Design SPAX Screws to the NDS

SPAX (a brand of Altenloh, Brinck and Co.) manufactures self-drilling structural wood fasteners, sold in the US as the X-Series. Their screws are recognized under ICC-ES ESR-5358, 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 follows the SPAX US database, organized by the X-Series tip and head system evaluated in ESR-5358.

XF series (4CUT tip)

• Pancake, hex, washer, flat head partially threaded; cylinder heads fully threaded, in 1/4, 5/16 and 3/8 in.

XC series (CUT-point tip, fully threaded)

• Flat and cylinder heads, in 5/16 and 3/8 in.

XS series (sharp tip)

• Hex head, 1/2 in.

XR series (fully threaded)

• Hex head, 5/8 in., in lengths beyond nine feet.

Heads other than hex use a star drive recess. The screws are hardened carbon steel; several finishes are offered, including the black HCR corrosion-resistant coating for use in treated wood. Diameters run from #14 to 5/8 in.; diameters and lengths are as listed in ESR-5358.

At a glance, in the US scope the SPAX X-Series fasteners support:

• Wood-to-wood and metal-to-wood connections, with steel side members.
• Sawn lumber, structural glued laminated timber, LVL, LSL, and the face of CLT.
• Withdrawal, head pull-through and lateral loading, and combined lateral-plus-withdrawal, per the NDS.
• Both ASD (allowable) and LRFD (design) methods.
• Dry service, with the HCR coating for treated-wood exposure conditions.

• Steel-to-wood as well as wood-to-wood. The report covers steel side members (minimum yield strength 36 ksi, minimum tensile strength 58 ksi), so the range carries timber-to-timber and timber-to-steel; the cylinder-head styles are limited to wood-to-wood.
• LVL and LSL among the substrates. Alongside sawn lumber, glulam and the face of CLT, the report covers LVL and LSL, with test-based lateral values for LVL connections.
• Into lag-screw and threaded-rod sizes. The XS series reaches 1/2 in. and the fully threaded XR series 5/8 in., in lengths well beyond a typical structural screw, for heavy timber and mass-timber assemblies.
• HCR coating for treated wood. The black HCR coating is the coating evaluated for corrosion resistance in contact with micronized-copper-azole treated wood, within the report’s exposure conditions.

The SPAX US screws are available in the Screw module and in the 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-5358 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-5358 supplies reference (allowable) design values in imperial units for withdrawal, head pull-through and lateral resistance, along with allowable fastener steel strengths. 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 (with lateral design limited to a specific gravity of 0.55 or less), and steel side members are designed per AISC 360 or AISI S100. The evaluation is for dry service, with wet-service use limited to the XF (1/4, 5/16 and 3/8 in.) and XS series; saltwater exposure, treated-wood contact other than with the HCR coating, and lateral design with inclined fasteners are outside scope. The screws were also shown to comply with the 2022 California Building and Residential Codes, the 2023 Florida Building Code, and the City of Chicago and City of Los Angeles codes, through the report’s supplements.