# How Far Can a 2×10 Span? (Joist, Rafter, Beam)

Selecting the appropriately sized lumber for a project can take a lot of research and often depends on species and grade of wood, potential loads, plus how they will be used. Not all species have the same strength, and the grading often affects the distance they can safely span. Additionally, using them for a joist, rafter, or beam also affects the span. So, if you’re wondering how far a 2×10 can span, we’re here to help.

A #2-2×10 joist can span between 11’-5” and 18’-0”, as a rafter between 13’-9” and 21’-7”, and as a beam 3’-6” and 13’-0” or more. The span depends on spacing, lumber species, and grade, and for a beam, the lamination thickness, as well as numerous other factors.

In this guide, we’ll identify what span means, how far a 2×10 can span in different applications, and how far a doubled or tripled 2×10 can span. We’ll also discuss how far a 2×10 can be cantilevered. We reference the 2021 International Residential Building Code (IRC) for much of the information in this guide. Our goal is to provide you with the information you need for your project.

## Span Construction Definition

In the construction industry, span is the term used to identify the unsupported distance a structural member or component traverses or bridges between supports. It refers to the distance, gap, or space between supports that carry the structural piece. It typically is used when identifying the free or unsupported distance of a beam, joist, slab, floor, header, or rafter between structural supports such as posts, walls, or beams.

You may come across the terms single span, multi-span, long span, and even span-by-span in construction. Don’t let them confuse you, they are just ways to identify unique aspects of different structural spans.

Single Span: means the structural member – beam, joist, floor, slab, or rafter – is only supported, pinned, or fixed at its ends.

Multi-Span: commonly refers to a structural member spanning across multiple supports to minimize bending stresses. For example, a beam carrying a floor being supported at the ends and with equidistance intermediate posts along its length. The bean is multi-spanned, as is the floor being supported.

Long Span: identifies a construction method that typically results in buildings with unobstructed support free spaces greater than 100-feet, such as factories, warehouses, stores, sports arenas, and barns.

Span-by-Span: a term used to identify construction methods for erecting bridges or other large structures requiring multiple long spans often of precast, prefabricated or pre assembled components.

Free Span: typically, another term for span, it is the free or unsupported space provided between the supports of a structural component.

## Maximum Spans for Joists, Rafters and Beams Chart

The distance a joist, rafter, or beam can span depends on the wood species, grade of lumber, loads, and how they are used. Quite often, the distance a beam can span is also determined by the spacing of joists or rafters it will support, and vice versa. Additionally, the span of joists and rafters is affected by the spacing, typically 12”, 16”, 19-1/2”, or 24” between each other.

The International Residential Building Code (IRC) is used in most of North America as a guide for National, State, Provincial, and local codes. It is updated every 3 years, most recently in 2021, and identifies the maximum safe loads and spans for beams, joists, and rafters in an effort to minimize or negate structural failure and human injury or death. Before finalizing structural plans or beginning to build, it is best to check with your local Building Department or a Structural Engineer.

### Common Construction Lumber Species

The species of lumber available in your area commonly is what grows within inexpensive shipping distances. The further it is shipped, the greater the costs. Most lumber yards, however, carry a variety of construction lumber and can order in different species, usually at premium prices.

The IRC and the American and Canadian Wood Councils test and publish tables and information on maximum structural loads, spans, and standards for different species and grades of wood materials and products.

The lumber species most commonly used in construction are Southern Pine (SP), Douglas Fir-Larch (DF-L), Hemlock-Fir (Hem-Fir), and Spruce-Pine-Fir (SPF), while #2 is the most common grade used. It should be noted that other species are also tested, we’ve chosen the four species identified in the IRC which are most commonly used in construction.

### Southern Pine (SP or SYP)

A strong, durable wood composed of 4 major species of southern pine with similar qualities and appearance with overlapping ranges. The trees range from as far north as New Jersey and south along the coast into Florida. They reach westward into Missouri and Texas and through many of the southeastern states. Southern pine makes up about 37% of lumber used in the US. It dries quickly, absorbs chemical treatment and paint easily, and is used in all aspects of construction.

### Douglas Fir-Larch (DF-L)

One of the strongest and most durable species, it is known for its plate and nail holding ability and is a favorite of engineers and architects. It has excellent dimensional stability and high resistance to the forces of weather. It is used in single and multi-story residential, commercial, and industrial construction.

### Hemlock-Fir (Hem-Fir)

A highly versatile combination of Western Hemlock and Fir species known for its light coloring and weight, while still being strong, durable softwood lumber. Although excellent for structural use, due to its coloring and appearance, it is also used for millwork and molding.

### Spruce-Pine-Fir (SPF)

A lightweight versatile combination of lumber species often used for framing. Typically harvested from mixed stands of coniferous, making it easier to combine than separate the species.

While spruce has low resistance to decay outdoors, it does well when treated or used indoors. SPF is common across the continent making it an inexpensive choice for all aspects of residential, industrial, commercial, and agricultural construction.

Lumber is graded for stress use, non-stress use, and appearance. The important grading for construction use is stress test grading. 2” through 4” dimensional lumber is stress graded for structural use based on characteristics such as grain, knots, checks, and other deformities that affect its bending strength. Grading is standard and uniform across the industry, so the grades mean the same from Barrow Alaska to Brownsville Texas, and all points east and west in between.

• Select Structural (SS) – The highest and strongest grade, and can span the furthest. With a grain slope of 1/12, tight well-spaced knots, and few seasoning checks, it is used for all structural and carpentry applications, often where its blemish-free surfaces can be seen.
• No.1 or Construction Grade (#1 or #1&BTR) – Stronger than lesser grades, it has a grain slope of 1/10, slightly larger tight well-spaced knots, and few splits or checks. Commonly used for structural and carpentry purposes, including decking, railings, posts, shelves, and furniture.
• No. 2 or Standard Grade (#2 or #2BTR) – A strong grade with a grain slope of 1/8, it has more knots, blemishes, and occasionally some wane or bark edges. Commonly used for beams, framing, joists, rafters, trusses, lintels, and fencing. #2 does everything #1 or SS can do except span as far. Since it is less costly, it is typically the lumber of choice for framing and structural uses. It should be noted that #2&BTR does not mean #1. If the lumber is #1, it is stamped #1.
• No. 3 or Utility Grade – Has a grain slope of 1/4 and more splits, checks, larger knots, and more wane than the above grades. Typically used for light construction, studs, or ceiling joists where it disappears under drywall or sheathing. It is also used for bracing and shipping and packaging crates. Not used for beams, floor joists, or rafters.
• No. 4 or Economy Grade – Contains more splits, knots, knot holes, and other defects than better grades. The lumber doesn’t absorb paint or chemical treatment well. May be used for studs, concrete cribbing, bracing, or other temporary uses. #4 isn’t used for span and support purposes.

For purposes of comparison, we’ve generated the following span tables using #2 – 2x10s. It should be noted that beam span is dependent on the effective joist span length, which ranges from 6 to 18 feet in the IRC. The shorter the joist span, the greater the beam span allowable. The interior beam span is also affected by the number of floors and roof load unless it is a clear span using trusses. A beam supporting two stories instead of one typically has spans shortened by about 25%.

 Maximum Spans For #2 – 2×10 Lumber 2×10 Lumber Spacing Joists* Rafters** Southern Pine 12” 16’-2” 19’-5” 16” 14’-0” 16’-10” 24” 11’-5” 13’-9” Douglas Fir-Larch 12” 18’-0” 21’-7” 16” 15’-7” 18’-9” 24” 12’-9” 15’-3” Hemlock-Fir 12” 16’-10” 21’-0” 16” 15’-2” 12’-11” 24” 12’-5” 14’-10” Spruce-Pine-Fir 12” 17’-3” 21’-4” 16” 15’-5” 18’-5” 24” 12’-7” 15’-1”

Information from IRC 2021 – Tables R502.3.1(2) and R802.4.1(3)

** Rafter span based on 30PSF Snow Load, 10PSF Dead Load, and rafters not attached to the ceiling

 Maximum #2 – 2×10 Beam Span (40PSF Live Load, L/∆ = 360) Wood Species Beam Size Effective Joist Span in Feet 6 8 10 12 14 16 18 Maximum Beam Span Southern Pine 1 – 2×10 7’-0” 6’-0” 5’-5” 4’-11” 4’-7” 4’-3” 4’-0” 2 – 2×10 10’-4” 9’-0” 8’-0” 7’-4” 6’-9” 6’-4” 6’-0” 3 – 2×10 13’-0” 11’-2” 10’-0” 9’-2” 8’-6” 7’-11” 7’-6” Douglas Fir-Larch Hemlock-Fir Spruce-Pine-Fir 1 – 2×10 6’-8” 5’-10” 5’-1” 4’-6” 4’-1” 3’-9” 3’-6” 2 – 2×10 10’-0” 8’-7” 7’-9” 7’-0” 6’-6” 6’-0” 5’-6” 3 – 2×10 12’-6” 10’-10” 9’-8” 8’-10” 8’-2” 7’-8” 7’-2”

Information from IRC 2021 – Table R507.5(1)

## How Far Can a 2×10 Span

The distance a 2×10 can span depends on the wood species, grade, moisture content, spacing, and load parameters, along with other factors. Using it for a beam, floor joist, header, ceiling, or rafter also affects the maximum span. Doubled, tripled, or thicker laminations of 2x10s increase the load capabilities and the span distances too. Span values are drawn from the 2021 IRC, but it is advisable to check with your local building department or a Structural Engineer.

### Floor or Deck Joists

A floor or deck joist span depends on the spacing between joists and the loads anticipated, plus the wood grade and species. Typically, a dead load of 10PSF and a live or snow load of 40PSF are common, unless a hot tub or other heavy load is planned. For the loads identified, a DF-L SS can span 19’-1” with a spacing of 12” between joists, 17’-4” with 16”, and 15’-2” with 24” spacing. Choosing a different grade and species usually results in shorter spans – #2-Hem-Fir at 24” centers have span limits of 12’-5”, #2-SP 11’-5”, and a #2-SPF 12’-7”.

Headers have a few more factors affecting span than just species and grade of lumber, such as interior or exterior walls, snow load, number of floors, center bearing vs clear span, and building width.

A double 2×10 header of #2 lumber in a one-story structure can span from 9’-2” with one jack stud per end in a 12’ wide building, and 5’-3” with 2 jack studs per end for a 36’ wide building.

A triple 2×10 header will span 11’-5” and 6’-7”, and a 4-ply 2×10 header 13’-3” and 7’-8” in similar structures.

Adding a second floor decreases the spans as it increases the loads. A doubled 2×10 can span 5’-11” and 3’-7” for 12’ or 36’ building widths. A triple 2×10 header can span 7’-5” and 4’-6”, while the 4-ply stretches to 8’-6” and 5’-3” respectively.

### Ceiling

Ceiling joists have several additional factors that affect their span in addition to species, grade, loads, and spacing. Whether the attic space is uninhabited without storage or uninhabited with limited storage affects the span too. Turning an attic into a living space typically involves strengthening the floor, so the services of a Structural Engineer are recommended.

For an uninhabited attic without storage, all SS, #1, and #2 2x10s of common species of construction timber can span 26’ or more at 12” and 16” centers, except for #2 Southern pine which maxes at 25’-7” at 16” centers. At 24” centers, a #2-DF-L will span 23’-3”, a #2-Hem-Fir 22’-7”, #2-SP 20’-11”, and a #2-SPF 22’-11”.

Even #3-grade lumber will span between 16’-1” and 25’-2” depending on species and spacing. Using the attic space for limited storage reduces the spans, so check the local codes for distances.

### Rafter

Rafter spans depend on wood species, grade, spacing between rafters, snow or live loads, dead loads, and whether the ceiling is attached to the rafters or not. Rafters without an attached ceiling can span further than those with it attached. Additionally, the lower the snow or live load, the greater the span possible. Plus, if the spacing between is 12” the span is greater than if it is 24”, so keeping all the factors straight is important.

At 12” centers, rafters can span between 10’-7” and more than 26’ depending on species, grade, spacing, attached or unattached ceiling, and snow or live loads. At 16” centers, the spans are between 9’-2” and more than 26’. At 24” spacing, the rafter spans range from 8’-4” and 23’-9” depending on all factors.

### Beam

Beam span depends on the species and grade, as well as the effective joist span. The greater the joist span, the less the beam span. Additionally, a 2, 3, 4, or more ply beam can carry greater loads and span further than beams of lesser plies but similar depths.

A single #2-SP 2×10 beam can span between 4’-0” and 7’-0” if the joist span is 18’ and 6’ respectively. However, a #2-SPF 2×10 will only span 3’-6” to 6’-8” at those joist spans. Use a 3-ply #2-SP 2×10 beam and the spans increase to 7’-6” and 13’-0” for the same joist spans, and 7’-2” and 12’-6” for a triple 2×10 #2-SPF beam.

## How Far Can a Double 2×10 Span Without Support?

The distance a double 2×10 can span without support depends on its species, grade, spacing on center, load parameters, wet or dry service condition, and its purpose. A doubled 2×10 joist has different spans and conditions than a double 2×10 beam, header, or rafter. A double #2 – 2×10 header spans from 3’-7” to 9’-2”, depending on the number of stories and building widths, plus other factors. It’s always best to check all factors that can affect the span, or consult a Structural Engineer.

A double 2×10 beam’s span is dependent on species, grade, the spacing and span of the joists it supports, and the number of floors and load parameters. A 2 ply 2×10 beam of #2-Southern pine with a live load of 40PSF can span between 6’-0” and 10’-4” with a joist span between 6’ and 18’. One of DF-L, Hem-Fir, or SPF under similar conditions can span between 5’-6” and 10”-0”. Shorter joist spans mean longer beam spans, as do better wood grades, but heavier loads result in shorter beam spans.

Doubling or sistering a 2×10 joist is usually done to strengthen or repair an existing plank of the same dimensions, not extend its length. Joists may be doubled to turn an attic into a living area, to support a grand piano, or a hot tub. The species, grade, and spacing commonly affect the length, with a double #2-2×10 DF-L at 12” centers spanning 18’.

## How Far Can a 2×10 Cantilever?

The distance a 2×10 can cantilever depends on what and how it will be used, the spacing between joists, roof width, floor and roof live loads, ground snow loads, as well as grade, species, and other general factors. Typically, 2×10 joists at 16” centers can cantilever a maximum of 1/4 of their back span. So, one spanning 16’ should be able to cantilever 4’.

Having said that, though, Table R507.6 of the 2021 IRC limits a 16’ Southern pine to 3’-4” and DF-L, Hem-Fir, and SPF to 3’-3” for 14’ or longer spans with live loads of 40PSF. As the load increases, however, the spans decrease. Additionally, many local codes max cantilevers at 24”, so it’s best to consult your local building department or a Structural Engineer.

## How Far Can a Triple 2×10 Beam Span?

A triple #2 – 2×10 beam of Southern pine can span between 7’-6” and 13’-0” with a live load of 40PSF depending on the joist span. Using DF-L, Hem-Fir, or SPF and the span changes to 7’-2” and 12’6” under the same conditions. Switching to Western cedars or Redwood and the span ranges from 6’-11” to 12’-0”, again, depending on joist span lengths.

## Conclusion

The distance a 2×10 can span depends on many variables, including the depth of one’s pocket. A #2-2×10 joist and rafter max at 18’-0” and 21’-7” respectively, and a 3-ply beam at 13’-0” based on selected factors.

Change up the grade and load factors and the spans can increase or decrease. To stay in the safe zones, consult your local building department or a Structural Engineer. Hopefully, we’ve provided you with the information required for your project.

Written By: Yevgen

I'm a DIY nut, and the founder and chief editor here at Weekend Builds.
This site is a result of my DIY passion, and to share the joys I have experienced fixing, building, and creating things over the years.