How to Loosen Lag Bolts

Coarse threads keep lag bolts in place.

Lag bolts, or lag screws, create a structural connection between two or more wooden beams. The amount of force required to install a lag bolt increases the difficulty needed to remove it from a wooden structure. Corrosion formed on the threads of a galvanized lag bolt increases the difficulty of the removal task. Exerting too much force on the head of a stuck lag bolt will result in a broken fastener. Loosening the hold of the lag during removal will increase the chances of successfully removing the lag bolt from a structure.

Things You'll Need

• Socket
• 3/8-inch ratchet handle
• Breaker bar

Instructions

1. Fit a socket to the head of the installed lag bolt. Attach the socket to a 3/8-inch ratchet handle.

2. Attempt to remove the lag bolt by turning it counterclockwise. Set the direction of the ratchet handle to "forward." Turn the lag bolt clockwise 1/4 turn if it will not move in the reverse direction.

3. Attach the socket to a breaker bar if the lag bolt refuses to move.

4. Push the breaker bar handle counterclockwise to release the bond between the lag bolt and the wood. Pull the breaker bar handle 1/4 turn clockwise if it refuses to move. Continue alternating turning directions until you break the bond between the lag bolt threads and the wood.

5. Move the socket from the breaker bar to the 3/8-inch ratchet handle. Turn the ratchet handle counterclockwise to remove the lag bolt.

References

• This Old House: Building a Safe Deck
• "The Dock Manual: Designing, Building, Maintaining"; Max Burns; 1999
• "Porches, Decks and Outbuildings"; Taunton Press; 1997