Thanks to the pockets that are already milled at the factory, the wall can be fitted quickly, and the crane is free for the next element © Buhl
Stefan Buhl knows that time is of the essence on the construction site. However, the master timber constructor is also aware that often, complications and thus delays can occur, especially when positioning walls – regardless of whether it is made from cross-laminated timber (CLT) or a timber frame construction. "A lot depends on the team and the used connectors," explains Buhl who runs a carpentry as well as the contract joining company "Abbund Technik Allgäu" in Obermaiselstein. "When using conventional metal connectors for walls, ceilings and roof elements, the available clearances are usually very small, or the connectors are placed too low, which often means that components can get jammed during assembly. On top of that, there is always the possibility that the connectors are installed incorrectly which costs additional time and frays nerves."
With this in mind, Buhl started working on a new connector two years ago already: one that would eliminate mistakes during assembly and would substantially simplify installation. These efforts resulted in "Buhl SV15", a large connector, and "Buhl KR46", a small, round connector.
Dovetail principle
Thanks to the differently sized holes, incorrect assembly becomes impossible. "Any person who can screw in an 8mm Spax screw is also able to install the timber connector," Stefan Buhl is convinced © Buhl
The Buhl SV15 is a wooden connector pin; its position is precisely specified by two marking holes of different sizes, thus ruling out incorrect assembly and installation. Its counterpart is a pocket which is milled into the wood and tapers considerably towards the bottom. "By providing ample space at the top where the pins are inserted, we can prevent possible jamming which significantly simplifies installation at the construction site," Buhl points out a key advantage of his product.
A CNC joining machine takes care of milling the marking holes and pockets; the connector is matched to standard mills, and data is entered via CAD. In common programs like Dietrich‘s, cadwork and others, a separate "Buhl component" has already been integrated which can be added at the click of a mouse. In practice, every employee – from apprentice to supervisor – can premount the connectors in a short time, whether on the construction site or still in the factory. Furthermore, the Buhl connector can also be used in manual joining. For this purpose, bars are milled in the grid in advance and later cut to length as required.
A lot of programs, such as cadwork shown here, offer a ready-made "Buhl component" © cadwork
For all flat wooden components
Stefan Buhl with the connector he developed: on the right, the connector, and on the left, the generously designed pocket for easy positioning © Günther Jauk
According to Buhl himself, the area of application for the connector is wherever flat wooden components are to be joined – from timber frame walls to solid wood or CLT walls. "Even in cases where a planking layer continues around a corner or where everything is processed via a wall station, our timber connectors can be used," the developer emphasizes. For Buhl, the biggest advantages of the connector are time savings and ease of installation.
Tested and impressed
Bauer Holzbau from Satteldorf-Gröningen/ DE was one of the first to test the new connector. They erected a building where they alternately used conventional connectors and Buhl timber connectors in the different floors. Since then, the company has been convinced of the advantages of the novel connector, as Klaas Lühmann from the department for timber construction and expansion, work preparation at Bauer Holzbau reports: "For the corner connection of our timber frame walls we rely on the Buhl SV15. The position of the connector in component production is clearly defined by the two different centering holes which are milled with the joining system. When placing the walls on our prefabrication line tectofix, the connector is screwed to the element joints. Due to the excellent accessibility of the line, this can be done by only one employee in a short time. During element assembly, the connector is inserted into the mounting pocket above the dovetail. Dovetail connections are easy to fit together and therefore guarantee secure element joints. With the connector from Buhl, we have found a simple and quick solution for both manufacturing and element assembly".
