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Is it essential to paint a treated pine deck?

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  1. #1
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    Default Is it essential to paint a treated pine deck?

    Hi Folks,

    First post and I'm from Adelaide where as you may know it doesn't rain all that often! I live in a seaside suburb, half a block back from the beach and being retired, don't have unlimited funds. I want to build a timber deck over an existing concrete slab - it'll be on joists on some sort of stirrup mounts - maybe the KlevaKlips. Most of the deck will be under a pergola roof that will shelter it from direct rain although there may be some minor water ingress on the western side. I would very much like to minimise annual maintenance. The deck will be used mainly for relaxing and socialising although it will inevitably be our garden access point as well and is immediately adjacent to where my wife does lots of plant potting etc.

    I'm favouring using treated pine for the deck surface, mainly because I like the lighter colour, the cheaper price, the ease of handling and the fact that it's a locally grown product. I've read that the projected life for a treated pine deck is 15-20 years which is fine by me - extended longevity doesn't seem that important as I figure that by the time the deck is 'worn out' it'll be someone else's problem.

    What I'd appreciate thoughts on is the question of painting/oiling/staining the deck timber. Is it essentially to paint treated pine decking? If it does need to be painted in some way, are there finished available which do not darken the timber significantly? Can something as simple as linseed oil be used? And if painting is required, does it need to be an annual task?

    Thanks, Sam.

  2. #2
    Community Moderator phild01's Avatar
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    I always favour painting a TP deck and use Cabots decking paint but it is a solid finish. I think you are referring paint as an oil or stain finish which needs annual upkeep as a minimum. To avoid splitting, the new timber should have a finish as soon as it is laid and after the evident treatment residues are gone.

  3. #3
    Old Chippy 6K
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    No painting or other finishing coat is required at all. If you've ever been to council park or national park you would have seen what happens to it - it progressively turns a silver grey colour in full sun & weather. Sometime small cracks open up, sometimes some some splinters appear, but a light sand is all that is needed. In your application it will stay the greenish light colour longer or might get some greying at the edges where more exposed.

    There is no need for any coating unless you want a particular look or colour. TP is meant to be maintenance free and largely is - which is why it's used on wharves and in by councils and so on. Note that the paint companies and most decking companies all say you need to wash and coat every year - this is a big business and they sell both the coating products and the services to do the job.

    The deck will last longer if coated even if using a DWD product which are clear, but will darken the colour. Note on a TP (LOSP) deck oil based finishes are preferred. Do not use water based finishes and do not use linseed oil or other 'natural oils' - they do not like UV and they will darken and discolour and are a PITA to prep for any recoat.

    I have used uncoated TP decking around pools and they have seen decades of service.
    Advice from me on this forum is general and for guidance based on information given by the member posing the question. Not to be used in place of professional advice from people appropriately qualified in the relevant field. All structural work must be approved and constructed to the BCA or other relevant standards by suitably licensed persons. The person doing the work and reading my advice accepts responsibility for ensuring the work done accords with the applicable law.

  4. #4
    Community Moderator phild01's Avatar
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    If you leave the CCA stuff raw you can end up with splintering and extensive cracking. The NZ stuff (an LOSP type) can expand a lot and close the gaps with significant cracking as well. Being under cover all this is greatly minimised.

  5. #5
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    Thanks everyone for your comments and advice. It sounds as though - given the relatively sheltered circumstances in which I am proposing to use this treated pine decking - that I can indeed reasonably leave it 'unpainted' (that is, unsealed, unstained or whatever) as long as I am prepared to tolerate some degree of checking or cracking. I have been doing some further reading on the acronyms some of you have used and it is LOSP timber that I'll be using (probably the 'Timberlink' or 'Ironwood' brands). I'll do some further research about finishes and see if there's something available as a 'once-off' treatment that won't stain the timber, doesn't require annual treatment and is worth the effort to apply. If there isn't anything that meets these criteria I'll probably leave it untreated as I really do not want to face on-going maintenance other than a sweep once a week!

    The deck area I'm facing is essentially 2 x joined rectangles (ie; 'L' shaped) 4.4x4.6 meters and an extension 2.4x2.3. The Ironwood 90x22mm decking available from Bunnings actually comes in two sizes that conveniently fit the lengths that these two rectangles would need. I'm a reasonably skilled home carpenter but I've never built a deck before, at least nothing beyond a cubby for my son!

    So I'd like to ask a couple of supplementary questions if I may about fastening.

    Would it be better to buy the timber in the two specific lengths that fit each of the two rectangles I'm dealing with (that is 2.5m and 4.8m) or would it be preferable to buy it in mixed or random lengths. One will require 'double screws' only at the joints along the joist where the two rectangles meet, the other would entail double-screws at joints all over the deck's total area. I'm afraid I have no idea what the structural or aesthetic imperatives are here and your advice would be appreciated.

    I'd also appreciate advice about choice of fasteners. Bunnings sell Zenith plated and stainless steel fasteners as well as some specific ones made by Macsim and Camo. I think one of the latter may have a unique design. What do you recommend please?

    Thanks, Sam.

  6. #6
    Old Chippy 6K
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    Much easier off you can get same lengths - no cutting and joining makes for faster fixing and fewer spits at ends. Not quite sure what you mean by 'double screws'? I guess you mean at the abutting ends - if you have random lengths then there will be more of them.

    You should be pre-drilling with a DeckMate or similar anyway. I've been ceramic coated steel screws from Scrooz for years now as they are stronger than SS and look much the same. https://www.scrooz.com.au/screws/dec...hload-ceramic/

    For ease of estimating use BlockLayers site: https://www.blocklayer.com/deckcalculator.aspx

    The hidden fastening systems are not a good choice for DIY as you need to buy special accessories and gear & for a single small job it's not worth it IMO. They look great, but require some practice and knowledge to do well. I've used the Camo system and it goes great result, but I would by the tools for a single small deck. I've used the KlevaKlip system too and it too gives ahold result https://klevaklip.com.au but unless they've added recently it doesn't have a fasteners for 22mm TP, juts merbau or the composite decking
    https://klevaklip.com.au/Merbau-clips
    Advice from me on this forum is general and for guidance based on information given by the member posing the question. Not to be used in place of professional advice from people appropriately qualified in the relevant field. All structural work must be approved and constructed to the BCA or other relevant standards by suitably licensed persons. The person doing the work and reading my advice accepts responsibility for ensuring the work done accords with the applicable law.

  7. #7
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    Thanks Bloss - that's reassuring advice on purchasing 'even' lengths. Yes - you interpreted my reference to 'double screws' correctly - where the ends abutt each other.

    Now a 'Deckmate' - is that some sort of combined drill and countersink? The only 'deckmates' I can find are either a hidden fastening system (using grooved-edge boards) or a tool from the USA used for accurately locating screw holes. The Scrooz website tells me that the ceramic coated screws don't need predrilling/countersinking - but I'm guessing you'd say that you get a better result using them if you do pre-drill?

    I've had a good look at the KlevaKlip system as I was initially considering 90mm Merbau. The cost is a bit of a problem although I suspect that I may still use their adjustable joist mounts for at least some of the deck supports. My brother - who is a very accomplished bush-carpenter with a number of shearing shed-type structures to his credit - reckons that the 1926 slab I'm building over is so solid that I could just fasten the joists to the house foundation at one end, put a KlevKlip support at the other and use piles of concrete pavers in between! I think I'll go for a slightly more 'engineered' solution ;-). Thanks, Sam.

  8. #8
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    Paint will last a long time, but oil looks better (IMHO). One good thing about oil is that it's a case of increasing returns - after the first few years of annual coating, it tends to soak into the boards and need less frequent treatment. We had a TP deck installed a few years ago - we coated it with water-based 'oil' with a Merbau tint and it looks great. One hassle: after the first year we left it a bit too long, followed by a rainy season and one part went mouldy. We water blasted and sanded those sections, treated with mould killer, then re-coated. The mould hasn't come back (it's now under a pergola, which keeps most of the rain off, so that helps too). If we were doing it again we'd probably go for a lighter tint, as the dark tints get quite hot in the sun - probably not great for the boards/coating and sometimes too hot for bare feet.

    For the joist supports, have you considered plastic pedestals? They are easily adjustable for levelling and some types can take up to 800kg. Bunnings sell such a product, but I've found the ones from Keksia are a) cheaper, b) have a better span of heights. The one downside of pedestals is that they rely on gravity - if you have a bowed joist, you can't tie it down. https://www.keksia.com.au/

  9. #9
    Deactivated User Marc's Avatar
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    I have a deck built with TP imported from Fiji about 25 years old. It was built upside down with the grooves up to add insult to injury. It is covered and has been oiled reluctantly every 3 to 4 years. It is still sound with no rot and looks decent. Had it been in the open it would have rotten completely 10 years ago.
    It does get some water in a deluge on the edges, but there seems to be no difference between the edges and the rest of the deck.
    Painting a TP deck, or any deck that is not under cover is a sensible choice. I remember when I was suggesting to paint decks in the open over 15 years ago, it was like suggesting pedophilia is OK.
    Under cover most timbers do much better and the choice of coating is not that important.

    An outdoor timber deck is a temporary structure, the decking boards are temporary and so is the frame. Painting the frame with two coats of quality water based exterior paint during construction, can add 10 years to the frame's life. Painting the boards will add life to the deck and the owner.

  10. #10
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    Thanks for relating your experiences Marc and DaveOh, I should clarify that when I referred to the question of 'painting' the treated pine I was actually thinking of oil or stain - I hadn't considered an regular opaque paint as such. If fact I wasn't aware that painting a deck was something to be considered. I guess it does make some sense in that an opaque (pigmented) paint would screen out the effects of sunlight more effectively as well as protect from rain. But I guess I was considering more the possible beneficial effects of an oil or stain soaking into the surface of the timber and providing some sort of 'barrier' protection. But as Marc suggests, if under cover it may not be that important anyway. Thanks again, Sam.

  11. #11
    Community Moderator phild01's Avatar
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    I much prefer to use a solid paint on select knotless pine decking. Cabots deck paint is a great choice. Natural timber finishes over exposed horizontal surfaces is just too much pain.

  12. #12
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    Quote Originally Posted by Bloss View Post
    ...There is no need for any coating unless you want a particular look or colour. TP is meant to be maintenance free and largely is - which is why it's used on wharves and in by councils and so on. Note that the paint companies and most decking companies all say you need to wash and coat every year - this is a big business and they sell both the coating products and the services to do the job.

    The deck will last longer if coated even if using a DWD product which are clear, but will darken the colour. Note on a TP (LOSP) deck oil based finishes are preferred. Do not use water based finishes and do not use linseed oil or other 'natural oils' - they do not like UV and they will darken and discolour and are a PITA to prep for any recoat.....
    Hi All (and Bloss in particular),

    I realise that I'm returning to this topic after going away for a couple of months, but - now I have made (slow) progress and am ready to set my joists and set things up for laying the deck - the question of 'finishing' has come up again. I've basically put in place a wall plate and a single joist along one side of the deck area. I've done this first to ensure I have reference 'levels' as the concrete I'm decking over slopes away from the house and is distinctly uneven in places - I'll need these 2 joists for reference as the rest of the joists go in.

    What has struck me is the 'Ironwood' H3 treated pine joists from Bunnings are 'blonde' and not the green 'copper-arsenate' colour I associate with treated pine from past experience - in fact it looks just like standard, untreated pine.

    Is this blonde 'Ironwood' H3 material the 'LOSP' material that Bloss refers to above? Apparently the H3 decking from Bunnings is this same light-coloured material. Although it seems your collective advice is that I don't have to treat it, I'm thinking that, because the wood is so light, some sort of slightly darker stain might be a good thing just to hide the inevitable dirt, stains etc.

    Does anyone have any experience of this 'Ironwood' stuff, how it's treated and how I should specifically approach staining it (ie; water-based, oil-based, 'natural' based etc etc). Any products to recommend? Should I maybe stain before the decking is screwed down?

    Thanks, Sam.

  13. #13
    Seasoned DIY droog's Avatar
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    Have a look here
    http://www.bendigotimber.com/p/addit...d_Micropro.pdf
    https://www.koppersperformancechemicals.com/micropro/

    I would steer clear of any water based product for outside timber decking they are film forming and if not fully maintained then a full sand of the deck is the only option to bring it back.
    Oil based all the way.

    BTW colour of the timber has no relationship to the treatment level of the timber.

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