Wood filler fordecking boards

[TJG]

Hi all,
I'm new to this web site but have found a lot of interesting stuff here.
I posted a deck question late yesterday, I think in the wrong place (apprentice - first day), so here goes in the deck forum:

We are preparing our spotted gum deck for re oiling using Wattle Weatherguard oil based decking oil. We put 2 coats on when we finished the deck 5 months ago but it has not lasted in the exposed areas. We will try 3 coats this time. Should we sand the whole deck, just the badly faded area or the area under cover that still looks good?

Also some boards have split where they were nailed near the ends of the boards and there are also a few knot holes. Should I fill these cracks to stop them getting worse? If so what should I use? All of the Wattyl wood fillers are interior use only. I tries some putty yesterday but it was a bit messy and the colour is not right. Any advice would be very timely and much appreciated.
Tony

[strangerep]

For best results, sand the whole thing, clean heavily with Napisan and Oxalic, and try Cutek (which is a better oil product than most others -- though sometimes harder to get).

Re filling: it's almost hopeless. Exterior timber swells and shrinks under the action of the weather. Many fillers will simply re-emulsify and gradually disappear. Others will simply cling to one side of the crack when it re-opens a bit further. The most ambitious thing I've tried is marine epoxy resin with sawdust as a filler but (a) it's *really* time consuming (b) it's *really* hard to sand (c) it still bonds to only one side of the crack, and several applications are necessary (d) it's epoxy, therefore not UV stable, so it won't last indefinitely.

It's ultimately a total waste of time trying to fill decking timbers.

[r3nov8or]

You should find that if you protect the board ends to allow them to dry out completely most of the cracks will close up. It may take a few weeks. Then use a highly protective oil to keep the moisture out, and keep it manitained, especially on the ends. If what you have used lasted only 5 months I would look elsewhere. Cutek CD50 is mentioned often. I've also just noticed this sub-forum has a new sponsor that looks to have an interesting waterproofing product for wood.

[stevoh741]

X2 for cutek and I also wouldn't bother trying to fill. If you really feel the need the only thing I'd even consider using would be (black) sikaflex. Sticks like a bitch, will handle movement and is sand able.

[TJG]

Many thanks guys. You've confirmed my suspisions in relation to the filler. I think I will just leave the cracks and go ahead and oil the deck. We have 10L+ of the Wattle Oil left, so I will use it up first, perhaps go with 3 coats a day apart and try something like Cutek next time . If only I can get a completely dry day!