10×20 Concrete Slab (4 inches): Yards, Feet & Bags
A 10 ft x 20 ft slab is perfect for a patio or gazebo base. Decide between bags or ready-mix based on access and waste considerations before starting your project.
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Quick Answer
Tip: Always confirm the yield printed on your bag label. Bag yield guide
Large pour: consider ready-mix delivery for speed and consistent results. Bag counts this high can take significant mixing time.
Project Notes (Unique)
When ordering, round to 0.25 yd³ and check yield on the label to ensure you have enough material for your slab.
Ensure your base is well-prepared and forms are sturdy to prevent shifting or settling during the pour.
For a smooth finish, use a float and allow the slab to cure naturally, keeping it moist as needed.
10×20 Slab Thickness Check
For a walkway, a 4-inch slab fits many medium load jobs, but subgrade quality, reinforcement, and local requirements still matter.
Current spec
This page estimates a 10×20 slab poured at 4 inches.
Load check
Best fit depends on whether this is mainly pedestrian use, storage, or heavier wheel traffic.
Upgrade trigger
If you expect heavier loads later, compare this design against the alternate thickness before ordering.
What to Prepare Under a 10×20 Concrete Slab
Most slab problems start below the concrete. Keep the base level, compacted, and consistent before you pour.
- Strip loose topsoil and organic material until you reach firm subgrade.
- Compact the base in lifts so the 10×20 slab does not settle unevenly.
- Check form height and diagonal measurements before concrete arrives.
- Plan reinforcement, joints, and edge support based on the intended walkway use.
Worked Example for 10×20 at 4 Inches
Step-by-step calculation for this exact slab:
- Convert thickness to feet: 4 ÷ 12 = 0.3333 ft
- Compute area: 10 × 20 = 200 sq ft
- Volume in cubic feet: 200 × 0.3333 = 66.67 ft³
- Convert to cubic yards: 66.67 ÷ 27 = 2.469 yd³
- Add 10% waste buffer: 2.469 × 1.10 = 2.716 yd³
How to Order Concrete for 10×20
This slab needs about 2.47 yd³ of concrete, or 112 80 lb bags before waste. With a waste cushion, plan around 2.72 yd³.
For this volume, ready-mix is usually the safer plan. Round up, confirm delivery minimums, and make sure your crew can place and finish the slab without delays.
Adjust dimensions in the slab calculator or compare bag counts here.
Bag Counts by Waste Buffer for 10×20
Pick a buffer based on site conditions: smooth forms and good subgrade can run leaner; uneven excavation or hard-to-reach pours need more cushion.
| Buffer | Yards (yd³) | 80 lb bags | 60 lb bags | 40 lb bags |
|---|---|---|---|---|
| +5% tight pour | 2.59 | 117 | 156 | 234 |
| +10% typical | 2.72 | 123 | 163 | 245 |
| +15% rough subgrade | 2.84 | 128 | 171 | 256 |
What to Expect After Pouring This walkway
For a walkway slab, light foot traffic may come sooner than vehicle loads, but finishing quality still depends on keeping the slab damp and protected early on.
First 24 hours
Protect edges, prevent washout, and avoid unnecessary traffic while the slab sets.
Days 2-7
Maintain curing conditions and monitor joints, surface drying, and weather exposure.
Up to 28 days
Concrete keeps gaining strength, so wait for the right service window before heavy use.
How to Estimate This Slab in 3 Steps
Measure
Length 10 ft, width 20 ft, thickness 4 in.
Compute Volume
Area: 200 sq ft → volume: 66.7 ft³ → 2.47 yd³.
Add Waste
Add a small buffer for spillage and uneven subgrade, then round up when ordering.
Planning Notes
Common uses: patio, gazebo base, walkway section.
For more context and conversions, see the Concrete Calculator hub.
Frequently Asked Questions
What are the advantages of using ready-mix concrete over bags?
Ready-mix is convenient for larger projects, saving you time and reducing the need for multiple trips to the store.
How should I prepare the base for my slab?
Excavate to a stable subgrade, compact the soil, and add a gravel layer for drainage before pouring.
What thickness should I choose for my slab?
A thickness of inches is generally sufficient for patios and walkways, but consider heavier loads for thicker options.
How do I determine how much concrete I need?
Measure the area and depth, then account for a waste factor to ensure you have enough material.
Related Slab Sizes
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