Design Klimas Screws to Eurocode 5

Klimas (Wkret-met) is a European fastener manufacturer based in Poland, with more than three decades of production experience and a range of structural fasteners for timber-frame, CLT and glulam construction. Its self-tapping timber screws are covered by European Technical Assessment ETA-18/0817 of 7 June 2023 (DIBt), under EAD 130118-01-0603, for design to Eurocode 5.

The EU integration presents the Klimas structural screw families grouped by role. Full characteristic design values are read from the Klimas database and applied at calculation time, not interpolated, so no per-article numbers are printed here.
Connection screws (partial thread)

• WKCS, countersunk head (3 to 10 mm, 30 to 600 mm).
• WKCP, flat washer head (5 to 10 mm, 40 to 600 mm).
• WKCR, round head (6 to 10 mm, 40 to 600 mm).
• WKCH, hexagonal head, for timber-to-steel connections (6 to 10 mm, 40 to 600 mm).

Reinforcement screws (full thread)

• WKFC, cylindrical head, and WKFS, countersunk head (6 to 10 mm, 50 to 600 mm).
• WKFC-SD and WKFS-SD, the same families with a self-drilling tip.

Connector screw

• WKLC, round head, full thread (5 mm), for fixing connectors and thin steel plates.

Each family is offered in a standard coating and a -D enhanced-coating variant. The screws are carbon steel with an anti-friction coating, in diameters from 3 to 10 mm and lengths from 30 to 600 mm; reaction to fire is Class A1.

At a glance, the Klimas families support:

• Solid timber, glulam, glued solid timber, CLT (softwood; face and edge fixing), softwood LVL, and wood-based panels on the head side.
• Timber-to-steel connections (WKCH hexagonal head; WKLC with thin steel plates).
• Angled insertion.
• Reinforcement, using the full-thread WKFC and WKFS families.

• Reinforcement in all three modes. The full-thread WKFC and WKFS screws provide tension and compression reinforcement perpendicular to grain, and at 8 mm they also provide shear reinforcement inclined at 45 degrees.
• Compression screws checked against buckling, not just push-in. For the WKF screws in compression the assessment takes the lower of the push-in resistance and a buckling resistance on the surrounding timber (a buckling-on-elastic-foundation check with a reduction factor and a 1000 N/mm2 yield strength), so a compression reinforcement screw is limited by buckling as well as by pull-out.
• Self-drilling reinforcement variants. The WKFC-SD and WKFS-SD full-thread screws carry a drill point, so reinforcement screws can be driven without pre-drilling.
• Softwood LVL among the base materials. Alongside solid timber, glulam and CLT, the range carries dedicated softwood-LVL embedment and withdrawal values (with the LVL wide-face angle factor and withdrawal to 15 N/mm2).

All Klimas screws are available in:

• the Screw module;
• the connection detail calculators: panel-to-panel (half-lap, spline and butt joint), slab-to-wall, wall-to-wall, floor-to-wall, and beam-to-beam and beam-to-column;
• the rib-deck calculator, for flexible connection design to Eurocode 5.

The full-thread reinforcement families (WKFC and WKFS, including their -SD variants) additionally appear in the reinforcement connection details: beam notch, beam penetration, and beam compression perpendicular to grain.

Design follows EN 1995-1-1, with axially loaded screws verified to §8.7.2. Clause 8.7.2(1)P lists buckling under compression among the failure modes to consider, which the assessment quantifies for the full-thread WKF screws. Both the 2004 and 2025 editions of Eurocode 5 are supported. The assessment is CE-marked under Regulation (EU) No 305/2011 (EAD 130118-01-0603). The same product data is used for design in the AUS and NZ markets in accordance with the applicable design standards there.