SHARP METAL: hooked plates for high-stiffness timber connections

Just as the automotive sector replaced glue in brake systems with safer, more reliable solutions, the timber construction industry has similarly developed technologies that are more efficient and sustainable than structural adhesives.
With SHARP METAL, Rothoblaas brings a true game-changer to the timber connections market: a mechanical solution combining rapid installation with high performance.

Why wait for adhesive to cure when a metal plate can deliver the same performance in just a few minutes? Both on site and in the factory, designers and contractors have long faced the typical challenges of glued joints — challenges that simply do not affect timber connectors:

• Downtime due to adhesive curing,

• The need to control temperature during installation,

• Pre-treatment of surfaces to ensure adhesion,

• Specialised labour required for assembly,

• Difficulty of quality control on glued surfaces.

All factors that slow production and increase risk – now overcome with hooked plates that work as a kind of “structural Velcro for timber”.

SHARP METAL: dry-bonding timber connectors

SHARP METAL is a thin metal strip (<1 mm) equipped with opposing hooks. When inserted between two timber elements and pressed together, the hooks simultaneously penetrate both surfaces, creating an exceptionally stiff and secure connection. It is an actual dry bond: no chemical adhesion but purely mechanical interlocking. What’s more, no specialised labour is required for installation – any carpenter can make the assembly.

Key technical features

The shear stiffness of SHARP METAL exceeds the typical values of traditional mechanical connections, delivering performance comparable to a structural adhesive. Compression between timber elements is ensured by TBS MAX screws, developed specifically for this application: 8 mm diameter, reinforced head and extended thread, able to drill through both the timber and SHARP METAL plate to maximise the clamping effect.

Hooked plates - Main applications

Thanks to its versatility, SHARP METAL adapts to a wide range of timber construction requirements. The main areas of application, identified through on-site testing and customer feedback, include:

• Structural reinforcement of existing beams through the addition of a “dry-bonded” collaborating section (using hooked plates)

• Joint stiffening. With SHARP METAL, screws and dowels no longer act alone: the connector stabilises slip and improves stiffness.

• Ribbed floors and CLT. Composite floors can be built without adhesives or presses, reducing installation time and making most efficient use of the material.

SHARP METAL or traditional bonding?

The choice of connection system depends on the project requirements. SHARP METAL is ideal for projects requiring rapid installation, as well as on sites with straightforward service layouts, variable environmental conditions and the possibility for installation by any carpentry team.

Structural adhesive bonding, on the other hand, is more suited to factory conditions where the environment can be more precisely controlled and consistent bonding over large surfaces ensured.

Technological and production advantages of SHARP METAL

The CLT industry has experienced rapid growth over the years, focusing more on entering new markets than on maximising timber efficiency. Today, the drive for more efficient and sustainable use of raw materials, combined with the need to compete with steel and reinforced concrete, calls for more rational construction solutions. In this context, ribbed floors are now widely used, allowing a reduction in the volume of timber used per square metre without compromising structural performance.

SHARP METAL excels precisely in the development of ribbed floors, where it overcomes the limitations of traditional connections. Being compatible with both industrial presses and screws, it is unaffected by temperature and humidity conditions while also allowing on-site assembly.
Hooked plates for timber-to-timber connections offer an efficient choice for the timber construction industry: they reduce the volume of timber required per square metre of flooring without compromising structural performance.

Structural performance and quantitative comparison

To understand the full potential of SHARP METAL, a quantitative comparison is useful.
ETA-24/0058 certification confirms that joints made with SHARP METAL achieve a shear strength of 1.72 MPa – around 50% of the shear strength of GL24h timber (3.50 MPa).

The most significant figure, however, concerns stiffness, which reaches 3.05 N/mm³ – equivalent to 150 kN/mm for a 1-metre strip – values that indicate an exceptionally stiff connection.

To better understand the effect of SHARP METAL, we consider two joints with the same geometry: the first connection is made using only TBS MAX screws (grey curve), while the second combines the same screws with SHARP METAL (blue curve).

The connections made solely with screws exhibit markedly ductile behaviour, reaching their maximum strength only at large displacements (>15 mm). By contrast, the connection with SHARP METAL reaches its maximum strength at displacements of just 2–3 mm, with an almost linear initial response typical of rigid connections. The TBS MAX screws continue to provide pressure and ductility, with strength stabilised even after the peak load is reached.

The combined use of SHARP METAL and TBS MAX screws delivers the best of both worlds: stiffness comparable to a structural adhesive bond and the ductility typical of screws, allowing deformations to be absorbed without sudden failure. The result is a sturdy, safe and high-performing connection combining strength, stiffness and ductility in a single system.

Moreover, the slope of the grey and blue curves clearly shows that SHARP METAL combined with screws achieves stiffness levels roughly ten times higher than screws alone.

SHARP METAL: certified mechanical solutions for timber construction

SHARP METAL represents a new generation of timber connectors: quick to install, independent of environmental conditions and capable of delivering strength comparable to structural adhesive bonding. Its increasing use in ribbed floors and CLT systems is not only a technological leap but also a tangible response to the demand for more efficient and sustainable construction.

For designers, it provides a reliable tool to combine stiffness and ductility, streamlining operations while reducing complexity. For contractors, it provides the opportunity to standardise processes and ensure consistently high quality. A true game changer for timber construction.

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