Connection technology for the permanent connection of precast concrete elements - BT-Spannschloss®

The BT-Spannschloss® (turnbuckle) is part of an easy to use connection system – without additional materials and tools.

The BT-Spannschloss® (turnbuckle) enables efficient and precise assembly and durable connections for precast concrete elements. By using BT-Spannschloss® (turnbuckle) and corresponding connection materials, precast elements can be joined together without using mineral grouting. This means no curing or standstill times due to low temperatures. The BT-Spannschloss® (turnbuckle) can be fully loaded
straight away. You can view the application of BT-Spannschloss® in our product video.

The general technical approval (Z-14.4-599) and the European Technical Assessment (ETA 19/0013) certify the reliability of the product. The BT-Spannschloss® (turnbuckle) is offered in three sizes - M12, M16 and M20 - and is available in galvanised or stainless steel. On 12 March 2021, BT-Spannschloss® M12, M16 and M20 received the CE marking for use in the European Economic Area.


  • dry screw connection  
  • no joint grouting, no special tools
  • can be loaded immediately, no curing times
  • assembly regardless of weather, even in low temperatures or precipitation
  • able to be disassembled – removal of temporarily installed structures
  • three-point connection possible


  • Angle support walls in flood protection
  • Residential and commercial construction
  • Agricultural systems (e.g. bio-gas systems, silos)
  • Sewer and civil engineering (e.g. shaft structures, media channels, amphibian tunnels)
  • Temporary structures

You can also purchase BT-Spannschloss® and other products in our online shop!

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The BT-Spannschloss® means that prefabricated concrete parts can be connected without any additional materials or resources.
Without any need to comply with cure times, the connection can immediately bear a full load and thus generates significant time and cost savings in comparison to other established systems.



The BT clamping system can be used efficiently and universally in the widest possible range of applications. For instance, in the assembly and connection of angle brackets and shaft elements for road building and underground construction, in building operations in the field of coastal protection, in floor and wall connections for the residential and commercial construction field and many more construction connections for prefabricated concrete parts.

Note: The load bearing capacity of the clamping system depends to a significant extent on the type of anchor used. Several types of authorised anchorage systems can be used according to the application requirements (you can find the data in the manufacturer’s instructions).
In general, the load bearing capacity of the clamping system is many times higher than that of the anchorage system.


For each of the three sizes of the BT-Spannschloss® (turnbuckle) there is a suitable recess body. The standard version of the recess body is made of polyethylene and has sloping sides to ease the removal after production. It is possible to customize the recess body in dimension or shape according to customer requirements.

The PE recess bodies are particularly dimensionally stable and can therefore be reused many times. They enable a particularly stable positioning of the anchors and also ensure sufficient concrete covering for the anchor and the BT-Spannschloss®. They can be equipped with magnets for faster and more reliable application. Depending on the installation situation, however, it is also possible to screw or drill into the recess bodies if required.



Do you have questions?

1. What connection situations are there?

In general, the BT-Spannschloss® (turnbuckle) can be used as a butt, corner or three-point joint. Depending on usage, the type of recess in the precast concrete plant differs. While with butt joints, the recess must be inside a unit entirely, the recess former can be separated into two units with the corner joint. For further information on the specific usage of recess formers, please ask your BT contact person.

2. What is the system made of?

The BT-Spannschloss® turnbuckle is available in three different sizes: M12, M16 and M20. Both in the galvanised and stainless-steel versions, the connection system is made up of three main components: the BT-Spannschloss® (turnbuckle), the washers and the hexagon head bolts.

3. What tolerances can be compensated by the BT-Spannschloss® (turnbuckle)?

Dimensional tolerances of the joints and the involved components are tolerable, as long as the tensile strength of the anchor is ensured with enough space and the minimum screw-in-depth of the screws can be reached.

4. How does the conformation of the correct joint width work?

The joint width can be altered with the use of different screws. The correct combination of screws also allows for the installation of the BT-Spannschloss® (turnbuckle) in accordance with the rules with present component tolerances. However, the minimum and maximum screw-in-depth must always be observed.

5. Is the BT-Spannschloss® (turnbuckle) protected from corrosion and in accordance with fire safety regulations?

Yes, the BT-Spannschloss® (turnbuckle) is protected from corrosion when installed compliant with approval standards. If there are any additional, strong exposures to chemicals, the stainless-steel version can be used. Our BT-Spannschloss® (turnbuckle) also fulfils various fire safety regulations. You can get detailed results of fire safety tests from your BT contact person.