Deck Joist Sizes, Runs, and Spacing (Full Guide) (2023)

Homeowners looking to build a deck often have questions about joist size and spacing. This article will answer all your questions so you can start building the deck of your dreams!

The International Residential Code (IRC) determines the size of your deck joists. IRC covers the maximum spans of wooden beams, from 2×6 to 2×12. The IRC also specifies the size and span of the deck joists based on the spacing between the joists, typically 16 inches on center, but can vary between 12 and 24 inches.

This post covers everything you need to know about deck joist sizing and span. We'll go over ways to measure your deck joists and give you some tips on how to repair undersized joists.

What is span and spacing between deck joists?

A roof beam span is a distance between two support points. Deck joist spacing is typically 16 inches on center, but can range from 12 to 24 inches. The deck joist spacing you choose depends on several factors, including the size of the deck, the joists, the deck foundation, and the type of deck you plan to install.

IRC also has minimum requirementsbar sizes. In most cases, your deck beams must be at least a certain size to support a payload of 40 pounds per square foot. Deck joists are measured in inches by thickness (for example, "a deck joist is a 10-inch floor joist"). If you're not sure what size deck joist to use, don't worry, we'll discuss it in the next section.

Deck joists are generally 6, 8, 10, or 12 inches wide, with 8 or 10 inches being the most common sizes. Deck joists are available in dimensional lumber lengths from 8 to 16 feet.

As discussed in this article, the span of deck joists is important in the construction of decks that support heavy loads. Deck joist spans depend primarily on how much weight the deck will support. Decks with hot tubs require bracing and closer joist spacing.

Exterior Coverings of the 2018 International Residential Code (IRC)

The IRC is the authoritative document for all home construction in the United States. It is updated every three years and the 2018 edition was published in November 2017. The IRC covers everything from the minimumfloor joistsSizes and distances to the allowable roof loads.

One of the most critical areas of IRC when it comes to deck bars isSection R507. This section discusses traditional lumber sizes, spacings, and spans. Table R507.6 provides maximum spans for different sized wood joists depending on their location, type, size, and spacing.

If you are a homeowner looking to build a deck, you need to understand the IRC joist span and size requirements.

What types of wood are available?

Many homeowners are looking for a great resource to help them with deck joist sizing and span. These are the types of decks available.

southern pine

Southern pine is a good choice forfloor joistssince it is strong and resistant to contraction and deformation. Southern pine has several advantages over other woods, including its low cost. The main disadvantage is that it is susceptible to rot and termites.

douglas fir larch

Douglas fir is the most common wood used for ceiling beams and joists. It is strong, resistant to shrinking and warping, and is available in long lengths. The main disadvantage of Douglas fir is that it can be expensive compared to other woods and is not readily available in some places.

hem-for

Douglas fir is not readily available in some areas, so hemlock pine (also known as 'hemlock fir') is a good alternative. This wood has properties comparable to Douglas fir and can be used in most situations.

spruce pine spruce

Fir is the cheapest type but has the lowest strength rating. It's a good choice for regions where moisture is likely to be a problem, as it doesn't warp or break down quickly. Spruce should not be used in areas with high humidity or snowfall, as it can quickly become damaged.

Secoa

Redwood is a species of wood native to North America. It is one of the most popular types of wood for decking because it is strong and weather resistant. Redwood can also bestained or paintedto match any color scheme. Redwood decks last longer than other decks made from less expensive wood species.

western cedars

Western cedar is a species of wood native to the Pacific Northwest. They are often used for decks because they are strong, weather resistant, and naturally resist rot. Western cedar decks can last up to 30 years with proper care.

Ponderosa-Kiefer

Ponderosa pine is a very suitable wood species for deck construction. It has high strength, weather resistance and durability. It has always been popular for construction because it was available at low cost.

One downside for some homeowners is that ponderosa pine often contains knots or other blemishes that require additional work during deck construction. There are also fewer color options than redwood or cedar decks, so painting may be necessary if you can't find what you need in the natural form of that wood species.

red pine

Red pine is a native wood species to the eastern United States. It is often used for decking because it is strong, weather resistant, and inherently resistant to rot. Red pine decking can last up to 30 years with proper care.

What is treated wood?

Wood that has been treated with chemicals to prevent rot, insect damage, and fire is called "treated wood." There are three types of joint treatments:

• CCA (chrome copper arsenate)
• ACQ (alkaline copper quaternary)
• MCA (copper and mercury arseniate)

Althoughtreated woodIt does not cost much more than traditional untreated wood, it is much more harmful to the environment. Arsenic is a poison that contaminates water supplies over time.

Pressure-treated cypress and redwood do not pose the same hazards as regular treated lumber, making them a much better option. The main reason why cypress and redwood are not used for housing is that they are expensive.

How wood is classified

The following information is to be considered for homeowners seeking information on deck joist size and span. If you're not sure what wood you're buying, you should be able to find a white tag pinned to the board with the grade and type of wood marked on it. If the tag falls off, the wood has a black stamp.Holzwith variety and variety.

The four grades of wood include Select, 1, 2, or 3. Wood rated 1 is of better quality than 2 or 3. The highest grade, Select, is free of knots and other weakening blemishes. Selected woods can carry heavy loads.

Per IRC R507.2.1, decking wood must be grade #2 or better and must be preserved in accordance with Section R317 or an approved inherently durable wood termite protected as required by Section R318.

Explanation of the load of the floor joist

You should consult your local building codes when seeking information on the size and span of deck joists. Deck joists can typically support a certain weight depending on the quality of the wood, the type of wood, and the dimensions of the joist. Deck joists are typically spaced in 12-, 16-, or 24-inch increments.

How far can the ceiling beams span?

The length of a joist defines the joist span of the deck. For example, the maximum span of a Douglas Larch, 2×12 carrying a payload of 40 (PSF) and a dead load of 10 (PSF) at 12″ spacing is 18 ft 3 .

Is there a standard span for ceiling joists?

Because every home is unique, there is no standard joist span. There are too many variables to set a standard for floor joist spans.

Any wingspan over 20 feet is rare, as can be seen infloor joistsdistribution tables. It is hard to findMarcoLumber over 20 feet long, which is typically more expensive when available. Contractors will install a beam to break 20 foot beam spans.

Maximum light for southern pine

Maximum light for Douglas Fir-Larch, Hem Fir and Spruce-Pine-Fir

Maximum light for Redwood, Western Cedars, Ponderosa Pine and Red Pine

Joist Spacing for Composite Decks

Composite decking is a great alternative to traditional wood due to the need for different spacing between joists. The composite deck should not be more than 16 inches apart. Before building your deck, check with your professional contractor to make sure you are using the correct joist spacing for your composite.

Deck Stabilizers Explained

An overhang is a deck section that extends beyond the support beams. You can use this to create a screened-in porch or extended seating area. The maximum outrigger spacing is 4 feet 6 inches, but it's best to keep it within 2 feet for most decks.

Cantilever Max Chair for Southern Pine

MaxCantilever for Douglas Fir-Larch, Hem Fir and Spruce-Pine-Fir

Max Cantilever para Redwood, Western Cedars, Ponderosa Pine y Red Pine

Diploma

Deck joist sizing and span can be a tricky subject, but we've done our best to make it simple. You can use these tables to determine deck joist sizes, spacing, and runs based on wood species.

Check out our other articles on decks and deck railings:

• What size deck joist do you need?
• Tips for maintaining your wooden terrace