Colin FosterBy Colin Foster

Updated November 2026

A sunken in fire pit sits below ground level, so the flames stay lower, the wind has less effect, and the seating area around it feels more like a room. This guide walks you through choosing a site, digging and lining the pit, and checking local rules before you light the first fire. The steps below suit a typical residential backyard with a firm, well-drained soil base.

Check Local Rules and Pick the Right Spot

Before you dig, call your local fire department or building office. Many towns set minimum distances from structures, property lines and overhanging branches, and some require a permit for permanent pits. Common guidance from fire agencies is to keep a pit at least 10 to 25 feet from houses, fences and sheds, but your local code controls. Also call 811 before digging so buried utility lines can be marked.

Shopping for one? See our guide: 6 Best Liquid Propane Fire Pit Models for Patios and Backyards (2026).

Choose a flat, level area with good airflow and no low tree limbs above it. Avoid slopes where water will run into the hole and places directly under power lines.

Dig and Shape the Pit

  1. Mark a circle with a garden hose or rope. A diameter of 36 to 42 inches is common for a sunken pit that seats several people.
  2. Dig down 12 to 18 inches, keeping the sides as straight as you can. Slope the bottom very slightly toward one edge so any rainwater can drain away.
  3. Remove roots, rocks and loose soil. Tamp the base firmly so it will not settle unevenly.
  4. Check that the rim will sit level with the surrounding ground. Adjust the depth before you add any stone or liner.

Line the Walls and Add a Base Layer

A sunken pit needs a barrier between the flames and the soil, and drainage at the bottom. Spread a 2 to 3 inch layer of compacted gravel across the base, then add a layer of sand to level it. Use fire-rated stone, such as firebrick or dry-stacked natural stone, for the walls. Never use river rock or stones that trap moisture, because trapped water can cause them to crack or pop when heated.

Stack the wall material so each course sits tight against the one below. Leave a small gap of about half an inch at the top of the wall if you plan to install a cover or insert later. Check level with a long board after every few courses.

Create a Drainage Path

Run a short trench from the lowest point of the gravel base to a lower patch of lawn or a gravel bed. This gives standing water a route out. A simple drainage path is often enough for a pit that sits above the water table.

Set Up Seating, Clearance and Safe Use

Place seating so people sit at least 4 to 6 feet from the flame edge. Keep a clear zone of at least 3 feet around the pit free of dry leaves, mulch and furniture. Keep a hose, a bucket of sand or a fire extinguisher within easy reach. Burn only dry, seasoned wood and never use lighter fluid on a hot or smoldering fire.

Common Mistakes to Avoid

  • Skipping the utility check, which can cause serious injury or service interruption.
  • Digging too shallow, so flames and heat reach the sides and surrounding grass.
  • Using stones that hold moisture or are not fire-rated, which can crack or shatter.
  • Letting water collect in the bottom because no drainage path was dug.
  • Placing the pit too close to a fence, deck or low branch.

If you are not sure about soil stability, drainage or gas line routing, consult a licensed landscaper or contractor before digging.

  • Fire-rated bricks for the lining: Firebrick holds up to repeated heating far better than standard landscape block. View on Amazon
  • A fire-safe spark screen: A mesh screen keeps embers inside the pit and is useful when children or pets are nearby. View on Amazon
  • A long level: Checking the rim and each wall course keeps the pit even and stable. View on Amazon

Sunken Fire Pit FAQ

How deep should a sunken fire pit be?

Most sunken pits are 12 to 18 inches deep. That depth keeps flames low and protects the surrounding lawn from heat.

Does a sunken fire pit need drainage?

Yes. A layer of gravel and a small drainage path help prevent water from pooling and freezing inside the pit.

Can I build a sunken fire pit on a slope?

It is possible but harder. A sloped site needs extra retaining work, and water can run toward the pit, so a level spot is usually the safer choice.

Conclusion

A well-built sunken in fire pit needs the right location, a stable dig, fire-rated lining and a clear safety zone. Check local rules first, then work through the steps in order. With good drainage and proper clearance, your pit will be comfortable and safe for many seasons.

Ready to choose one?

Colin Foster

About Colin Foster

Colin Foster is part of our editorial team and reviews and edits our backyard living & play guides, checking product details against manufacturer specifications and owner feedback.