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Timber construction adhesives for highest requirements

The Maggie’s Centre in Leeds, GB. © Blumer-Lehmann

“What binds the timber construction world’s innermost core together? At Blumer Lehmann, it is the PUR adhesives from Jowat.” This quote freely adapted from Goethe’s “Faust” may seem a bit over the top – but from the technological aspect, Blumer Lehmann's timber construction world is certainly top-notch. Many high-quality timber buildings and spectacular free-form constructions bear witness to this. The timber construction company from Switzerland has long been one of the top addresses internationally. Requirements are extremely high. Blumer Lehmann meets them with exceptional competence and in collaboration with partners like the adhesives specialist Jowat Swiss AG.

Quality from one source – from the log to the finished building

Spectacular timber structures like the new mosque in Cambridge, England, or the Swatch S1 office building in Biel are the result of those extraordinary feats of engineering. “We are able to deliver them because all the cog wheels at our company interlock precisely,” says Richard Jussel, former Managing Director at Blumer Lehmann, who recently handed over the reins to a team of three. One of the things that make the Lehmann Group and its companies special is the central management of the entire value chain: From the cutting of logs at Lehmann Holzwerk AG to the planning and construction of finished buildings or silos by Blumer Lehmann.

One hundred percent trust and concerted action

For years, Blumer Lehmann has relied on Jowat’s innovative strength, quality and leading adhesive technologies. The cooperation goes far beyond a usual supplier-purchaser partnership: “We have an intensive collaboration with Jowat. We exchange ideas on upcoming projects at an early stage, analyse feasibility and jointly develop solutions, even completely new ones if necessary. You can only do that with suppliers, who you trust one hundred percent,” says Jussel.

All parties benefit from this cooperation. “We are very proud to continually improve our PUR adhesives together with partners like Blumer Lehmann,” says Marco Rüegg, Product Manager and Strategic Assistant to the Managing Director at Jowat Swiss AG. “This is how we develop innovative products that help revolutionise timber construction. It takes the entire industry forward and forces our competitors to also keep developing further.”

One-component polyurethane adhesives from Jowat significantly expand the design possibilities in wood construction. That is why Blumer Lehmann has been using high-performance adhesives like Jowapur® 687.10, 687.30 and 687.60 for many years, especially in free-form wood construction. There is a good reason for that. Adhesive joints in free-form construction have to withstand high stress forces. An extreme example of this is the so-called magician’s hat at the children's zoo in Rapperswil. The event location was opened in 2020 and has a curved timber structure as roof looking like a 26 metre high magician’s hat.

“This free-form architecture creates very high tension forces in the structure,” explains Florian Gantenbein, Head of Elements Production and Executive Board member. “Therefore it was extremely important to use a joint-filling adhesive that can transfer the forces across the joint.” This was made possible by the latest adhesives from the Jowapur® product family. One major secret behind the superior performance of those adhesives are the specially developed high-tech fibres that are incorporated into the adhesive using a special procedure. Benefits: The high-tech fibres have a reinforcing effect in the cured adhesive joint and also strongly reduce foaming during curing. The result is a very homogeneous, virtually bubble-free adhesive joint coupled with significantly higher bonding strengths.

Clean and convenient processing

The adhesives also impress during handling. “What our employees appreciate most about the Jowapur® adhesives is the highly convenient processing characteristics. The pseudoplastic and thixotropic properties facilitate a very clean and precise application. Everything fits, nothing spills,” is how Gantenbein sums it up. The adhesives only become liquid under pressure and can be metered precisely. This makes them perfect for bonding, even on the construction site. Another advantage: In its liquid state, the adhesive is clearly distinguishable from the surrounding wood in terms of colour and structure. But when it cures, it becomes virtually invisible.

Economically attractive to the core

What makes the outstanding Jowapur® adhesives also more economically attractive for Blumer Lehmann than other alternatives is not only the superior quality and the long shelf life of the Jowat products. Another key feature of Jowapur® adhesives is that they are completely unfilled. A short explanation: Construction adhesives with a density of 1.3 g/cm³ and more are considered highly filled products. Such adhesives usually contain industrial chalk as a filling agent. That makes the adhesive heavy. So heavy, in fact, that although they might seem cheaper compared to unfilled products at first when looking at the price per kilogram, in fact they are not. Why is that? When bonding, the joint must be filled completely; it is the volume that counts and not the weight of the adhesive. The supposed kilo price advantage is therefore none at all. Gantenbein confirms this: “In the past, we also worked with filled products. However, the quantities required made these adhesives significantly more expensive for us overall than the new, unfilled products.” In addition, adhesive systems containing chalk have an abrasive effect on the applicator systems and can damage nozzles and pumps there.

Ecologically sustainable and regional

Climate protection and sustainability are part of the DNA of timber construction, so to speak. Especially at Blumer Lehmann. These aspects are of paramount significance to the enterprise and the same is expected from partners. “Saving energy, keeping transport routes short and reducing CO2 emissions as much as possible – we live by these standards and make a daily effort to meet them,” says Jussel. In this way, Blumer Lehmann is doing its part to achieve the goals agreed to in the Paris climate accord. “We are specifically looking for partners from the same region who think, act and manufacture just as sustainably as we do. Jowat Swiss AG meets that requirement.”

The article is published in the magazine ''WirHOLZBAUER 01/2021" in German language. You can download the original article down below.