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Hi everyone – new here, and need help 
I've recently purchased a home in regional NSW, and it comes with a fair few retaining walls constructed of treated pine logs & posts.
They've been in place for about 25 years I'd say, and a retaining wall guy recently came round and said I could expect another 7-10 years out of them. In some places they still seem in good knick, in others there's a few that appear rotted/swollen/warped, and I'm getting these logs replaced.
Given the age of the retaining wall, I'm assuming it's CCA treated pine (is there a way to check?) – though any new logs I purchase probably won't be.
I'm here because I want to achieve 2 outcomes:
(i) alter the appearance so the retaining wall colour becomes as close to black/charcoal as possible, and
(ii) ensure I'm doing what I can to preserve the retaining wall so its life is extended as long as possible (I understand the back of the logs are what will fail first, but still).
I've done what feels like a mountain of research, but I still can't determine the best way forward...
To colour the treated pine walls, I need to adequately prepare them and then stain them (I've decided against painting) – but:
1. In my situation, is a water-based stain or oil-based stain best? I believe that water-based stains (such as Porter's Palm Beach Black) come in a deeper pure black and need less frequent re-application than oil-based stains (such as FeastWatson's Black Japan Timber & Deck Stain), but that water-based stains tend to fade worse than oil-based stains over time?
2. Is a stain (ie. either of the above) also going to provide some protection against the elements, or do I need to follow staining up with a protective wood finish/sealant? I know the pigment in stains protect against UV, but what about water, mould, etc.
3. If a stain is sufficient and does not need to be followed up with a protective finish/sealant, does an oil-based stain provide more protection than a water-based stain or is it much of a muchness?
4. If a stain does need to be followed up with a protective finish/sealant (which counteracts some advice I've received that stains should be standalone products), which would be best?
5. What do I make of a product like FeastWatson's Wood Shield in Black? is this an exterior protective finish with a stain (i.e a 2-in-1)?
6. Lastly, my gardener suggested he was going to pressure clean the logs and apply Creosote, but after reading about the hazards of Creosote, and the potential that the logs look faded dirty brown, instead of black, and remain oily for some time, I'm not in favour of this, unless I'm missing something?
Big thanks to anyone for their help!
Cheers
Hi Jen (@jleel),
I'd suggest going with a 200 x 75mm sleeper, as they'll provide more support than the 200 x 50mm versions.
Mitchell
