Lumber prices aren’t going down, so selecting the best material for your project can really pinch the budget. Whether building a deck, shed, or framing a wall, knowing the strengths of different dimensional lumber is helpful. A 2×6 is less expensive than a 2×8, so if you’re wondering how much weight can a 2×6 hold, we’re here to help.
A 2×6 can carry 53lbs per linear foot on edge according to the Building Codes. Longitudinally it will support 662 to 998lbs as a column, or 7061lbs sheathed and blocked in a wall as a stud before buckling. Flat-face up, a 2×6 is rated for 4lbs per linear foot before deflection, although it will support more weight.
In this article, we’ll discuss how much weight a 2×6 can hold, factors that affect the load-bearing capacity, and which is the strongest orientation for the lumber. We’ll also explore the effect of pressure treatment on a 2x6s strength and if a 2×6 will weaken over time. Hopefully, you’ll have a better idea of whether a 2×6 will do the job or not.
- How Much Weight Can a 2×6 Hold?
- What Does Affect 2×6 Load Bearing Capacity?
- How Much Weight Can a 2×6 Support Vertically?
- How Much Weight Can a 2×6 Hold Horizontally?
- What Is the Compressive Strength of a 2×6?
- How Much Weight Can a 2×6 Hold on Edge?
- How Much Weight Can a Pressure-Treated 2×6 Hold?
- Does a 2×6 Get Weaker Over Time?
How Much Weight Can a 2×6 Hold?
The amount of weight a 2×6 can hold depends on its orientation. A 2×6 used as a stud (vertical), rafter (diagonal), truss (horizontal), or flat-face up as a ramp or decking means stresses are applied differently to the wood structure. The strength of the wood, the direction those forces are applied, the duration, moisture content, type of wood, and the location of any support all affect the strength and load capacity.
Lumber is viscoelastic and orthotropic. It has characteristics that are both elastic and plastic-like when forces are applied – in other words, it stretches or flexes with a load and returns to its original position when the load is removed. It can flex independently radially through the rings, tangentially with the rings, and longitudinally end to end – so, it’s orthotropic.
The longer a load is applied though, the more difficult it may be for the wood to return to shape – a shelf with books for example. Additionally, if the load, force, or stress is too great, the wood may not only become deformed, it may fail, shear, or break.
The thickness of the wood and grain orientation are also important when addressing flexing in the direction of the forces applied. Grain orientation is one of the characteristics used when grading lumber for strength.
The thickness and width of the wood affect its strength and deflection. The cross-sectional area of a 2×6 is (1.5”x5.5”) 8.25 square inches (in²) – a 2×4 is only (1.5”x3.5”) 5.25 in². The cross-sectional area is important when determining the strength of a board in any directional orientation. Downward forces, or weight, will cause a 2×6 to flex, twist, or buckle in different directions depending on its weakest surface or thickness, and any defects such as knots, checks, and cracks.
Compression forces applied vertically through the length of a 2×6 will commonly cause it to flex on its thinnest profile. A 2×6 stud, sheathed, blocked, and at 16”-centers as in standard wall construction, will support close to 4 times as much as a similar 2×4 stud, or 7061-pounds of compression before buckling. However, a single 2x6x8’ used as a support post will only support between 525 and 998-pounds depending on species, grade, and moisture content before buckling.
The distance a 2×6 can span between supports, its dead load and live load expectations, plus wind force and seismic requirements, are all available in the local building code, or the IRC (International Residential Building Code – 2021). The greater the combined live and dead, the shorter the allowable span.
According to the Codes, a 2×6 on edge with the weight pressing through 5.5” of wood will support approximately 53lbs per linear foot. So, an 8-foot length will support about 424lbs. However, a short span 2×6 on edge can support between 600 and 900lbs depending on wood species, grade, and other factors.
An 8-foot 2×6 oriented flat-face up, with the force traveling through 1.5” of wood, is rated to support about 4lbs per linear foot or 32lbs on the 8-foot span before bending, depending on species and other characteristics. Spanning shorter distances though will also increase the amount of weight the plank can support. A 2×6 on flat can support between 80 and 120psi of compression, so it will support more than 4lbs per linear foot.
A 2×6 on edge is more rigid than one on flat, and the slope of a diagonal rafter increases the cross-sectional area, and thus the rigidity of the member. When looking at a piece of wood, the strength, mathematically, is based on the square of its depth. A 2×6 on edge has a square of 30.25, while one on flat has a square of 2.5, so the strength of the one on edge is significantly stronger.
Distributing the weight between parallel joists on edge will share some of the load, allowing a 2×6 on edge to span up to 12’-6” with 40 and 50psf loads, and 11’-4” with a 60 psf combined live and dead load. Using 2×6 stock for rafters the span can reach 18’-0” with a 30 psf load, and 20’-8” for ceiling joists supporting 15 psf.
The spacing, grade, and wood species affect the load configurations and span, so always consult the Codes or a Structural Engineer. Additionally, the angle a rafter rests at increases the vertical cross-sectional area, which can also increase its load capacity.
What Does Affect 2×6 Load Bearing Capacity?
Wood or lumber are divided into hardwood and softwood families. Softwood is the primary material used for construction, and hardwood commonly used for furniture, trim, and flooring. The load capacity of wood, whether hardwood or softwood, is affected by the wood species, grade of lumber, type of load, span, and moisture content in the wood.
Wood species commonly used in construction today tend to be from softwood families. They are usually lighter in weight, straighter, and faster growing than many hardwood species. Softwoods are rated by species based on characteristics such as good workability, strength, small knots, ability to hold screws and nails, which are important for construction. According to the 2021 IRC, Douglas fir-larch (DOUG FIR-L) is the strongest overall, followed by Hemlock-fir (HEM-FIR), then Southern yellow pine (SYP), with mixed spruce-pine-fir (S-P-F) finishing up the list.
Lumber is graded as structural or for appearance. Structural is based on natural characteristics observed in the wood that affect its strength, while appearance looks at how pretty the wood is – heartwood, sap pockets, planer skips, and torn grain – not necessarily how strong.
The US and Canadian softwood industries visually grade and stamp lumber for the construction industry based on natural characteristics inherent in the wood. The characteristics include the presence of bark or wane, location and size of knots, the slope of the grain in relation to the long axis of the wood, plus the size of checks, splits, and shakes.
The lumber is identified as Structural Select (SS), No. 1 or construction grade, No. 2 or standard grade, No. 3 or utility grade, and No. 4 economy grade. The strength of No. 1 and No. 2 do not differ greatly, just the appearance, and are often graded as ‘No. 2 and Better’.
Type of Load
There are three types of loads that act on structures – vertical, horizontal, and longitudinal. Vertical loads include dead, live, and impact loads. Horizontal loads include wind loads and seismic loads, and longitudinal loads include braking and tractive forces. In most situations, vertical and horizontal types of loads against a 2×6 or structural member are considered when determining the strength and load-bearing ability.
The dead load is often the first load considered. It is the weight of materials attached to or resting on structural members. The weight doesn’t normally move, so it is considered permanent or stationary – walls, flooring, wall sheathing, siding, masonry veneer, roof, beams, some permanent furniture, and fixtures, etc. It is calculated by volume and unit weight and reflects the weight of the building.
Live loads or imposed loads are loads that are moveable or moving, and so change with time. They are not considered to have any impact or acceleration force. People, pets, movable furniture, and machinery are part of the live load. The weight may stay still for a period of time but isn’t fixed in that location.
- Snow load is sometimes considered a live load as it is often temporary in nature. It can also lead to an impact load when it slides and strikes other structural components.
- Wind loads are horizontal forces that usually have a prevailing direction. The velocity and force of the wind, along with the shape and size of the structure, determine the wind load.
- Seismic loads depend on the location of the building. They include horizontal and vertical forces. Most modern buildings are designed to reflect some seismic activity.
The distance a 2×6 can span depends upon the wood species and grade, and on its structural purpose and load expectations. The maximums for different species, grades, and purposes are identified in the Building Code. However, decreasing the unsupported distance a 2×6 spans increases its resistance to applied forces. In other words, it increases its carrying ability.
The moisture content of wood affects its strength. The less moisture, the stronger the wood, with dry wood being up to 50% stronger than greenwood. Air-dried lumber averages 12 to 13% moisture content (MC), while kiln-dried (KD) can have an MC as low as 6 to 8% – especially for material used for millwork.
To prepare green lumber for the building market, many mills will kiln dry to 19% (KD19), which means the lumber will average closer to 15% MC. It should be noted though, that MC greater than 15% adversely affects the strength of lumber used for construction.
Framing lumber may arrive at the job site with an MC between 15 and 20%. However, by the time the framing is ready to button up, the MC usually has dropped to 12 to 13%.
How Much Weight Can a 2×6 Support Vertically?
The amount of weight a 2×6 will support depends on the wood species, grade, moisture content, use, and how it is supported. A 2×6 used vertically as a stud in a sheathed wall with blocking at prescribed intervals will support 7061lbs before buckling.
A single 2×6 as a column, though, will support between 525lbs (a wet service #2S-P-F) and 998lbs (a dry service SS-DF-L) depending on species, grade, and moisture content before failing. The ‘2×6 Wood Column Compression Strength’ table below provides more information.
How Much Weight Can a 2×6 Hold Horizontally?
A 2×6 can be used horizontally on edge or on flat. The amount of weight one can support in those two orientations differs greatly, and also depends on the span, duration, and species of wood. The amount of weight a 2×6 will support before it begins to sag or deform, twist, crack, break, or shear also differs.
Building Codes restrict weight based on use within construction practices and set the limits based on spans and loads that won’t cause a support member to bend or fail. Based on the Codes, a 2×6 on edge and properly supported and blocked will safely support 53lbs per linear foot. That means a 6-foot 2×6 should support 318lbs and an 8-foot length 424lbs across that length without showing any stress. Having said that though, a 2×6 on edge can support 6 to 900lbs or more but may show some signs of stress such as bending or cracking.
A 2×6 on flat offers a wider surface but less thickness than one on edge and is rated for about 4lbs per linear foot before it will begin to flex. At that weight, an 8-foot length could support about 32lbs before sagging. Adding supports along its length will increase the amount a 2×6 on flat will carry. For example, many outdoor decks are finished with 2×6 boards which span joists set at 24”-centers and support significantly more than 4lbs across their length.
What Is the Compressive Strength of a 2×6?
The compressive strength of a 2×6 depends upon its species, grade, moisture content, span, location, use, and other factors. The bearing strength of softwood used in construction needs to be determined to ensure it can carry the loads for the duration expected. Stress tests have been done and calculations performed to determine different wood species compressive or shear strength.
The Building Codes identify the acceptable ‘maximums’ for deflection or bending to ensure public safety. It should be noted though, that an individual 2×6 will support more than the Codes recognize. The aim, however, is to prevent structural failure, not encourage it by building to the breaking point.
Compression strength is also based on the direction the force is applied to a piece of timber. Force can be applied against the wood longitudinally (end to end), parallel to the grain (2×6 on edge), or perpendicular to the grain (flat-face up). The amount of force needed for structural failure varies depending on the characteristics of the wood, as well as indoor (dry use) or outdoor (wet use) too. The table below identifies the compressive strength of 2x6s based on the parameters identified.
|2×6 Wood Column Compression Strength
Fc(psi) = 1,000 Emin (psi) = 400,000 8.5ft
|Species||Grade||Parallel to Grain
|Perpendicular to Grain
* Information from Jonathan Ochshorn—Structural elements calculators (jonochshorn.com)
How Much Weight Can a 2×6 Hold on Edge?
The amount of weight a 2×6 on edge can hold depends on the wood species, its characteristics, duration, and span. The Codes allow for a 2×6 joist to support 53lbs per linear foot, which means an 8.5-foot length could support approximately 450-pounds across that length. Although a 2×6 will support more before failing, the aim is to prevent it from failing.
Shortening the span may also increase the amount the wood can support. As noted in the ‘2×6 Wood Column Compression Strength’ table, the compressive strength applied parallel to the grain (or on edge) can range from 1097.01psi to 1649.1psi depending on all factors.
How Much Weight Can a Pressure-Treated 2×6 Hold?
Pressure-treated wood is commonly lumber intended for exterior use, so its strength is limited to the species and all associated characteristics, plus a ‘wet service factor’. The treatment process infuses water-borne chemicals into the wood using pressure. Once the wood dries, it has a similar weight-bearing capacity to the untreated species, it’s just better protected against insects and rot.
When calculating the strength of pressure-treated wood, a maximum duration factor, according to the American Wood Council, of 1.6 should be used – which really only affects impact loads. Additionally, incised pressure-treated wood is derated by 20% for compression strength perpendicular to the grain. The incising process cuts or presses holes or slots into the wood for deeper chemical penetration, which can weaken its strength.
For structural purposes, according to the Codes, pressure-treated lumber on edge, like untreated wood, will support 53lbs per linear foot. Longitudinally, the lumber will support between 600 and 900lbs, and perpendicular to the grain about 4lbs per linear foot. However, the compressive strength parallel to the grain is between 1097 and 1484psi, and between 80 and 110psi perpendicular to the grain, so a 2×6 will support more weight than the Codes allow for.
Does a 2×6 Get Weaker Over Time?
As cut wood dries it becomes up to 50% stronger than greenwood, a process that can take days to a matter of months. From there, however, the process can go downhill. Wood can become weaker due to applied stresses, overloading, rot, bugs, moisture, sunlight, and other factors.
But, and this is an important but, wood that is protected from the elements, such as stick-framing, tends to show little change in strength or mechanical properties over time. However, as wood ages, it can become brittle, which structurally normally only affects impact strength, something that isn’t a common concern in most structures.
Exposed or exterior 2x6s can become weaker over time due to rot, bugs, UV deterioration, and other factors. Most 2x6s used for interior, dry, or protected construction should maintain their structural strength over time unless they are subjected to overloading and other unusual stresses.
The strength of a 2×6 depends on a variety of factors. In general, though, a 2×6 stud, sheathed and blocked in a wall will support more than 7000lbs. Individually as a post or column, it will support between 660 and 998lbs. A 2×6 can withstand compressive forces between 1097 to 1649psi parallel to the grain, and 81 to 122psi perpendicular to the grain.
Additionally, pressure treatment doesn’t affect the strength of the wood overall, however, since it is used outside and exposed to moisture fluctuations which do decrease its strength, it is rated slightly less.
Hopefully, you have a better awareness of the characteristics of 2×6 lumber, its strengths, and weaknesses, plus the different forces the timber can withstand.