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76 posts

Master Geek

#209134 14-Mar-2017 09:45
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Hi there, wanting some advice on looking after an old Kwila deck.




We brought a place 2 years ago with a very large and elaborate Kwila deck.


Its probably about 40-50 m2 plus with inbuilt seating and fencing and gates completely around it. The previous owner said he had it built in the 90's. Said it cost him $25,000. So it is probably around 20-25 years old


It is completely silver/grey, not sure if it has ever been oiled or stained.


It's overall condition is pretty good. The most sun exposed bits like capping on the seats and fences are looking very dry and weathered. There are a couple of damp and shaded patches that look to have a surface layer of rot. A single plank is splintering (which I will replace with some old 2nd hand stuff I have brought).




I've been getting conflicting advice about whether to stain/oil it. An old builder telling me it doesn't need it and once you start, you are stuck having to do it every year to keep it looking good. Which would be quite a bit of work given the size.




I'm also not sure how to clean it up, I have a waterblaster, but have been told it would damage the wood.




Any advice, experience and resources would be much appreciated.







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3257 posts

Uber Geek

  #1736198 14-Mar-2017 09:58
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You can clean it with hot soapy water and a stiff broom, then just give it a hose down. You can buy proper products to clean it too, pretty much any hardware shop will sell them. 


As for staining or oiling, it will help protect the surface, but the builder is right in that the UV protection breaks down after about a year. So will need another coat. You'll find the oil will soak it lots the first time you do it, but after that a single coat should be fine yearly. 






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1891 posts

Uber Geek

  #1736203 14-Mar-2017 10:02
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Our JSC timber notes on file in the office state:


Cleaning & Washing
Hardwood decks should be cleaned with a stiff brush at least once a year to clear gaps and remove surface mould which can be a slip hazard in wet weather.  It is also important for the life of the deck to keep it clear of leaf litter, moving pot plants or other large objects that may hold moisture to the top of the deck.


Hardwood decking can be waterblasted BUT it is important to do so at a low pressure so as not to damage the fibres of the board by going too hard and/or too close.  Care must be taken not to stop at the end of the stroke but to lift the nozzle away when changing direction.


Washing/brushing the deck down with a mild solution of janola and water (1:16), or suitable equivalent, will remove any build up of resin or extractives that may leach out of the timber as the pieces “season” in situ.  There are also various chemical cleaning agents available, from detergents through to acids.  Follow manufacturer’s instructions and be conscious of the run off.  


Kwila has quite considerable reserves of extractive and readily stains all adjacent materials.  It can only be removed with chemical stain removal products, such as Timber Wash  


The amount of run off will depend on the specie, how dry it is before the decking is laid and how long  exposed the deck is to the weather.


Always follow the manufacturer’s specification for re-coating. 




As for the coating of the kwila itself, if you start staining, expect to get about two summers out of it (depending on location) before it need to be re-coated. The same would go for oils, too. I suspect it's not been done before due to the size of the deck. And to be honest, so long as it's well ventilated and you give it a clean after each winter, there's no reason to start now if you don't mind the silver look.



244 posts

Master Geek


  #1736205 14-Mar-2017 10:08
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I like to clean/restain mine every couple of years.


It was indeed a pain when I was using a brush, but the last couple of cycles I've used a Cabot's lambswool applicator (with broom handle) which makes the process much simpler/faster.


3355 posts

Uber Geek


  #1736528 14-Mar-2017 21:36
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If you're pulling up a plank or two, experiment on that.  Silvered, weathered wood might not take a stain or oil very well.


I always clean my deck with a waterblaster. As long as you're not using a petrol powered one and are reasonably careful, I've never marked mine. I use deck cleaner with a stiff broom and then wash it off. Advantage of a water blaster is you can get a nice fan shape going and sweep all the crud away.


Then as @kiwi_64 said, the cabots lambswool mop works amazingly fast (I'd recommend the proper bucket too). 50m2 you will do in no time.


76 posts

Master Geek

  #1736835 15-Mar-2017 12:58
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Thanks for the replies.


Sounds like first step is a good mold treatment brush clean, probably with a careful water-blast.




I don't mind the silver/grey look. It would probably look better stained, but I'd leave it unstained if its not likely to be causing problems.




Some friends have said that stain/oil helps prevent splinters. As far as I can see there is only one rouge plank that is clearly splintering. The really exposed planks (mainly the capping on fences and seats) have become quite rough and feel like you could pick up a splinter in them. So I have wondered about giving them a light sand.


As suggested experimenting on a plank or two sounds like a good idea.







7724 posts

Uber Geek

  #1739867 15-Mar-2017 15:00
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The advantage of kwila and similar hardwoods is that they don't need to be oiled.  They look better oiled to some tastes but it isn't required.


Persistent wet is the biggest issue with Kwila.


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