How Much Gravel Do I Need for a Shed Foundation?

A gravel shed foundation for sale in NY, PA, NJ, DE, and MD.

Thinking about buying or building a backyard shed or storage building?

Before you start your project, you’re going to want to think about providing a solid and level foundation for your shed. Not planning properly for your shed site prep is likely to cost you time and money down the road.

Planning for your gravel shed foundation

A gravel shed foundation is a job you may be able to tackle yourself. (If you do, be sure to read our step-by-step guide on how to install a gravel shed foundation.) It’s important to plan ahead and collect all the necessary equipment and supplies before you begin. In this article, we’ll think through the different components that will be part of your project.

Of course, if the project gets out of your depth, you can always hire a professional site preparation company to level and prepare the shed foundation for you!

Clearly, the most important part of the project is the gravel itself, and we will try to answer the question, “How much gravel do I need for a shed foundation?” There are a number of variables that we will examine further down, but for a simple answer, you will need approximately 3 to 4 cubic yards (about 5 tons) of gravel for the average shed foundation.

Workers building a gravel shed foundation in PA

Supplies for building a gravel shed foundation

Before you rush out to buy gravel, there are a few different building materials required for a gravel shed foundation. They are:

  • Treated lumber for the perimeter of your shed foundation.
  • Rebar for fastening the corners of your lumber perimeter.
  • Woven landscape fabric weed barrier
  • Gravel! (Isn’t that a surprise?)

Since it’s sitting on the damp soil, you will want to choose a lumber that is treated to be in contact with a lot of moisture. Make sure the lumber you choose is rated for GC (Ground Contact). 4”x6” is generally a good size of lumber for your shed foundation perimeter.

It’s a good idea to use 1/2” rebar or a similar fastener to connect the corners of your lumber.

When it comes to the gravel, you will want to use a size that can be compacted to make a firm foundation, while also being permeable enough to let water soak through. The goal is to avoid both runoff and puddling. ¾” drainage stone is an excellent choice for your shed foundation. It’s also a good idea to add a fabric weed barrier beneath the gravel. This will give your gravel shed foundation more overall stability by separating the stones from the dirt below and help prevent pesky plants from sprouting around your building.

A gravel shed foundation company working in PA, NY, and NJ

Calculating the size of your shed foundation.

Before you figure for how much gravel you will need to purchase, it’s important to calculate how large your shed foundation will be. As a rule of thumb, your gravel shed base should extend at least 12” further than each side of your shed.

Site Preparations, LLC installing a gravel shed foundation

For example, if you are building your shed foundation for a 10×12 structure, you should make it at least 12×14. This will allow water running down the side of your shed and dripping off the eaves to drain away easily. If the eaves of your shed are extra-long, you will want to extend the border of your shed foundation accordingly.

In addition to planning the width and length dimensions of your shed foundation, you will also want to calculate the necessary depth. In general, 4” to 6” is a good depth range for a gravel shed foundation.

How much gravel do I need for a shed foundation?

Now we get to the big question! How much gravel do I actually need for a shed foundation? The answer will of course depend on the size of the foundation that you calculated in the last steps. Gravel is usually sold by the ton or the cubic yard. A cubic yard of gravel is 27 cubic feet and weighs roughly 1.4 tons. For ease of calculation we will use cubic yards.

To determine the amount of gravel you will need for your shed foundation first calculate the square footage. In the example diagram shown, a 12×14 shed foundation, the square footage is 168. Next, multiply the square footage by the depth of gravel. If we use 6” of gravel, or 0.5 feet, our cubic footage is calculated as 168 x 0.5 = 84 cubic feet. Divide the number of cubic feet by 27 to find the number of cubic yards needed. In this case, 84/27 = 3.11 cubic yards of gravel or about 4.5 tons should do the trick.

Diagram of how much gravel is needed for a shed foundation
A site preparation contractor installing a gravel garage pad
Installing gravel for a shed foundation in PA

Let’s look at several examples to get an idea of how much gravel each shed foundation will need. We’ll assume each shed foundation is 6” deep with gravel.

8×12 storage shed – this is a popular small prefab storage shed size.

  • 10x14x0.5 = 70; 70/27 = 2.6 cubic yards or 3.6 tons of gravel

12×18 storage shed – this is a medium size backyard storage shed.

  • 14x20x0.5 = 140; 140/27 = 5.2 cubic yards or 7.3 tons of gravel

24×24 modular garage – this would be a large foundation for the placement of a two-car modular garage.

  • 26x26x.05 = 338; 338/27 = 12.5 cubic yards or 17.5 tons of gravel

As you can see there is a fairly wide range of possible sizes for a gravel shed foundation, each demanding a different amount of gravel. With this guide, though, you should be able to make a good estimate.

Tips for Proper Installation of Your Shed Foundation

The actual installation of your shed foundation deserves an entire article of its own. However, here are a couple other tips to remember.

You should level the ground beneath your shed foundation before placing your gravel. Once you’ve marked out the corners of your future shed pad, you can use a 2×4 and a level to check the grade.

Your site should be perfectly level before you install the gravel. For a more detailed breakdown on the steps in this process, read our article about how to level ground for a shed.

A site preparation contractor installing and gravel shed foundation
A shed foundation company installing gravel for a shed foundation in PA

Once your gravel is in place, make sure you compact and level it properly. Compacting the gravel is an optional, but recommended step, because it helps to identify and eliminate soft spots in your foundation.

As you compact, make sure the gravel is level over the entire surface of your shed foundation. Higher gravel on the edges of your foundation can cause the floor of your shed to sag and bounce over the years.

While it’s not the most complex construction project you will ever see, getting your shed foundation right is an important first step in your backyard upgrade project. From figuring out how much gravel you need, to putting the final touches on your new building, it’s important not to cut corners. You want to get your money’s worth out of this investment! If you want to make sure your shed foundation is installed correctly, consider hiring a professional site preparation contractor!

All the best with your shed project!

Storage shed on a gravel foundation prepared by Site Preparations, LLC

Read about 7 common mistakes made when doing ground preparation for a shed

32 thoughts on “How Much Gravel Do I Need for a Shed Foundation?

  1. Site Preparations LLC says:

    George, if you run the calculations we suggest in the article, you should need 5-6 cubic yards (7-8 tons) of gravel if your foundation is on level ground.

  2. Paula Horne says:

    So if I calculated correctly, I’ll need 8 cubic yards of gravel for an 8×20 shipping container foundation. How many tons needed (11?) Thanks

  3. Site Preparations LLC says:

    Paula, you should only need about 3 cubic yards (4.2 tons) for an 8×20 foundation with 6″ of gravel. (8x20x0.5)/27 = 2.96
    Hope that’s helpful!

  4. Site Preparations LLC says:

    Hi Holly, for a 12×40 run-in, we’d recommend going 5″ deep with the stone. So you would need about 12 tons.

  5. Christian P. says:

    What lengths for 4×6’s should I get for a 10’x12’ shed? And if it going to be two rows deep (12” with qty 2, 4×6 edge down), how many cubic yards of gravel will I need?

  6. Justin says:

    The foundation I planning to build is on a slop and the lowest point will be about 2 below level. Do I have to fill in all 2 feet with gravel or can I save some money and fill it in with soil and then 4 inches of gravel? If soil is ok, what kind of soil?

  7. Site Preparations LLC says:

    Justin, if you do fill in with soil, just be mindful of the weight that it will be supporting. Adding a loose soil runs the risk of settling over time; it’s more difficult to tightly tamp loose soil than crushed stone. That being said, it can be done if you compact the soil tightly.

  8. Mike says:

    Is it ok to put a 8×10 shed with a gravel base on an uneven slope over a septic drainage field. I don’t want to dig holes and think this would be a good alternative.

  9. Site Preparations LLC says:

    Hi Mike,
    We’d recommend completely avoiding the septic drainage field. Even with a gravel shed foundation, the instability of the soil is a major risk.

  10. Colleen says:

    So a shed that is 12×16 you need 14x18x.05=126~27=4.66 cubic yard = 7 tons is this correct

  11. John says:

    I am planning on placing a prebuilt 12×24 or 12×16 shed in the middle of a field, where there is a solid shelf of rock that is even with the surface of the field. There may be 2 to 4 inches of variation in level on this surface. Can I just put a thin covering of gravel on top of this surface to even it out? Digging won’t be possible to level the rock. Any sugestions? Thank you!

  12. Site Preparations LLC says:

    Hi John,
    The only concern we’d have is whether the gravel will eventually work its way off the rock with the slight grade variation. Alternately, you could see about placing a shallow lumber perimeter on top of the rock and anchoring it into the rock in some way (not sure how hard the rock is…rebar stakes might work or you might need a dedicated masonry anchor). Just some ideas…hope they help!

  13. Mark says:

    Do you see any problem with the shed sitting about 2″ lower inside the surrounding 4×6 timber structure? The shed floor joists will be 2×6’s which sit on the typical 4×4 skids, so the finished floor elevation will be about 10″ above the crushed stone base, or 8″ above the timbers. I’ve confirmed that the doors will be high enough to clear the surrounding timbers. There are 4 to 6 inches of gravel throughout, and I’ve laid a 4″ corrugated drain line under the lowest point. Bottom line, I’m a little short on gravel and I’m just reluctant to pay another delivery charge for 1 or 2 more yards of gravel.

  14. Site Preparations LLC says:

    Hi Mark, if you’re comfortable with the height the doors will end up at, you should be fine. Just make sure it won’t cause issues if you have a ramp on the shed.

  15. christopher blair says:

    i want to put in a crushed rock shed pad and the shed is 10 x 20 ft according to the article i know i should go 11 x 21 with the pad from what i read the site is on pretty level ground how many inches of crushed stone should i go in depth

  16. Site Preparations LLC says:

    Hi Christopher,
    We actually recommend 12″ on each side of the shed…so a 12×22 pad for your shed. You should have a minimum of 4″ of crushed stone at every part of the shed foundation.

  17. Steve says:

    Hi. I’m planning on installing a prebuilt 12×32 yard shed. The ground is fairly level, within 2-3 inches on the long side. I want to use two rows of concrete retaining wall blocks equaling 7 inches in height for the pad border. (Only because I have about 250 on hand from a past project ). Do you see anything wrong with this type of border? They are the typical blocks with slanted sides and a lip to set back each row. How thick of a base would you recommend for this size of a shed? Also, could you please calculate the amount of crushed stone, in tons, needed including the 1 foot overage on all sides? Thank you.

  18. Site Preparations LLC says:

    Hi Steve,
    If you use blocks, make sure they are fastened/staked well to prevent shifting and also make sure that the gravel doesn’t leak out through gaps around the edges. We recommend a pressure-treated perimeter as it leaves no gaps for crushed stone to escape and can also be screwed and staked.
    As far as the amount of gravel needed, we recommend a minimum of 4″-6″ for a shed that size. You can use the formula provided in the article above to calculate how much you’ll need for your specific shed foundation. Good luck!

  19. James says:

    I am planning a base for a pre-built shed. Regarding the base material….how do you regard crushed limestone ? I live in an area that the bedrock is strictly limestone, so it’s the dominate material. If I could get crushed metamorphic rock, that would be my preference. What your opinion?

  20. Site Preparations LLC says:

    Hi James, we actually prefer ‘3/4″ clean’ limestone for our pads as it locks together well when compacted. Metamorphic rock isn’t as readily available (at least not in our area) so it’s hard for us to compare the two. You can read more about our crushed stone recommendations here, under the section titled “Crushed Stone”.

  21. Spencer says:

    Hey James, this is an incredibly helpful website, and I appreciate all your insight here. I am going to build a gravel foundation for my Shed and have a few questions for you, mainly to make sure my math is correct haha. Let me know! thank you again.

    10×8 Plastic/Resin Shed (with a floor of it’s own) and the plan is to build a frame out of 2×4’s and then fill with a weed barrier and gravel. My ground has been leveled out and that area is about 11 x 9.

    1.) Should my 2×4’s just go directly on the ground? Don’t want to do cinder blocks and raise it up too much. It will be treated wood, but is there anything else I should put underneath to protect?

    2.) 11 x 9 x 3.5 (inches with 2×4) = 28.875 cubic. feet > 1.069 cubic yards > about 1.52 tons of gravel. Is my math correct?

    3.) I am seeing a ton of different articles and opinions on the gravel being used. I’ve seen where people suggest pea gravel, but then also that pea gravel may be too small and cause movement. Would 1/2 inch do the trick?

    4.) Does my having a plastic shed change anything about what my approach should be to all this?

    Thanks so much for reading and all your insight

  22. Jason says:

    Hi – thank for this site, and your thorough responses to all of the questions. I have a 10’ x 12’ shed I’m planning on placing on an area of soil that was formerly a 12’ x 14’ garden, now down to compacted soil.

    This area already has a 18” concrete walkway perimeter, and so I’m wondering if I should lay the compacted gravel pad to simply butt up against this existing path. Or, if I should separate with a 2” x 4 “ wall of treated lumber between the gravel and existing perimeter.

    I’m also wondering if a concrete foundation is recommended, to be laid on top of the gravel pad. I’ve seen conflicting recommendations/methods online. Moderately heavy tools and equipment will go in the shed. I live in the Central Valley of California, there is no natural slope.

  23. Site Preparations LLC says:

    Hi Spencer,
    You’re in luck…we actually have a full step-by-step guide to building a gravel shed foundation that answers all those questions!
    1. We recommend treated lumber (4×6 actually); it can go directly into the ground.
    2. We recommend that shed foundations should extend 12″ on each side of the shed. So a 10×12 foundation for an 8×10 shed. We also recommend the gravel be at least 4″ deep at all points of the shed.
    3. We recommend ‘3/4″ clean’ stone.
    4. We follow the specs above, even for plastic/resin sheds. You may be able to tweak the exact specs for your shed; of course, you’re then assuming any associated risks. 😀
    Definitely check out the guide for more details and feel free to leave us a Google review if we’ve helped. Good luck with your shed foundation!

  24. Site Preparations LLC says:

    Hi Jason,
    If you dig down 4″ or so next to your existing concrete walkway, that should serve as a sufficient barrier to keep your crushed stone from escaping. We recommend simply compacting the stone before placing your shed on the foundation; a concrete foundation is generally unnecessary for sheds with pre-built floors. This article compares gravel shed foundations vs. concrete shed foundations. We also have a full guide to building gravel shed foundations here.
    Glad you found our site helpful! Feel free to leave us a Google review if you have a moment.

  25. Site Preparations LLC says:

    Hi Paul,
    It depends on what type of floor/foundation the house has. If it’s a fully prefabricated building with a built-in wood floor on treated lumber runners, a gravel pad should be fine. We suggest checking with the manufacturer to see what type of foundation they recommend.

  26. Site Preparations LLC says:

    Hi Paul,
    You can use the formula shared in the article to calculate the amount of gravel needed for your specific project. Keep in mind that you should have at least 4″ of gravel at all parts of the foundation.

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