# Concrete slab calculator

> 10′ × 10′ slab, 4″ thick: 1.23 cu yd of concrete; order 1.5 cu yd, plus the gravel base, mesh and forms. Bags or ready-mix yards, gravel base, rebar or mesh and forms for a slab, a pad or footings.

## What to buy (10′ × 10′ slab, 4″ thick)

Every line shows the quantity to buy and how StudSheet got it: the spacing, the waste and the package size, so you can check it before the supply house or the quote.

| Buy | Material | How StudSheet counts it | What it is for |
|---|---|---|---|
| **1.5 cu yd** | Ready-mix concrete (delivered) (4000 psi, 5–7% air) | 10′ × 10′ × 4″ = 33.33 cu ft (1.23 cu yd), +10% for an uneven base and spills, rounded up to the next quarter yard. Small loads carry a short-load fee at most plants — ask when you order. | Ordered by the cubic yard (by the cubic metre in Canada) from a local plant; the truck chutes it into the forms. |
| **1.5 cu yd delivered** | Crushed stone base, bulk (¾″ minus, with fines) | 100 sq ft × 4″ deep, +20% because gravel compacts = 40 cu ft loose (80 bags — order it in bulk). | Crushed stone with fines (¾″ minus), delivered in bulk from a landscape or stone yard. Compacts into a firm base. |
| **3 sheets** | Welded wire mesh, 5×10 ft sheet (6×6 W1.4×W1.4, 5×10 ft) | Covers 9′ 8″ × 9′ 8″ (2″ in from the edges); sheets lap one full square plus 2″, +10% for cut-offs. | 6×6 W1.4×W1.4 (10-gauge) mesh: holds cracks tight in patios, walks and shed floors. Set it on chairs so it ends up inside the slab. |
| **16 chairs** | Rebar chairs or dobies (2″ chairs) | About one every 3 ft each way, so the mesh ends up at mid-depth instead of lying on the gravel. | Plastic chairs or small concrete blocks that hold mesh or rebar at the right height while you pour. |
| **1 roll** | Rebar tie wire (16-gauge roll) | Ties the sheet laps together. | 16-gauge annealed wire that ties bars where they cross and laps together. |
| **3 boards** | 2×4 (2×4 × 10′) | Forms on the open sides (10′ + 10′ + 10′), on edge with the top at the finished height. A 2×4 is 3-1/2″ wide: set its top at the finished height and the concrete fills the last 1/2″ under it. | Framing lumber, actually 1½″ × 3½″. |
| **15 stakes** | Wood stakes (18″) | One every 3 ft on the outside of the forms and one at each end of every side. | Hold form boards in place. |
| **1 box** | Duplex (double-head) nails 16d | Through the stakes into the forms; the second head makes stripping them easy. | The second head stays proud so forms come apart easily. |
| **1 strip** | Expansion joint filler, 10 ft strips (½″ × 4″ strips) | 10′ along the house: an isolation joint lets them move apart without cracking either one. | ½″ asphalt-impregnated fiber strip that separates a new slab from the house, steps and old walks so they can move apart. |
| **1 gallon** | Concrete cure-and-seal compound | 100 sq ft at about 250 sq ft per gallon, sprayed on as soon as the sheen is gone. | Sprayed or rolled on right after finishing; it holds the water in so the concrete cures strong. About 200–300 sq ft per gallon. |

### In Canada (3.05 m × 3.05 m slab, 102 mm thick)

Set to Canada, the Sheet works the job out again for Ontario: metric sizes, bag sizes, the frost depth and the code notes. It doesn't just convert feet to meters. The first lines:

- **1.25 m³, Ready-mix concrete (delivered):** 3.05 m × 3.05 m × 102 mm = 0.94 m³, +10% for an uneven base and spills, rounded up to the next 0.25 m³. Small loads carry a short-load fee at most plants — ask when you order.
- **1.5 m³ delivered, Crushed stone base, bulk:** 9.3 m² × 102 mm deep, +20% because gravel compacts = 1.13 m³ loose (80 bags — order it in bulk).
- **3 sheets, Welded wire mesh, 1.52×3.05 m sheet:** Covers 2.95 m × 2.95 m (51 mm in from the edges); sheets lap one full square plus 51 mm, +10% for cut-offs.
- **16 chairs, Rebar chairs or dobies:** About one every 914 mm each way, so the mesh ends up at mid-depth instead of lying on the gravel.
- **1 roll, Rebar tie wire:** Ties the sheet laps together.
- **3 boards, 2×4:** Forms on the open sides (3.05 m + 3.05 m + 3.05 m), on edge with the top at the finished height. A 2×4 is 89 mm wide: set its top at the finished height and the concrete fills the last 13 mm under it.

## The steps, in order

> **PRO STEP: most of it is DIY-friendly; one step needs a licensed pro.** About 17–26 hours of work for this example.

1. Call 811 (NJ One Call) at least 3 full business days ahead and wait for the utility markings.
2. Lay out the slab with stakes and a string line, 10′ × 10′, and square it by measuring the diagonals. Plan the slope: ⅛–¼″ per foot away from the house.
3. Dig out 8″ (4″ of concrete on 4″ of gravel), plus 6″ past the edges for the forms. Strip sod and soft soil down to firm ground and tamp the bottom.
4. Set the forms on the open sides: 2×4s on edge, stakes every 3 ft on the outside, tops at the finished height with the slope built in. Nail through the stakes with duplex nails, and fasten the expansion strip against the house.
5. Spread the gravel in 2″ layers and compact each one; finish it flat, 4″ below the form tops.
6. Lay the mesh 2″ in from the edges, sheets lapped one full square plus 2″ and tied; set it on 2″ chairs about every 3 ft.
7. Pour: have the crew, wheelbarrows, a concrete rake and the screed ready before the truck comes. Start at the far corner and fill to just above the forms.
8. Strike it off with the screed, sawing it along the form tops, then float it once. Wait for the bleed water to soak back in before the next pass.
9. Edge the slab and tool the control joints 5′ apart at most (4 panels), 1″ deep with the groover; then broom it across the slope for grip.
10. Cure: spray the cure-and-seal as soon as the sheen is gone. Keep it from freezing for 48 hours.
11. Strip the forms after 1–2 days and backfill along the edges.

## Tools (25)

Must-have tools first, then the ones that help and the ones to rent for the day.

| Tool | Need | Why |
|---|---|---|
| **Rebar cutter-bender** | **Must have** | Cuts the mesh to fit (bolt cutters work too) |
| **Pump sprayer** | **Must have** | Puts the cure-and-seal on in an even coat |
| **Tape measure (25 ft)** | **Must have** | The red boxes every 16″ on the blade are stud spacing. |
| **Mason's line + stakes** | **Must have** | A tight string that sets a straight, level line for block courses. |
| **Line level** | **Must have** | A tiny level that hangs on a string line. |
| **4-ft level** | **Must have** | Checks plumb and level over a long span. |
| **Round-point shovel** | **Must have** | Digs. |
| **Landscape rake** | **Must have** | Spreads gravel and soil level. |
| **Circular saw** | **Must have** | Cuts the form boards |
| **Framing hammer** | **Must have** | Drives the duplex nails |
| **Sledgehammer** | Good to have | Drives stakes into hard ground |
| **Plate compactor** | Rent | Compacts the gravel in 2″ layers; a hand tamper can’t get 100 sq ft tight |
| **Sod cutter** | Good to have | Lifts the grass in clean strips before you dig |
| **Screed (magnesium straightedge)** | **Must have** | Strikes the concrete off flat with the form tops (a straight 2×4 works) |
| **Bull float + handles** | **Must have** | Smooths a slab this size from its edge |
| **Concrete float + edger** | **Must have** | Rounds the edges and touches up where the bull float can’t reach |
| **Concrete groover** | **Must have** | Cuts the control joints 1″ deep while the concrete is still soft |
| **Concrete finish broom** | **Must have** | A broom finish across the slope keeps it from being slick when wet |
| **Kneeboards** | Good to have | To reach the middle of a slab wider than 8 ft |
| **Concrete rake (come-along)** | **Must have** | Pulls the concrete out of the chute and along the forms |
| **Wheelbarrow** | **Must have** | Moves gravel, soil and block. |
| **Square shovel** | **Must have** | Cuts clean trench walls, moves gravel. |
| **Rubber boots + waterproof gloves** | **Must have** | Wet concrete burns skin: rubber boots and waterproof gloves |
| **Safety glasses** | **Must have** | Every cut, every nail, every time. |
| **N95 dust masks** | Good to have | For dusty cutting and sweeping |

## Mistakes and how the math works

### Mistakes that cost a callback or a second trip

- **Adding water to make it pour easier:** Extra water makes weak, dusty concrete that cracks and scales. Use the water the bag or the plant says; rent a mixer instead.
- **Finishing over bleed water:** Troweling the water back into the surface makes it flake off after the first winter. Wait until the sheen is gone.
- **Joints too far apart, or too shallow:** Concrete shrinks and cracks: cut joints ¼ of the depth and about 8′ apart at most, so you decide where.
- **Pouring on soft, muddy or frozen ground:** The slab settles and cracks where the ground gives. Firm, compacted base; never pour on frost.

### What the calculator assumes

- Concrete: 100 sq ft × 4″, +10% for an uneven base and spills. 80 lb bag ≈ 0.6 cu ft (Quikrete); ready-mix rounded up to the next quarter yard.
- Base: 4″ of crushed stone with fines, +20% loose because it compacts.
- Control joints: no farther apart than 24–36 times the thickness or 15 ft, panels no longer than 1.5 × their width, cut ¼ of the depth (at least 1″), sawn 4–12 hours after finishing (NRMCA CIP 6). This Sheet plans 24 times: 8′ for 4″.
- Mesh: 6×6 W1.4×W1.4 sheets lapped one square plus 2″, held at mid-depth on chairs (IRC R506: from the middle to the upper third). It keeps cracks tight; it doesn’t stop them.
- Outdoors: no vapor retarder (the IRC exempts patios, walks, driveways and unheated buildings).
- Curing: keep it wet or sealed for 5 days in warm weather, 7 when it’s 50–70°F, and from freezing for 48 hours (Quikrete). Walk on it after 1–2 days, light use after a week, full strength at 28 days.

## Code, permits and safety

The Sheet sets its code notes for the job's state or province. These are New Jersey's and Ontario's; the [code reference](https://studsheet.com/codes) has more. Always confirm with your building department.

- **Outdoor concrete in freezing winters:** Where winters freeze, porches, steps and garage floors take 3500 psi air-entrained concrete, 5–7% air (IRC Table R402.2); order the same for driveways and patios. Bagged mixes usually aren’t air-entrained: seal them and keep de-icing salt off the first winter.
- **Pour day is a crew job:** A truck brings 1.5 cu yd at once, and in warm weather you have an hour or two to place and finish it. Plan at least 3 people for the first yard and one more for each one after, or hire a finisher for pour day.
- **Call 811 first — it’s the law:** In New Jersey, call 811 (NJ One Call) at least 3 full business days before digging. Free. Wait for the utility markings.
- **Ask your town about zoning:** Patios and walks on the ground usually need no construction permit in New Jersey, but many towns want a zoning permit for new paving (lot coverage, drainage). Ask your town.
- **Click Before You Dig:** Before you dig, request a free utility locate from Ontario Dig Authority (ontariodigauthority.ca) at least 5 business days ahead, and wait for the markings.
- **Usually no permit:** A patio or walk at grade usually needs no building permit in Canadian cities. Zoning may limit paved area and water draining toward neighbours: ask your municipality’s building department if unsure.

## Questions

### What materials do I need to pour a concrete slab?

For the worked example, a 10′ × 10′ slab, 4″ thick, the Sheet counts 10 lines with waste included, starting with ready-mix concrete (delivered) (1.5 cu yd), crushed stone base, bulk (1.5 cu yd delivered), welded wire mesh, 5×10 ft sheet (3 sheets), rebar chairs or dobies (16 chairs). Each line's math is in the table above. Put in your own sizes in the [concrete calculator](https://app.studsheet.com/p/concrete) and every line is counted again.

### How long does it take to pour a concrete slab, and can I do it myself?

About 17 to 26 hours for the worked example, in 11 steps. StudSheet stamps it **PRO STEP**: dIY with a pro for one step.

### What tools do I need to pour a concrete slab?

25 in all. The must-haves start with rebar cutter-bender, pump sprayer, tape measure (25 ft), mason's line + stakes, line level, 4-ft level. On the Sheet you mark each one as owned, to buy or to rent.

## Ask about it

Stuck while you pour a concrete slab? Ask in the [Concrete slabs and footings group](https://studsheet.com/forum/concrete) of the StudSheet community with this Sheet attached. Homeowners who've done it and verified pros answer, and anyone can read it.

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