Building a deck, floor, beam, or other structural platform may require heavier dimensional lumber. Much will depend on the orientation of the lumber, its species, grade, moisture content, and other factors. If you’re wondering how much weight can a 2×12 hold, we’re here to help!
A 2×12 on edge can support between 345 and 2765 PPL or more depending on span, species, grade, and other factors. Used flat as a shelf or ramp it can carry between 24 and 466 PPL or more depending on span and other factors. Depending on grade, species, and bracing, a single 2×12 post can support up to 2039 pounds depending on species, grade, span, and other factors.
In this guide, we’ll discuss how much weight a dimensional 2×12 can hold on edge, flat, and vertically as a post. We’ll explain compressive strength, the factors that affect lumber strength, and how pressure treatment affects wood strength. Plus, we’ll explore 2×12 beam load capacity and a 2×12 load capacity calculator. Our aim is to provide you with helpful information for your next project.
- How Much Weight Can a 2×12 Hold?
- What Does Affect 2×12 Lumber Load Bearing Capacity?
- How Much Weight Can a 2×12 Hold Vertically?
- How Much Weight Can a 2×12 Support Horizontally?
- What Is the Compressive Strength of a 2×12?
- How Much Weight Can a 2×12 Hold on Edge?
- How Much Weight Can a Pressure-Treated 2×12 Hold?
- 2×12 Beam Load Capacity
- 2×12 Load Capacity Calculator
How Much Weight Can a 2×12 Hold?
The load potential of a common softwood dimensional 2×12, like any lumber, depends on wood species, grade, span, spacing, moisture content, and even load duration.
Southern pine (SP) and Douglas Fir-larch (DF-L) have greater strength than hemlock or SPF (spruce, pine, Fir). However, their grade also affects their strength. Select Structural (SS) has the greatest strength, while grades #1, #2, #3, and #4 have less strength in that order. #1 and #2 are most often used for building and construction, although SS is used in visible locations or when its strength gives it the edge over other grades.
Used on edge as a floor or deck joist, rafter, or other support, weight is often shared with other members, and blocking prevents twisting. A 2×12 is actually 1-1/2” by 11-1/4” and has a cross-sectional area of 16.875 square inches (in²), so on edge, it is much stronger than smaller dimensional lumber.
Under the best conditions, an 8-foot northern Douglas Fir can carry a uniform load of up to 2765 pounds per linear foot (PPL), a 10-foot about 1400 PPL, a 12-foot almost 820 PPL, and a 16-footer approximately 345 PPL before deflection becomes excessive and the 2×12 could fail.
Orienting lumber so it is flat as a ramp or shelf is a weak orientation for any lumber. Like other dimensional lumber, the 2x12s thickness is actually 1-1/2”, the same as a 2×8 or 2×4. However, its greater width makes it more than 6 times stronger than a 2×8 in this orientation.
The amount of weight it can support will depend on the distance between supports, load placement, and any movement or momentum applied. A 2×12 northern Douglas Fir spanning 8 feet can support a center load of 24 pounds, a 196-pound center load if spanning 4 feet, and a center load of 466 pounds if spanning 3 feet.
The strength of a 2×12 placed vertically as a post or support often depends on the length, spacing, bracing, sheathing, and load sharing. A single 8ft Douglas Fir 2×12 used as a support post can hold between 1712 and 2039 pounds before buckling depending on grade and other factors.
Switching to Southern pine the load values change to between 1507 to 1951 pounds and if using SPF from 1505 to 1626 pounds under the same conditions.
What Does Affect 2×12 Lumber Load Bearing Capacity?
There are several factors that affect the load-bearing capacity of a 2×12. The wood species, grade, moisture content, and span are commonly used to determine strength.
Spacing between structural members, sheathing, load placement, and inertia or movement also need to be considered. It is recommended that a certified building professional review all plans where human safety is a concern.
Lumber is graded for strength or visual appeal. Strength grading assesses grain angle, size and number of knots, checks, splits, and wane.
Strength grades are Structural Select (SS) which is the strongest, followed by #1 or construction grade, #2 or standard grade, #3 or utility grade, and #4 or economy grade. SS, #1, and #2 are commonly used for construction. This grading system is standard across most of North America and based on scientific testing.
Visual or appearance grading looks at how clear of defects a piece of lumber may be, so how good it looks, regardless of grain angle or strength. Appearance grading is determined by individual mills or even stores and can combine SS, #1, #2, and #3 in the same appearance grade.
This grading system uses letters A through E to rank lumber from best looking to least desirable. Terms such as ‘Prime’, ‘Select’, ‘Superior’, ‘Quality’, ‘Choice’, and ‘Common’ are also often used as visual qualifiers too.
Softwood lumber from coniferous trees is commonly used for construction and hardwood species for furniture, cabinetry, and decorative purposes. However, historically, oak, maple, and other hardwood species were used for beams, posts, stairs, wall panels, flooring, and other purposes.
The most common softwoods used in U.S. and Canadian construction projects in order of strength are Douglas Fir, Southern pine, Hemlock-Fir, or SPF (spruce, pine, Fir). The different species vary in consistent strength based on grain, density, straightness, and other factors.
Moisture content in wood can significantly increase its weight and make it weaker. The moisture can cause the cells to expand which decreases its strength per unit area.
Most lumber is either kiln-dried or air-dried after milling and arrives at lumber stores and yards with a moisture content between 15% and 19%. However, humidity and precipitation can cause the content to be higher.
Wood in buildings is protected from the elements, so the moisture content will decrease to between 6% and 12% over time, making the lumber stronger by increasing the number of cells per unit area.
Homes that are climate-controlled year-round will maintain a more consistent internal humidity, whereas buildings that aren’t will be affected by humidity. Due to this fluctuation potential in moisture content, the design strength of lumber is commonly based on higher moisture content values to ensure safe building practices.
The unsupported distance a 2×12 plank traverses is its span. Span is affected by the load variables, number of stories, and building dimensions. All of which also affect wood selection and dimension.
The span also depends on whether the plank is doubled, tripled, or quadrupled as a beam or header, or single as a joist or rafter. The distance depends on the wood species and grade, plus moisture content, bracing, spacing between similar parallel components, blocking, and even sheathing.
Always check with the most current IRC (International Residential Building Code), your local Building Department, or a certified Structural Engineer to identify span. According to the 2021 IRC, the maximum span for a 2×12 joist is between 11’-0” and 25’-7” and the maximum for a 2×12 rafter is 15’-11” to more than 26’-0” depending on all factors.
How Much Weight Can a 2×12 Hold Vertically?
The vertical strength of a 2×12 depends on wood species, grade, density, and moisture content. Spacing between vertical members, blocking, and sheathing also impact vertical load potential too.
A 2×12 used as a single post will support less than a double or tripled post or a blocked and sheathed wall of 2x12s. Comparing the more expensive Douglas Fir with the less costly southern SPF will demonstrate the importance of species and grade.
Ochshorn’s wood column calculator is a helpful tool for identifying the amount of weight a 2×12 can hold vertically. An 8’ structural select (SS) Douglas Fir 2×12 can hold 2,039 pounds, doubling the post increases the load to 9,255, and tripling will carry 27,363. Switching to a #2 DF the load values drop to 1,712 for a single, 7,740 if doubled, and 22,620 if tripled.
Using a different species will also affect the load possibilities. Using southern SPF (spruce-pine-fir) lumber under the same conditions the SS will support 1,389 pounds singly, 6,323 doubled, and 18,822 tripled, while a #2 will carry 1,182 singly, 5,372 if doubled, and 15,927 if tripled. So, wood species, grade, and doubling or tripling of the post can make a significant difference in load capacity.
How Much Weight Can a 2×12 Support Horizontally?
A horizontal 2×12 on flat is the weakest orientation for any lumber spanning unsupported distances. The greater the distance, the lower the load ability, and the more noticeable the sag caused by gravity and the board’s own weight. Wood species, grade, and other factors, plus the placement of the load are important too.
Using a 2×12 as a shelf or ramp provides more than 6 times the load potential over a 2×8. Both boards are 1-1/2 inches thick, but the 2×12 offers 11-1/4 inches of width instead of 7-1/4 inches in the 2×8 upon which to spread the load. The placement of the load must also be considered. An equal load across the distance versus a center load can be telling when used for a ramp or shelf.
A northern Douglas Fir (DF) 2×12 spanning 8’ can support a uniform load of about 393 pounds but only a center load of 196 pounds under the best conditions before the sag becomes excessive. Switching to pine-spruce those load maximums change to 270 pounds and 135 pounds respectively.
Reducing the span to 4’ the DF can support 1,573 pounds equally distributed or a center-load of 786 pounds while the pine or spruce is only 1,089 and 544 pounds. Dropping the span to 2’ allows the DF to carry an even load of 6,292 pounds or a center load of 3,146 pounds, and the pine-spruce 4,359 and 2,179 pounds comparably.
What Is the Compressive Strength of a 2×12?
Compressive strength refers to the amount of force, load, or weight required to compress or crush a material. The compressive strength of a 2×12 depends on wood species, grade, density, moisture content, plus other factors. The orientation of the wood and grain to the applied load also needs to be considered.
A Douglas Fir with a moisture content of 12% has a compressive strength parallel to the grain of 6,903 PSI and about 769 psi perpendicular to the grain. A pine-spruce, though, has a compressive strength of 5656 psi parallel to the grain and 725 psi if perpendicular. Hardwood typically has greater compressive strength than softwood too.
How Much Weight Can a 2×12 Hold on Edge?
A 2×12 on edge as a floor, deck, or ceiling joist or as a rafter or beam has differing load parameters. The unsupported span, spacing between common parallel members, species, grade, and other factors also must be considered. Additionally, the building codes restrict spans and load maximums to ensure safety.
Under ideal conditions, a 16-foot 2×12 Douglas Fir can hold 345 PPL (pounds per linear foot), approximately 820 PPL at 12 feet, around 1400 PPL at 10 feet, and 2765 at 8 feet. Using pine or spruce instead, those values change to 237 PPL, 563 PPL, 972 PPL, and 1900 PPL respectively before deflection becomes excessive.
How Much Weight Can a Pressure-Treated 2×12 Hold?
Pressure-treated lumber commonly refers to dimensional softwood lumber that has been pressurized and chemically treated to resist insects. The brown or green coloring is for outdoor use and identifies proximity to grade and the type of chemical used. Other common colors for interior use are pink/red for a fire-resistant coating and blue for moisture-resistant lumber.
The amount of weight a brown or green pressure-treated 2×12 can carry depends on wood species, grade, moisture content, and load variables. Since moisture content tends to be higher in freshly treated lumber, a wet-service factor is applied which decreases its maximum load strength by approximately 10% compared to its dry strength.
However, most building codes include a safety factor so load failure maximums aren’t reached. Thus, for residential purposes, a pressure-treated 2×12 will hold as much weight as a comparable untreated 2×12.
2×12 Beam Load Capacity
A 2×12 beam or girder may be below or level with the joist or rafter framework of a floor, deck, or roof. The beam capacity usually depends on the wood species, grade, spacing between supports and joists, and other factors. Total typical loads range from 40 to 90 PSF (pounds/square foot) of combined live and dead loads.
Main living areas commonly have a design value of 40 PSF live load combined with a dead load of 10 PSF. Sleeping or upper-story rooms tend to have a 30 PSF live load and 10 PSF dead load. The dead load usually ranges from 5 to 20 PSF depending on variables.
Live load ranges from 15 to 70 PSF or more and can be affected by use, purpose, wind, snow loads, and various other factors too. All load values should be checked by a certified Structural Engineer for accuracy based on individual designs.
A single #1 pine-spruce 2×12 beam spanning 16’ can support a maximum uniform load of 237 PPL (pounds per linear foot), 563 PPL over 12’, and 1900 PPL over 8’. Doubling the beam width and the values change to 475, 1126, and 3800 PPL respectively.
Tripling increases the load variables to 712, 1689, and 5700 PPL, and quadrupling takes the maximums to 950, 2252, and 7601 PPL. Changing to Douglas Fir, Southern pine, or Hemlock and the load capacity increase even more.
2×12 Load Capacity Calculator
Using online calculators makes determining spans and loads easier. There are numerous span calculators but only a limited selection of load calculators.
Jonathan Ochshorn’s wood column load calculator and wood beam load calculator for Architects and Builders are very helpful for calculating loads. They allow you to input wood species, grade, and other information for a working load value. However, the values and design should always be checked by a certified Structural Engineer or your local Building Department.