A 10×12 shed — the most popular size, right at the 120-square-foot permit threshold — costs about $1,500 to $3,000 in materials if you build it yourself, while a prefab of the same size runs $4,000 to $7,000 delivered. The 2026 all-in average across every size and route sits near $3,500. Here's how the build routes compare, what the foundation actually costs, and how to count the materials before you swipe the card.
Build, if the question is purely dollars. The three routes on a 10×12, from current pricing:
| Route | 10×12 cost | What you trade |
|---|---|---|
| DIY from scratch (materials) | $1,500-$3,000 | Several weekends, a skill wall, your own tools |
| Prefab delivered | $4,000-$7,000 | Money; you get a square, dry building in a day |
| Custom / contractor-built | $4,000-$12,000+ | The most money; you get exactly what you drew |
The DIY savings run $2,000 to $4,000 on this one size. For scale reference on smaller footprints, a DIY 10×10 runs about $1,500 in materials against roughly $5,600 pro-built. What prefab buys you isn't just labor: factory sheds are built square and dry indoors, they arrive finished, and site prep is a pad and an anchor rather than a build. What DIY buys you — besides the savings — is thickness: a self-built shed can use real lumber spacing, better siding, and hardware you chose, not the lightest spec that survived transport.
A representative 10×12 breakdown, the kind of budget the shed calculator sizes board by board:
| Budget line | Typical range | What moves it |
|---|---|---|
| Framing lumber | $600-$1,000 | Studs at 16 vs 24 in OC; treated vs standard |
| Plywood (floor, walls, roof) | $400-$700 | 3/4-in floor decking; 5/8 vs 1/2 in walls |
| Siding | $300-$600 | Smart-panel vs board-and-batten vs metal |
| Roofing | $250-$500 | Three-tab shingles; underlayment and drip edge |
| Foundation | $200-$600 | Gravel pad vs pier blocks vs concrete slab |
| Door, hardware, fasteners | $150-$350 | Prehung vs sliding barn door; hinges, anchors |
Those lines sum to the honest middle of the $1,500-$3,000 range. Two lines people forget: fasteners and the door. A box of framing nails, screws, hangers, and anchors quietly runs $100-plus, and a decent shed door — the only part that moves every day for a decade — is worth buying well. Add 10% on lumber for cutting waste; materials come in 8-foot boards and 4×8 sheets, and offcuts are taxes, not free wood.
Three tiers, priced by what sits on them. A gravel pad — 4 to 6 inches of crushed stone inside a treated-lumber frame — runs a few hundred dollars and suits almost anything light. Concrete pier blocks under treated skids cut it further and keep the structure "movable," which matters for permits. A slab is the permanent answer, and its cost is pure arithmetic:
| Slab at 4 in thick | Cubic yards | 80-lb bags | Ready-mix @ ~$150/yd |
|---|---|---|---|
| 8 × 10 | 0.99 | 45 | ~$149 |
| 10 × 12 | 1.48 | 67 | ~$222 |
| 12 × 16 | 2.37 | 107 | ~$356 |
Do the bag math against the yard math: 67 eighty-pound bags at $6 to $7 each runs $400 to $470, while the 1.48-yard pour is about $222 of concrete plus a short-load delivery fee. Bags win only under about a yard, and even then the price is your back — each bag is 80 pounds mixed by hand. The concrete calculator runs the volumes and costs for any slab you're considering, including the gravel base beneath it.
The material count is the difference between a clean weekend project and four trips to the lumber yard. The basics for a 10×12 with 8-foot walls, studs at 16 inches on center: roughly 30 wall studs plus 15 more for doubled corners and door framing, three 2×4 plates running each wall, floor joists at 16 inches on center if you're framing a wood floor instead of a slab, and 4×8 sheets covering floor, walls, and roof — each 32 square feet, plus 10% waste. The shed calculator computes all of it from your dimensions, including siding squares with the door opening deducted and roofing bundles from the pitch you pick.
One habit worth borrowing from contractors: price the whole list before buying anything. Lumber prices swing week to week, and knowing your total sheet count tells you whether the store's bulk pricing or delivery fee changes the math. A materials list is also the permit application, in most jurisdictions that want one.
Usually not at 10×12, often yes above it. The common trigger is 120 square feet — the line that separates a shed from an accessory building in typical codes — and many areas exempt smaller structures outright, especially on non-permanent foundations like piers or skids. Setbacks matter too: even an exempt shed usually can't sit against the property line. One phone call to the building department settles it, and the call is free; moving a poured slab is not.
Bigger sheds cost less per square foot, because the fixed costs — one door, one foundation perimeter, one roofing edge treatment — don't scale with footprint. But value has two sides, and the second is use: the standard advice is to build for what you'll store in five years, not this season. A 10×12 fits a mower plus bikes plus the overflow that always finds a shed; an 8×10 fits the mower and one of those categories. Since 120 square feet is also the permit line in most places, 10×12 is the classic sweet spot — maximum storage, minimum paperwork.
Studs, plates, siding squares, roofing bundles, and slab yards from your shed dimensions.
Shed Calculator →Building a 10×12 shed yourself runs $1,500-$3,000 in materials against $4,000-$7,000 prefab delivered, with custom builds stretching past $12,000; the 2026 average across everything sits near $3,500. Pick the foundation first — gravel, piers, or the ~$222-plus-fees slab pour — then count every board with the shed calculator before you shop. The concrete calculator prices the slab and the lumber calculator totals the framing order, so the only surprise left is what you decide to store in it.
Building is cheaper in dollars: a 10x12 DIY build runs $1,500-$3,000 in materials against $4,000-$7,000 for a prefab delivered — a savings of roughly $2,000-$4,000. Prefab buys back your weekends, though, and factory builds are square and dry. The honest comparison is materials cost against the value of several full weekends plus whatever tools you'd have to buy.
A 10x12 slab at 4 inches thick is 40 cubic feet, or 1.48 cubic yards — 67 eighty-pound bags or 89 sixty-pound bags. At that scale ready-mix by the yard is usually cheaper and far less labor once you count mixing 67 bags by hand.
Four inches is standard for storage sheds on well-drained soil. Go 5 to 6 inches with rebar or wire mesh if the shed will hold a riding mower, tractor, or vehicle, and always pour on 4 to 6 inches of compacted gravel.
Often not for small ones — 120 square feet is the common permit trigger, since that's the line separating sheds from accessory buildings in typical codes. Rules vary by jurisdiction, and some areas exempt sheds on movable foundations entirely. Call your building department before pouring anything.
Cost scales with footprint but the price per square foot falls as sheds grow, because the expensive parts — a door, a foundation perimeter, roofing edge — don't multiply. A 10x12 (120 sq ft) sits at the permit threshold in most codes and handles a mower plus general storage, which is why it's the most popular size.