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. There are a variety of shed foundations available, but we typically recommend a gravel shed foundation as the best option.
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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.
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.
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.
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.
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. The amount of crushed stone needed for other types of gravel pads, such as a gravel base for a hot tub or a gravel fire pit patio area, will vary. 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 or about how to build a shed base on uneven ground.
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!
Read about 7 common mistakes made when doing ground preparation for a shed.
How much gravel do I need for a 12×20 shed
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.
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
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!
How much gravel is needed for a 12X40 run-in shelter
Hi Holly, for a 12×40 run-in, we’d recommend going 5″ deep with the stone. So you would need about 12 tons.
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?
Christian, you’ll need a 12’x14′ foundation for a 10’x12′ shed. (Refer to this article for more details: https://www.siteprep.com/gravel-shed-foundation-12-wider-shed/)
If your entire foundation is 12″ deep with gravel, you’ll need about 6.25 cubic yards of gravel.
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?
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.
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.
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.
So a shed that is 12×16 you need 14x18x.05=126~27=4.66 cubic yard = 7 tons is this correct
Yes, that math looks correct!
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!
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!
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.
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.
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
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.
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.
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!
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?
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”.
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
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.
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!
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.
Is this gravel ok to use on a 14ft long 10ft wide summer house tgank you
And how much gravel will a need tgank you so much very helpful your site
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.
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.
Is 6AA crushed (washed) Limestone an acceptable alternative? It is described as 1/4 -3/4 size. My local supplier does not carry “3/4 clean”.
Hi Lori,
6AA is an acceptable alternative to ‘3/4″ clean’ for a shed foundation.
THANK-YOU!!
You’re welcome, Lori!
This article is so helpful! I’m installing a 7 by 10 resin shed on ground that is nearly level and I’d prefer to use standard cinder block for my perimeter.
I’d finish the leveling, place the blocks about 2 inches deep, and secure with rebar before adding the fabric and gravel.
Would that work or does it have to be lumber?
Hi Lisa,
It sounds like that plan should work. A few things to keep in mind:
1. You’ll definitely want to stake your perimeter in place. If there is a slope of more than 12-16″, you may need to add some type of additional reinforcement to support the block perimeter.
2. Make sure there aren’t large gaps between the blocks where the crushed stone could start to sneak out.
3. Keep in mind any step-up that might be created in front of your shed door.
Hope that helps!
Thank you very much for the guide. I have 2 questions :
1 – how do you level the 6×4? Do you use rock dust?
2- do you put a piece of fabric understand the 6×4?
3- how deep I should put the rebar? I will use 6×6.
Hi Jack,
Thanks for your questions! I believe you’ll find answers to them in our complete guide to building a shed foundation.
Hope that helps!
Thank you so much for your help, I have one more question that I have not been able to find an answer for anywhere else.
When I am reinforcing my concrete block perimeter with rebar, is there a length I should consider? I was going to do 24″ but I don’t know if that’s overkill or not.
Thank you again.
Hi Lisa,
18″-24″ should be about right. Best wishes!
How much gravel will I need for a 8 by 16 ft shed. And would a gravel grid do the job.
Hi Wendy,
You’ll need at least 2.5 cubic yards of crushed stone if your site is level.
Gravel grids generally seem to work best on level ground and not as well where there’s a slope. However, we don’t install gravel grid shed foundations, so we can’t offer a specific recommendation.
Hopefully that helps!
If the site is quite level to start (end of driveway), is the 4″x6″ lumber border required or no? If yes, would (1) layer of border be acceptable? that would result in digging 6″ deep to lay the border flush to the soil, then filling w/ Gravel.
Hi Chris,
Even in cases like that, we prefer adding the lumber perimeter to keep the gravel together and compacted; with no border, the gravel can tend to loosen and shift over time. One course of lumber is sufficient. Hope that’s helpful!
Hi I’m building a platform for a 7 x 7 Resin shed. I’m using concrete squares 10 x 12. How much gravel would I need.
Hi Donna, you can use the formula shared in the article to calculate the exact amount needed for your project. Hope the project goes well for you!
How much gravel will I need 57 at 2 inches thick for a 14×20 concrete pad ty
Hi Kevin, you can use the formula shared in the article to calculate the exact amount needed for your project. Hope the project goes well for you!
The guy I hired used bigger stone then what you recommended for the foundation. He said it’s level though. My shed is being built on a skid. Will shed be ok even though we used bigger stone and also didn’t tamper it? Thx
Hi Joe,
You should be fine. We typically recommend 3/4″ clean crushed stone, but it’s better to go with a larger size than a smaller size.
Hi, great site!
In regards to using 4×6 PT over 4×4 PT, which side (4″ or 6″) will be in the ground for stability? How much should be above ground to hold the clean stone? Can i just place them on top of my leveled area or do i just dig down 4″? My shed will be 10×12 so I think I need 2.05 tons. Thank you so much!
Hi Dan,
Place the lumber on the 4″ edge, about 2″ into the ground. We actually have an entire how-to guide for installing your shed foundation! Hope it’s helpful!
My plan is to build a 10×16 foot shed on a gravel foundation. The ground where the gravel foundation is going is level, hard, and compact. The frost line is 42 inches deep. In the early spring, as the snow is melting, this area of ground has about 1.5 inches of water puddling on top that is eventually absorbed into the ground after a few days. During the summer months, after a heavy rain, a puddle will also occur but will be absorbed into the ground after about one day. Will a gravel foundation still work with this puddling situation?
Hi David,
A gravel foundation works quite well for draining water away from your shed, so it sounds like a good option in your case. When installing the shed foundation, you may want to also consider doing some ground work to eliminate as much of the puddling as possible directly around the shed. Hope that helps!
Wow! You guys are awesome with all these questions! So… I am planning on putting a 6’ x 10’ lean to shed next to my house in Texas. Soil around the properties here is pretty hard and no huge equipment is going into the shed. The side of the house has positive slope and great drainage away from the foundation, and I don’t want to disrupt that. The question is, can I lay some sort of base material for the gravel down over the existing soil and build it up level then compact it, then add 3-4 inches of gravel or 3/4” clean limestone on top of the base and compact that. Thus having a level surface on top of the positively sloped lawn? Area next to house around shed is 11’ x 12’ and the shed will be placed so that the 10’ wall of the shed spans the 12’ section of “foundation”.
If this is possible, what type of base material for gravel would you suggest?
Hi Hans,
If the soil is well-compacted, we’d recommend building your perimeter, adding a layer of stabilization fabric, and adding at least 4″ of 3/4″ crushed limestone. Be sure to check out our step-by-step guide to building a gravel shed foundation…it should answer a lot of your questions in more detail. Good luck!
Hi,
Id love to do this for plastic shed as well. Do i need to have something in-between the shed and the gravel? Like does there need to be something for the shed to sit on, on top of the gravel. Or can i place my shed directly on the gravel?
Hi David,
You can place the shed directly onto the compacted gravel.
what type of gravel do I use and how much will I need for a plastic shed base 8×6 ft
Hi Irene,
We recommend 3/4″ clean crushed stone. You can calculate the amount needed for your project using the formula in the article above. Good luck with the project!
I want to build a gravel foundation on which I will assemble a small (12’x16′) post and beam structure. I imagine my completed building will be a good deal heavier than a typical 2×4-constructed or pre-fabricated shed. What are the weight limitations for a gravel foundation?
Hi John! There are no weight limitations on a stone foundation.
how do you keep the gravel locked in place? Here is the 3/4 gravel from local source and it doesn’t seem to lock in place after compacting with a plate compactor. Are they too big and do I need to mix with smaller gravel?
[Link deleted]
I just built a gravel shed foundation based on the your guide. But the gravel seems to be loose even after compacting it several times with a plate compactor. how do you keep the gravel locked in place? Here is the 3/4 gravel from local source and it doesn’t seem to lock in place after compacting with a plate compactor. Are they too big and do I need to mix with smaller gravel? I have some photos but your site doesn’t seem to allow any links.
Make sure you’re not using river stone (river stones is technically the same as real gravel). The best type of gravel for a foundation is 3/4″ ‘clean’ crushed stone. Here’s a bit more on the topic: https://www.siteprep.com/how-to-install-a-gravel-shed-foundation/
Again, make sure you’re using 3/4″ ‘clean’ crushed stone and not river stone (technically real gravel). Here’s a link to more info: https://www.siteprep.com/how-to-install-a-gravel-shed-foundation/
Hello, I’m building a shed in a few days (the shed is 12×7, so 14×9 would be the foundation size), how much gravel would I need for that?
I have 20 x 30 level excavated area with about 5-6 inches of crushed gravel. Putting 16 x 24 2 story shed that I want insulate. The floor is 2×6 treated wood that is 16 in on center. This will sit directlty on gravel base. I want insulate in those openings so the floor is R19 rolls of pink insulation..What kind of vapor barrier do you suggest between the gravel base and open floor joists?
To find the amount of gravel you’ll need, multiply the square footage of the pad (126 sq. ft.) by the depth of gravel (typically 6 in. or 0.5 ft.) to find the cubic footage of the pad. Divide the number of cubic feet by 27 to find the number of cubic yards needed. This is all detailed out in this article: https://www.siteprep.com/how-much-gravel-for-a-shed-foundation/
Because we do not typically work with shed installation or insulation, that may be a better question for your shed builder.
If the soil within the perimeter is well compacted, but it is slopped (5 in deep on one side and 12 in deep on the other side), is it necessary to level the dirt before placing the gravel? Would there be any negative consequences of having more gravel in one are than another (other than the extra expense)? Thank you so much!!!
Your wood perimeter would be difficult to install level. Here’s an article where you can learn more: https://www.siteprep.com/how-to-install-a-gravel-shed-foundation/
I am about to begin my site prep for my 12×20 shed. My site is nearly level already, within 3-4 inches from high side to low side. Do I need multiple courses of lumber for the perimeter or will one course of 4×6’s be sufficient, with the interior dug out to 6 inches below the top line of the lumber?
Hey JB. This article might be a helpful resource as you begin site prep. https://www.siteprep.com/how-to-install-a-gravel-shed-foundation/
Thanks for this info – very helpful. I’m planning to install a gravel shed foundation and would prefer to use finer gravel than 3/4” since I also want to install a gravel path, and finer screening gravel tends to be more comfortable to walk on. I know this may provide less drainage – is it something you would recommend not foing, or do you have advice for how to best use finer gravel?
Hey Whit, glad you find the article helpful! This article might be able to shed a little more light on your question: https://www.siteprep.com/how-to-install-a-gravel-shed-foundation/
Great, helpful article and site! My question is about how much the gravel settles after compacting–I don’t see any reference in your calculations regarding that, so is the amount the surface drops minimal? I’m thinking of doing a mix of piers and gravel pad, and I’d like the gravel pad to be as level with the top of the piers as possible so it can help distribute the weight. Thanks in advance!
Can you use drainage rock ?
Hi Ed, please give us a call or use the provided link to reach out to us. By doing so, we will be able to assist you more effectively. Thank you! https://www.siteprep.com/get-quote/ (717-799-7311)
Great tutorial! You recommend a gravel shed base should extend at least 12” further than each SIDE of the shed, but if the shed eaves are extra-long, we should extend the border of the shed foundation accordingly. What is “extra long”? My shed will have a 12 in. eave around three sides, and a 24 in. eave around one side. Should the shed foundation MATCH the dimensions of the roof above it, or extend beyond these eaves by a certain number of inches?
Hi Rod, I would recommend going 5 inches wider than the eaves, so if they have a 12 inch eve, I would go 17 inches all the way around.