Gravel Shed Base: Size, Depth and How Much

A gravel shed base is a pad of compacted crushed stone under the floor frame of your shed. Pressure-treated skids sit on top of it, the floor frame sits on the skids, and the stone carries water away from the wood. You buy stone and fabric, rent a compactor, and skip the concrete truck.

This guide gives you the pad size, the depth, the right kind of stone and the cubic yards for the sheds people actually build. The numbers come from the shed designer, so they match the cut lists on our free plans, and the calculator below works out any other size. For the rest of the foundation options, including deck blocks and slabs, start with the shed foundation guide. If you are comparing every kind of shed base, from a concrete slab to paving slabs, plastic grids and timber frames, or building in metres, the shed base guide covers them all.

Is a gravel shed base right for your shed

Yes for most backyard storage sheds. The gravel does the draining and the skids do the carrying. Before you dig, check that your shed, your ground and your town agree.

When a gravel base works

A gravel shed base suits flat or gently sloping ground where water drains away instead of pooling. The designer’s skid foundation is built on exactly this idea: 4x6 pressure-treated skids set on edge, running front to back, with a 2x6 pressure-treated floor frame on top. The shed rests on the ground instead of being anchored to footings, which is why it is called a floating foundation.

Walk the spot after a hard rain. If water stands there, the pad will need to be raised and the ground around it graded away from it, or you should pick another spot.

When to choose something else

Steep slopes, soft fill, and buildings you plan to heat, plumb or load with heavy machinery are the cases where you should look at deck blocks, piers or a slab. The foundation guide compares them. The designer offers two floor types, skids on gravel and beams on deck blocks, and nothing else, so for a slab or piers you plan the foundation on your own.

Does a gravel shed base pass your building department

That depends on where you live. One city accepts a gravel base outright, and another waives the permanent foundation only when conditions are met.

• Elgin, Illinois defines a shed as an accessory structure of no more than 150 sq ft, and its quick guide says “a gravel base with code-approved tie-downs is an acceptable foundation.” The same guide accepts a concrete slab at least 4 inches thick on a minimum 4 inch compacted gravel base (City of Elgin, Shed Quick Guide, checked 2026).
• Prince William County, Virginia exempts sheds up to 256 sq ft from a permanent foundation when five conditions are met. They include a floor no more than 18 inches above grade, ground-contact treated wood where it touches the soil, and anchoring for wind loads (Prince William County Development Services, Guidelines for Building a Shed, 2021).
• The model code (2021 International Residential Code, section R105.2) exempts one-story detached accessory structures up to 200 sq ft from a building permit. The same section says the exemption does not authorize work that violates the code or other local laws.

Two different questions hide in those examples: whether you need a permit at all, and what foundation the local rules accept. Your town can answer yes on one and no on the other. Thresholds and foundation rules vary by jurisdiction, so call the building department and read our shed permit basics before you buy stone.

How big and how deep should a gravel shed base be

Build the pad a foot bigger than the shed on every side and at least 4 inches thick. The size is simple arithmetic. The depth depends on your soil and your local rules.

Pad size

The designer sizes the pad as the shed footprint plus 12 inches on every side. An 8x10 shed gets a 10x12 pad, a 12x16 shed gets a 14x18 pad. The extra foot gives you room to walk and work around the walls, keeps the outer skids and rim joists well inside the stone, and lets rain run off the pad instead of undercutting its edge.

Measure the footprint from the outside of the floor frame, then add 12 inches to each side. Mark the pad corners with stakes and run string between them.

Pad depth

The designer figures the pad at 4 inches thick. Common practice for a gravel shed base is 4 to 6 inches of compacted stone. Four inches is the depth the designer uses, and it is the depth Elgin, Illinois names for the compacted base under a slab. Go toward 6 inches when the ground is soft, when the spot is low, or when you want the shed higher above the surrounding grade.

Depth is what the pad ends up at after compaction, not the depth of loose stone you dump. Building codes and local rules can ask for more, so treat 4 inches as a floor you confirm, not a promise of compliance.

Crushed stone or pea gravel

Use crushed stone with sharp, angular faces. Do not use round pea gravel for the pad.

The U.S. Forest Service’s Equestrian Design Guidebook (2007) is a guide to equestrian trails and trailheads, not to sheds, but it explains the material clearly. It calls round gravel “a poor choice for trails, roads, parking areas, and parking pads because it doesn’t compact well,” because the rocks roll against each other. It says crushed rock, with its angular faces, compacts relatively well and suits subbases for parking areas and parking pads.

A shed pad asks the same thing of the stone as a parking pad does: stay put under load. Angular faces lock together under the compactor, and round stones keep shifting under a skid.

Fines and what to ask for

The same guidebook says crushed rock combined with fines and well compacted is generally preferred for surface courses on parking pads, and warns against crushed rock without fines as a surface because it does not compact well. Fines are the stone dust and small particles that fill the gaps between larger pieces.

Suppliers use different names for compactable base stone in different regions, so do not order by a name you read online. Call a local aggregate supplier, say you are building a compacted base for a shed pad, and ask which product they sell for that. Ask for its weight per cubic yard while you have them on the phone.

Skip the decorative bag

Bagged decorative pea gravel and river rock at a garden center are meant to look good on top of the ground. Stone for a base comes from an aggregate supplier by the cubic yard or the ton, delivered by truck.

How much gravel do you need

To get cubic yards, multiply the pad length in inches by the pad width in inches and the depth in inches, then divide by 46,656, the number of cubic inches in a cubic yard. The pad is the shed footprint plus 24 inches in each direction. This table applies that math to all 16 gable sizes in our free plans, at 4 inches, the depth the designer uses, and at 6 inches.

Sq ft is the pad area, and yards are cubic yards. These are volumes for the finished pad, and they include nothing for compaction and nothing for waste.

Order more than the table

Compacting squeezes stone into a smaller volume, so the stone that arrives on the truck has to be more than the pad you finish. Penn State’s Center for Dirt and Gravel Road Studies builds this into its materials calculator: it uses densities and compaction ratios, lets you enter a compacted or a loose depth, and always reports cubic yards of loose material and US tons as shipped.

We do not have a compaction factor we can source for every stone in every region, so we do not print one. Tell your supplier the pad size and depth, ask how much loose stone that compacts to, and ask for the tons per cubic yard of the stone they quote. Stone is often sold by the ton, and that weight figure is what turns the table above into an order.

Prices

Stone prices depend on the quarry, the haul distance and the delivery fee. Get two quotes for the delivered price, with and without spreading, and compare them per ton.

Bags are the expensive way to buy stone. At one Home Depot store in San Diego County, California (Otay Mesa, ZIP 92154), on September 29, 2026, a 50 lb bag of 3/4 inch gravel was $5.47 and a 1,100 lb bulk bag of 3/4 inch gravel and crushed rock was $32.37. The same 1,100 lb in 50 lb bags is 22 bags, or $120.34, about 3.7 times the bulk-bag price. That is one store on one day, not a national price, and it says nothing about what a quarry charges by the ton. We do not print how many bags fill a cubic yard, because that depends on the weight of the stone. Whichever you buy, check that it is crushed, angular stone: a product name alone does not tell you.

The number for your own size

For any size not in the table, use the calculator above or do the math by hand. A 9x14 shed has a pad of 11x16 ft, which is 132 inches by 192 inches. At 4 inches, that is 132 x 192 x 4 / 46,656, or about 2.17 cubic yards. Open the shed designer to see the skid count and the full material list for the same shed.

Build the gravel pad step by step

The build is the same for every size: mark, dig, fabric, stone in lifts, compact, screed.

Before you dig

Call 811 a few business days before you break ground. It is the free national before-you-dig service, and it gets buried utility lines marked so your shovel stays off them (Common Ground Alliance, call811.com). Check your setbacks and the property line at the same time, so the pad does not end up in the wrong place.

Steps

1. Mark the pad. Stake the four corners 12 inches outside the footprint on every side and run string between the stakes. Measure both diagonals and adjust the stakes until they are equal, so the pad is square.
2. Strip the site. Remove sod and topsoil inside the string, down to firm subsoil. Dig deep enough that the finished stone lands at your chosen depth, with the top a little above the surrounding grade so water leaves the pad.
3. Rake the bottom flat and firm. Fill soft spots with stone and tamp them. Do not leave loose dirt under the pad.
4. Lay landscape fabric. Roll it across the whole bottom, overlap the seams, and run it up the sides. The fabric keeps soil from working up into the stone.
5. Spread the stone in lifts. Add it in two or three even layers, and compact each layer before adding the next. Wet the stone lightly if it is dusty and will not settle.
6. Compact every lift. A rented plate compactor gives the best result. A hand tamper works on a small pad if you work slowly and cover every square foot.
7. Screed the surface. Drag a straight 2x4 across the stone and fill low areas until it stops rocking. Check the pad with a long level in both directions.
8. Let it settle, then recheck. Rain will settle the surface a little. Check level again before you set skids.

Check before you set skids

Skids on the pad, and tie-downs

Set 4x6 pressure-treated skids on edge on the finished pad, running from the front to the back of the shed. The designer uses 4x6 skids on edge for the skid foundation, with the floor joists running across them. Wood that touches the pad needs to be rated for ground contact: the AWPA category UC4A covers wood in contact with the ground, and pressure-treated lumber for that use is what the designer’s parts list assumes (Preserved Wood, AWPA Use Categories).

How many skids, how far apart

The designer takes the shed width in feet, divides by 4, rounds up and adds 1, with a minimum of two skids. The spacing works out as follows, measured center to center.

The skids are as long as the shed is deep. A 10x12 shed sits on four 12 ft skids. The shed on skids guide covers the floor build on top of them.

Tie-downs

A shed on a gravel base is held down by its own weight and by whatever you fasten it to. The designer’s parts list includes four ground anchors, one near each corner, with a note to check local wind rules. Elgin’s guide, quoted above, accepts a gravel base only with code-approved tie-downs, and Prince William County requires anchoring for wind loads. Ask your building department which tie-downs it approves for a shed on skids, and follow the maker’s instructions for whatever anchor you buy. The guide to anchoring a shed goes through the options by foundation.

Kits and prefab sheds

If you are setting a prefab shed on the pad, its manual sets the base size. The Duramax 4x8 Sidemate manual, for example, says the base should be at least 4 inches larger than the shed and that the shed must be firmly anchored to its pad. That is one resin shed’s rule, not a rule for a wood shed built from our plans.

Common gravel base mistakes

Most gravel base problems show up a year later as a door that binds or a floor that stays damp. They are easy to avoid at the start.

Using the wrong stone

Round pea gravel and rounded river rock do not lock together. Order compactable crushed stone from an aggregate supplier and describe the job to them.

Making the pad too small

A pad that ends at the wall leaves the outer skids and rim joists at the very edge of the stone, with no margin for runoff and no room to work. Keep the 12 inches on every side.

Skipping the compaction

Loose stone settles unevenly, and the skids follow it down. Compact every lift, and check level again after the first heavy rain.

Ignoring drainage

Level is not the same as dry. Slope the ground away from the pad and keep the stone above the surrounding grade.

Forgetting the rules

Foundation rules and permit thresholds differ from town to town, and a shed of any size can be subject to zoning and setbacks even where it needs no building permit. Call first.

Where to go next

The gravel pad is the first job of the build. When it is level and compacted, the floor frame goes on top of the skids, then the walls and the roof. How to build a shed walks through every stage with the numbers for an 8x10. If you want a finished plan with the cut list for the floor, walls and roof, open the 10x12 gable shed plan or the 12x16 gable shed plan.