2×4 vs 2×6: What’s the Difference?

Building sheds, cabins, garages, and houses, although a challenge, can be a lot of fun. Once you’ve decided on the plan, you need to determine the best material for what you’re building. Selecting 2×4 vs 2×6 lumber for framing is one of the first steps, and the choice depends more on their differences than the similarities.

A 2×4 is actually 1-1/2” thick by 3-1/2” wide and a 2×6 is 1-1/2” by 5-1/2”. The greater width makes the 2×6 stronger and heavier, so walls are thicker and heavier too. Both sizes can be used to frame walls, but thicker walls may mean higher R-values and construction costs.

In this guide, we’ll look at 2×4 and 2×6 framing material, some key points of comparison, and their differences. We’ll discuss when it’s best to use each, identify the pros and cons of 2×6 exterior walls, and compare 2x4s vs 2x6s vs 2x8s. Our goal is to help you determine which is better, 2×4 or 2×6, for your project.

What is 2×4 Lumber?

A 2×4 is typically milled from a variety of coniferous species for a plethora of uses by the construction industry. It was initially rough cut to 2” by 4” and would dry to a range of smaller dimensions. The rough-cut lumber had squared edges that often split, and the grain would feather to cause splinters when handled.

Today, the lumber is cut when drier, and then planed, edges rounded, and sometimes sanded to a uniform industry-wide 1-1/2” by 3-1/2” dimension, making it better for construction. The boards are available in different lengths, such as 88” and 92-5/8” stud length, 8’, 10’, 12’, and 16’, and even 20’ and 24’ lengths upon request.

When selecting 2x4s, check how they are graded, some are graded for construction strength (#1, 2, 3, or 4) and others for appearance (A, B, C, D), or both. The cost per plank varies based on grade and appearance, so choose the best for the task.

Most framing lumber is #2-grade or better (#2-BTR) and doesn’t need to be pretty as it will be covered. If making furniture or an exposed partition, appearance-grading may be better or use square-edge 2×4 lumber.

What is 2×6 Framing Lumber?

The standard dimensions for 2×6 framing lumber is 1-1/2” by 5-1/2”, and are commonly available in 92-5/8”, 8’, 10’, 12’, and 16’ lengths. The planks are sawn from softwoods like pine, fir, spruce, and hemlock, and planed and sanded to the uniform dimension. Based on different characteristics, the lumber is sorted into grades. and marked with their grade and species, with #1 and #2 typically being used for construction.

A 2×6 is 2-inches thicker or wider than the 2×4, offering greater strength and more space for insulation, plumbing, soundproofing, and HVAC ductwork. It is commonly viewed as an upgrade in construction as the lumber is more costly.

Some building codes now require 2×6 framing for exterior walls as well as interior plumbing walls. So, the 2×6 is becoming more common in residential construction.

Selecting 2x6s for framing affects the depth of windows, doors, and insulation, as well as the overall interior space. Standard windows and doors are manufactured for 2×4 framed walls, so expect to pay more for deeper window boxes and sills plates.

Additionally, every 6 linear feet of 2×6 wall eats up 1 square foot of floor space. For an 8’x12’ shed, that adds up to 6.67sqft of floor space and for a 25’x40’ home a loss of almost 27sqft.

2×4 vs 2×6: Key Points

 

Comparing 2×4 framing to 2×6 framing is a matter of differences, not similarities. Strength and use depend on wood species, grade, moisture content, and other factors. So, if they are the same species and grade of wood, the 2×6 has more wood for support, making it stronger. Check out the table below for a comparison of key points.

*PLF – pounds per linear foot

What Is the Difference Between 2×4 and 2×6?

Choosing which lumber is best to use when building can be challenging. Both 2x4s and 2×6 are used to frame houses and other structures and are basic dimensional softwood lumber available at most lumberyards and building supply centers. They are used as studs to frame exterior and interior walls, and also used for joists, headers, and rafters. However, there are some significant differences, and it is the differences that determine which is best for your project. Always check with a Structural Engineer or your building department prior to construction.

Dimensions

A 2×4 is actually 1-1/2”x3-1/2” in width and depth while a 2×6 is 1-1/2”x5-1/2”. Both are commonly available in 92-5/8” stud length, 8’, 10’, 12’, and 16’, and can be ordered in 20’ and 24’ lengths.

Framing Strength

The framing strength of any lumber depends on its species, grade, moisture content, type of load, spacing, and several other factors, plus its planned use. 2x4s and 2x6s are common stud materials used for construction. A 2×4 stud or column can support between 369 and 636-pounds depending on wood species and grade, and a 2×6 between 579 and 998-pounds.

According to the IRC-2021, 2x4s at 24” O.C. can support a roof-ceiling assembly or one floor of equal height without a roof assembly. At 16” O.C., 2x4s can carry one floor and a roof-ceiling or attic living space. 2x6s can do all that at 24” O.C., and at 16” O.C. they can support 2 floors with a ceiling-roof or attic living space. Additionally, 2×4 studs are limited to supporting roofs spanning 32 feet or less, while 2×6 stud walls can support greater roof spans.

Interior Wall Studs

Interior stud walls may be load-bearing or non-load bearing. Load-bearing walls typically support and transfer loads from upper floors or the roof structure to the foundation, and also act as partition walls. They are normally 2×4 framing which maximizes square footage unless they are a plumbing wall, in which case they are of 2×6 construction. Non-load bearing walls commonly act as partition walls used to divide the floor space into rooms and are usually framed with 2x4s.

Exterior Walls Framing

Exterior walls can be 2×4 or 2×6 construction. The thinner framing increases interior square footage while the deeper 2×6 framing allows for thicker insulation and stronger walls. Exterior walls carry upper floor and roof loads, so some local codes require 2×6 framing.

Additionally, 2x6s can be spaced at 24” O.C. for single-story structures, which decreases the number of framing studs. When structurally sheathed and blocked as a stud wall, a 2×4 can support 1820 lbs and a 2×6 of similar lumber can support 7061 lbs.

Another issue is the location of the ‘dew point’ – where moisture may occur when warm moist air meets a cool exterior barrier or wall. With 2×4 framing the dew point is close to the exterior of the wall but nearer the middle of the wall with 2×6 framing. As a result, moisture may occur inside walls during heating or cooling periods, especially if the exterior wrap doesn’t breathe.

Floor Joists

Floor joists carry live and dead load weights that can vary with location and use. The wood species, grade, spacing, and other factors also affect the strength of both 2x4s and 2x6s, especially in relation to the distance they can span. 2×6 joists can span living areas from 5’-7” to 12’-6”, depending on the variables.

A 2×4 cannot be used as a joist in a living space. They may, however, span between 5’-5” and 7’-11” at 12” O.C. – depending on the variables. They are commonly used for porch or stair landings, porch pads, or ground-hugging decks.

Rafters

Rafter spans depend on wood species, grade, loads, and other factors. A 2×4 rafter can span between 4’-5” and 11’-6”, and 2×6 rafters can span from 6’-6” to 18’-0”, depending on all the variables.

Insulation R-Value

The depth of the wall channel between studs determines the thickness and R-value of insulation that can fit between the studs. The 3-1/2” deep space between studs in a 2×4 wall will hold battens between R-13 and R-25, while the 5-1/2” deep cavity between 2x6s will hold between R-19 and R-39. The thicker wall also allows for 2-1/2” of rigid insulation at the headers for a better thermal barrier.

Basement Walls

Finishing or framing basement walls is commonly done with 2×2, 2×3, or 2×4 studs to maximize floor space. The foundation walls typically carry the house loads, so most walls aren’t load-bearing, making heavier 2x6s overkill unless it’s a plumbing wall. Some contractors prefer to use blue-treated (Borate Pressure-treated) 2x4s, lumber that has been treated for use in damp areas to prevent mold and mildew growth and resist termites and other damaging insects.

Beam

Beams are typically used to carry other structural members such as joists and walls over a larger expanse like a basement, loft, or even window and door openings. The span is affected by load factors, wood species and grade, and even the width of the building. Additionally, the spacing and span of joists being carried also affect the beam size and span.

A double 2×4 beam can span 42-inches if the width of the structure is 20’ or less and only has a roof-ceiling structure above. Increase the width to 36’, and the span drops to 29-inches. A single 2×6 beam can span between 2’-1” and 4’-7”, 3’-3” and 6’-11” when doubled, and 4’-6” and 8’-6” when tripled as a deck beam. As a double 2×6 header beam, the span is between 25 and 73-inches depending on load factors.

Shed Walls

Most sheds are small structures used for storage and don’t need to be insulated, so 2×4 framing is common. The narrower framing maximizes floor space, whereas 2x6s eat it up – both an 8’x12’ and 10’x10’ shed lose 6.67 sqft of space. Structurally, there isn’t any reason to use the larger dimensional lumber as 2x4s will easily carry the roof loads.

Deck Framing

Deck framing often refers to joist layout. The spacing and span of the joists affect beam placement and span, as do other load factors. 2×6 joists at 12” O.C. can span between 7’-11” and 9’-11”, at 16” O.C. between 7’-1” and 9’-0”, and at 24” O.C. from 5’-9” to 7’-7”. 2x4s are not typically used for deck framing, although they may be used for railings, landings, and as deck boards. 2x6s are also used for railings, stairs, and decking.

Decking

Pressure-treated 2x4s and 2x6s can both be used for decking. Each will span perpendicular to joists at 24” O.C., and 16” O.C. when laid diagonally. The choice is often a matter of aesthetics, time, and money.

2x6s are wider, so have fewer gaps and cover the same area with fewer planks, requiring less time. 2x6s are about 40% more expensive than 2x4s, but the savings in lumber and time usually make them the preferred decking choice.

Weight

The weight of any wood depends on its species, density, moisture content, and treatment, and is often identified by board foot measure (FBM =1”x12” x12”) or by pounds per linear foot (PLF). Kiln-dried lumber often has a moisture content between 6% and 15%, pressure-treated lumber less than 19%, and freshly felled green or wet wood between 75% and 200% depending on relative humidity.

Southern yellow pine (SYP) is heavier than most other species of dimensional construction grade lumber, so if using Douglas fir, hemlock, or SPF the weight will be less. Some boards will feel lighter than others in the same stack due to where they were cut on the log, location in the stack, moisture content, and relative humidity.

A 2×4 of SYP has the approximate weight of 2.74 PLF if green-wet, 1.3 PLF if kiln-dried, and 2.1 PLF if pressure-treated. The approximate weight for a 2×6 SYP is 4.58 PLF for green-wet, 1.97 PLF for kiln-dried, and 3.2 PLF for pressure-treated lumber. So, the weight of an 8-foot 2×4 can range from 10.4 to 22-pounds, and a 2×6 between 15 and 37 pounds – based on contributing variables.

Cost Difference

Lumber is a commodity, so prices can vary from day to day, region to region, and store to store, and also depends on species and grade of lumber. A quick canvass across the U.S.A. shows price differences of almost 20%, and one city in the mid-west had a similar range between its three lumber stores, so shop around.

The cost of framing lumber in my area is $6.23 for a 2x3x8’, $7.98 for a 2x4x8’, a 2x4x92-5/8” stud is $7.98, and a 2x4x88” stud is $7.85. A 2x6x8’ is $13.85 and a 2x6x92-5/8” stud is $11.98. That’s a difference of $5.87 per 8’ board! So, using 2x6s instead of 2x4s will increase the framing cost by more than 40% on lumber alone, which may be the reason many prefer 2x4s.

When to Use 2×4 vs 2×6

Building single-story framed structures is typically done using 2x4s, which at 16” O.C. usually exceed code requirements for strength. Most interior walls, including basements, are also framed with 2x4s to maximize floor space.

Plumbing walls, however, are commonly made with 2x6s to ensure there is enough room for wastewater and feed pipes. Additionally, some interior walls may use 2×6 construction to allow the passage of HVAC ductwork.

Some regions require 2×6 exterior framing for the higher R-value or to support heavier snow or wind loads. Some builders will use 2x6s at 24” O.C. if local codes allow to achieve greater R-values and to reduce costs by using fewer pieces of lumber, but most contractors prefer the structural framework and strength of studs at 16” O.C. Structures with a second story also typically require 2x6s for exterior and load-bearing walls due to their greater strength.

Pros and Cons of 2×6 Exterior Walls

When designing and building anything, there are always pros and cons to consider when selecting materials. Framing material is no exception, so unless your local building code requires 2×6 exterior walls, the choice is yours.

Pros

Cons

2×4 vs 2×6 vs 2×8

Comparing dimensional lumber for residential construction projects usually depends on the differences. A 2×4 is actually 1-1/2” by 3-1/2”, a 2×6 is 1-1/2” by 5-1/2”, and a 2×8 is 1-1/2” by 7-1/4”, making a 2×8 more than twice as wide as a 2×4. The cost of an 8-foot 2×4 is $7.98, a 2×6 is $13.85, and a 2×8 is $18.98, so if framing at 16” or even 24” O.C., the stud cost alone is telling.

2x6s and 2x8s are typically used for joists, headers, beams, and rafters, whereas 2x4s are commonly used for studs and rafters. The 2×8 is stronger and will span further than a 2×6, which spans further than a 2×4. The actual spans differ with wood species and grade, as does the price.

A 2×4 stud will support 369 lbs to 636 lbs, a 2×6 between 579 and 998 lbs, and a 2×8 between 762 and 1317 lbs depending on grade, species, and other factors. Framed exterior walls that are structurally sheathed and blocked have greater strengths based on stud dimensions. In such a wall, a 2×4 can support up to 1820 lbs, a 2×6 7061 lbs, and a 2×8 about 4000 pounds more.

Thicker walls mean either enlarging the overall square footage or losing interior floor space. Additionally, a 2×8 wall is significantly heavier than a 2×4 wall. Plus, most windows and doors aren’t manufactured for the thicker walls, so more material and labor will be needed to finish them.

Wall construction techniques and materials are changing and often reflect the move to reduce lumber and energy costs. The potential R-value of the thicker lumber is higher, but recouping the additional framing costs may not happen in your lifetime. Consider using 2×8 plates with staggered 2×4 framing to decrease costs while achieving greater thermal rewards.

Which Is Better 2×4 or 2×6?

Choosing between 2×4 or 2×6 framing is a matter of structural requirements, budget, and aesthetics. Unless building codes require framing with larger dimensional lumber, 2×4 framing at 16” O.C. will do the task as well as 2x6s or 2x8s. The smaller lumber also maximizes interior floor space and requires less expensive doors and windows.

The smaller 2×4 is easier to mill from second or third-growth forests than the larger 2x6s or 2x8s, resulting in better quality. Even though the lumber disappears inside a wall, many 2x6s have large knots, bark, or wane which can make some construction uses difficult. Another consideration is weight, a 2×4 wall is lighter to lift and place than larger dimension stud walls.

To achieve greater R-values, many builders are using advanced building practices, including increasing the insulation on the exterior of the wall. To reduce the cost and due to the poor quality of 2x6s available today, some builders are using staggered 2×3 studs with 2×6 or 2×8 plates and others use 2x4s for the exterior support wall portion and a non-structural finger jointed 2×3 wall on the inside for greater savings on budget and energy costs, and for sound transfer reduction.

Whether building heated or unheated single-story structures, 2×4 framing is all you need. However, if you plan to spend a lot of time heating or cooling your home, thicker walls allow for greater R-values and greater savings on utility costs. Don’t expect, though, to recoup the extra lumber costs for a couple of decades. Deeper window and door openings may improve the aesthetics, but that is typically a matter of personal preference, as in most cases is the choice between 2x4s or 2x6s.