Can I Use 2X6 For Floor Joists?

Choosing what size of lumber to use for your floor joists can be challenging. And if you're planning to use 2x6 lumber for your floor joist, we researched if you could use it. Here is what we found.

Yes, you can. However, there are still limitations on the maximum distance a 2x6 piece of lumber can span.

Keep reading to learn more about these limitations. In addition, we'll discuss how much weight 2x6 lumber can hold and if you can use it for the construction of other parts of your home.

We'll also cover the types of floor joists and whether you should use pressure-treated lumber. We'll also see if you can repair any floor joist damage by yourself.

House framing floor construction showing massive solid wood joists trusses. - Can I Use 2 X 6 For Floor Joists?

How Long Can A 2x6 Floor Joist Span?

The wood type, load specifications, spacing, and application all affect how far a 2x6 can span. Span rises as the spacing comes closer but falls as the loads rise. How far a joist could span is also influenced by the grade and wood species.

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Here is an elaborate list of 2x6 floor joist spans for different wood types and spacing:

  • Southern Pine
    • 12" Joist Spacing- 9'-11"
    • 16" Joist Spacing- 9'
    • 24" Joist Spacing- 7'7"
  • Spruce-Pine- & Hem-Fir, Douglas Fir-Larch,
    • 12" Joist Spacing- 9'-6"
    • 16" Joist Spacing- 8'-4"
    • 24" Joist Spacing- 6'10"
  • Western Cedars, Redwood, Red Pine, Ponderosa Pine
    • 12" Joist Spacing- 8'-10"
    • 16" Joist Spacing- 8'
    • 24" Joist Spacing- 6'10"

What Factors Influence The Span Of Your Floor Joists?

Building Frame at Construction Site.

These are the factors that you should consider when choosing the right floor joist size:

  • Spacing. The normal distance between joists is 16 inches, however, it can also be 12, 20, or 24 inches. The size of lumber used for the joists determines their spacing and their capacity to span a greater or smaller distance.
  • Load. Before choosing what size joist to use, you must be aware of the load that the floor must bear. Your floor must carry these two types of loads: 
    • Live Load: This is an estimate of the weight of temporary goods inside a building, such as occupants, furniture, appliances, etc. A home typically has a living load of 40 lbs/ft².
    • Dead Load: This measurement encompasses all of the structure's enduring components, such as the floors, walls, ceilings, etc. A residential building typically has a dead load of 10 lbs/ft².
  • Wood Species. The strength qualities of various wood species vary, with some having a substantially higher bending strength than others. Slow-growing species typically have more growth rings per inch and are, as a result, significantly stronger than fast-growing trees.
  • Lumber Grade. The strength of a piece of lumber increases with the number of flaws it has. Higher lumber grades will be stronger since they have fewer faults.

How Strong Is A 2x6 Floor Joist?

Up to 4 lb per linear-ft can be supported by a horizontally laid 2x6 with the large, 5.5" surface set flat. It will start to flex if the load weighs more than this amount. So, a 10-foot-long 2x6 would be able to support a consistent weight of 40 pounds before bowing.

However, this increases if the weight is directly on top of another supportive component or decreases if the weight is applied to the middle of the span.

A 2x6 put horizontally won't be able to sustain much weight before sagging or breaking. Although using a 2x6 flat can have advantages, and there are times when doing so is wise, it also does not support as much weight as alternative orientations.

Can You Use 2x6 Lumber For Other Parts Of Your House?

Interior view of a new house under construction with an open layout

Yes, you can. 2x6s come in a variety of spans for the same grades and species and can be used as rafters, floor joists, or ceiling joists.

If the deck is low enough to the ground that guard railing is not necessary, you can utilize 2x6 as deck joists. When using S-P-F 2x6 deck joists, the span cannot exceed 9'0" when the joists are at 16" on center and 9'10" with a 12′′ spacing.

What Are The Types Of Floor Joists And Their Pros And Cons?

An example of the use of I-beam from OSB

There are three types of floor joists used in residential construction. You can refer to the table below:

Floor Joist Type




Solid Lumber

Contiguous boards constructed of solid lumber called joists are typically harvested from old-growth trees. Things like species, the board size, spacing, and deflection all have an impact on their span distances. Although the availability of trees is running out, utilizing younger trees for the joists can lead to warped wood because solid lumber joists are still frequently used on construction sites.
  • last more time in a fire
  • typically the most affordable option for joists, though the cost will vary depending on wood species, the board size, and timber grade
  • harmful to the environment
  • span distance is short

Open-Web Floor Trusses

The top and bottom of this type of floor joist are made of 2x4 boards, and the middle is filled with a "web" of diagonal boards that are fastened together with metal plates. Because they eliminate the need to measure and cut openings for items like pipelines and electrical wiring, these trusses are popular with builders.
  • more durable design than I-joists
  • lengthier spans
  • able to accommodate electrical, plumbing, and HVAC without cutting
  • possess set lengths and cannot be reduced
  • costly


Because of their resemblance to the capital letter "I," I-joists, also known as TJI joists, got their name from it. The "I" is divided into various pieces composed of various materials. Frequently, the tops and bottoms are constructed from laminated veneers or wood.
  • extends longer than solid wood
  • lighter for simpler movement
  • quicker to fail in a fire
  • expensive

Every floor joist type has its distinct advantages and disadvantages; therefore, carpenters generally have a preferred floor joist choice even though they must be knowledgeable about all types of floor construction.

Should You Use Pressure-Treated Floor Joists?

Large stacks of cut timber logs at a sustainably managed pine forest.

Many homeowners choose pressure-treated wood when building decks, porches, and other outdoor buildings. However, you can choose not to use pressure-treated lumber for your floor joists in your crawl space.

Due to its pressure treatment, the wood is resistant to termites, rot, and decay, making it perfect for moist situations. Pressure treated lumber is required for joists in these situations:

  • the floor structure is 18 inches or closer to the ground
  • wood girders are 12 inches or closer to the ground

Most floor joists are made of pre-cut or dimensional lumber that this untreated. Hem-Fir, Douglas-Fir, Spruce-Pine-Fir, or Southern Pine are common varieties for joists.

Can You Repair A Damaged Floor Joist By Yourself?

Repair and replacement of wooden deck or patio with modern composite plastic material

Although it's not recommended, homeowners can occasionally fix issues with already-installed lumber joists.

Due to their complexity, floor trusses and I-joists should not be fixed or changed by the average person; instead, they typically need the help of a structural engineer.

Even with wood joists, significant breakage, drooping, cracks, and twisting necessitate a structural engineer's inspection and advice on how to fix the damage.

Final Thoughts

While you can use 2x6 lumber for floor joists, you have to be mindful of the span distance. So, if you have high-grade lumber and the load that your joists carry is light, then the allowable span of your floor joist may be long.

Also, fortunately, you can use untreated lumber for your floor joists. But if it's 18" or below closer to the ground, then using pressure-treated lumber is a requirement.

You can check out these other articles to learn more:

How To Fix Floorboard Not Resting On Joist

Why Is My Bathroom Floor Sinking?