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, why don't you have a think about installing composite decking which will allow you to be level with the door sill without the worry of run-off into the house due to the 5mm gap between the boards. Composite doesn't required coating so the maintenance issues are significantly less, just a hose down and sweep or mop with water. You would still need to excavate approx. 250mm below the finished deck level to allow for the sub-frame but if you use treated pine framing with, either H4 stumps in concrete, or galvanised stirrups to anchor the framing into the soil. Check with your local decking pro for further advice and brand options. Generally, the USA made composites like Trex or Timbertech are better quality and the concealed fixing systems are easy to install. Your soil type may be the only issue with water, ie clay which retains water, or sand which tends to drain more quickly. 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.

I've coated many decks and the best advise I've been given is "leave it natural". Most timbers go grey after a few months and don't look too bad. If you want a bi-annual maintenance job the other bit of good advise I've had directly from the manufacturer is put down four coats minimum. The third and fourth coats won't use so much oil because they don't soak in. A very light sand between coats keeping in the direction of the grain is a good idea to retain a finish without wood grain or dust spoiling the final appearance. Two coats, no matter which brand or type of oil will last about a year in our sun.