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What Size Pergola Posts and Beams Are Best to Use?

What Size Pergola Posts and Beams Are Best to Use?

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Doing research ahead of building or installing a pergola is a good idea. You want to make sure that you get things right so that it will look great on your property.

You might be confused about certain aspects of the design. For example, you could be wondering what size the pergola posts and beams need to be.

Keep reading to learn about pergola posts and beam sizes. You’ll have a better understanding of how to figure things out once you’ve read the information below.

Getting this information ahead of time should save you from making certain common mistakes. It’ll make it easier to have a smooth building experience.

Choosing Pergola Post and Beam Sizes

Choosing the right size beams and posts for your pergola will be important. If you choose the wrong size you might build a pergola that isn’t structurally sound.

The beam size will differ based on the dimensions that you’re using for the pergola. If you are building a pergola with a 12-foot span, you’ll be using 2”x4” beams.

For a 14-foot span, you’ll use beams that are 2”x6”. Building a pergola with a 20-foot span will require 2”x12” beams.

As you can see, the beam sizes go up the wider the pergola is going to be. So choose the right beam size based on your desired pergola dimensions.

The posts are usually going to be 6”x6”, but they can be different sizes as well. It’s not uncommon to see pergolas with posts that are as long as 12 feet.

Once again, it all comes down to how big you want the pergola to be. Choosing the right post size is simply about your expectations and needs on your property.

Can You Build a Pergola With 4”x4” Posts?

You might have some 4″x4″ posts sitting around that you need to use. Perhaps you’re hoping that this will work as support for a pergola.

This can work out okay, but it all depends on the size of the pergola. For a large pergola, 4”x4” posts won’t work as support.

However, 4”x4” posts can work nicely when building a small pergola. So if you’re keeping the pergola small it’ll be fine to use the posts that you have.

Otherwise, it’d be better to go out and buy 6”x6” posts. These are quite a bit sturdier and will give the pergola a wider look while also ensuring that it can bear more weight.

Be sure to make the right decision based on the size of the pergola that you wish to build. Otherwise, you’ll encounter problems during the building process.

Do the Posts Need to Be Buried?

Yes, pergola posts need to be buried in most circumstances. The posts need to be secured to the ground.

This is usually done by sinking the posts in the ground and using heavy concrete to anchor them. You could technically have a pergola with posts that aren’t buried, but you’d need to secure them in another fashion.

For instance, you could use heavy anchors that are made out of concrete to moor the posts. Typically, it’s a lot easier to just bury the posts and cover them in concrete.

So most pergola designs are going to involve digging post holes and sinking the posts. This is the standard method for building a pergola and ensuring that it will be secure.

How Big Can a Pergola Be With Four Posts?

A pergola with only four posts needs to be small. So if you’re using 4”x4” posts and going with a smaller design, you’ll have less space between the posts than most standard pergola designs.

Small pergolas will usually have between four and six feet of space between each post. So you’ll want to stick with this type of design if you’re going with four posts with 4”x4” supports.

How Far Apart Can the Posts Be?

How far apart pergola posts can be will depend on the size of the pergola. As mentioned above, it’s common for small pergolas to have between four and six feet of space between posts.

This information differs when you’re looking at larger pergola designs. These designs have substantially more space between the posts.

The exact dimensions will depend on the design that you’re using. Pergola designs can vary quite a bit depending on the materials being used, how tall the pergola is, and more.

So you just need to make sure that the dimensions match up properly. You want the structure to be sound and safe to use.

If you don’t have experience designing structures and determining structural stability, it’d be better to follow an established blueprint. You can find simple pergola designs online and use those to build your own pergola.

How High Should the Posts Be?

Generally, pergola posts are going to be between eight and twelve feet high. However, there isn’t a strict limit that says pergola posts can only be so high.

There might be rules and regulations in your area about building pergolas. Often, people have to get permits when they wish to build pergolas that are larger than a certain size.

So it’s common for people to stick to building pergolas with posts that are between eight and twelve feet high. It’s not that unusual to see taller pergolas under certain circumstances, though.

You might see taller pergolas that are attached to buildings. Pergolas might be taller when they’re being designed to match up with certain buildings for aesthetic purposes.

How Far Apart Should Pergola Beams Be?

The pergola beams are going to form the rafters. You need to make sure that these beams are a certain length apart to make things turn out right.

The most common spacing for pergola beams is between sixteen and twenty inches. So long as the pergola beams are spaced out somewhere in this range, all will work out well.

It should be noted that the spacing needs to be consistent, though. You don’t want to have one pergola beam spaced sixteen inches apart while other beams are twenty inches apart.

All of the beams should be an equal distance apart. When you’re building the pergola you should measure things carefully to ensure that everything is done right.

Take the extra time to measure twice just to be sure that the beams are spaced properly. It won’t take much extra effort and it keeps you from making mistakes.

What Size Carriage Bolts Should You Use?

You’ll be using quite a few carriage bolts when building a pergola. It’s important to buy the right size to get the best results.

Buying 10” carriage bolts will help you to get the job done. You can buy these carriage bolts from the hardware store easily.

What Size Screws Are Best?

Most people choose to use screws that are 6, 8, or 10 mm in diameter for pergolas. You need to use larger screws when building larger pergolas.

There might also be some differences based on the materials that you’re using to build the pergola. Some people go with different types of screws.

The best thing to do is to follow a blueprint and use the exact recommended materials. This will allow you to get the best results.

Make Good Choices

Now you should have the information that you need to make good choices. You want to choose the right sizes when buying various things for the pergola.

The first thing to figure out is the exact dimensions of the pergola that you’re building. You want to draw everything up so you can understand what beam and post sizes you will need to accomplish your goals.

From there, you’ll be able to choose the right screw sizes and get everything else that you need. You have the spacing information that you need and you should understand the basics of what you’re doing.

If you’re ready, you can proceed and build your pergola. Otherwise, you can choose to reach out for help if you’re not ready to tackle this project.

Some people don’t like having to build their own pergolas. So they choose to buy pergola kits instead.

This is a lot easier, but you’re not getting a bespoke pergola. If you need a custom pergola, there’s always the option of reaching out to professionals.

Doing so will be more expensive, but it might be worth it if you don’t have the time to tackle this project yourself. Weigh your options and then figure out what to do so that you can start enjoying having a pergola on your property as soon as possible.


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Sunday 3rd of December 2023

Hello, Ben. Nice articles, right along the lines of what I'm looking for at the moment. I have footers in the ground (in Minnesota) that are in place for a future pergola. The footers create, on centers, rectangle that is 14' x 16'. As I'm now trying to lay this out, my plan was to lay beams across the 16' front span and then rafters running perpendicular to and on top of the beams. For such a 14 x 16 pergola, would 6 x 6 posts be adequate (or should I go with 8x8s?). Would 2x10 beams be adequate (or should I go with 2x12s?) What about doubling up the beams. I'd also like to have 1-1/2 foot overhangs on the beams and rafters.

Consider all to treated southern pine.

Ay help or guidance is appreciated. Thank, Jay