Lag Bolts vs Carriage Bolts

Lag bolts and carriage bolts on a white background.

Carriage bolts are just one type of common fastener that is used in many different large construction projects. For the DIY homeowner, the choices are almost endless when it comes to different kinds of screws, bolts, and other fasteners to use for their project. Sometimes there is a need for several different types of fasteners for elaborate projects like decks, children's play areas, sheds, docks, and other similar projects. Here are some ways to discern when to use which type.

Each Has Its Own Job

The important point to remember when dealing with the different types of fasteners is that they have their own function that they perform. This means that a deck screw is not going to be adequate for putting up drywall. When it comes to carriage bolts and lag bolts, people often get them confused or classify them as the same thing. However, they are different in many ways.


The carriage bolt is more of a bolt than its lag counterpart. The carriage bolt is a straight cylinder with a flat edge. The top has a small square neck that resists turning when it is fastened into place. This means that you have to countersink the bolt for it to perform as it is supposed to. The lag bolt, on the other hand, has a point at the end and wide threads for use in wood construction.

Uses of Carriage Bolts

It is important to remember the difference in the construction of the two different bolts. If you can keep this in mind, then you will be better able to distinguish what each bolt can be used for. Because of the flat end of the carriage bolt, you will need to use a washer and a nut for completing the fastening.

Pergola Construction: When adjoining two pieces of wood, you can use a carriage bolt if you drill completely through them both. The carriage bolt is then inserted into the hole and secured with the washer and nut.

Docks: There are plenty of areas on a dock that will require the use of a carriage bolt. The frame and rails are just two examples.

Children's Swingsets: One of the major uses of a carriage bolt is in the construction of a children's play area or swingset.

Uses of Lag Bolts

With the pointed tip of a lag bolt, you can screw them directly into wood without needing to make a hole. This means that anytime you need extra strength in the construction, a lag bolt is commonly used.

Decks: When connecting the ledger board of a deck to a home, lag bolts make the best option because they are screwed directly into the studs.

Rafters: Building a shed, garage, or another outbuilding that requires screwing into a larger base will require a lag bolt.

You can use this new knowledge for your next project.