The deck is around 10 years old and looking pretty shabby. The timber is Merbau but I wasn't sure what the original coating put on the deck was - something with a coating that peeled off in parts (as opposed to an oil).
Subsequent oiling never got a brilliant result despite how much I scrubbed and blasted with the pressure cleaner - it was clear that a full sand back to the bare timber was needed.
In preparation for hiring a floor sander I purchased an orbital sander and sanded back the edge around the perimeter of the deck with 40 grit paper. With our cedar battens (railings) it was clear that the floor sander wasn't going to be able to get into the corners and along the edge of the deck. It's hard work on the hands and knees but I was happy with the initial results, giving me confidence that the deck was going to come up well after the job was complete. Here's a rough example:
I hired a floor sander for the job. They are heavy beasts but surprisingly easy to use. It's a job anyone can do - even those with limited skills like me! Again I used 40 grit paper for the first sand, then went over again with an 80 grit.
The floor sander is a big heavy machine and a little intimidating. I got confidence from the fact that if I botched it I could always replace some decking boards as they are not expensive! But it really wasn't difficult at all and in no time I could see a vast improvement.
The final step in the sanding process was to get the orbital sander out again with the 80 grit paper and tidy up any spots that were a little rough or needed a little more work.
After cleaning up (getting rid of any sawdust that might contaminate the surface) I started oiling the deck. I got two coats done that weekend and a third the following week. I used Intergrain Ultradeck in Merbau.
It was a big improvement and a project well worth doing. I was really pleased with the end result.
The stairs leading up to the deck suddenly looked very shabby in comparison to the deck itself so I got cracking on them next with the orbital sander. I also borrowed a multi-tool to do the edges and can now see why people rave about them.
Before and after
Although the Bunnings How-to video below is showing how to sand internal floors, I found it was a great help for my project as the same principles apply to the timber deck.
Tips for your deck renewal project
As mentioned in the video, preparation is important. Make sure you get all the nail heads down well under the timber surface. Replacing the sanding belts gets expensive and can take a while (I was using strips rather than the easier circular ones shown in the video) and obviously you also risk damaging the machine or worse if you hit a nail.
Go with the grain and be really slow and cautious when "dropping" the sander onto the wood. I found it to be the only time you risked sanding unevenly and gouging out a trench. The model I hired didn't have a lever to drop the drum like in the video - this would have been very helpful.
I was (probably very naively) surprised at how quickly the machine wanted to scurry along. You do need to hold it back and go reasonably slowly for an even result. And obviously don't go backwards, always forwards!
Replace the paper dust collection bag well before its full. If they tear then dust flies everywhere!