How To Attach 4x4s To Each Other

Ossiana Tepfenhart
by Ossiana Tepfenhart

When you first start woodworking, you’re probably using 2 by 4s. They’re easy to attach to one another, not to mention to other wood measurements. When you need something sturdier, a 4×4 is what you’re going to grab. Attaching two of these to each other, though, can be a little bit tricky. So, how can you do it?

The most common way to attach 4x4s to each other is to use a half-lap joint with galvanized washers and bolts. However, you can also use a rabbet joint combined with steel plates if you need to make your construction hurricane-proof. If it’s for something along the lines of fencing, you can just use dowels.

Attaching 4x4s to each other will take a wide range of different forms, all depending on what you’re doing and how you’re working the two together. Before you start a project, it’s a good idea to know what you can use and how you can use it. So, keep reading already!

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Before You Begin: Choosing The Right Process

Every project will require different joining methods, especially when you’re talking about things as different as roofing and fencing. Trying to come up with a “one size fits all” solution isn’t going to work. Heck, even working on the same project in different states will yield different requirements!

Before we broach the subject of common joining methods, we suggest that you do the following when planning the joint connection for your project:

  • Check to see if your project has instructions first. If you’re doing a DIY project from Pinterest, check to see what they suggest when you’re working on connecting your 4x4s. In most cases, you should have some instructions telling you which connection works.
  • Look up local building codes. Working on a roof or a part of your home? You need to check what local building codes say when it comes to joining wood as part of your project.
  • Ask fellow builders. If you are doing a specialty project, going on online forums dedicated to that type of woodworking can help give you the answers that you need.
  • Think about the angle in which you’re connecting the two posts together. The options that you’ll have for a 90-degree angle won’t always be the same as the options that you have when you’re trying to connect those posts end to end.

What Joining Method Should I Use?

The best method for the job will vary, period. With that said, these methods tend to work fairly well when you’re working with 4x4s…

Half Lap Joints

A half-lap joint cuts away a two-inch square at the corner of each of the two poles that you want to join. Then, they are placed at a 90-degree angle and glued together. With many projects, this can be enough to hold the two pieces of wood together. However, it’s often better to use galvanized bolts and washers to further secure the two pieces of wood together.

If the half-lap alone isn’t enough, you might want to consider getting steel reinforcement plates for your joining job.

Rabbet Joint + Steel Plates

If you are working on a heavy-duty project, then you might want to take a look at using a rabbet joint with a steel plate to reinforce the joining. The rabbet joint alone is usually only good for lighter projects, and won’t be able to hold a roofing project or home structure. To ensure that your project remains intact, use steel plates to reinforce it.

For example, North Carolina hurricane codes suggest cutting a 24-inch rabbet joint, then using steel plates to reinforce the connection. Once everything is connected, finish the reinforcement with four long bolts.


Another classic way to connect two 4x4s is to use the age-old tradition of using dowels or connecting rods. This involves drilling almost entirely through the two pieces of wood. Then, a dowel or connecting rod can be inserted in the hole.

If you’re using dowels, you will need to add wood glue to keep it in place. If you are using a connecting rod, you might have additional hardware that you need to install in order to keep your two pieces of wood in place. We suggest that you take a look at the type of metal joining plates you’re using before you jump to a conclusion.

How To Make The Most Of Your Joint

Obviously, there are going to be issues that arise with any type of joining method that you use. Here are some tips to make sure that you get a solid bond from your joining:

  • A good option for almost any type of joining is to use steel plates that match your needs. You’ll still need to make a joint, but having these will help reinforce it and hold it in place.
  • Do think about your focus. Do you need it to be as sturdy as possible? If so, put aesthetics on the backburner. Do you want your two boards to be part of a statement furniture piece? Chances are that you might be in need of something that also looks good but doesn’t require the strength to maintain thousands of pounds.
  • When possible, work with what you know. If you are a wiz at half laps, then work with half-laps. If you work best with doweling, you might want to opt for a dowel.
  • Use good wood glue. This sounds like it’s common sense, but it needs to be said again. The materials that you use are going to make a difference in the overall outcome of your project.
  • If you live in a hurricane-prone area, then you need to look into hurricane-galvanized steel reinforcements. Galvanized steel is meant to be used as a way to reinforce building structures against major perils like hurricanes and earthquakes. Depending on what you’re doing, this could be a mandatory part of your building routine.

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Related Questions

Can deck posts sit on concrete?

While you might think that a concrete foundation is a good idea, the truth isn’t that sunny. You shouldn’t let your wooden deck posts sit on concrete if you can help it. It may damage the posts and can also be an unstable foundation.

Can I use a wedge anchor in a brick wall?

Though the wedge may seem like it’s a good match for brick, it’s not a good idea. Brick and surfaces like brick are too porous to properly hold the wedge anchor in place. It’s better to use an expansion-type anchor like a sleeve anchor on these types of surfaces.

Should I use 4×4 posts on a deck?

For the longest time, 4x4s were almost considered to be a standard material in decks, but not anymore. Studies show that 4x4s have a tendency to warp, bend, and even break. Even if your deck is just three or four feet off the ground, you might end up seeing serious sagging. We suggest using 6×6 posts and deck-specialized materials whenever possible.

Do wooden posts rot in concrete?

They can. Concrete being poured directly on wooden fencing can increase the risk of rot and exacerbate rot that already exists. When grounding a fence post in concrete, make sure to follow proper procedures when pouring it in.

Ossiana Tepfenhart
Ossiana Tepfenhart

Ossiana Tepfenhart is an expert writer, focusing on interior design and general home tips. Writing is her life, and it's what she does best. Her interests include art and real estate investments.

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