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DTT Tension Tie & Holdown
DTT Tension Tie & Holdown
DTT2 Illustration
DTT2 Illustration
DTT1Z Illustration
DTT1Z Illustration

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. It can also be utilised in horizontal applications as a tension tie to provide balustrade or similar support. It installs easily with the Strong‑Drive® SDS Heavy‑Duty Connector screws (included). The DTT is ideal for retrofit or new construction projects. They provide high-strength, post-pour, concrete-to-steel connections.

The DTT2 is a safe, cost-effective way to attach deck-railing posts to the deck framing for stronger, safer railings. Because the post is tied back into the deck joists, rather than to the boundary joist alone, the connection is stronger than typical through-bolt installations.

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

Material & Finish
  • Carbon Steel & 316 Stainless Steel 2mm thick
  • ZMAX® Galvanised: DTT2Z; DTT1Z
  • 316 Stainless Steel: DTT2SS
Features & Benefits
  • Stronger and safer than typical through-bolt installations for deck post connections
  • Engineered swages for extra strength and to minimise deflections
  • Suitable for lighter duty holdown applications on single or double studs
  • Ties the guardrail post into deck framing for a stronger, safer connection
  • The DTT2 is ideal for lateral-load connections between the deck and house
  • Helps prevent a common type of deck failure
  • 15mm diameter anchor hole can accommodate Simpson Strong-Tie M12 Titen HD Screw Anchor or any M14 threaded rods
  • Available in 316 Stainless Steel for more corrosive environments such as coastal areas
  • Installs easily with Strong-Drive® SDS screws (included)
  • Use all specified fasteners
  • The DTT requires a standard cut washer (included with DTT2Z, DTT2SS) be installed between the nut and the seat
  • Bottom Plate Holdown
  • Deck Framing
  • Deck Post Connection
  • Deck-to-House Lateral Load Connection
  • Vertical Floor Connection
  • Mid Floor Wall Bracing
  • Engineered Wood Products (EWP)
  • Cross-Laminated Timber (CLT) 
Model No. Table

Model No.

Dimensions (mm)


Minimum Timber Member Size (Depth x Breadth, mm)

Design Tension Capacity (kN)
k1 = 1.0






Anchor Bolt Dia (mm)

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









8 – SDS6.4 x 38

90 x 38


90 x 75









6 – 40 x 3.75

90 x 38


6 – SD#9 x 38


  1. Design Capacity is the lesser of (1) the Characteristic Capacity multiplied by the NZ Strength Reduction Factor (φ), and applicable the k modification factors following 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. 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 New Zealand Joint Group J5 per NZS 3603 Table 4.1.
  5. The Designer must specify anchor bolt type, length and embedment.
  6. 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.
  7. Post or beam design by Designer. Posts may consist of multiple members provided they are connected independently of the holdown fasteners.
  8. 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.
  9. Simpson Strong-Tie stainless-steel connectors require stainless-steel fasteners.
  10. Values in the table reflect installation into the wide face.
  11. Holdowns and tension ties are for use in vertical or horizontal applications.
  12. 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.
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Technical Data & Docs

Technical Data Sheets

PDF icon Technical Data Sheet - DTT



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Request a Demo/Sample

Experience the innovation design of Simpson Strong-Tie's 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 schedule a time to talk and give you a personal demo of Simpson Strong-Tie products.

Request a Demo/Sample

Experience the innovation design of Simpson Strong-Tie's 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 schedule a time to talk and give you a personal demo of Simpson Strong-Tie products.

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 Timber Connectors NZS 3604 Catalogue.

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. Download the Timber Construction Connectors Catalogue (2016-2018).

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.