How to Build a Concrete Fire Pit in One Weekend

Build a Concrete Fire Pit in One Weekend: Complete DIY Guide

A concrete fire pit is the ultimate backyard upgrade—it creates a focal point, extends your outdoor living season, and adds significant value to your property. Best of all, you can build one in a single weekend with basic tools and materials. This guide walks you through the entire process from planning to first fire.

Why Concrete Fire Pits Work

Concrete fire pits are:

• Durable: Last decades with minimal maintenance
• Customizable: Any size, shape, or finish you want
• Cost-effective: Example cost: approximately $200-$500+ in materials vs. $1,500-$3,000+ for pre-made units
• Heat-resistant: Concrete handles high temperatures without cracking (when done correctly)
• Permanent: No moving parts, no rust, no replacement needed

Planning Your Fire Pit

Before you start, decide on:

Size: Most fire pits are 36-48 inches in diameter. Smaller (30 inches) for intimate gatherings, larger (48+ inches) for bigger groups. Consider your space and how many people you want to seat around it.

Location: Minimum 10 feet from structures, 25 feet from overhanging branches. Check local fire codes. Ensure good drainage—don't build in a low spot that collects water.

Height: Standard is 12-18 inches tall. Lower (12 inches) for ground-level seating, higher (18 inches) for chair-height seating.

Shape: Round is most common and easiest. Square or rectangular works but requires more complex forms.

Materials You'll Need

For a 36-inch diameter, 16-inch tall fire pit:

• Concrete mix: approximately 4-6 bags (80 lb bags) depending on thickness
• Rebar: approximately 20-30 feet of #3 or #4 rebar
• Wire mesh: approximately 10-15 square feet
• Sonotubes (concrete forms): 2 tubes (one for inner wall, one for outer)
• Gravel: approximately 0.5 cubic yards for base
• Release agent or form oil
• Tools: shovel, level, tape measure, mixing container, trowel

Example cost breakdown (for reference only): Materials typically range from approximately $200-$500+ depending on size and material choices. Actual costs vary.

Step 1: Excavation and Base

Mark your fire pit location. For a 36-inch pit, dig a 42-inch diameter hole, 6-8 inches deep. This creates space for the base and allows the pit to sit slightly below grade for stability.

Fill the hole with 4-6 inches of compacted gravel. This provides drainage and a stable base. Compact thoroughly—use a hand tamper or rent a plate compactor for larger projects.

Level the gravel base. This is critical—an uneven base creates an uneven fire pit.

Step 2: Build the Forms

You'll create two concentric circles: an inner wall and an outer wall. The space between them is where you'll pour the concrete.

Outer form: Use a Sonotube (cardboard concrete form) cut to your desired height (typically 16-18 inches). For a 36-inch outer diameter, you'll need a 36-inch Sonotube. Cut it to height with a circular saw.

Inner form: Use a smaller Sonotube for the inner wall. For a typical fire pit, the inner diameter is 24-30 inches (leaving 3-6 inches of concrete wall thickness). Cut this to the same height.

Positioning: Center the outer form on your gravel base. Use stakes or rebar driven into the ground to hold it in place. Center the inner form inside the outer form. The space between them should be even all around (3-6 inches is typical).

Pro tip: Use a level to ensure both forms are plumb (vertical). This ensures your fire pit walls are straight.

Step 3: Reinforcement

Concrete needs reinforcement to handle the heat cycles and prevent cracking. Use both rebar and wire mesh.

Rebar: Cut rebar to fit vertically between the forms, spaced approximately every 6-8 inches around the circumference. These vertical pieces should be the height of your wall minus 2 inches (so they don't stick out the top).

Wire mesh: Wrap a piece of wire mesh around the rebar to create a continuous reinforcement cage. This prevents the concrete from cracking under thermal stress.

Important: Keep reinforcement 2 inches away from both the inner and outer forms. This ensures concrete completely surrounds the steel.

Step 4: Mixing and Pouring

Mix concrete according to package directions. For fire pits, use a standard mix—you don't need special "fire-resistant" concrete (regular concrete handles fire fine when properly reinforced).

Consistency: Mix to a workable consistency—not soupy, not dry. It should hold its shape when you form a ball but still be pourable.

Pouring: Pour concrete into the space between the forms in layers. Fill about 1/3, then use a stick or rebar to consolidate (remove air bubbles). Continue filling in layers, consolidating each layer.

Leveling: Once filled, level the top with a trowel or straight board. The top should be flat and even.

Work quickly: You have about 45 minutes from mixing to when it becomes unworkable. Have everything ready before you start mixing.

Step 5: Finishing

While the concrete is still workable (first 30-60 minutes), finish the top edge. You can:

• Leave it flat (simple, functional)
• Create a rounded edge with an edging tool (more finished look)
• Add texture with a broom or brush (non-slip surface)

If you want a smooth finish, use a steel trowel. If you want texture, use a broom or brush while it's still wet.

Step 6: Curing

Cover the fire pit with plastic sheeting to prevent moisture loss. Keep it covered for at least 3-7 days. Mist with water daily if it's hot and dry.

Don't remove forms too early: Wait at least 48-72 hours before removing the inner and outer forms. The concrete needs time to gain strength.

Full cure: Concrete reaches full strength in 28 days, but you can use the fire pit after 7 days for small fires. Wait the full 28 days before building large, hot fires.

Step 7: Drainage (Critical)

Fire pits need drainage to prevent water from pooling inside. Before the concrete sets completely, drill or create 4-6 drainage holes in the bottom of the inner wall (near the base). These should be 1-2 inches in diameter.

Alternatively, leave the bottom open (no inner form at the base) so water can drain naturally into the gravel base.

Step 8: First Fire

After 7 days, you can start with small fires. Build gradually:

• Week 1-2: Small fires only (kindling, small logs)
• Week 3-4: Medium fires
• After 28 days: Full fires

This gradual approach allows any remaining moisture to escape slowly, preventing steam explosions that can crack the concrete.

Common Mistakes to Avoid

1. Skipping reinforcement: Fire pits experience extreme heat cycles. Without reinforcement, they will crack.

2. Too thin walls: Walls less than 3 inches thick are prone to cracking. 4-6 inches is ideal.

3. No drainage: Water pooling inside will freeze and crack the concrete in winter.

4. Removing forms too early: Wait at least 48-72 hours. Premature removal can cause the walls to collapse.

5. Building fires too soon: Wait 7 days minimum. Large fires before full cure can cause cracking.

Maintenance

Concrete fire pits are low-maintenance but benefit from occasional care:

• Clean out ash regularly to prevent buildup
• Check for cracks annually and repair if needed
• Reseal every 2-3 years if you want to maintain a specific appearance (optional)
• Keep drainage holes clear

Safety Considerations

Clearance: Maintain 10 feet minimum from structures, 25 feet from trees

Never use accelerants: Gasoline, lighter fluid, etc. can cause explosions

Have water nearby: Keep a hose or bucket of water ready

Check local codes: Some areas require permits or have restrictions

Extinguish completely: Make sure fires are completely out before leaving

The Bottom Line

Building a concrete fire pit is a rewarding weekend project that adds significant value to your backyard. With proper planning, the right materials, and attention to detail, you can create a permanent, beautiful fire feature that will last for decades.

The key to success is proper reinforcement, adequate wall thickness, and patience during curing. Follow these steps, and you'll have a fire pit you can be proud of—and enjoy for years to come.

Need help with your fire pit project? Contact Local Concrete Contractor for professional installation or guidance on your DIY project.