Lag Bolt

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Lag Bolt

What is Lag Bolt?

A heavy-duty wood screw with a hexagonal head that requires a wrench for installation, used for securing heavy structural members and creating strong wood connections in construction applications.

Description

A lag bolt is a heavy-duty wood screw with a hexagonal head that requires a wrench for installation, used for securing heavy structural members and creating strong wood connections in construction applications. Also known as lag screws, these fasteners feature coarse threads designed to bite into wood fibers and provide exceptional holding power for structural connections. Lag bolts are essential hardware for timber framing, deck construction, and other applications requiring strong, reliable wood-to-wood or wood-to-metal connections.

The primary purposes include creating strong structural connections in wood framing, securing heavy beams, posts, and structural members, providing reliable fastening for deck and outdoor construction, enabling removable connections for maintenance access, meeting structural load requirements in timber construction, offering superior holding power compared to standard screws, and providing cost-effective solutions for heavy-duty fastening needs.

Construction and design involve hexagonal heads, coarse threads, shank design, and material specifications for optimal performance.

FAQs

  • What is a lag bolt?

    A lag bolt is a heavy-duty wood screw with a hexagonal head that requires a wrench for installation, used for securing heavy structural members and creating strong wood connections.

  • How is a lag bolt different from a regular screw?

    Lag bolts are larger, have hexagonal heads requiring wrenches, feature coarse threads for wood, and provide much higher holding power than regular screws.

  • Do you need to pre-drill for lag bolts?

    Yes, pilot holes should be drilled approximately 75% of the lag bolt’s root diameter to prevent splitting and ensure proper installation.

  • What sizes do lag bolts come in?

    Common sizes range from 1/4 inch to 1 inch in diameter and 1 inch to 12 inches or more in length, depending on application requirements.

  • Where are lag bolts commonly used?

    They’re commonly used in timber framing, deck construction, structural connections, and anywhere heavy-duty wood fastening is required.

  • What tools are needed to install lag bolts?

    Installation requires wrenches, sockets, or impact drivers that fit the hexagonal head, plus drill bits for pilot holes.

  • Are lag bolts removable?

    Yes, lag bolts can be removed and reinstalled, making them suitable for applications requiring maintenance access or modifications.

Fun Fact

Fun Fact: Lag bolts got their name from their original use in “lagging” – the wooden planks used to line mine shafts and tunnels! The hexagonal head design was adopted from carriage bolts in the 1800s to provide better torque application. Some lag bolts can withstand over 1,000 pounds of withdrawal force when properly installed. Interestingly, despite being called “bolts,” they’re technically screws since they thread directly into wood without requiring nuts!

CSI Code

06 05 23

NAHB Code

610