The Simpson Strong-Tie DTT1Z Deck Tension Tie is a structural connector designed to meet updated building code requirements for lateral load resistance in deck construction. As of 2015, the International Residential Code (IRC) mandates that decks include connections capable of withstanding 750 pounds of lateral load, and the DTT1Z fulfills this requirement. This article provides a detailed overview of the DTT1Z, including its specifications, fastening options, installation configurations, and compliance with relevant building codes. The information is derived from official product descriptions, technical bulletins, and manufacturer documentation.
Overview of the DTT1Z Deck Tension Tie
The DTT1Z is a 7-inch by 1.5-inch steel connector designed to transfer lateral loads from a deck ledger to a house’s framing. It is intended for use in wood-framed structures and is specifically engineered to resist outward forces that could otherwise lead to structural failure, particularly in the event of wind or seismic activity. The connector is constructed with a zinc-coated (ZMAX) finish for corrosion resistance, making it suitable for both interior and exterior applications.
According to the provided documentation, the DTT1Z is compatible with a variety of fastening methods, including self-drilling screws, lag screws, and bolts. It also offers flexibility in installation due to its design, which does not require direct contact between the connector and the wall surface. This feature allows for the use of longer fasteners without the need for precise length calculations that account for siding, sheathing, and wall thickness.
Fastening Options and Installation Requirements
The DTT1Z can be installed using one of three primary fastening methods, each with its own set of specifications and advantages:
1. Timber-Hex HDG Screws
Simpson Strong-Tie’s Timber-Hex HDG (hot-dipped galvanized) screws are a recommended fastening option for the DTT1Z. These screws feature an integral washer head, which eliminates the need for a separate washer. The large diameter of the washer helps distribute the load more evenly and reduces the risk of splitting the wood.
One key advantage of using these screws is that they do not require a pre-drilled pilot hole or clearance hole, which is typically necessary when using lag screws. This simplifies the installation process and reduces the time required to prepare the connection.
2. 3/8-Inch Galvanized Lag Screws
An alternative to the Timber-Hex HDG screws is the 3/8-inch diameter galvanized lag screw. When using this method, a separate washer must be installed under the head of the screw to ensure proper load distribution and to prevent damage to the wood. The lag screw must also be driven into the wood at an appropriate depth to meet the minimum 3-inch penetration requirement into the framing.
Unlike the Timber-Hex HDG screws, lag screws typically require a pre-drilled pilot hole to prevent splitting and to ensure proper alignment. This can be a drawback for installers who prefer a more streamlined process, but it remains a viable and commonly used method for securing the DTT1Z.
3. 3/8-Inch Galvanized Hex-Head Bolts
For installations where access to the interior framing is available, 3/8-inch galvanized hex-head bolts can be used. This method involves securing the DTT1Z with a bolt, nut, and washer on the interior side of the wall. This configuration is particularly useful in situations where a more rigid and adjustable connection is desired.
Bolts provide a high degree of adjustability and can be tightened to ensure a secure fit. However, this method typically requires more time and effort due to the need to align and secure the bolt through both sides of the wall.
Installation Configurations and Code Compliance
The DTT1Z is designed to be installed in a variety of configurations, depending on the specific requirements of the project and the availability of framing access. According to the documentation, the connector can be mounted in a standard configuration as outlined in the 2015 IRC, or it can be adapted to suit other installation scenarios.
One of the most notable aspects of the DTT1Z is its flexibility in accommodating different wall thicknesses and construction materials. The connector does not require direct contact with the wall surface, which means that installers can use longer screws that penetrate through the siding, sheathing, and into the framing without the need for precise length calculations. This is a significant advantage in real-world applications where wall thickness can vary and pre-cut fasteners may not always be available.
The 2015 IRC (Figure R507.2.3(2)) mandates that at least four lateral load connections be made along the ledger of the deck. Specifically, two of these connections must be located within 24 inches of each end of the deck, and the remaining two should be spaced evenly along the ledger. This requirement ensures that the lateral load is distributed evenly across the structure, reducing the risk of failure at any single point.
To meet this requirement, the DTT1Z is typically installed in a kit format that includes multiple connectors and pre-packaged fasteners. The individual connectors cost approximately $2 each, while four-piece kits that include the Timber-Hex HDG screws are also available for convenience and cost-effectiveness.
Technical Installation Details
The DTT1Z is designed with six round holes for standard installation and two additional triangular-shaped holes for additional fasteners in cases where extra reinforcement is needed. These holes accommodate the various fastening options mentioned earlier and allow for flexibility in installation.
Fastening the DTT1Z to the deck joist or block can be done using either 10d x 1.5-inch galvanized metal hardware nails or Simpson Strong-Tie’s #9 x 1.5-inch Strong Drive SD Connector Screws. Both options provide sufficient holding power to meet the 750-pound lateral load requirement.
The choice of fastener may depend on the tools available to the installer and the desired level of precision. Screws, particularly the Strong Drive SD variety, offer a more controlled installation and are less prone to slippage or misalignment compared to nails. However, nails may be preferred in situations where speed and simplicity are more important.
Design Advantages and Practical Considerations
The design of the DTT1Z offers several advantages over traditional lateral load connectors. One of the most notable is its ability to accommodate longer fasteners without requiring the installer to measure and cut them to a specific length. This is particularly useful in situations where the wall includes multiple layers such as siding, sheathing, and framing, which can complicate the selection of the correct fastener length.
Another advantage is the integral washer head found on the Timber-Hex HDG screws. This feature eliminates the need for a separate washer and helps to distribute the load more evenly across the wood, reducing the risk of splitting or deformation. The large head size also provides a larger surface area for contact, which can help prevent the fastener from loosening over time.
From a practical standpoint, the DTT1Z is relatively easy to install and can be completed with basic hand tools or power tools. The use of self-drilling screws further streamlines the process by eliminating the need for pre-drilling, which can save time and reduce the risk of misalignment. However, for larger projects or commercial applications, the use of power tools and pre-packaged kits may be more efficient.
Compatibility and Application
The DTT1Z is compatible with a wide range of wood types and framing configurations, making it suitable for both residential and commercial deck construction. It is particularly well-suited for use in new construction or renovations where code compliance is a priority. The ZMAX finish provides protection against corrosion, making it suitable for use in both dry and moist environments.
In terms of application, the DTT1Z is commonly used in wood-framed structures where a deck is attached to a house. It is not intended for use with concrete or masonry walls, as these materials require different types of connectors and fastening methods. The connector is also not suitable for use in high-rise or multi-story structures, where additional structural considerations may be required.
Conclusion
The Simpson Strong-Tie DTT1Z Deck Tension Tie is a versatile and code-compliant solution for lateral load connections in deck construction. It meets the 750-pound lateral load requirement specified in the 2015 IRC and can be installed using a variety of fastening methods, including self-drilling screws, lag screws, and bolts. Its design allows for flexibility in installation and accommodates different wall thicknesses and construction materials.
The connector’s ability to use longer fasteners without requiring precise length calculations is a significant advantage, particularly in real-world applications where wall thickness can vary. The integral washer head on the Timber-Hex HDG screws further enhances the connector’s performance by distributing the load more evenly and reducing the risk of wood splitting.
For installers, the DTT1Z offers a straightforward installation process that can be completed with basic tools. The availability of pre-packaged kits and multiple fastening options makes it a practical choice for both residential and commercial projects. When used in accordance with the manufacturer’s specifications and building codes, the DTT1Z provides a reliable and durable solution for lateral load resistance in deck construction.