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HDU Heavy Duty Holdown

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Product Details
HDU8_SDS2.5
HDU8_SDS2.5
HDU8-SDS2.5 Illustration
HDU8-SDS2.5 Illustration
S/HDU9 Illustration
S/HDU9 Illustration

Simpson Strong‑Tie offers a wide variety of holdown devices engineered and tested to perform and manufactured to the highest quality standards. The HDU Holdown is pre‑deflected during the manufacturing process, virtually eliminating deflection under load due to material stretch. This super heavy duty HDU is suitable for residential and commercial projects, sub diaphragm floor, seismic upgrades, mid floor vertical connection applications. 

The HDU installs with Simpson Strong‑Tie® Strong‑Drive® SDS Heavy‑Duty Connector screws which install easily, reduce fastener slip and provide a greater net section when compared to bolts. The HDU is also ideal for retrofit or new construction projects. They provide high-strength, post-pour, concrete-to-steel connections.

Please check the Corrosion Information to see if it is suitable for your application.

Material

Carbon Steel 3.5mm thick

Finish

Z275 Galvanised

Features & Benefits
  • Pre-deflected body virtually eliminates deflection due to material stretch
  • Uses Strong-Drive® SDS Heavy-Duty Connector screws which install easily, reduce fastener slip and provide a greater net section area of the post compared to bolts
  • Strong-Drive SDS Heavy-Duty Connector screws are supplied with the holdowns to ensure proper fasteners are used (HDU8-SDS2.5 includes 20 – SDS 6.4mm x 64mm screws)
  • Easy to install
  • No stud bolts to countersink at openings
Installation
  • Use all specified fasteners 
  • The HDU requires no additional washer
  • Strong‑Drive SDS Heavy‑Duty Connector screws install best with a low speed high torque drill with a 3/8” hex head driver
Model No. Table

Model No.

Dimensions (mm)

Fasteners

Minimum Timber Member Size (Depth x Breadth, mm)

Country

Design Tension Capacity (kN)

Strap
Thickness

W

H

B

CL

Anchor Hole Dia (mm)

Post (Nails: No. - Length x Dia., Screws: No. - Dia. x Length, mm)

HDU8-SDS2.5

3.5

75

420

90

35

20

20 – SDS6.4 x 64

90 x 75

AU

k1 = 1.14

32.58

NZ

k1 = 1.0

26.83

90 x 90

AU

k1 = 1.14

36.20

NZ

k1 = 1.0

29.81

115 x 90

AU

k1 = 1.14

38.85

NZ

k1 = 1.0

32.00
  1. Design Capacity is the lesser of (1) the Characteristic Capacity multiplied by the Australian Capacity Factor, or the NZ Strength Reduction Factor (φ), and applicable the k modification factors following AS 1720.1 and NZS 3603 and (2) the Serviceability Capacity which is the load at 6.4mm joint slip, which includes fastener slip, anchor elongation and holdown deformation. Design Capacity is the minimum of test data and structural joint calculation.
  2. For Australia, the Capacity Factor (φ) is 0.85 for nails and screws for structural joints in a Category 1 application. Reduce tabulated values where other Category applications govern. For NZ, the Strength Reduction Factor (φ) is 0.80 for nails in lateral load and 0.70 for other fasteners.
  3. Duration of Load Factor (k1) is as shown. Reduce Duration of Load Factor where applicable. Capacities may not be increased.
  4. Timber species for joint design is seasoned Radiata Pine, which is Australia Joint Group JD4 per AS 1720.1 Table H2.4 and New Zealand Joint Group J5 per NZS 3603 Table 4.1.
  5. Simpson Strong-Tie Strong-Drive SDS Heavy Duty Connector screws are HDU8.
  6. The Designer must specify anchor bolt type, length and embedment.
  7. Anchor bolt nut should be finger tight plus 1/3 to 1/2 turn with a hand wrench. Care should be taken not to over-tighten the nut.
  8. Post or beam design by Designer. Posts may consist of multiple members provided they are connected independently of the holdown fasteners.
  9. Structural composite timber columns have sides that either show the wide face or the edges of the timber strands/ veneers, known as the narrow face.
  10. Simpson Strong-Tie stainless-steel connectors require stainless-steel fasteners.
  11. Values in the table reflect installation into the wide face.
  12. Holdowns and tension ties are for use in vertical or horizontal applications.
  13. Holdowns and tension ties may be installed raised up to 460mm above the top of the concrete with no load reduction, provided that additional elongation of the anchor rod is taked into account.

Model No.

H
(mm)

Fasteners

Stud
Quantity

Stud
Member Thickness (mm)

LRFD Tension Load

(kN)

Deflection at LRFD Load4 (mm)

Nominal Tension Load5 (kN)

Anchor Hole Diameter (mm)

Stud Fasteners

S/HDU9

327

22

18 - 14g

2

0.75

49.5

4.8

58.6

2

0.95

68.9

6.4

97.0

2

1.15

71.0

5.7

108.9

Steel Fixture

4.76

91.2

4.5

139.9
  1. Designer shall specify the foundation anchor material type, length, embedment and configuration.
  2. Stud design by Specifier. Tabulated loads are based on a minimum stud thickness for fastener connection.
  3. Self-drilling tapping screws of 6.35 mm diameter can be substituted for 14g.
  4. Deflection at LRFD Loads includes fastener slip, holdown elongation and anchor bolt elongation (L=102mm).
  5. Nominal Tension Load is based on the average ultimate (peak) load from tests. AISI Lateral Design standard requires holdowns to have nominal strength to resist the lesser of the amplified seismic load or the maximum force the system can deliver.
Brochures & Catalogues

Brochures and Catalogues

PDF icon Flyer - HDU Heavy Duty HoldownPDF icon Catalogue - Timber Connectors NZS 3604PDF icon Catalogue - Cold-Formed Steel Construction ConnectorsPDF icon Catalogue - Mass Timber ConstructionPDF icon Flyer - Engineered Structural Connections
Installation Guides

Installation Guides

PDF icon HDU Installation Guides.pdf
Technical Data & Docs

Technical Data Sheets

PDF icon Technical Data Sheet - HDU

Report Links

ESR-2330
FL10441

Warranty

Warranty

CAD Library

Download

jpg: 
Image icon HDU8-SDS2.5_Detail_Holdown.jpg
dxf: 
Binary Data HDU8-SDS2.5_Detail_Holdown.dxf
dwg: 
File HDU8-SDS2.5_Detail_Holdown.dwg
PDF: 
PDF icon HDU8-SDS2.5_Detail_Holdown.pdf

Download

jpg: 
Image icon HDU8-SDS2.5_Detail_Lateral Load Connection.jpg
dxf: 
Binary Data HDU8-SDS2.5_Detail_Lateral Load Connection.dxf
dwg: 
File HDU8-SDS2.5_Detail_Lateral Load Connection.dwg
PDF: 
PDF icon HDU8-SDS2.5_Detail_Lateral Load Connection.pdf

Download

jpg: 
Image icon HDU8-SDS2.5_Detail_Mid Floor Holdown.jpg
dxf: 
Binary Data HDU8-SDS2.5_Detail_Mid Floor Holdown.dxf
dwg: 
File HDU8-SDS2.5_Detail_Mid Floor Holdown.dwg
PDF: 
PDF icon HDU8-SDS2.5_Detail_Mid Floor Holdown.pdf

Download

jpg: 
Image icon S-HDU9_Detail_Steel Frame Holdown.jpg
dxf: 
Binary Data S-HDU9_Detail_Steel Frame Holdown.dxf
dwg: 
File S-HDU9_Detail_Steel Frame Holdown.dwg
PDF: 
PDF icon S-HDU9_Detail_Steel Frame Holdown.pdf

Download

jpg: 
Image icon HDU8_3D.jpg
RFA: 
Binary Data HDU8-SDS25_3d_Cad.rfa

Download

jpg: 
Image icon S-HDU9_3D.jpg
RFA: 
Binary Data S-HDU9_3d_Cad.rfa
Package icon Download Full Set (4.75 MB)
Alternative Products

Alternative Products

DTT

DTT Tension Tie & Holdown

Simpson Strong‑Tie offers a wide variety of holdown devices designed and tested to address many applications and load demands. The DTT Tension Tie & Holdown is designed for lighter‑duty holdown applications on single or double studs.

HTT4

HTT Tension Tie & Holdown

Simpson Strong‑Tie offers a wide variety of holdown devices designed and tested to address many applications and load demands.

Inspiration

Inspiration

HDU8-SDS2.5_Application_01.jpg

HDU8-SDS2.5_Application_02.jpg

HDU8-SDS2.5_Application_03.jpg

HDU8-SDS2.5_Application_04.jpg

S-HDU9_Application_01.jpg

S-HDU9_Application_02.jpg

This is a Holdown! Introduction to Simpson Strong-Tie HDU, HTT and DTT ≠ Holdowns and Tension Ties

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Request a Demo/Sample*

Experience the innovation of Simpson Strong-Tie products and how we can help you build safer, stronger structures. Please fill out your details and submit the form below. We’ll be in touch to provide you a demo and/or send you samples*.

* Start typing address and select from the autocomplete.

Privacy policy

Structural Connections

 

Unmatched Quality from the Truss to the Foundation

With nearly 60 years of field and R&D experience, Simpson Strong-Tie® timber connectors are manufactured to the industry's highest standards. From framing angles to straps to heavy-duty joist hangers, we offer the most diverse product line so that you have the right product for the job.

Simpson Strong-Tie® connectors offer unmatched quality with laboratory and field testing, and are backed by our uncompromising commitment to customer service. As the company that built the connector industry, you can count on Simpson Strong-Tie® to work closely with builders, engineers and building officials to deliver innovative, building code-compliant solutions to help build safer, stronger structures economically. Download the Structural Connectors Overview Flyer.

Timber Connectors

From testing to service to availability, everything we do is engineered to ensure your project's success. With every product, you know you are getting the quality, value, service and on-time delivery that we have built our reputation on for the past 60 years.

From straps and ties to joist hangers and much more, Simpson Strong-Tie® structural connectors increase the strength and safety of timber-frame structures. Each connector is unique to Simpson Strong-Tie and is designed for specific applications without the need to adapt metal plating to suit a connection. 

Steel Frame Connectors

From fully tested and engineered connectors and clips Simpson Strong-Tie® provides comprehensive structural solutions for cold-formed steel construction. From steel-to-steel connections to full-scale lateral solutions and curtain wall connectors, we remain committed to developing new technology that helps to advance the cold-formed steel industry.

Find out how Simpson Strong-Tie timber connectors can help you build the right way every day. Download the Cold-Fromed Steel Construction Connectors Catalogue.