What Is A Lag Bolt?

Lag bolts, known as lag screws, are heavy-duty fasteners with hex heads and coarse threads made for wood projects. DIYers will find lag screws especially useful for projects like deck construction, woodworking, and framing.

In this article, we’ll take a deep dive into lag bolts, including what they are and how to use them for your projects.

• What Is A Lag Screw?
• What Are Lag Screws Used For?
• What Are The Different Types Of Lag Bolts?
• What’s The Difference Between Lag Bolts VS Lag Screws?
• What’s The Difference Between A Lag Bolt VS Carriage Bolt?
• What’s The Difference Between A Lag Screw VS Wood Screw?
• How To Determine Lag Screw Sizes
• How To Install A Lag Bolt?
• How To Choose The Right Lag Bolt

What Is A Lag Screw?

Lag bolts or lag screws, are heavy-duty fasteners commonly used in woodworking and construction projects where durable and secure connections are required.  

Unlike regular screws, lag screws have a thick, coarse thread and a hexagonal head that’s driven in with a wrench or socket. They are typically made from steel and can be coated with zinc or galvanized to improve their corrosion resistance and durability. 

What Are Lag Screws Used For?

Lag screws are most commonly used in projects such as deck construction, framing heavy lumber, and mounting heavy objects. Their ability to create strong, load-bearing joints makes lag screws especially useful in connecting large pieces of wood and other heavy materials.  

What Are The Different Types Of Lag Bolts?

There are different types of lag bolts designed for use across a variety of construction projects. Here’s a look at the different types of lag bolts: 

• Standard Lag Bolts: Traditional lag bolts have a hexagonal head and coarse thread, ideal for wood-to-wood connections and ensuring a firm hold without the need for pre-drilled hardware.
• Galvanized Lag Bolts: Coated with zinc for enhanced corrosion resistance, galvanized lag bolts are perfect for outdoor projects that may be exposed to rain and snow.
• Stainless Steel Lag Bolts: As stainless-steel lag bolts offer excellent resistance to corrosion and wear, they are commonly used in environments exposed to moisture or chemicals, such as marine settings.
• Flange Head Lag Bolts: These lag bolts feature built-in washers, providing greater surface area and distributing load more evenly. This pressure distribution helps prevent material damage under heavy loads.

What’s The Difference Between Lag Bolts VS Lag Screws?

A lag bolt is inserted into a pre-drilled hole and used with a nut, while a lag screw is driven into a pre-drilled hole and secured without a nut. While the terms “lag bolt” and “lag” screw” are used interchangeably, they are distinct fasteners.

To determine whether you have a lag screw or a lag bolt, check out the tip of your fastener. A lag screw will have a pointed tip while a lag bolt will have a flat end.  

What’s The Difference Between A Lag Bolt VS Carriage Bolt?

Lag bolts and carriage bolts differ primarily in their head design, threading, and installation methods.

Lag bolts have a hex head and are threaded with sharp, coarse threads. They are ideal for projects requiring superior, load-bearing connections, such as attaching beams or ledger boards in deck construction.

Carriage bolts feature a rounded head and a square neck beneath it, designed to lock into wood or metal to prevent turning. They offer a smooth, finished look that's ideal for wooden furniture, playground equipment, and other visible applications where a clean appearance is desired.

What’s The Difference Between A Lag Screw VS Wood Screw?

Lag screws are large fasteners with a hexagonal head and coarse threads. They are designed to be driven in with a wrench and require pre-drilled holes. Lag screws are intended for heavy-duty applications, such as securing large beams or heavy timber structures, where solid, load-bearing connections are essential.

In contrast, wood screws are generally smaller with a tapered, pointed end and finer threads, designed to hold two pieces of wood together without splitting. They are typically used in lighter woodworking tasks, such as assembling furniture or cabinets.

How To Determine Lag Screw Sizes

Selecting the right lag screw size is essential for a strong, reliable connection. Start by assessing the materials' thickness to ensure the lag screw is long enough to grip securely. As a rule of thumb, it should extend half the thickness into the second material. 

Consider the diameter based on the load requirements of your project. Larger diameters offer more strength, which is crucial in heavy-duty applications. Refer to the manufacturer guidelines or lag screw sizing charts to make an informed choice. 

How To Install A Lag Bolt?

To install a lag bolt, drill a pilot hole into the material using a drill bit slightly smaller than the lag bolt's diameter. This helps prevent splitting and makes it easier to drive in the bolt.

Next, insert the lag bolt into the pilot hole and use a wrench or socket to tighten it. Ensure the bolt is flush against the material. To remove a lag bolt, simply reverse the process with the wrench, turning it counterclockwise until the bolt is free from the material.

How To Choose The Right Lag Bolt

Choosing the right lag bolt will extend the time your project spends standing and sturdy. Size and material are two of the most important factors to consider when choosing a lag bolt for your project. Consider the materials’ thickness and the load they will bear to select the appropriate length and diameter for a secure fit. 

Additionally, opt for galvanized or stainless steel if exceptional corrosion resistance is needed, otherwise zinc-coated lag screws will do. Ultimately, buying from a trusted supplier can provide you with the expert guidance and premium fasteners that your project deserves. 

About Fastener Depot

Founded in 2015, Fastener Depot is a family-operated small business committed to offering a wide range of high-quality lag bolts at affordable prices. We take great pride in providing outstanding customer service, quick shipping, and responsive customer support. Each order from Fastener Depot is carefully packaged to ensure your order arrives in perfect condition. Please get in touch for personalized assistance.