Lag Bolts - What they are and why we love them!

Lag bolts, also called lag screws, are large wood screws with hexagonal heads that are perfect for projects like mounting your new flat screen TV in your house. While using heavy-duty lag bolts for hanging your TV might be overkill, there are some things that you really don’t want falling and that’s where we love lag bolts.

Generally, Lag screws are used to connect something semi-permanently to wood after predrilling the pilot hole into the securing wood beam. Driving lag bolts is easy to do with an impact driver or wrench, but care needs to be taken for the final torquing of the bolt as its not uncommon to pop the heads due to over tightening of the bolts and that’s a quick way to ruin your afternoon.

Lag bolts have a sharp gimlet point and coarse threads for maximum holding force in wood, but due to their large diameter must be predrilled. Extra care must be taken to make sure the pilot holes are in the center of the stud and that the predrilling is to the depth the entire screw will eventually be.

• Roof beams
• Garage pillars
• TV wall mounting
• Heavy construction

• 1/4” lag bolt - 2.0 inch embedded depth, 272 lbs. shear
• 5/16” lag bolt - 2.5 inch embedded depth, 368 lbs. shear
• 3/8” lag bolt - 3.0 inch embedded depth, 432 lbs. shear
• 1/2” lag bolt - 3.0 inch embedded depth, 624 lbs. shear
• Threads must be embedded in the side grain and must be located in the middle third of the structural member for maximum strength.
• Read full article for particulars including links at bottom of page.

• For a 5/16" lag bolt, pull-out force is between 205 - 307 lbs per inch of threaded depth, depending on the wood choice used.
• Threads must be embedded in the side grain and must be located in the middle third of the structural member for maximum strength.
• Read full article for particulars including links at bottom of page.

• Length is from the under-head bearing surface to the extreme tip of the screw.
• Diameter is the width of the major thread diameter or unthreaded shoulder of the screw.

• Steel 60,000 psi minimum
• Stainless Steel 100,000 psi minimum (18-8 stainless steel)

• Hammer the center punch in the middle of the broken bolt so the drill bit will have a starting point.
• Drill a pilot hole and using a specialty extraction bit proceed to SLOWLY and in reverse, drill the bit into the pilot hole. It may be helpful to gently tap the drill containing the extraction bit into the pilot hole with a light hammer tap before attempting to drill. If all goes well, continue reversing until the bolt is removed or you can get some vice grip pliers onto the bolt to remove it fully.

• Are Lag Bolts Structural?

  Lag bolts are not typically considered structural fasteners but provide strong holding power for connecting wood.

• Are Lag Bolts Strong?

  Yes, lag bolts are designed to handle heavy loads and provide a secure hold in wood.

• Are Lag Bolts the Same as Wood Screws?

  Lag bolts are a type of wood screw but are much larger and have hexagonal heads for heavy-duty applications.

• Are Lag Bolts Self-Tapping?

  No, lag bolts require predrilling of pilot holes before installation.

• Can Lag Bolts Be Used for Framing?

  While not typically used for framing, lag bolts can be used in situations where a strong, secure connection to wood is needed.

• How Many Lag Bolts Do I Need?

  The number of lag bolts needed depends on the specific application and the load requirements. It’s essential to follow guidelines for spacing and depth.

• How Many Lag Bolts Per Beam?

  The number of lag bolts per beam depends on the size of the beam and the load it will carry. Proper spacing is critical to ensure structural integrity.

• Why Use Lag Bolts?

  Lag bolts provide superior holding power, are suitable for heavy-duty applications, and offer a secure connection in wood.

• Where to Place Lag Bolts on Beams?

  Lag bolts should be placed in the middle third of the beam's width and spaced according to load requirements.

• What Length Lag Bolts Should I Use?

  The length of lag bolts depends on the thickness of the materials being joined. Typically, the lag bolt should be long enough to penetrate at least halfway into the second material.

• What Size Lag Bolts for 2x6?

  For joining 2x6 lumber, a common size is 3/8” diameter with a length sufficient to penetrate both pieces of lumber securely.

• Are Lag Bolts Good for Wood?

• Are Lag Bolts Good for Concrete?

Lag bolts are not typically used directly in concrete. For concrete applications, sleeve anchors or wedge anchors are more appropriate. However, lag bolts can be used in conjunction with plastic or lead anchors to attach items to concrete or masonry.

• Are Lag Bolts Strong?

Lag bolts are very strong and can handle significant loads. Their design allows them to distribute weight and stress effectively, making them ideal for heavy-duty applications. The strength of lag bolts can vary based on their size and the material they are made from, such as steel or stainless steel.

• Are Lag Bolts and Lag Screws the Same?

Yes, lag bolts and lag screws are the same. The terms are often used interchangeably. They both refer to large, heavy-duty screws with hexagonal heads designed for creating strong connections in wood and other materials.

• Are Lag Bolts Stronger Than Screws?

Lag bolts are generally stronger than regular screws due to their larger diameter and coarse threads, which provide a better grip and holding power. They are designed for heavy-duty applications and can handle more stress and weight compared to typical wood screws.

• Can You Use Lag Bolts in Brick?

Yes, lag bolts can be used in brick when used with suitable anchors. Pre-drill holes into the brick and insert plastic or lead anchors. The lag bolts can then be driven into the anchors to secure items to brick walls or surfaces.

• How Many Lag Bolts for Deck Ledger?

The number of lag bolts needed for a deck ledger depends on the size of the ledger board and the load it will carry. Generally, lag bolts should be spaced 16 inches apart along the length of the ledger board, but it's crucial to follow local building codes and guidelines for specific spacing requirements.

• What Lag Bolts to Use for Deck Posts?

For deck posts, use lag bolts that are at least 3/8 inch in diameter and long enough to penetrate the post and the supporting beam securely. Typically, 4 to 6 inches in length is recommended, but the specific size may vary based on the dimensions of the materials being used.

• What Size Lag Bolts for TV Mount?

The size of lag bolts for a TV mount depends on the weight of the TV and the type of wall studs. Generally, 1/4 inch to 5/16 inch diameter lag bolts are suitable, with a length of 2.5 to 3.5 inches to ensure they penetrate the wall studs securely.

• Can Lag Bolts Be Used in Metal?

Lag bolts are not typically used in metal. For metal applications, bolts and nuts or metal screws are more appropriate. However, in some cases, lag bolts can be used with metal if they are secured into wood or another material beneath the metal.

• How to Prevent Lag Bolts from Stripping?

To prevent lag bolts from stripping, ensure you use the correct size drill bit for the pilot hole, drive the bolts in straight, and avoid over-tightening. Using a high-quality impact driver or wrench can also help prevent stripping.

• What Coating Should Lag Bolts Have for Outdoor Use?

For outdoor use, lag bolts should have a corrosion-resistant coating, such as galvanized or stainless steel. This ensures they withstand the elements and prevent rusting, which is crucial for maintaining their strength and durability over time.

* How much bolts can hold in depends on many factors including, but not limited to, wood type, threaded depth, load angle. Full technical data from American Wood Council can be found here - AWC Calculator found here, Kinetics Data for lag screws