How to build a steel fire pit

🔥 How to Build a Steel Fire Pit — Weekend Fabrication Guide for Australian DIYers

What is involved in building a steel fire pit for Australian backyards?

A steel fire pit is a practical weekend fabrication project that suits Australian backyards, especially ahead of winter and outdoor entertaining season. This guide covers planning, cutting, welding, assembly and first burn-off, with a focus on mild steel, beginner-friendly fabrication methods, and safe backyard use.

For most DIY builders, a simple square or round fire pit made from 3 mm to 5 mm mild steel is the best balance of durability, ease of cutting and manageable welding. If the fire pit will support significant weight or form part of a permanent structure, refer to AS/NZS 1554 for welding quality requirements on any load-bearing components.

What skill level is required to build a steel fire pit?

What tools are required to build a steel fire pit in Australia?

What materials are needed for a DIY steel fire pit?

Safety Requirements

Step-by-Step Guide

Step 1: Plan the fire pit size and design

Choose a simple design that matches your tools and skill level. For beginners, a square fire pit is easier to measure, clamp and weld than a round rolled shell.

A practical backyard size is:

This size gives enough room for decent firewood without becoming too heavy to move. If portability matters, stay closer to 3 mm steel. If longevity matters more and you have enough welder capacity, go 5 mm steel.

Decide whether you want:

💡 For a first build, keep it simple: four side panels, one base, and short legs or a basic angle-iron stand.

Step 2: Mark out your steel accurately

Measure and mark each panel carefully using a tape, square and soapstone. For a square pit at 600 mm x 600 mm x 350 mm high, cut:

If the base sits inside the side walls, allow for steel thickness so it fits neatly. Accurate marking here saves headaches during fit-up.

Mark any air holes or drainage holes now. Common options:

💡 Do not overdo side air holes. Too much airflow can make the fire burn excessively hot and shorten the life of the pit.

Step 3: Cut the steel panels

Use an angle grinder or plasma cutter to cut all parts cleanly. Support the steel properly so cuts don’t pinch the disc.

After cutting:

If your steel comes with mill scale, MIG will generally tolerate some scale, but cleaner weld zones will produce better arc stability and fusion.

For MIG welding 3 mm mild steel, a good starting point is:

For MIG welding 5 mm mild steel, start around:

Settings vary by machine, so always run test welds on offcuts first.

Step 4: Prepare the joints and fit-up

Lay out the four side panels on a flat non-combustible surface. Check all edges are square and reasonably straight.

For 3 mm to 5 mm steel, a simple butt or outside corner joint works well. Leave a small root gap only if needed for fit and penetration. For most DIY fire pits, tight clean fit-up is fine.

Clamp the panels together using magnets or corner clamps and verify the diagonals if building a square pit. Equal diagonals mean your assembly is square.

If using a base panel inside the walls, dry fit it before tacking. You want enough clearance to drop it in without forcing it.

💡 Tack first, measure second, weld last. Many beginner projects go out of square because they’re fully welded too early.

Step 5: Tack weld the shell

Tack each corner with small welds, roughly 15 mm to 20 mm long. Start with one tack at the top and one near the bottom of each joint.

Re-check:

If needed, tap the shell gently into alignment before adding more tacks.

For those using stick welding, E6013 2.5 mm or 3.2 mm electrodes are beginner-friendly on mild steel. Typical starting ranges:

MIG is still the easier process for thin to medium fire pit plate because heat is easier to control and cleanup is quicker.

Step 6: Fully weld the corners with heat control

Weld the corner joints in short runs rather than one long pass. This helps reduce warping, especially on 3 mm steel.

A good sequence is:

Aim for consistent fillet welds with good tie-in at both panel edges. You do not need oversized welds. A neat, moderate fillet is stronger and cleaner than a large cold blob.

If the fire pit is primarily decorative and for backyard use, outside welds may be enough. If you want extra stiffness and longer life, you can also seal or stitch weld the inside corners once the shell is stable.

💡 On fire pits, slight gaps and stitch welding are acceptable in many DIY builds. Fully sealing every seam can trap moisture if drainage is poor, and overheating the steel can increase distortion.

Step 7: Fit and weld the base

Position the base panel inside the shell. Support it evenly so it sits level, usually slightly above the bottom edge if you want an ash gap or directly at the bottom if keeping things simple.

Tack the base in several spots first, then stitch weld around it. Continuous welds are not always necessary for a backyard fire pit, provided the base is secure and ash won’t spill excessively.

If you have not yet drilled drainage holes, do so now. A few 10 mm to 12 mm holes in the base help water escape when the pit is left outdoors.

If you prefer a longer-lasting setup, some fabricators create a sacrificial inner base plate that can be replaced later after repeated heat cycles.

Step 8: Add legs, stand or feet

A fire pit should be raised off the ground where possible to reduce heat transfer and improve safety on hard surfaces.

Simple options include:

Cut all legs to equal length, clamp in place, and tack them first. Check the pit sits level before final welding.

If building a larger pit, an angle frame gives much better stability than small legs welded directly to thin plate.

Refer to AS/NZS 1554 principles for sound weld quality where supports are carrying weight.

Step 9: Clean up and finish the welds

Grind only where needed. On a fire pit, leaving sound welds visible is perfectly acceptable and often looks better than over-ground joints.

Focus on:

Wipe the exterior with degreaser before painting. Only use high-temperature paint on the outside surfaces. The inside will burn coatings off quickly, so leave it bare steel.

Do not paint surfaces that will contact direct flame unless the coating is explicitly rated for that use.

Step 10: Burn-off, inspection and placement

Before regular use, perform a first burn outdoors in a clear area. This burn-off helps remove residual oils, marking compounds and any remaining contaminants.

Check during and after the first burn for:

Place the fire pit on:

Keep it clear of fences, decking, dry grass, furniture and eaves. Also check local council rules, strata bylaws, and total fire ban restrictions before use.

💡 Even a well-built steel fire pit will eventually warp with repeated heat cycles. That’s normal. Good drainage, sensible plate thickness and controlled airflow help maximise life.

Common Mistakes to Avoid

Pro Tips

Recommended Tools

If your welder, plasma cutter or fabrication package is over $1,000, equipment finance through Local Knowledge Finance is worth considering to spread the cost of a better-quality setup.