When choosing an outdoor fireplace, there's lots of considerations to think about from which style through to materials, performance, and longevity. We understand it's an investment and want you to love your outdoor fireplace from day one.
Below, we address the three most common concerns we’re asked, clearly, honestly, and without the jargon. Because, understanding what’s normal, what to expect over time, and when to seek advice helps ensure you get the most out of your fireplace.
1. Cracks & Surface Imperfections in Concrete
Concrete is valued for its strength, durability, and architectural appeal, but it’s also a porous material that responds to heat, weather, and movement.
What’s normal?
Fine hairline cracks and subtle surface variations are common, particularly noticeable in finishes such as board-form or bare concrete. These typically form during curing or as the fireplace heats and cools over time. In most cases, they are purely cosmetic and do not affect performance or safety.
Outdoor fireplaces are exposed to:
- High heat during use
- Cooling cycles once the fire goes out
- Seasonal temperature changes
- Minor ground or structural movement
All of these contribute to natural expansion and contraction.
What’s not normal?
Structural cracks, those that widen, progress, or impact the integrity of the fireplace, are not normal. These are rare when a fireplace is manufactured, installed, and used correctly, but should always be assessed by a professional if they occur.
Why finishing or sealing concrete matters
Trendz recommends finishing bare concrete fireplaces from an aesthetic standpoint. Plus, finishing or sealing your concrete outdoor fireplace does help protect the surface from moisture, staining, and accelerated weathering.
While sealing won’t prevent all natural movement, it does support long-term appearance particularly in exposed outdoor environments.
Not so keen on the concrete look? A popular finish we offer at Trendz, is 'plaster and paint', allowing you to have your Trendz outdoor fireplace painted in any Resene, Dulux or Colorbond colour you'd prefer.
2. Corten Steel “Bleeding” and Runoff
Corten steel, also called 'weathered steel' it is an option for woodboxes for the Mini Burton and Burton fireplaces. Corten steel is designed to weather and develop a protective patina. This evolving surface is a feature, not a flaw.
Why it happens
As Corten steel begins to weather, moisture can carry surface rust particles away from the steel. This can cause temporary runoff or staining on nearby surfaces, especially in the first few months after installation and during wet conditions.
What to expect over time
As the patina fully develops, it stabilises and acts as a protective barrier. Once this process is complete, runoff significantly reduces or stops altogether, leaving a rich, earthy finish that many homeowners love.
Planning makes the difference
To manage early-stage runoff:
- Avoid placing Corten over light or unsealed surfaces
- Seal adjacent concrete and paving
- Allow for drainage during the weathering phase
With the right planning, Corten steel delivers long-term durability and character with very little ongoing maintenance. There is the option to upgrade from 'weathered Corten steel' to a powder-coated black corten steel, when selecting your woodboxes. Or skip the steel woodboxes all together and go with GRC woodboxes.
3. Smoke & Wood Choice
Smoke is one of the most common performance concerns we hear about, and in most cases, it’s not caused by the fireplace itself.
The most common causes of a smoky fire
Excess smoke is usually linked to:
- Unseasoned or damp firewood
- Burning softwoods, treated timber, or garden waste
- Poor fire-starting technique
- Wind conditions that affect airflow
- Improperly installed flue/cap
Outdoor fireplaces rely on proper combustion. A small, hot fire built with dry kindling and well-seasoned hardwood will always perform better than forcing large logs of firewood too early.
When smoke is normal?
Some smoke during lighting, when adding new firewood, or on windy days is expected. Once the fire is established, smoke should settle quickly.
When to seek advice
If excessive smoke persists despite using dry hardwood, correct lighting technique, and favourable conditions, it may indicate an airflow or setup issue. In these cases, stop using the fireplace and seek professional guidance, taking a video or some pictures will help the Trendz team investigate what's going on.
Love Your Outdoor Fireplace
Outdoor fireplaces are built to last, but they’re also designed to live outdoors. Understanding how materials naturally behave helps avoid surprises and ensures you enjoy your fireplace for years to come.
Most concerns can be managed with:
- Informed material choices
- Proper installation
- Correct use and ongoing care
If you’re ever unsure whether what you’re seeing is normal or needs attention, our team is always happy to chat and help you find a solution.
Have a question? Contact us