Shed on Skids: How Many You Need and How to Build

A shed on skids has its floor frame resting on long timbers, the skids, that lie on the ground or on a gravel pad. No concrete, no holes, no footings. You lay the skids, level them, and build the floor on top.

This guide covers what the skids do, how many you need for your width, what size to buy, and how to build the floor on them. The counts and sizes come from the shed designer, so they match the cut lists on our free plans. If you are still choosing between skids, deck blocks and other foundations, read the shed foundation guide first.

What a shed on skids is and when it works

A shed on skids is a floating foundation: the building rests on the ground instead of being tied to footings. Two or more skids run from the front of the shed to the back. The floor joists run across them, the subfloor covers the joists, and the walls sit on the subfloor.

What the skids do

The skids carry the weight of the floor and everything on it, and they lift the floor frame off the pad. The designer builds them from 4x6 pressure-treated timber set on edge, with the 5-1/2 inch face vertical.

When skids work

Skids suit a storage shed on flat or nearly flat ground that drains well. They are simple, and the designer builds the whole floor around them: skids on a gravel pad, a 2x6 pressure-treated floor frame, and a 3/4 inch tongue-and-groove subfloor.

When to pick something else

On a slope, the usual alternative is 4x4 beams on deck blocks, which is the designer’s other floor type. For a slab, piers or a permanent foundation, you plan the work yourself. The foundation guide compares the options. If your town requires a permanent foundation, skids may not be accepted, so ask before you buy lumber.

How many skids do you need

Take the shed width in feet, divide by 4, round up, and add 1. The result is the number of skids, with a minimum of two. The skids run front to back, so the width decides the count, and the depth decides how long each skid is.

An 8 ft wide shed gets 3 skids, a 10 ft wide shed gets 4, and a 16 ft wide shed gets 5. The table applies the rule to the designer’s gable sizes. The first number in the shed size is the width, and the second is the depth.

Why width sets the count

The floor joists span from one skid to the next. Keeping the skids about 4 ft apart or closer means no joist spans more than that gap. A 6 ft wide shed still gets 3 skids, because two would sit 68-1/2 inches apart, past the 4 ft the designer allows. Add a skid and the gap shrinks.

Long skids

A 4x6 timber longer than 16 ft is hard to find on a store rack. For a 10x20, 12x20, 12x24 or 16x20 shed, the designer builds each skid from two shorter timbers with a butt joint, staggers the joints from one skid to the next, and lists a 4 ft 2x6 pressure-treated splice plate on each face of every joint. If you would rather use one-piece skids, set the longest board to 20 or 24 ft in the designer. Lumber yards stock long timbers, and big-box stores often sell them online or by special order, so call ahead before you plan your delivery day.

Check your own size

The table covers the presets. For any other width and depth, open the designer with the skid floor selected, for example a 10x12 shed on skids, and read the count and lumber list.

Skid size and spacing

Use 4x6 pressure-treated timber, set on edge, with the skids spaced up to about 4 ft apart on center. That is what the designer draws, puts in the lumber list and checks the joists against.

Why 4x6 on edge

A 4x6 is not 4 inches by 6 inches. Softwood lumber is sold by nominal size, and a 4x4 measures 3-1/2 by 3-1/2 inches (Southern Pine Inspection Bureau, citing the PS 20 lumber standard). The designer’s 4x6 is 3-1/2 inches wide and 5-1/2 inches tall when set on edge. Set that way, it is stiffer than on its flat side, and it lifts the floor frame 5-1/2 inches off the pad.

What the joists can span

Skids are close enough together that the joists work easily. At 16 inches on center, the designer lets a 2x6 SPF No. 2 joist span 8 ft 7-13/16 in under a 50 psf live load, and the widest skid spacing in the table is 47-1/8 in. That check is a planning aid, not an engineering seal, and it does not cover a heavy point load such as a large machine or a loaded rack in one spot.

Ground contact rating

Skids sit on the ground or on stone, so the lumber must be rated for it. The wood preservers’ use categories put wood in contact with the ground in UC4A, ground contact, general use (Preserved Wood, AWPA Use Categories). The designer’s parts list calls the skids, the floor joists and the rim joists pressure-treated for ground contact. Read the tag on the lumber and buy the ground-contact grade, not the cheaper above-ground grade.

What the skids cost

At one Home Depot store in San Diego County, California (Otay Mesa, ZIP 92154), on September 29, 2026, a 4x6 pressure-treated timber was $37.78 at 10 ft and $45.18 at 12 ft. At that store, the four 12 ft skids under a 10x12 shed came to $180.72 before tax. That is one store on one day, not a national price, so ask your own yard, and read the tag for the ground-contact rating before you pay.

Other skid sizes

The designer uses 4x6 for every skid. We do not have a sourced size chart for other skid timbers, so we do not give one. If you want to use different lumber, ask your lumber yard and your building department.

Build the floor on the skids

The floor is the same frame for every size. The numbers below are for the designer’s default 8x10 shed, which sits on 3 skids of 10 ft.

Step by step

1. Set the skids. Lay them on edge, running front to back, at the spacing in the table. On an 8x10 they are 46-1/4 inches apart on center. Level each skid along its length and to its neighbors.
2. Cut the rim joists and joists. The 8x10 floor has two 2x6 rim joists 10 ft long and 9 joists 93 inches long, all pressure-treated. Joists sit 16 inches on center by default.
3. Build the frame. Nail each joist through the rim joist at both ends. The designer’s list counts three 16d common nails (3-1/2 x 0.162 inch) at each joist end, the count in the model code’s fastening schedule.
4. Square the frame. Measure both diagonals and rack the frame until they match.
5. Fasten it to the skids. Toenail the frame to each skid or use straps, so it cannot shift while you sheathe the floor.
6. Sheathe the floor. Glue and screw 3/4 inch tongue-and-groove plywood to the joists with the long edges across them and the end joints staggered. The 8x10 uses 3 sheets, 4x8, about 150 2-inch screws and 2 tubes of adhesive.

How high the floor sits

With 4x6 skids on edge, a 2x6 floor frame and a 3/4 inch subfloor, the top of the subfloor sits 11-3/4 inches above the pad. That is the height every door threshold and ramp has to work with, and the shed ramp guide turns it into a ramp length.

Then the walls

Once the subfloor is down, the frame is ready for wall framing. How to build a shed walks through every stage after the floor.

Skids on gravel or on the ground

The designer’s skid foundation is skids on a compacted gravel pad. You can set skids on bare ground, but the pad is the better choice.

Skids on a gravel pad

A gravel pad drains water away and gives the skids a level bed you can adjust. The designer sizes it as the shed footprint plus 12 inches on every side, 4 inches thick, which is 2.07 cubic yards for a 10x12 shed before you add for compaction. The gravel shed base guide has the volume for every size, the right stone, and the step-by-step pad build.

Skids directly on the ground

Skids are sometimes set straight on leveled soil. Soil and sod hold moisture against the wood and settle under load, and a settled skid takes the floor frame down with it. If you skip the pad, strip the sod, pick the highest and driest spot, tamp the ground firm, and use lumber rated for ground contact. Call 811 a few business days before you dig anywhere (Common Ground Alliance, call811.com).

Common mistakes with a shed on skids

Skid problems are quiet ones. The floor looks fine on day one and a door binds a year later.

Using the wrong lumber grade

Skids that touch soil or stone need the ground-contact grade. The tag on the board says which one you have, so check it at the yard, before the boards are on your truck.

Setting skids too far apart

The count comes from the width, and the table above is the shortcut. Spacing the skids wider to save one board puts more span on every joist.

Skipping the level check

A skid that sits a quarter inch low is a floor that rocks. Level along every skid and between them before you build the frame, because shimming is far easier before the joists are nailed down.

Building on soft ground

Skids spread the load, but they cannot fix ground that gives way. On soft or wet ground, build a gravel pad first and consider another foundation if the spot stays wet.

Permits and skids

Whether a shed on skids needs a permit is a local question. A skid foundation does not answer it.

Skids and the permit threshold

The 2021 International Residential Code, section R105.2, exempts one-story detached accessory structures up to 200 sq ft from a building permit, and it says that exemption does not authorize work that violates the code or other local laws (Grant County, WA, reprinting IRC 2021 R105). Local codes change the numbers: Elgin, Illinois defines a shed as an accessory structure of no more than 150 sq ft. Zoning rules, such as setbacks, apply even where no building permit is needed. Read our shed permit basics and call your building department.

The foundation question

Some places regulate the foundation type separately. Prince William County, Virginia exempts sheds up to 256 sq ft from a permanent foundation when they meet five conditions, including a floor no more than 18 inches above the ground, ground-contact treated wood where it touches soil, and anchoring for wind loads (Prince William County Development Services, 2021). The designer’s skid floor sits 11-3/4 inches above the pad. That county measures from the floor to grade, so add however far your pad stands above the ground before you compare it with the 18 inch limit, and remember your town has its own rules. We do not have a source that says skids are exempt from permits anywhere, so do not assume it.

Anchoring

The designer’s parts list includes 4 ground anchors for a skid shed, one near each corner, with a note to check local wind rules. What holds a skid shed down is a local rule too. Ask your building department which tie-downs it accepts. Our shed anchoring guide covers the anchors, the straps and the install for a skid shed.