The Simpson 4 x 4 Deck Post Tie - ZMAX Finish is a structural connector from Simpson engineered to attach 4x4 vertical posts to the outside face of stair stringers, rim joists, and other wood members on decks and stairs. Fabricated from 14-gauge steel with a ZMAX galvanized finish, this deck post tie is built for exterior and pressure-treated lumber applications where corrosion resistance is critical. Whether you are working on new construction or retrofitting an existing deck or stair assembly, this connector offers a faster, more straightforward installation compared to traditional through-bolting methods.

Key Features

• Attaches 4x4 posts to stair stringers and rim joists in new or retrofit construction - gives you a reliable, tested fastening solution whether you are building a new deck or reinforcing an existing one
• Simpler installation than through-bolting - reduces labor time and complexity on the job site without sacrificing structural integrity
• Designed for a nominal 4x4 post size - ensures a proper, snug fit with the specific lumber dimension this connector is engineered to support
• Made from 14-gauge steel - provides the structural strength and rigidity required for load-bearing deck and stair post connections
• ZMAX galvanization offers extra corrosion resistance for exterior and treated-wood applications - protects the connector against moisture and the chemicals found in pressure-treated lumber, extending the service life of the connection
• Typically installed in pairs - using two connectors per post creates a balanced, secure attachment that distributes load evenly on both sides of the post

Why This Product

• Purpose-built for deck and stair post connections - unlike generic hardware, this connector is specifically designed to fasten 4x4 posts to the outside of rim joists and stair stringers, making it the right tool for a very common and structurally important deck-building task
• ZMAX finish for long-term exterior performance - the advanced galvanized coating goes beyond standard zinc finishes to resist the corrosive conditions common in outdoor environments and alongside pressure-treated lumber, helping the connection hold up over time
• Faster than through-bolting with no compromise on strength - Simpson engineered this connector to simplify post attachment without eliminating structural reliability, making it a practical upgrade for both professional contractors and serious DIYers
• Works in new builds and retrofit projects alike - the flexibility to use this connector on existing decks and stair assemblies means you are not limited to new construction, giving you a versatile solution across a range of project types

Specifications

• Manufacturer: Simpson Strong-Tie
• MPN: DPT7Z
• Member Size: 4x4
• Gauge: 14-gauge steel
• Finish / Coating: ZMAX
• Install With: 3/8 in. diameter machine bolts and 10d x 1-1/2 in. nails or #9 x 1-1/2 in. Strong-Drive SD screws
• Country of Origin: United States

Approved Applications

• Attaching 4x4 vertical posts to the outside face of stair stringers on decks and stairs
• Securing 4x4 posts to rim joists in new deck construction
• Retrofit installation on existing decks and stair assemblies
• Exterior applications involving pressure-treated lumber where corrosion resistance is required

Frequently Asked Questions

What size post is the DPT7Z designed to work with?

The DPT7Z is designed for a nominal 4x4 post size, connecting the post to the outside of stair stringers, rim joists, or other wood members.

What fasteners are required to install the DPT7Z?

Install with 3/8 in. diameter machine bolts and 10d x 1-1/2 in. nails or #9 x 1-1/2 in. Strong-Drive SD screws. Note that lag screws are not permitted in place of machine bolts.

Why is the ZMAX finish important for this connector?

ZMAX galvanization provides extra corrosion resistance compared to standard galvanized finishes, making the DPT7Z suitable for exterior applications and use with pressure-treated wood where moisture and chemical exposure can accelerate corrosion.

How many DPT7Z connectors are typically needed for an installation?

The DPT7Z is typically installed in pairs, with two connectors used together to properly secure a 4x4 post to the adjacent structural member.