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 think your house could be lovely with a bit of spit and polish! As per the previous comment, a paint job would do wonders. Our house is similar in that the ground floor is brick and the top is (now) weatherboard (over fibro). We lived in the old fibro for years before we could afford to renovate. It gave us more of an idea of what we would ultimately like. Here is our before and after. As you can see, we added a deck and changed part of the the roofline too.

I have 2 massive decks front and back around the pool. Unfortunately they are painted a hideous light green and some timbers are rotten. Would appreciate any suggestions on how to improve them. I can;t afford to rip the existing ones up but would love the natural timber look?

I've been doing a lot of research on composite decking. Have narrowed down to TimberTech and Trex composite decking. Both are US products. For people who have installed either of these products in Australia, I'm seeking your opinion and advice. Also, do you know any builder who is qualified to install either TimberTech or Trex composite decking in Sydney?