Shop slab sizes in Austin: 30x40, 40x60 and more
The two sizes people search most are 30x40 and 40x60, and both are big enough that a few cents per square foot adds up. Here they are with the other common shop footprints, from both Austin sources:
| Shop slab | Area | HomeBlue Austin (Sep 2024) | projectcosted Austin rate (Aug 2026) |
|---|---|---|---|
| 24x30 | 720 sq ft | $4,320 to $7,200 (computed) | $4,054 to $8,107 (computed) |
| 30x30 | 900 sq ft | $7,700 to $13,200 | $5,067 to $10,134 (computed) |
| 30x40 | 1,200 sq ft | $10,300 to $17,600 | $6,756 to $13,512 (computed) |
| 30x50 | 1,500 sq ft | $9,000 to $15,000 (computed) | $8,443 to $16,886 |
| 40x60 | 2,400 sq ft | $20,600 to $35,200 | $13,512 to $27,024 (computed) |
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HomeBlue figures are 4 to 6 inch reinforced slabs; computed HomeBlue rows use its $6 to $10 per sq ft rate. projectcosted publishes 1,500 sq ft directly; other rows use its $5.63 to $11.26 per sq ft.
Size check in the concrete slab calculator; for the steel building side of a shop, anchor bolts and column edges, see the metal building slab page.
How thick a shop slab should be for what you do in it
Thickness follows the heaviest thing that will sit or roll on the floor. MBMI's steel building guide gives 4 to 6 inches for most agricultural and light commercial buildings and 6 to 8 inches for heavy equipment.
| Shop use | Starting point | What to check |
|---|---|---|
| Woodshop, storage, hobby garage | 4 in | Point loads from tall shelving |
| Pickups, boats, side-by-sides | 5 to 6 in | Tire loads at the door apron |
| Two-post or four-post car lift | Lift maker's minimum | Installation manual: thickness, strength and edge distance |
| Tractors, skid steers, heavy equipment | 6 to 8 in | Engineer's design on clay |
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4 to 6 in and 6 to 8 in ranges from MBMI; lift requirements come from the lift manufacturer, not a general table.
Joints, drainage and finish on a large slab
Joint layout
A 40x60 slab can't be one panel. NRMCA's joint guidance (CIP 6) caps joint spacing at 24 to 36 times the thickness, 15 feet at most, with panels no longer than 1.5 times their width, and saw cuts made within 4 to 12 hours of finishing. Planning the grid so joints don't run under a lift post saves a headache later.
Slope and drains
A slight fall toward the overhead door or a trench drain lets wash water and rain blown in through the door leave the building. For garages the residential code requires the vehicle area to slope toward a drain or the main vehicle door.
Finish
Shop floors are usually power troweled smooth. Epoxy or polished floors come later from a different trade; if you plan one, say so up front so the slab is finished and cured with it in mind.
Before you order the shop building
- Final building size and the maker's anchor bolt plan
- Door sizes and locations, including any walk doors on a slab step
- Where a lift, compressor, sink or floor drain goes
- Whether any part will be heated, cooled or lived in (vapor retarder)
- Lot zoning and impervious cover headroom inside the City
