Design Klimas Screws to the NDS

Klimas (Wkret-met) is a European fastener manufacturer based in Poland, with a range of self-tapping structural wood screws. In the US, their screws are recognized under ICC-ES ESR-5302, which publishes reference design values for use with the ANSI/AWC NDS under the IBC and IRC. SPEC Toolbox designs the screws using those values, in both ASD and LRFD.

The US integration presents the Klimas families evaluated in ESR-5302, grouped by role.

Connection screws (partial thread)

• WKCS countersunk head, WKCP washer head, WKCR round head, and WKCH hexagonal head for steel-to-wood connections (1/4, 5/16 and 3/8 in.).

Fully threaded screws

• WKFC cylindrical head and WKFS countersunk head (1/4, 5/16 and 3/8 in.), including the self-drilling WKFC-SD and WKFS-SD variants.
• WKLC, a smaller-diameter fully threaded connector screw.

Double-thread screws

• WKPC cylindrical head and WKPS countersunk head are not yet supported in the platform.

The screws are carbon steel, heat-treated, and corrosion-resistant coated, offered in yellow zinc, white zinc and SQ Ceramic coatings (SQ Ceramic carries a D suffix). Diameters and lengths are as listed in ESR-5302.

At a glance, in the US scope the Klimas families support:

• Wood-to-wood and steel-to-wood connections.
• Sawn lumber, structural glued laminated timber, LVL, and the face of CLT panels.
• Withdrawal, head pull-through and lateral loading, and combined lateral-plus-withdrawal, designed per the NDS.
• Both ASD (allowable) and LRFD (design) methods.
• Dry service (member moisture content of 19 percent or less).

• Steel-to-wood as well as wood-to-wood. The WKLC, WKCR and WKCH screws carry tabulated lateral values for steel-to-wood connections (steel side plates with a minimum tensile strength of 58 ksi, holes predrilled to the nominal diameter), so the same range covers timber-to-timber and timber-to-steel.
• LVL among the substrates. Alongside sawn lumber, glulam and the face of CLT, the report covers LVL (as a structural composite lumber with a minimum equivalent specific gravity of 0.50), with its own withdrawal and head pull-through values.
• Self-drilling fully threaded variants. The WKFC-SD and WKFS-SD screws carry a drill point, so the fully threaded screws can be driven without a pre-drilled hole.

The Klimas US screws are available in the Screw module and in the wood-to-wood connection detail calculators, worked in ASD or LRFD to the NDS:

• panel-to-panel joints (half-lap and spline);
• slab-to-wall, wall-to-wall and floor-to-wall.

Reference values are selected for the assigned specific gravity of the connected members, and end, edge and spacing requirements are applied per the NDS and the ESR-5302 geometry, including the separate predrilled and non-predrilled cases and the larger distances required in denser species such as Douglas fir.

Design follows the ANSI/AWC NDS under the IBC and IRC. ESR-5302 supplies reference (allowable and design) values in imperial units for withdrawal, head pull-through, lateral resistance and screw steel strength. These are adjusted by the applicable NDS factors for the chosen method, among them load duration, wet service, temperature, group action, geometry and end grain, to give allowable (ASD) or design (LRFD) values. Reference values are keyed to the member’s assigned specific gravity (per the NDS specific-gravity tables), and steel side members are designed per AISI S100 or AISC 360. The evaluation is for dry service (moisture content 19 percent or less); treated wood, saltwater exposure and lateral design with inclined fasteners are outside its scope.