How Deep Should Concrete Piers Be?

Building on Solid Ground

Concrete piers are a popular and dependable foundation method used in a range of construction, from decks and sheds to cabins and full additions. If you’re planning to build on piers, one of the first questions you’ll need to answer is: How deep should they go?

The answer depends on several factors, including your region’s frost line, the condition of your soil, and the type of structure you're building. In this guide, we’ll walk you through the key decisions that go into planning a concrete pier foundation. This way, you can pour with confidence and get the job done right the first time.

What Are Concrete Piers?

Concrete piers are vertical structural elements made by pouring concrete into deep holes in the ground, typically reinforced with rebar or placed inside form tubes. Once cured, these piers act like legs for your structure, transferring the weight from above down into stable soil below. Unlike a full slab or foundation wall, concrete piers isolate load points and are spaced apart to support beams, floor joists, or posts.

This type of foundation is especially useful in areas where:

• A full concrete slab isn’t necessary

• The soil has uneven stability

• The site has slopes or hard-to-access areas

• Structures are lightweight or elevated

They’re often used as the foundation for:

• Backyard decks

• Tiny homes and cabins

• Crawl-space homes

• Post-frame and beam-supported buildings

• Transmission pole foundations and remote builds

Depending on your project, piers may support wooden posts, steel beams, metal anchors, or concrete blocks.

How Deep Should Concrete Piers Be?

When you're planning a pier foundation, depth is the difference between long-term stability and costly repairs. Setting your piers at the right depth gives your structure a solid base that resists shifting, settling, or frost damage. Here’s what to know before you dig.

General Guidelines

• Minimum Depth: At least 12" below ground (or per your local code)

• Frost Line Depth: Typically 36"–48" in colder climates

• Average Pier Depth: 3–6 ft for small buildings, 10–15 ft for larger/heavier structures

Factors That Affect Pier Depth

The ideal pier depth isn’t the same for every project. It depends on a mix of environmental and structural conditions that affect how your foundation performs over time.

• Soil Condition: Clay, loam, sand, and expansive soil each react differently to weight and weather

• Load Requirements: Heavier structures need deeper piers

• Local Building Codes: Always check with your local jurisdiction

• Frost Line: In colder regions, piers must go below the frost line to prevent heaving

What Type of Hole Do You Need?

Before you start mixing concrete, you need to make sure your pier holes are the right size, shape, and depth to support the structure above. The hole itself is just as important as the concrete you pour into it. Getting this step right helps prevent settling, shifting, and early failure.

Hole Diameter & Depth

• Standard diameter: 12"–24" depending on load

• Use an auger or post-hole digger for consistent depth

• Line holes with fiber-form tubes (concrete pour tubes) for clean shape and strength

• Ensure the bottom of the hole is flat, with no loose soil or debris

Pier Footing Recommendations

In soft or unstable soils, widen the base of your pier:

• Add a pier footing pad or dig a bell-shaped base

• Lay gravel at the bottom for drainage and support

• Insert rebar vertically before pouring for added strength

What Happens if Piers Aren’t Deep Enough?

If your concrete piers aren’t set deep enough, your structure could face serious problems down the line. Shallow piers are more likely to be affected by frost heave, which can lift and crack the foundation during freeze-thaw cycles. In loose or unstable soils like clay and sand, inadequate depth can lead to settling or shifting over time. That movement puts stress on everything above and compromises the structural integrity of the entire build.

To avoid these issues, always dig to a depth that accounts for your local soil conditions and the weight of your structure.

Can I Dig the Holes Myself?

You can absolutely dig the holes yourself, especially if you’re handling a small or mid-sized project. Many DIYers use manual post-hole diggers for shallow piers, while power augers make quicker work of deeper holes. For sites with roots, rocks, or compacted earth, a sturdy shovel and digging bar can help clear the way. As long as you take your time and measure carefully, digging pier holes is a manageable step in the build process.

Tips for success:

1. Dig straight down, not at an angle

2. Use a tape measure to confirm depth

3. Keep holes free of loose dirt and moisture

How Much Concrete Per Pier?

Use the chart below to estimate how much concrete you'll need per pier. For reference, one 80-lb bag yields ~0.6 cubic feet.

 

Pier Spacing and Layout Best Practices

Getting your spacing right is just as important as digging to the right depth because even perfectly poured piers won’t help if they’re in the wrong place. Proper layout ensures your beams and floor joists are fully supported, your structure sits level, and your project stays on track from the ground up.

Foundation pier spacing depends on the weight of your structure and the span between beams or joists:

• Rule of thumb: 4–8 ft apart

• Use a string line to maintain alignment

• Always double-check opposite corners and bolt hole positions

• For deck layouts: include corner piers, center piers, and mid-span piers based on span

Misalignment here means rework later. Measure twice, dig once.

Do You Need Rebar in Concrete Piers?

In most cases, yes. Concrete piers should include rebar, especially if your pier is taller than three feet, built on expansive soil, or supporting heavy loads like a house foundation. Rebar adds strength and helps the pier resist cracking, shifting, and lateral movement over time. It's a simple addition that greatly improves the long-term durability of your foundation.

Rebar Setup Tips

1. Insert two vertical rebar rods spaced evenly

2. Tie horizontal cross braces for taller piers

3. Make sure rebar is embedded at least 2 inches from the surface to avoid rusting

Step-by-Step: How to Build a Concrete Pier Foundation

1. Mark your pier locations using stakes and string.

Start by laying out the footprint of your structure using stakes, string lines, and a measuring tape. This helps ensure your piers are evenly spaced and properly aligned from the beginning. Double-check your measurements and make sure corners are square before digging.

2. Dig holes to the proper depth and diameter.

Using an auger or post-hole digger, dig each hole according to your pier spacing plan and depth requirements. Be sure to go below the frost line and match the hole diameter to your load needs, typically between 12" and 24". Clear out any loose soil or debris from the bottom for a solid base.

3. Place form tubes cut to the exact height.

Insert fiber-form tubes into each hole and trim them so the top of each tube is level across the build site. These tubes shape the concrete and help prevent soil from caving in. Use a level to ensure the tops are flush and ready to support beams or posts.

4. Brace the forms with stakes and wood.

Once your forms are in position, brace them on the outside with wood stakes and cross-bracing to hold everything steady during the pour. This prevents shifting and keeps your piers perfectly vertical while the concrete sets.

5. Use the MudMixer to mix and pour continuously.

With your holes and forms ready, it's time to pour. Use the MudMixer to mix bagged concrete with consistent water input, feeding it directly into the forms. The continuous mixing design allows for fast, uninterrupted pouring with fewer hands on deck. Just load, mix, and pour.

6. Insert anchor bolts or brackets while the concrete is still wet.

Before the concrete begins to set, insert any anchor bolts, metal post brackets, or hardware required for the next phase of construction. Make sure each insert is straight and at the correct depth, then leave them undisturbed as the concrete cures.

7. Let piers cure before placing beams or posts.

Give your concrete time to fully cure before adding any weight. Depending on weather conditions, this may take 24 to 72 hours. Refer to the curing time chart below for guidance, and only proceed once your piers are fully set and solid.

How Long Before You Can Build on Piers?

Once your concrete is poured, it needs time to cure before you can safely start building. For most pier foundations, a waiting period of 24 to 72 hours is recommended, depending on weather conditions. Warmer temperatures help concrete cure faster, while colder or damp weather slows the process down significantly. Even if the surface appears dry, the concrete underneath may still be setting.

You should only move on to placing beams, posts, or framing once the concrete is fully cured and dry throughout. If you're in doubt, waiting a little longer is better than rushing the next phase. Use the table below as a rough guide:

Monitoring the weather and giving your piers the right amount of time to cure is a small step that helps protect the long-term stability of your foundation.

Depth Isn’t Everything: Other Factors to Get Right

• Confirm piers are level and aligned

• Double-check opposite corners and pier height

• In some areas, a special inspection is required before pouring

• For poor soil, consider switching to a steel pier foundation or push pier system

• Use rebar for added structural support in all cases

In the Mix: Real-World Pier Build with MudMixer

Watch how one DIYer used the MudMixer to build pier foundations for a cabin in Western North Carolina - no concrete truck needed.

Why Use the MudMixer for Concrete Piers?

When it comes to pouring piers, consistency and efficiency matter. MudMixer was designed specifically to solve the common problems of hand mixing—uneven batches, wasted time, and physical strain. Whether you're handling a DIY build or a multi-pier foundation for a professional project, MudMixer delivers a faster, cleaner, and more manageable way to get the job done.

Built to Save Time and Labor

• Mixes and pours up to 45 bags/hour

• Continuous feed—no batch mixing

• Adjustable water input avoids wet or dry inconsistencies

• One-person job that used to require three

Built to Last

• 14-gauge heavy-duty steel construction

• Flat-free tires for tough terrain

• IP55-rated electric motor

• Backed by a 2-year warranty

Where to Buy or Rent a MudMixer

MudMixer is available through over 2,000 dealers nationwide, making it easy to get the right equipment for your next project, no matter where you’re located.

To make things simple, use our Dealer Locator to find a store near you. If you’re ready to invest in faster, easier concrete mixing, the easiest option is to purchase directly from MudMixer.com and have it shipped to your door.

Build on the Right Foundation

The depth of your concrete piers depends on your soil, region, and structure, but the success of your build depends on getting the basics right.

With the right planning and the right tools, like MudMixer, you can pour faster, more consistently, and with less stress. Build with confidence from the first bag to the final beam.