HDU/DTT2Z Holdowns

Installation

View step-by-step installation instructions

HDU Holdowns are pre-deflected during the manufacturing process, virtually eliminating deflection under load due to material stretch. They use Simpson Strong-Tie® Strong-Drive® screws (SDS) which install easily and provide reduced fastener slip. Using SDS screws results in a greater net section, when compared to bolts, as no material is removed.

The HDU series of holdowns are designed to replace previous versions of the product such as PHD’s as well as bolted holdowns. The HDU2, 4 and 5 are direct replacements for the PHD2, 5 and 6, respectively.

The DTT2Z tension tie is suitable for lighter-duty holdown applications on single or double 2x posts, and installs easily with Strong-Drive SDS screws (included). The DTT2Z has been tested in accordance with the ICC-ES acceptance criteria for Holdowns Attached to Wood Members (AC155) and meets the minimum requirements for many alternate braced wall panels per section R602.10.3.2 of the 2009 IRC (see table R602.10.6, item 1).

For more information on holdown options, contact Simpson Strong-Tie.

HDU Special Features:

Pre-deflected body virtually eliminates deflection due to material stretch.
Uses SDS screws which install easily, reduces fastener slip, and provides a greater net section area of the post compared to bolts.
SDS screws are supplied with the holdowns to ensure proper fasteners are used.
No stud bolts to countersink at openings.

Material: See table.

Finish: HDU—Galvanized; DTT2Z—ZMAX® coatings.

Installation:

Use all specified fasteners. See General Notes.
For use in vertical and horizontal applications.
The HDU requires no additional washer, the DTT requires a standard cut washer (included) be installed between the nut and the seat.
To tie multiple 2x members together, the Designer must determine the fasteners required to join the members to act as one unit without splitting the wood. See SDS Screw information.
See SB and SSTB Anchor Bolts for anchorage options.
SDS screws install best with a low-speed, high-torque drill with a 3/8" hex head driver.
Refer to Anchor Designer Software™ for ACI 318 for anchoring solutions.

For holdowns, per ASTM test standards, anchor bolt nuts should be finger-tight plus 1/3 to 1/2 turn with a hand wrench, with consideration given to possible future wood shrinkage. Care should be taken to not over-torque the nut. Impact wrenches should not be used.

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.

Allowable loads have been increased for wind or earthquake load durations with no further increase allowed; reduce where other load durations govern.
The Designer must specify anchor bolt type, length and embedment. See SB and SSTB Anchor Bolts. Refer to Anchor Designer Software™ for ACI 318 for anchoring solutions.
Structural composite lumber columns have sides that show either the wide face or the edges of the lumber strands/veneers. Values in the tables reflect installation into the wide face. See technical bulletin T-SCLCOLUMN for values on the narrow face (edge).
Post design by Specifier. Tabulated loads are based on a minimum 3 1/2" wide post (in a 3 1/2" wall). Post may consist of multiple members provided they are connected independently of the holdown fasteners. See Post Capacities for common post allowable loads.
Tension values are valid for holdowns flush or raised off of sill plate.
Deflection at Allowable Tension Load includes fastener slip, holdown deformation and anchor rod elongation for holdowns installed up to 6" above top of concrete. Holdowns may be installed raised up to 18" above top of concrete with no load reduction provided that additional elongation of the anchor rod is accounted for.
Tabulated loads may be doubled when the HDU is installed on opposite sides of the wood member provided either the post is large enough to prevent opposing holdown screw inferference or the holdowns are offset to eliminate screw interferences.
Noted HDU14 allowable loads are based on a 5 1/2" wide post (6x6 min.).
Requires heavy hex anchor nut to achieve tabulated loads (supplied with holdown).

					Legacy Reports
	IAPMO ES ER	ICC-ES ESR	CITY OF LOS ANGELES	STATE OF FLORIDA	ICC-ES NER	ICC-ES ER	ICC-ES ES
DTT2Z		ESR-2330 / ESR-2523 *	RR25720	FL10441
DTT2Z-SDS2.5	No code listing. Please contact us for test data.
HDU	See specific model numbers for code listings.
HDU11-SDS2.5		ESR-2330 / ESR-2523 *	RR25720	FL10441
HDU11-SDS2.5		ESR-2330 / ESR-2523 *	RR25720	FL10441
HDU14-SDS2.5		ESR-2330 / ESR-2523 *	RR25720	FL10441
HDU14-SDS2.5		ESR-2330 / ESR-2523 *	RR25720	FL10441
HDU2-SDS2.5		ESR-2330 / ESR-2523 *	RR25720	FL10441
HDU4-SDS2.5		ESR-2330 / ESR-2523 *	RR25720	FL10441
HDU5-SDS2.5		ESR-2330 / ESR-2523 *	RR25720	FL10441
HDU8-SDS2.5		ESR-2330 / ESR-2523 *	RR25720	FL10441

* ESR-2523 is an Index of many of Simpson Strong-Tie Stamped and Welded Cold-formed Steel Products for Wood or Cold-formed Steel Construction

Download the Simpson Strong-Tie® AutoCAD® Menu, which allows you to insert Ortho views directly into your AutoCAD drawing.

	ORTHOGRAPHIC	PERSPECTIVE
DTT2Z	DTT2Z: DWG \| DXF DTT2Z front view: DWG \| DXF DTT2Z left view: DWG \| DXF DTT2Z right view: DWG \| DXF DTT2Z top view: DWG \| DXF	DTT2Z: DWG \| DXF DTT2Z installed: DWG \| DXF
HDU	None for this model	None for this model
HDU11	HDU11: DWG \| DXF HDU11 front view: DWG \| DXF HDU11 right view: DWG \| DXF HDU11 top view: DWG \| DXF	None for this model
HDU14	HDU14: DWG \| DXF HDU14 front view: DWG \| DXF HDU14 left view: DWG \| DXF HDU14 right view: DWG \| DXF HDU14 top view: DWG \| DXF	None for this model
HDU2	HDU2: DWG \| DXF HDU2 front view: DWG \| DXF HDU2 right view: DWG \| DXF HDU2 top view: DWG \| DXF	High Wind-Resistant Construction D40: Stud to Band Joist: DWG \| DXF High Wind-Resistant Construction D7: Girder/Truss to Wall Framing: DWG \| DXF
HDU4	HDU4: DWG \| DXF HDU4 front view: DWG \| DXF HDU4 right view: DWG \| DXF	High Wind-Resistant Construction D6: Girder/Truss to Wall Framing: DWG \| DXF
HDU5	HDU5: DWG \| DXF HDU5 front view: DWG \| DXF HDU5 right view: DWG \| DXF	High Wind-Resistant Construction D19: Girder/Truss To Masonry/Concrete: DWG \| DXF High Wind-Resistant Construction D43: Floor to Masonry/Concrete: DWG \| DXF High Wind-Resistant Construction D88: Holdowns: DWG \| DXF
HDU8	HDU8: DWG \| DXF HDU8 front view: DWG \| DXF HDU8 right view: DWG \| DXF	None for this model