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HDQ/HHDQ Holdowns


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The HHDQ series of holdowns combines low deflection and high loads with ease of installation. The unique seat design of the HDQ8 greatly minimizes deflection under load. Both styles of holdown employ the Strong-Drive® SDS Heavy-Duty Connector screws which install easily, reduce fastener slip and provide a greater net section when compared to bolts. They may be installed either flush or raised off the mudsill without a reduction in load value.

Key Features

  • Strong-Drive SDS Heavy-Duty Connector screws are supplied with the holdowns to ensure proper fasteners are used
  • No stud bolts to countersink at openings


  • HDQ8 — 7 gauge; HHDQ — body: 7 gauge, washer: 1/2" plate


  • HDQ8 — galvanized; HHDQ — Simpson Strong-Tie gray paint; HHDQ11 — available in stainless steel


  • See General Notes for Holdowns and Tension Ties
  • No additional washer is required
  • Strong-Drive SDS Heavy-Duty Connector screws install best with a low-speed high-torque drill with a 3/8" hex-head driver


  • 5/8" of adjustability perpendicular to the wall

HHDQ11 / HHDQ14:

  • No additional washer is required
  • HHDQ14 requires a heavy-hex anchor nut (supplied with holdown)

Related Literature

Load Tables

    These products are available with additional corrosion protection. Additional products on this page may also be available with this option, check with Simpson Strong-Tie for details.

    For stainless-steel fasteners, see Fastener Types and Sizes Specified for Simpson Strong-Tie Connectors.

  1. HHDQ14 requires a heavy-hex anchor nut (supplied with holdown).
  2. HDQ and HHDQ installed horizontally achieve compression loads with the addition of a standard nut on the underside of the load transfer plate. Refer to ICC-ES ESR-2330 for design values. HDQ8 requires a standard nut and BP 7/8-2 load washer (sold separately) on the underside of the holdown for compression load. Design of anchorage rods for compression force shall be per the Designer.

Code Reports & Compliance