Pier Foundation Calculator
— How Much Do You Need?

A pier foundation is a structural support system that uses vertical columns, called piers, to transfer the weight of a building down to stable soil or bedrock below the surface. Instead of spreading that load across a continuous slab, piers concentrate it at specific points, which makes them well suited for sloped terrain, soft or unstable soil, and areas with high moisture or expansive clay. Pier foundations are commonly used under houses, decks, porches, sheds, and light commercial structures. Each pier is typically formed from poured concrete, though steel and masonry piers exist as well. Aggregate materials play an important supporting role throughout a pier foundation project. Clean gravel or crushed stone is placed at the base of each pier hole to promote drainage and prevent moisture from collecting under the concrete. For pier and beam houses, gravel is also spread across the crawl space floor to manage moisture and improve drainage under the entire structure. Fill dirt and crushed stone are often needed for grading and backfill once the piers are set. Hello Gravel supplies all of these materials in bulk by the truckload, making it straightforward to get everything you need in one order.

The two main types are drilled pier foundations and driven pier foundations. Drilled piers, sometimes called bored piers or caissons, are by far the more common choice for residential and light commercial construction. A hole is augered or drilled into the ground to the required depth, a layer of gravel is placed at the base for drainage and stability, and then concrete is poured to form the column. These work well in most soil types and can reach depths of 10 to 20 feet or more depending on local frost depth and soil conditions. Driven piers are pushed or hammered into the ground using specialized equipment rather than drilled. They tend to be used in commercial and industrial applications or in situations where soil conditions make drilling impractical. For most homeowners and contractors, the drilled method is the standard approach, and gravel plays a key role in every single pier hole before any concrete is poured. If you are planning a multi-pier project and want to estimate how much gravel you will need across all your holes, the Hello Gravel calculator is a great place to start.

Pier depth is determined by three main factors: the frost line in your region, the type of soil beneath your site, and the load the pier needs to support. In cold northern climates, piers must extend below the local frost line to prevent the ground from shifting during freeze-thaw cycles and pushing the pier out of alignment. Depending on where you are building, that can mean depths of 42 to 60 inches or more. In warmer southern states where frost is not a concern, piers as shallow as 18 to 24 inches may be acceptable for lighter structures like decks or storage sheds. For larger or heavier structures, piers often need to reach stable subsoil or bedrock, which can push the required depth well beyond frost line requirements. Your local building code will specify the minimum depth for your area, so always check before you dig. From a materials planning standpoint, deeper piers mean more gravel at the base of each hole and more backfill material around each pier once it is set. If you are working on a multi-pier project, use the Hello Gravel calculator to estimate your total aggregate needs based on pier count, hole diameter, and depth. The team is also available to help you work through the numbers if your project has a lot of moving parts.

In many cases, yes. A pier foundation can cost significantly less than a full concrete slab, particularly on sloped or uneven terrain where extensive grading and forming would otherwise be required. With a slab, you are paying for continuous concrete coverage across the entire footprint of the structure. With a pier foundation, material is concentrated only where structural support is needed. That typically means less excavation, less concrete volume, and a simpler overall build. That said, the cost comparison shifts depending on your specific conditions. On flat, stable ground, a slab can sometimes be the more economical choice simply because of its straightforward installation. On challenging terrain, in areas with expansive or soft soils, or where drainage is a concern, pier foundations tend to win on both cost and practicality. One area where pier foundations consistently offer strong value is in aggregate savings. The gravel base under each pier and the crushed stone throughout the crawl space represent a relatively small material cost compared to what a full slab requires. Hello Gravel makes it easy to get that aggregate delivered to your site at upfront pricing with no hidden fees. Use the calculator on the product page to see what your project would require, or reach out to the team for help planning your order.

A properly built pier foundation is a permanent structure. When piers are correctly sized, installed below the frost line, and set on a stable gravel base, they can last 50 to 100 years or more with minimal maintenance. The factors that most affect longevity are installation depth, drainage, and concrete quality. Piers that do not reach below the frost line are vulnerable to seasonal movement. Piers that sit in poorly drained soil are at risk of moisture-related deterioration and settling over time. A clean gravel base at the bottom of each pier hole addresses both concerns by encouraging water to drain away from the concrete instead of collecting around it. Some people associate pier foundations with older or less stable homes, but that reputation tends to come from aging structures built before modern codes and materials were standard, not from the foundation type itself. A modern, code-compliant pier foundation built on a proper aggregate base is as durable and reliable as any other foundation system. If you want to give your piers the best chance at a long service life, the gravel base is one of the most important and cost-effective steps in the process. Hello Gravel supplies the clean crushed stone and gravel for that base layer in bulk, delivered directly to your site.