# Forum Home Renovation Decking  To oil or stain, OR leave totally untreated ... that is the question?

## Neophyte

About 3-6 months ago, we had a boardwalk (series of steps and landings) built down the entire side of our house, as well as a small deck on the opposite side of the house connecting to stairs leading to our back yard (the stairs also connect our downstairs verandah to back yard).  I say 3-6 months as the tradies were so slow with this project that the first part was completed probably 6 months ago and the job was finally complete about 3 months ago, so the period of ageing time for the timber is varied.  The boardwalk, decking and stairs are all constructed out of chunky treated pine planks (have attached photos). Note:  The boardwalk (first photo) is on the southern side of the house and the decking and stairs are exposed to the north. 
Our vision with all this decking was to achieve a wharf like feel and to allow the timber to weather and grey, for a couple of reasons.  1.  This is the look we like and the colouring would suit the grey tones we have selected for most of our exterior finishes.  2.  We are after low-maintenance and the idea of set and forget really appealed.  We discussed all this with the decking guy before commencement and he suggested the type of timber and assured us we could just leave it totally untreated.  We are now being told that we should have at least oiled the timber or stained it immediately to preserve the timber.  Although we would like to look after the timber, we do not want to preserve the green/yellow look of treated pine. It is starting to grey but along with that, cracks are starting to appear.  Every place we go to, we are getting different advice. Some are suggesting staining it a weathered grey colour, some are fans of oils and some are fans of water-based stains.  It seems that water-based will last longer but, if left too long, I fear we would need to sand back ... we don't want to ever have to sand this. 
My question finally is this:  Is it okay to leave this to just weather and grey, as we were initially advised?  If not, can anyone advise a solution that is hassle free maintenance, even if it means staining with an oil, eg. Cabot's Deck & Exterior Stain - Dusty Gum or Hunter Grey colour (Oil based) and then allowing it to continue to grey naturally underneath??

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## shauck

If you want it to grey and still protect it, Cutek CD50 is the product for you. It is a clear oil product which can be tinted but is sold as a clear. You'll find references to it in other threads in the decking forum. It will be my next choice for deck protection. When I finally get around to it.....

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## FletcherP

Unfortunate fact, but the 'weathered' look is actually the timber decomposing. You can get away with it on wharf structures because these are typically quality timbers in large profiles.  
There is definitely a trend towards weathered substrates, and this is where architects and engineers come to blows - form versus function. Look at Cor-ten steel, designed to rust to give the weathered look without failing, although it still eventual does fail, because it is still rusting, albeit in a more controlled manner. Same with timber. If you want a natural weathered look, you're not going to have it for as long as coated timber before it needs replacement. 
Personally, Teak is the only timber that I think looks good weathered, although I understand your wish to have it match your overall decor. The compromise here is to have a look at grey stains, as you've suggested. These are never going to look exactly like weathered timber, however they will give you the overall hues that you are looking for to match your house, and provide protection for the timber. 
As far as ongoing maintenance, decking stains will always outlast decking oils, but not last as long as decking paint. The more opacity, the longer time between maintenance.  
You should always use at least 2 coats of a stain to get a consistent appearance. However the more coats you use, the more the colour will develop, and you will progressively lose definition of the grain. 
My suggestion would be to apply 2 coats of a stain to an offcut and see if you're happy with the look. If you use a waterbased stain (which will dry quicker and last longer than an oil based one), you can then maintain it by overcoating in a few years (or whenever it needs freshening up) with a waterbased decking oil in a natural colour. That way you don't overdevelop the colour and appearance, although it may give a slight sheen that doesn't look weathered. If the colour starts to leave, you can overcoat with an extra coat of the original colour. Just use the best you afford, some brands have sample pots to check it out. 
Your other option is to let it weather and be prepared to replace it at some stage in the future. 
Not sure about products that claim to allow timber to weather, but protect it at the same time. Clear coatings on exterior timber are typically the shortest lived ones. 
Hope this helps, 
Cheers
Fletch

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## FletcherP

Neophyte, 
Quick correction on overcoating with a natural coloured oil for future maintenance - you may want to check the colour change before you did this. This is OK for going over brown stains, but for a grey stain it may not refresh the colour in the way you wish. Ideally, a grey decking oil (not sure if they exist) would be a maintenance coat. 
Cheers
Fletch

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## Bloss

Well I can't agree with FletcherP. This is exactly function over form - choosing the right materials which will last a long time with no maintenance. That is the smart engineering choice - the dumb 'architects' choice is to pretend that you can have fresh brilliant 'natural timber' colours as they are milled, for the life of the structure. That's a late 20th Century invention when it became possible to use coatings (with alkyd and polymer technologies amongst others) to preserve the look, not so much the timber (which correctly chosen last about the same time). 
And on your primary question - there is no such thing as low maintenance external finishes . . . unless you think it is OK to have to redo every 2-3 years or more (or put up with a bad look).  
Service life of treated pine is in exposed conditions with no treatment. Your timber is very new in a 20 to 30 or 40 year service life. It will get a few cracks and splits, but the surface will also turn silver grey, with a slight green undertone as that is the colour of the preservatives used. 
The discolouration in this case is not 'decomposing' in the sense of 'rotting' - the surface changes are due to the impact of the sun's UV-A & B light. Once the surface silvers up it does not go deeper with treated timber. It also does not do so in untreated timbers which have natural 'treatment' in the form of the oils - so for example the North American cedars and some birches and beeches and equivalents in Europe such as larch, all silver up over the first couple of years then can last anywhere from 100-500 years with no other treatments. The silvered surface in fact protects from further degradation. In Australia too there are plenty of timbers which will stay in good serviceable condition for 40, 50 and 100 years and more untreated - as many a fence post, telephone post, country shearing shed or old homestead proves. 
If the greyish colour is what you are after simply wait - treatment, even with a translucent finish will slow or stop the greying and the look will stay as it is now. My suggestion is to do what you planned - leave it alone and it will achieve exactly what you planned for it - the 'wharf look', just as do wharfs and other external timber work does all around Australia and all around the world. 
Start coating now and you a) change that look and b) start a maintenance requirement that pretty much never ends. Ultimately it is aesthetics - you can always paint it or coat it later if you really must, but exposed timber designed for that purpose is a good technical choice. 
Not that in the southern hemisphere a North and West facing exposure will get more sunlight so greying will happen faster than on South or East facing ones. Adding rainfall and temperature variations will also have an impact on how fast and how much greying occurs. Rotting and decomposition will occur in all timbers in joints and junctions where water can be captured and retained - the way yours is constructed looks well-drained so that indicates a good long life. Timber degradation is mainly about fungal rot from long exposure to high moisture levels - natural or synthetic protectants resist the fungi, but eventually through leaching, and sometimes chemical changes too, their concentration in the timber lowers and the timber fails. 
I reckon that work of yours looks great - leave it alone and enjoy it - it is what you planned on and over the next couple of years it will get there. Save your money and time.

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## FletcherP

Fair points Bloss, however I personally don't think treated pine ever ages gracefully - just ends up looking like old treated pine. It might grey to an extent, but it won't silver like other timbers. 
If the OP is happy with the appearance of old TP, then I agree, let it run it's natural course. 
Cheers
Fletch

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## Bloss

> Fair points Bloss, however I personally don't think treated pine ever ages gracefully - just ends up looking like old treated pine. It might grey to an extent, but it won't silver like other timbers. 
> If the OP is happy with the appearance of old TP, then I agree, let it run it's natural course. 
> Cheers
> Fletch

  Yeah - I am not a huge fan, but well-treated and well selected is OK if you like the look. I do lots of bushwalking and there are many places with 20 and 30 year old TP structures untreated in harsh conditions and they still look great. 
I think many have seen low quality and badly built TP - especially from 10-15 years ago when QA was poor (there were many treatment plants that were producing very ordinary stuff). 
If it starts to look ratty then fill cracks and use an opaque acrylic paint is my answer. The big advantage of course is cost, but as you say only if you like the look - that one in the OP's pics looks good to me.

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## strangerep

> Our vision with all this decking was to achieve a wharf like feel and to allow the timber to weather and grey,

  Having seen what this sort of TP decking looks like 10 yrs later, IMHO it looks like crap. It's not just greying, but also mold, etc, that gradually establishes a presence and needs some sort of chlorine-based bleach to thump it.   

> We are after low-maintenance and the idea of set and forget really appealed.

  There is no such thing with exterior timber. The nearest you'll get is paint, but the inevitable splitting of the timber as it ages means this doesn't keep an ideal appearance indefinitely. I painted some exterior TP steps with 3 coats of the old Cabot's timber colour paint, and it held up pretty well for quite a few years. Depends on how much foot traffic it cops, of course.   

> [...] oiled the timber or stained it immediately to preserve the timber.

   That's wrong. It's better to let the timber stabilize for a while, and allows some tannins to leach out from rain if they want to.   

> [...] a solution that is hassle free maintenance

   There's no such thing. Oils (of which Cutek is probably the best) need recoat every 1-2 yrs, plus a serious cleaning each time (see other threads about napisan and oxalic for this). Water-based products like Spa-n-Deck need sanding if you let them go too long. 
Personally, I think your deck and steps would look better if painted a grey colour which is the same hue as the surrounding grey paint (but probably a different tone of the same hue -- that would need experimentation with sample pots). It'll certainly last longer than any finish which tries to preserve the woodgrain appearance, but you'll still be repainting in X years time. 
IMHO, the wise strategy when weighing these options is to think about what will still look "reasonable" in 5-10 years time, and be easy to recoat, rather than what looks "fantastic" in the short term, but quickly degrades in a year or two if not given enough TLC.

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## jmn

Hi Neophyte 
Great looking deck. Looking to build the same type of deck using wide boards. Love the look of the "wharf style" deck. 
What size boards did you use for this job? 
Are they treated pine boards? Was thinking of using hardwood boards but will be easier to use treated pine.  
Josh

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## Neophyte

> What size boards did you use for this job? ...  Are they treated pine boards? Was thinking of using hardwood boards but will be easier to use treated pine.

   Yes, they are treated pine planks.  I've just been out to measure the boardwalk down side of house and: for the Platform sections, the planks are about 195mm wide by 50mm thickness;for the Steps he has used 2 planks for each tread of 150mm wide by 50mm thickness.

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## Neophyte

Thanks everyone for your words of wisdom. I appreciate that treated pine is not for everyone, especially you chippies who understand and respect the beauty of the various hardwoods. We weren't averse to hardwood for our decking but, after giving our brief on what we were after, these chunky treated pine planks are what the decking guy recommended, and he had advised we could just leave to weather like you would at a wharf/marina. 
After considering the various opinions/advice, I think we will just leave this to weather and keep an eye on it. 
Also, we don't mind a bit of maintenance ... I was just trying to minimise and mainly trying to avoid having to sand this decking/boardwalk.  At our previous house, we were recommended a water-based product (Arbitone I think) over oiling our deck.  It did last quite some time, especially the deck as it was covered, but no where near the 5 years we were promised. The handrail (Merbau) was more exposed to the elements and we had left it too long so there was no choice but to sand it right back and that was hard work ... for my husband, not me.  I don't mind, however, having to scrub the decking down occasionally and, thanks to the wonderful advice I found on this forum I was able to return the unused Feast Watson Deck Cleaner ($58.75) that I had only just purchased and bought a tub of Napisan instead for <$5.  _BTW, will scrubbing the decks with the napisan solution take away the grey weathered look and return it to looking more like the original treated pine, which is not what we want._   

> Personally, I think your deck and steps would look better if painted a grey colour ... It'll certainly last longer than any finish which tries to preserve the woodgrain appearance, but you'll still be repainting in X years time.

  Thanks 'strangerep' for your candid comments and, should the weathering process not be producing the look we are after, we probably will paint a colour to match the grey tiles on our verandah. We are certainly not out to preserve a woodgrain appearance as there is barely any woodgrain in treated pine.   

> IMHO, the wise strategy when weighing these options is to think about what will still look "reasonable" in 5-10 years time, and be easy to recoat, rather than what looks "fantastic" in the short term, but quickly degrades in a year or two if not given enough TLC.

  This was exactly our fear as we are very busy and have been known to not give enough TLC in the past and which is why I posted this question as I didn't want to create more work down the track by choosing the wrong course of action now.

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## jmn

Thanks for the info Neophyte

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## Bloss

Once the colour is as you like it, maybe in a couple of years there are a number of water repellant coatings which can darken the colour a bit, but will then protect from the weather at the state it is when applied. Usually needs to be re-applied every couple of years, but easy to do.

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## strangerep

> [...] I was able to return the unused Feast Watson Deck Cleaner ($58.75) that I had only just purchased and bought a tub of Napisan instead for <$5.

  I vaguely remember that the FW cleaner product is basically dilute oxalic acid -- hence overpriced. You can buy oxalic acid in crystalline form in larger containers much more cheaply.   

> _BTW, will scrubbing the decks with the napisan solution take away the grey weathered look and return it to looking more like the original treated pine, which is not what we want._

  The 3 cleaners: Napisan (sodium percarbonate), chlorine bleach, and oxalic acid each tend to be more effective against different types of stain. Napisan is good as a general purpose cleaner. Chlorine is superior against mold/mildew. Oxalic is good against tannins and a few other things. All of them tend to bleach the timber to different extents, hence must be rinsed out really thoroughly. The bleaching doesn't matter in practice since it lifts the appearance, and decking oils usually contain tint anyway. 
So yes, they tend to remove the grey, chlorine and oxalic more so. But that's a good thing since the grey is basically degraded timber fibres. I've yet to see a naturally-greyed timber deck in someone's home that actually looks good -- typically there's all sorts of other gunk in there as well. 
Chlorine is something which should be only be used if you really do have a mold/mildew problem which the others won't shift. But all 3 need to be quite concentrated, with hot water. And you don't want to leave chlorine or oxalic on for too long before giving it a bejeezus rinsing. When it comes time for you to do serious deck cleaning, you might want to check back here for a few more details.

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## METRIX

> I was just trying to minimise and mainly trying to avoid having to sand this decking/boardwalk. .

  Don't sand this timber in the future as it contains nasty preservatives, which are not good for you if sanded and kicking up dust everywhere.
Just use one of the wet cleaning methods rather than sanding. 
Depending on the timber used, it would contain one of the following mixtures. 
BTW, it looks good for TP, but can become very slippery if not cleaned regularly due to the rougher / porus surface attracting mould etc, keep an eye on this.  *CCA Treating* The much discussed treatment type containing Arsenic. Whilst it is         being phased out around the world & throughout Australia it has long being considered a safe and cheap         treatment method for all treated pine. Although it was scientifically        found to be carcinogenic it is still the preferred choice for most builders.        Its mild carcinogenic properties are easily avoided with proper handling.        From March 2006 it will no longer         be able to be used in decking, handrails or playground equipment. A brief and honest overview of        of the CCA product with regards to gardening and vegetables. 
              There are a few producers of CCA chemical in the world, essentially they        are all use the same ingredients being Copper oxide, Chromium trioxide,        Arsenic acid and water.   *LOSP*
This was becoming the Arsenic Free substitute for        CCA products, however it is generally more expensive and far less        effective. Most LOSP treated pine must be painted to maintain its warranty        (which is half as long as CCA). Without painting LOSP treated timbers may        only last a few years) A       report by        the Australian Government highlights the possible failure problems        associated with the some types of LOSP treated pine. 
       Again, the        LOSP chemical is popular and widely available as a treatment solution. Due        to the fact the New Zealand government recognized its failures early on,        there have been some changes (albeit confusing). 
       Osmose LOSP is called        Protim and must be over painted. Its ingredients are Kerosene,        Tributyltin naphthenate, Dichlofluanide and Permethrin.
      Koppers LOSP is now called       Azure and may not require over        painting, please contact Koppers for clarification. It is a newer chemical        treatment and ingredients include tebuconazole,        propiconazole, Permethrin, and white spirit        (more refined than kero). The Koppers older LOSP treatment type is called        Vascol which is similar to the Protim product of Osmose. 
       NB: The exact type of LOSP treatment will        determine its lifespan, and if it has to be over painted. Always request        from your supplier written details of painting requirements for any LOSP        products. Additionally, due to the solvents in LOSP products they are        generally more flammable.   *ACQ*
This will be the alternative to ARSENIC FREE treated pine. It is        considered a very safe and very effective product with no risk to humans.        At the moment it is approximately 25% more expensive than the CCA,        additionally it is a little difficult to source, and as such is not very         popular. 
      We do not yet stock many ACQ products (except for Sleepers         available ex-yard only).The Osmose company produces an ACQ product        called        Naturewood. Its ingredients include Copper,        Didecyldimethylammonium chloride and water 
      Koppers produce a similar Copper azole product called       Ecowood        (also known as Tan.E). Its listed ingredients include Copper,        Tebuconazole and water

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