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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
Welcome to the Bunnings Workshop community @heykrazi. It's fantastic to have you join us, and many thanks for your question.
The logs are likely treated with CCA. I'm sure there is some type of test available that could check for the presence of arsenic, though I haven't heard of any that are readily available. Do you have any concerns about the treatment?
I have reservations about sealing with an oil or painting the front side of any retaining wall where water can enter the rear side. You would effectively capture water inside the timber by restricting its ability to breathe through the front and expel moisture. This would, in my opinion, accelerate the rotting process. A pure stain would likely be your best choice. However, most of the available stains are carried in an oil or water-based protective coating. I note in the Porter's Palm Beach Black specification sheet it states that it is not suitable for treated timber. I would like to contact FeastWatson after the weekend to check on the suitability of Black Japan Timber & Deck Stain in this application. I'll also check on the Wood Shield product.
The logs are H4 treated and suitable for above and below ground use. I don't believe the Creosote will give you the desired look as it has a brown tinge to it. An oil-based coating might nourish the timber and help prevent cracking, but I am unsure whether the benefits outway the potential issues. Do you see much timber splitting at the moment?
Let me mention @Adam_W to see if he had anything to add to the conversation.
Mitchell
Hi @heykrazi,
Just following up on my previous response. The Black Japan Timber & Deck Stain and Wood Shield can be used for coating the retaining wall. Two or three coats of either product should achieve the look you are going for. The Wood shield product is slightly thinner, so it will probably take three coats. If a substantial amount of moisture penetrates through the rear of the wall, then you'll need to do occasional touchups in the affected areas.
As @Adam_W has helpfully mentioned, you'll need to clean the wall before coating. Using Cabot's Deck Clean and a stiff bristle scrubbing brush would also be an option.
I look forward to following along with your project. Please let us know if you need further assistance or have questions.
Mitchell
Hi @heykrazi
(i) With CCA treated pine you should avoid any unnecessary disturbance including cutting or sanding.
Every state has their own recommendations which are based on national guidelines. Here are the ones for NSW and note that they recommend that if you are concerned about contact or leaching you "...paint the surfaces with an oil-based polyurethane product or paint...".
The following advice is from CSIRO;
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"...gloves should be worn to avoid splinters and so that any sawdust or dislodgeable arsenic collecting on the gloves can be easily removed with the gloves before eating or smoking. As a precaution, the hands and face should be washed before eating or smoking and food and drink should never be left where sawdust can settle. A dust mask should be worn when sawing, machining or sanding and cuts and abrasions should be protected from sawdust. Goggles should be worn when sanding and during sawing or machining if there is any risk to the eyes from flying particles. If possible, sanding should be performed in a |
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well-ventilated area. Overalls and gloves are recommended in very dusty situations." |
(ii) Most of the 'breathing' your wall will do will be through the gaps & drainage network. Yes, an oil-based product may trap more moisture in but that would really only possibly become an issue if there were no gaps and the wall was constantly damp. Any product that totally seals, oil or water, can do this as it closing off the treated face of the timber.
Regardless of what type of product you use if the moisture is coming through from behind the wall, therefore the back of the surface coat, this will shorten the lifespan of any surface coat.
(iii) Levels of UV protection should be the same or have negligible difference.
(iv) Water-based products are most often used these days as they are easier to apply & clean-up and can be nearly as effective as more traditional oil-based products. Many water-based products will also penetrate more effectively especially if timber is slightly moist as they will, to a small degree, dilute with that existing moisture and through capillary action go deeper into the timber. Oil-based products, on the other hand, will not bind well to even slightly moist timber.
Water-based products are, as a rule, also much lower in VOCs so safer for use in general for you & the environment.
(v) I'll be totally honest here... The wall has survived 20 or so years in pretty good nick. I'd be applying the 'if it 'aint broke, don't fix it...' principle.
Only do work to areas that need repair.
Also bear in mind that, as they say, it's more expensive to build a car from spare parts, meaning, if you keep replacing sections piecemeal you may end up paying more in small stages than it would have cost to replace the wall and have it trouble free for another 20+ years...
From a maintenance perspective, beyond replacing sections that have failed, I'd just be ensuring that any existing drainage is kept clear & functional.
I've attached a pic showing the sleepers I painted. This was with only one coat.
Hi @heykrazi,
When working with CCA treated timber products, it is always best practice to wear appropriate PPE gear, including a dust mask, goggles, gloves, long-sleeved shirt and pants.
There are water and oil-based protective timber finishes on the market, and although they have different bases, they do much the same thing and can be used interchangeably. When applying a black pigmented product, I am not aware of a situation where one would be better to use than the other. These products do contain pigments to protect from UV damage but are not pure stains. A pure stain is just the pigment without a water or oil base. Feast Watson Prooftint is an example of a pure stain, and it is spirit-based. The spirit base evaporates off and leaves the stain behind. If there were pure stains available for exterior use, this would be my preference for your application.
After speaking with the Feast Watson technical team and hearing of @Adam_W's recommendation, I am less concerned about you applying water or oil-based coatings to your timber. Water-based products are generally more penetrative, and oil-based products can also sit on the surface.
Looking at the four options, I note Black Japan has brown undertones, as seen in the two coats example. It's not until the third coat that it starts to resemble black. From my experience, I do not believe you will reach a black with UltraDeck Timber Stain, but perhaps light charcoal. You can always see our helpful team in-store, and I'm sure they would be more than happy to do a test section of the colour. I am most favourable of using either Porter's Palm Beach Black or Wood Shield. Looking at the images, the Porter's product achieves an intense black colour, and if that is the look you are going for would be my recommendation.
As @Adam_W mentioned, because of the age of the wall, any treatment you apply will not extend its life dramatically. I would select the product that's colour appeals to you the most, apply it, and enjoy it for many years to come.
Please let me know if you need further assistance or have questions.
Mitchell
Welcome to the Bunnings Workshop community Jen (@jleel). It's great to have you join us and I hope you'll get loads of help and inspiration for all your projects from our wonderful community members. Please don't hesitate to post whenever you need assistance with a project or have something to share.
Mitch will be back on the community tomorrow after some unexpected leave. Let me tag our other resident Bunnings D.I.Y. expert @EricL to see if he can share his thoughts later today.
Thanks for your patience in the meantime.
Jason
Hello @jleel
The posts you are after are available at the store. But both the 130mm and 150mm posts will need to be ordered at the special orders desk. They both come in 1.8m and 3m lengths. As a general rule the height of your wall above the ground should be the depth of your posts below it.
However, if you are installing your new posts in the same spot as the old one, you'll immediately see how deep they went when it was originally installed.
Here is a handy step-by-step guide: How to build a timber retaining wall
If you need further assistance, please let us know.
Eric
