By Mick O'Brien · carpenter & builder · sheds-to-homes, cabins and things that stay up in a storm

“After my first oven collapsed at 900 degrees, I learned a 200mm air gap is the only thing stopping your backyard cookout from becoming a structural failure.”

Stop wasting money on gas or electricity. An outdoor oven is the cheapest, most reliable way to cook off-grid in Australia. No fancy tools. No bullshit. Just dirt, fire, and food that tastes like it should.

What You Actually Need (Forget the Hype)

Cob vs. Brick vs. Pizza Oven

Most Aussies overcomplicate this. It’s simple:

• Cob (clay, sand, straw): Cheapest. $0 if you dig your own clay. But it’s slow to heat and needs a roof. Good for bread, not pizza.
• Brick (firebrick + refractory mortar): What you actually want. Holds heat like a champ. Costs $200-$400 for a basic setup. Pizza ovens are just a type of brick oven.
• Pizza oven: A marketing term. It’s a brick oven built for high heat. Don’t pay extra for the name.

Heat Retention: The Only Thing That Matters

Bad ovens are cold after 10 minutes. Good ones cook for hours. How? Three things:

• Thick walls (15cm+): Brick or cob. Thin walls = instant heat loss. Australian sun won’t help you here.
• Insulation layer: Crushed brick or vermiculite behind the firebox. $15-$30 at Bunnings. Skip it = oven dies fast.
• Firebox size: Small firebox (20cm x 20cm). Big fire = wasted heat. Burn a small log, not a tree.

Step-by-Step: Build It in a Weekend (No Skills Needed)

1. Base: Concrete slab or compacted gravel. 1m x 1m. Don’t use dirt – it’ll sink. Cost: $50 at Bunnings for 10kg of gravel.
2. Firebox: Build a 20cm x 20cm brick box (3 bricks high) at the back. Use firebrick ($15-$20/brick) or regular brick ($1-$2/brick). Mortar: refractory cement ($30 for 2kg).
3. Chimney: 15cm diameter pipe (1m tall) on top. PVC won’t last. Use stainless steel ($40 at hardware stores).
4. Insulate: Pack crushed brick or vermiculite behind the firebox. 5cm thick. This is non-negotiable.
5. Build the dome: Stack bricks in a circle over the firebox. Angle them inward. Use cob or mortar. Let it dry 3 days.

Australian Supplier Cheat Sheet

Don’t waste time online. Get it at your local hardware store:

Firebrick (Essential)

Bunnings

Price: $15-$20 per brick (100mm x 50mm x 25mm). Buy 10 bricks ($150-$200). Don’t use regular brick – it cracks.

Refractory Cement (For Mortar)

Bunnings / Mitre 10

Price: $30 for 2kg bag. Do not use regular cement. It’ll explode.

Insulation (Vermiculite)

Bunnings

Price: $15 for 10kg bag. Crushed brick from a demolition site is free. Ask around.

Chimney Pipe

Local plumbing supplier

Price: $40 for 1m stainless steel pipe (150mm diameter). Don’t use PVC – it melts.

Pro Tips That Save You $1000s

• Clay test: Mix clay with water. Roll into a ball. If it holds shape without cracking, it’s good. If it crumbles? Dig deeper.
• Wind protection: Build it against a wall or rock. A 2m windbreak (timber or rocks) cuts heat loss by 40%.
• First fire: Burn a small fire for 2 hours. Then 4 hours. Then 8 hours. This cures the oven. Skip it = cracked dome.
• Don’t use: Coal, treated wood, or anything that smokes. You’ll poison your food.

When to Call a Professional

While many off-grid projects are achievable as DIY, certain situations require licensed professionals:

• Electrical work beyond basic 12V DC additions — requires a licensed electrician
• Structural modifications to buildings or load-bearing elements
• Gas line installation or modification
• Solar array installations above safe voltage thresholds
• Any work that affects the structural integrity of your property

Always check local regulations and obtain necessary permits before commencing work.