I have miles of decking at two houses. All timber when put in the Australian sun will suffer. When building our beach house we decided to go for Spotted Gum and let it grey. Why fight it? We applied Cutek, and will on a regular basis. At our main house we have lots of Merabu or Quilla. Will not grey the same, and leaches lots of red stain. Cheap, but would not use again. What ever you use, use a good quality oil that seeps deep into the wood not a traditional stain/or top finishing product.

Hi Anne Marie, there are a few things that could be causing the black staining. Share it could be mould but that usually takes some time but usually moist and dark conditions too. If your timber has been exposed to the elements before it has been coated it may be the woods natural tannins coming out. This is normal for most decking timbers. If it is mould there are several outdoor mould sprays available. These are generally a chlorine based product and although it will kill the mould it may also bleach the timber. I suggest a test patch that is not in open view or on an off cut if you still have one. If it is the tannins coming out then you could use one of the available deck cleaners as per the instructions however you need to get the timber coated as soon as possible to make sure that you keep the awesome colour that blackbutt has. Have a look at my pics to see the blackbutt deck done for one of my clients. Good luck.

I have just gone through the same decision making process. I rejected the composites due to cost, scratching, smell, and how much heat they emit. I rejected merbau due to leaching of the tannins, unsustainable harvesting practices (despite what is preached), and the threat to orangutang habitats. I chose spotted gum for looks (more brown than red), reasonable cost, easy maintenance, and it is Australian grown and produced. There will be those who disagree with my decision, but at the end of the day I wanted a reasonably priced but attractive, durable, and low maintenance decking board. It takes longer to lay the hardwoods such as spotted gum as they have to be pre-drilled, but the total extra for a 5m x 5m deck was $1000 for labour / timber compared to merbau. A quick oil once a year is the only maintenance. Pinterest is a good resource for how they all look once down.

Spotted gum for sure, merbau is blar... no grain or aesthetic appeal whatsoever. You have to use a stain so it does not fade but make sure you don't buy it at Bunnings because they do not stock any product that is worth putting on any timber. The two decks are Organoil in red stain and the railing on them is livos Alis in light teak. I use the livos on my own timber work but it is expensive. All this timber has been in the full elements for well over 10 years.