How to Determine Shed Floor Joist Spacing [Easy Guide]

When I was building my first shed, I was curious about the proper shed floor joist spacing. When doing so, I ran into several questions regarding what lumber size I should use and what is the best approach to getting the job done correctly.

So, what is the proper shed floor joist spacing? Spacing joists in your shed 16-inches on center will give you a firmer feel with less bounce and increase the load capacity of the floor. While you may be OK with the joist span at 24 inches the floor will be maxed out to the limits.

Many other factors and considerations can arise when constructing your first shed, below are some of the other questions and problems I encountered during the construction of my first shed. Hopefully, this brief guide can make this project a walk in the park for you.

How Far Apart Should Floor Joist Be for A Shed?

So, how far apart should floor joist be for a shed? The answer is that it depends on several factors. The amount of weight that will be on the floor is going to be a big factor when determining your joist size and joist spacing. Also, you may have building codes to adhere to that can play a role in your overall joist spacing as well.

Some of the biggest considerations you need to take into account with joist spacing are factors including the lumber size, lumber grade, load, and wood species. In most cases, pine will be your wood of choice used in construction.

Building codes are usually structured based on engineering requirements. In many circumstances, 16 inches would be your standard spacing for shed floor joist, but this is just a rough guideline.

Two options that arise could be your wider 24”’ and your narrower 12” options for spacing. 2x8s are used frequently for these projects. 2×8’s come standard at 1-¾ inch thick. In this situation, your floor joist will be required to be 12 or 24 inches apart on center.

Other factors also come into consideration when constructing the framework for your shed. Let’s dive into some of those.

What Size Floor Joist Do I Need?

The most common option for your floor joist is your standard 2×6. A 2×8 will provide a few additional benefits and have some advantages, but overall, the 2×6 is the most commonly used and budget-friendly option for constructing your shed floor.

To get more exact numbers you can use tables and calculators to help you narrow down a more precise measurement. When using a calculator, enter the necessary information about the floor width, floor length and the on-center separation. This measurement will only give you the number of joists you need. It’s a good start, but more is necessary.

How Can I Calculate the Floor Joist Spacing for My Shed?

A calculator can help you with the basic part of the equation. Now we need to handle the actual joist spanning/spacing part of the equation. To start with, here’s a great calculator that can calculate the joist spacing based on species of wood, joist size, and joist spacing.

In addition, this calculator will also allow you to calculate the total number of floor joist needed to complete your shed based on the measurements you provide.

Other considerations can also come into play such as span and lumber grade. After making these determinations, you should be ready to crunch and dive into the numbers for your spacing with more ease.

2×4 or 2×6 or 2×8 for a Shed Floor: Which is Better?

Determining what size dimension lumber to use for your shed floor may also be intimidating. Should you use a 2×4, 2×6 or 2×8? In most scenarios, you will use a 2×6 or 2×8, but there are exceptions.

The size also depends on the load. What do you plan on putting in your shed? If you intend on storing hefty objects, you need a larger floor joist such as the 2×6 or 2×8. If you are storing lightweight items, then you can go with a smaller dimension.

Note, the 2×4 option is rarely used unless your plans include a very small shed with no intentions of heavy storage.

So before making the ultimate decision on which size, ask yourself, “what do I intend on using this shed for, and what do I plan on storing inside the shed?” This should help bring you to the right selection.

What if My Shed is Constructed on A Concrete Slab?

If you build a shed on a concrete slab, you do not need to worry about the construction and planning for your floor joist. If, however, your shed is on a different foundation such as concrete piers, deck blocks, concrete blocks, or skids then you can stick with a 2×6 for optimal results.

How Far Can You Span a 2×6 Floor Joist?

Again, this depends on the factors of species of wood, grade, and the intended load on the wood all come into play.

However, when running SPF 2×6 floor joists into the floor joist calculator referenced above, you get a maximum span of 9 Feet 8 inches with a minimum bearing length of 3 inches at each end on 12” centers. This a rough guideline. The rule of thumb is 6-foot span with a 2×6 on 16” centers. The heavier the load, the closer together the joists should be..

How Far Can You Span a 2×8 Floor Joist?

Apply the same rules and make sure you add all necessary calculations to the equation. With everything being equal your maximum floor span using SPF 2×8 will be 12 feet 8 inches with a minimum bearing length of 4 inches at 12” centers. The rule of thumb is 8-foot span with a 2×8 at 16” centers.

How Much Weight can a 2×8 Hold?

The amount of weight a 2×8 can hold is going to depend on the span of the joist and the distance to the next joist. Since you can span 13′ with a 2×8 SPF joist on 16 inch centers, but you ultimately decide to only span 8 feet with your joist on 12 inch centers, the weight bearing increases. Doing this is going to increase the weight the 2×8 can hold from a maximum load of 30 lbf/ft² to 60 lbf/ft²; a significant increase!

Variables come into play with maximum loads. For example, other items such as the total spacing, the floor material, and if additional mid-length supports are added affect your maximum values. Another consideration is dead load vs live load. A stationary load is different from one that moves.

Take your time, make sure you consider every angle and aspect of the project to ensure you are completing the project in a safe, compliant and up to code manner.

Should I use Pressure Treated Wood for a Shed Floor?

You may be wondering should you use pressure treated wood for a shed floor? Yes, pressure treated lumber is the best option for your shed floor. Keep in mind, however, that this doesn’t make it a requirement. You can still use non-pressure treated wood.

The problem you could run into if you don’t use pressure treated wood for your shed floor is how long it will last.. A floor close to the ground won’t last as long using non-pressure treated wood.

Be sure also to use ground contact pressure treated wood for any framing that will touch the ground. Pressure treated lumber is also essential for exposed areas of the shed that may be exposed to the weather and water.

Related Questions

Can I use 2×4 For My Shed Floor? It’s only recommended to use a 2×4 floor if you are constructing a tiny shed with no heavy-duty storage use planned in the future.

Conclusion

Many variables come into play when deciding your shed floor construction and joist spacing. However, following general guidelines and checking with the building department is always a great start. Base your decision on all the factors discussed in this post, as well as how you plan to use your shed. Best of luck on your project!