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MaterialCalc — 24x30 Garage Shell Material & Cost Calculator

Estimate prepared 09/02/2026. Estimates only; verify against your plans before ordering.

24x30 Garage Shell Material & Cost Calculator

Also the truss span, which drives the truss price.

Nine or ten feet if you might fit a lift later.

Count each garage door, service door and window.

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Result

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24x30 is a two-car garage with a real workshop bay at the end — 720 square feet, and the size most people wish they had built instead of 24x24. This works out the shell: slab, wall framing, sheathing and trusses. It is the part you can price precisely; the finishing is where quotes diverge.

Assumptions used

These are the numbers behind the result. Where one of them is soft, the cost range widens rather than pretending to a precision the data does not have.

Stud spacing, 16 in on center
16 in o.c.

International Residential Code (2021) — Published product data, checked 09/01/2026

Roof truss spacing
24 in o.c.

International Residential Code (2021) — Published product data, checked 09/01/2026

Garage slab thickness
4 in

International Residential Code (2021) — Published product data, checked 09/01/2026

Compacted gravel base under slab
4 in

Drains water away from the underside of the slab. Skipping it is the usual cause of a slab that heaves.

International Residential Code (2021) — Industry standard, varies by supplier, checked 09/01/2026

Welded wire mesh sheet coverage
150 ft²

One 5x10 ft sheet, less the overlap at the seams.

Home Depot / Lowe's published product data — Industry standard, varies by supplier, checked 09/01/2026

Crushed gravel density
105 lb/ft³

Compacted 3/4 in crushed stone. Varies by quarry and moisture; loose stone runs lighter.

USGS aggregate bulk density range — Industry standard, varies by supplier, checked 09/01/2026

Compaction allowance
0.2

Loose stone loses roughly a fifth of its volume once compacted, so order above the finished volume.

Standard earthwork practice — Rough figure — widens the estimate range, checked 09/01/2026

Ready-mix short-load threshold
1 yd³

Below roughly one cubic yard, most suppliers add a short-load fee that erases the price advantage over bags.

Regional ready-mix supplier schedules — Rough figure — widens the estimate range, checked 09/01/2026

Prices verified 09/01/2026 (US national average, big-box retail shelf price and regional ready-mix quotes). Regional adjustment: Blended from RSMeans city cost index bands and BLS construction wage differentials.

The formula

Slab = footprint × 4 in ÷ 27 for cubic yards, with base stone at the same footprint. Studs = (perimeter ÷ 16 in) + 1, plus seven per opening. Plates = perimeter × 3. Wall sheathing = perimeter × wall height ÷ 32 ft². Trusses = (length ÷ 24 in) + 1, two of which are gable ends.

Worked examples

24x30 with 9 ft walls, 4 openings

Garage length: 30 Garage width: 24 Wall height: 9 Doors and windows: 4 Waste: 10

720 ft², about 9.8 yards of slab concrete, 130 studs and 16 trusses. The shell for a serious two-car garage.

Same footprint with 8 ft walls

Garage length: 30 Garage width: 24 Wall height: 8 Doors and windows: 4 Waste: 10

Barely cheaper — a few sheets of sheathing and shorter studs. This is why the taller wall is almost always the right call.

24x24 for comparison

Garage length: 24 Garage width: 24 Wall height: 9 Doors and windows: 3 Waste: 10

576 ft². The 24x30 costs about 20% more in shell material for 25% more space, and it is the extra 6 ft that makes the building useful.

Choosing materials

  • Build the walls nine or ten feet, not eight. The extra studs and sheathing cost very little, and it is the difference between fitting a car lift or an overhead storage rack later and never being able to.
  • Six extra feet over a 24x24 buys a full workshop bay. Per square foot it is the cheapest space in the build, because the slab edge, the roof span and the door count barely change.
  • This is the shell only. Roofing, siding, garage doors, service door, windows, electrical, insulation and the concrete apron are all extra and together usually cost more than everything listed here.
  • Order trusses six to eight weeks ahead. At a 24 ft span they need a crane on the day, which has to be booked to match the delivery.
  • Check setbacks and lot coverage before designing. Many jurisdictions limit detached accessory buildings by footprint or by percentage of the lot, and 720 square feet crosses that line in some places.

Common questions

What does a 24x30 garage shell cost?

Slab, framing, sheathing and trusses typically run $14,000 to $24,000 in material and framing labor. Finished with roofing, siding, doors and electrical, a complete 24x30 detached garage usually lands between $35,000 and $60,000.

How much concrete for a 24x30 garage slab?

At 4 inches, about 8.9 cubic yards before waste and 9.8 with an allowance. At 5 inches — better under vehicles — it is 11.1 before waste. Add roughly 1.5 yards if you pour a thickened perimeter edge.

Is 24x30 big enough for two cars and a workshop?

Yes, comfortably. Twenty-four feet wide parks two cars with door clearance, and the extra six feet of depth gives a full workbench bay without either car overhanging it.

How tall should garage walls be?

Nine or ten feet. Eight feet is standard and rules out a car lift, overhead storage and a tall garage door forever. The upgrade costs a few hundred dollars at framing and cannot be added later.

How many trusses for a 24x30 garage?

Sixteen at 24 inches on center along the 30 ft length — fourteen commons and two gable ends. Gable end trusses cost about 40% more than commons.

Do I need a permit for a detached garage?

Almost certainly, and often a site plan showing setbacks. Many jurisdictions also limit accessory building size or total lot coverage, and 720 square feet is large enough to run into those limits. Check before you design.

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