When you pick a shed, the number on the sign is the footprint: 8x12, 96 sq ft. That is not what you get to fill. The shed designer now opens each starting design in a detail panel, and measures storage the way you use it: inside the studs, from the top of the floor.
The walls take their cut. An 8x12 framed with 2x4s has 84.7 sq ft of floor inside. That is 12% less than the 96 on the sign, before you hang a single shelf. An 8x8 loses 14%: 64 sq ft outside, 55 inside.
Per $100 of materials, at the store prices the tool starts with (seen 2026-10-29, before tax), the six starting designs give:
| Design | Materials | Floor inside | Per $100 | Volume per $100 |
|---|---|---|---|---|
| 8x8 garden shed | $2,548 | 55.0 sq ft | 2.2 sq ft | 18 cu ft |
| 8x10 | $3,017 | 69.8 sq ft | 2.3 sq ft | 21 cu ft |
| 8x12, ridge beam, 8 ft height limit | $3,026 | 84.7 sq ft | 2.8 sq ft | 22 cu ft |
| 8x12 classic, 8 ft walls | $3,251 | 84.7 sq ft | 2.6 sq ft | 23 cu ft |
| 10x12 | $3,693 | 107.5 sq ft | 2.9 sq ft | 27 cu ft |
| 12x16 | $4,700 | 176.0 sq ft | 3.7 sq ft | 35 cu ft |
Bigger is cheaper per square foot, as you'd expect: the door, the site prep and the boxes of nails don't grow with the floor. But a permit limit often caps you at 100 sq ft. Under that cap, the 8x12 with the ridge beam gives the most floor for the money of these six.
Headroom versus volume. The two 8x12s show a real trade-off. The classic has 8 ft walls and rafter ties across the room at the plates. The ridge-beam design has 7' 2-1/2" walls and no ties, so the middle is open to the underside of the beam, 8' 2-9/16" up. You get more standing room in the middle, and the roofline is 14" lower, for $225 less. The price is 12% less volume (667 against 762 cu ft), because the classic's taller walls and steeper 6/12 roof make a bigger box. The space above the ties counts as storage too, but only for things you can lift onto a tie.
What the panel shows. For each design:
- renders from the front corner, the back corner and the gable end;
- the price, broken down by shopping-list section (lumber, siding and roofing are the top three on every design here);
- footprint, wall height and peak;
- floor, volume, shelf wall (inside wall length with no door or window in it) and headroom;
- siding, roof, every door and window;
- the framing, and the most-used member from the structure checks.
Put two or three in Compare and they line up side by side, on a phone too. Rows that differ are highlighted, and the best on each row is tagged "best" in words, not by colour alone. "Start from this design" opens a copy in the editor.
These six are the old presets. Optimised designs under the 100 sq ft limit, from the design search other agents are building, will go in the same panel. The structure checks are allowable-stress checks under the loads you set. They are not engineering and not a code review.