely high load-bearing capacity. This makes NILCO® a very competitive solution, whether judged by the amount needed or the speed of assembly. Furthermore, no spacers are needed as NILCOs® can support the concrete reinforcement. They are also sturdy and safe enough to walk on with safety shoes, which is very practical on site.

With NILCO®, Peikko’s DELTABEAM® composite beam becomes even more powerful slim floor solution for hybrid construction. It allows for longer spans with an open flexible space.

“Hybrid construction is about combining and taking advantage of the best benefits of each material used, in the very spot where the outcome is optimal. This is what NILCO® further enables. In a sustainable construction, the materials are load bearing and not just a dead weight”, said Lehtinen.


Taking foothold on the market

Now NILCO® is on the doorway of the success. It has already received a lot of positive feedback from the industry experts, and the next step is real-life piloting for new construction projects. Establishing a new product to the market is slow, as it requires convincing the designers, updating the design tools, and shaping the construction methods. Nevertheless, NILCO®’s benefits are undeniable.

How about the future? The construction industry develops and if NILCO® is widely accepted as a standard for the industry, it could be preinstalled in the CLT slabs at the factory already. This would speed up the assembly phase and make the process even more cost-efficient.

“NILCO® has its roots in Finland, and this is how we want to keep it. The manufacturing expertise is an advantage that should not be wasted”, said Lehtinen.