How Much Space Between Joists For Decking?

Decks are the perfect addition to any outdoor living space, but you don't want to overspend on your decking, do you? We gathered all the best online sources to help you decide the proper spacing between your deck joists, and to make sure you get the most value out of your investment.

Standard spacing between deck joists is 12 to 16 inches. Most people prefer 16 inches, which is sufficient for comfortable and stable walking. The closer the spacing is, the more stable the deck will be. But this means you will have to spend for additional joists, which could be unnecessary.

The question of how much space you need between the joists of your deck may come up when you are considering building a new deck. To help you figure out if the space you have is adequate, keep reading.

Constructing a Wooden Flooring of a Terrace - How Much Space Between Joists For Decking

Why Do We Need Space Between Joists?

Joists carry the weight of your deck and a lot of it. If you want to add more strength to your home, you'll want to increase the number of joists. More joists mean closer spacing.

However, the spacing between joists isn't a given. And you should leave as much space or as little between joists as possible at your discretion.

Although the spacing between joists affects how much weight a deck can support, the overall structure of the deck is the most important factor when it comes to structural strength.

Similarly, factors like the type of lumber you use, the number of joists in the deck, and the amount of cross-bracing can also play a role in how much weight your deck can handle. 

How Much Space is Needed?

A new wooden, timber deck being constructed

Most homes have deck joists spaced 16 inches apart. This spacing is generally sufficient for most applications. In fact, most times, if the home has larger spans or the floor is intended for heavy-duty use, it can be a good idea to have joists spaced even closer.

Needless to say, if the joist spacing gets wider than 24 inches, the joist can sag and buckle over time. To compensate for this, you will need to increase the thickness of the deck boards to take up the extra load.

If you want to be on the safe side, you can check your local building codes to see what the minimum spacing should be. 

What to Do if the Joists Start to Buckle?

A new wooden, timber deck being constructed. it is partially completed. a drill can be seen on the decking.

As the weather warms up, you may notice your wood floors, and joists are starting to buckle. A number of different factors can cause this, including changes in humidity levels and temperature, and even the amount of weight that is placed on your floor.

This is why it’s important to maintain the health of your deck by sealing the joists with joist tapes to keep them looking their best and protect them from potential problems.

Joist tapes are also available to protect your joists from moisture and rot. They also help keep your joists dry, which equates to providing additional support to the floor structure. 

Click here to see this joist tape on Amazon

Can you Increase/Reduce the Space Between Joists?

If you're in the design phase, you can modify the spacing between joists on the deck to achieve a desired result or make it easier to install the deck.

If you have a contractor do the installation, they may be able to adjust the joist spacing during installation. 

However, if you are modifying the existing joists in order to cut costs and use the lumber for other purposes, you may be required to get a permit from your local building department.

Your local building department will need to approve your plans before they will issue the permit. They will want to make sure that the joists do not interfere with the support beams and the load-bearing capacity of the structure.

Watch the video below for a comprehensive explanation of joist spacing:

How Many Joists Do I Need for a 12x12 Deck?

A deck is a flat surface, typically built of wood, that supports a structure above ground level. If you want to build a deck, you need to know how many joists you need to support it. 

A joist is a horizontal piece of wood that keeps your deck in place. It is usually made of lumber and serves as the base for a deck. A joist is a beam that runs from one end of your deck to the other.

Needless to say, in order to create a sturdy structure for your deck, you will need to determine the number of joists you will need.

Typically, you will need to use 10 joists spaced 16 inches on center spacing for a 12x12 deck. This would require 10 joists to span the entire length and width of the deck.

Can Deck Joists be 24 Inches on Center?

There is no exact rule for joist spacing, but there is a standard that is practiced for both residential and commercial structures.

The most common spacing is 16 inches, with 24-inch spacing used when a larger deck area is required.

This will help ensure that you get quality decking and prevent issues down the road. Also, you don't want to deal with your local building inspector or county officials. They might not allow a deck with a joist spacing that is more than what the building code requires.

Do Joists Need Cross-Bracing?

When a deck floor joist wears out over time, it can cause unevenness in the floor. This unevenness can create a floor that feels "saggy" or "bouncy" underfoot.

If your floor seems to sag or bounce underfoot, it could be because your floor joists are sagging or may have developed a weak spot in the center.

Cross-bracing is often used to stabilize these floors, and it can be installed in the space between the joists. It adds a new layer of strength to the deck floor by preventing the joists from buckling under the weight of people going to and fro. 

terrace deck construction - man installing wpc composite decking boards

What Size Joists are Best for Decking?

In order to have a solid deck, you need to have a firm foundation. In most cases, you’ll want to use any of the following standard joist sizes: 2x6, 2x8, and 2x10.

A 2x6 joist is the minimum number of joists required in order to have a solid deck. It is considered the minimum size, as it provides enough strength to support the deck and its components.

However, there are many other factors that determine what size joist is best for your deck.

When designing your deck, you’ll want to have a look at your local building codes to see what size joist you can use.

It is also a good idea to consult a structural engineer. This way, you will know what is the best size joist for your deck.

What is the Best Timber for Decking Joists?

Pressure-treated wood is a good material for most decks. It is inexpensive and has proven itself over decades of use. However, you should consider how the wood is treated before you use it.

Some wood treatment products contain chemicals that may leach into the ground and contaminate the water supply. If you have a backyard pond or a garden with a lot of soil, you may want to look for alternatives.

In addition, if you choose pressure-treated timber, make sure you are only buying treated wood from companies that are certified by the United States Department of Agriculture.

Certified companies are required to meet certain standards, including testing the wood for toxicity and other harmful substances.

Alternatively, softwoods such as cedar and redwood are very strong and durable. As long as you select the right species, these timbers are better options for your outdoor deck.

Blurred abstract wide selection of pressure treated lumber, studs, wood trim and row of flatbed carts. Defocused lumber section of hardware store in America.

What is the Best Grade of Pressure-Treated Lumber?

The grade of wood you choose for your home will depend on a variety of factors. These factors include the intended purpose, cost, durability, availability, and ease of use.

For most structural applications, you'll want to go with the "select structural" grade (sometimes called the SS grade).

This is the highest quality grade, but it's also the most expensive. Select structural grade lumber comes from the highest quality trees. It is treated with chemicals to help it resist insects and rot.

This special lumber is available in all the standard lengths that you'll need for your project. 

While most homeowners choose SS-grade lumber for their decks, they should be aware that not all applications require the same level of structural strength.

For example, if you're building a temporary structure, then you can opt for lesser-grade lumber. 

Specialty grades can add a lot of interest to any project, and they can also be very expensive.

Final Words

Constructing a Wooden Flooring of a Terrace

We have collected some of the best resources available on the web about proper joist spacing. We hope that this will help you choose the correct spacing between your deck joists. With these tips and suggestions, you'll be well on your way to a gorgeous, relaxing deck that looks amazing but doesn't break your wallet.

You might also like the following supplemental articles:

How To Find Floor Joists Under Hardwood [Various Methods To Try]

Can You Sand A Deck After It Rains?


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