How to remove mould from Merbau deck?

[teddybear]

Used 60 grit sandpaper to remove black stains/mould from slightly cupped merbau deck boards that missed a protective coat last year.  Deckwash and pressure wash wasnt enough and 80 grit wasnt enough.  Wuestion do i need to use a finer grit before coating again? Hot position in sun.  Thanks

[JacobZ]

Hi @teddybear,

Welcome to the Bunnings Workshop community, it is fantastic to have you with us.

Typically, you would use a heavy grit like your 60-grit to do an initial sand aimed at removing the top layer of weathered timber, then follow up with a medium grit such as 120-grit to smooth and prepare the surface for coating. If you are looking for a really fine surface, then you could even follow up with some 180-240 grit, but this isn't usually 100% necessary.

At minimum, go back over your decking boards with some 120-grit, then feel the surface and see what you think. Most people will be happy with the feel after 120-grit.

Check out How To Sand A Deck and How To Oil Your Deck for some further guidance.

Jacob

[teddybear]

Thnak you.  Is it ok just to sand the damaged areas and not go over all the areas where the costing is still good eg u der eaves etc where no cupping or stains? Used aquadeck previously

[JacobZ]

Hi @teddybear,

Yes, that is fine, although you might notice a small difference in the transition between the two, but this will even out over time with weathering and use.

If you wanted things to look exactly the same all over right away, then you would need to sand everything back, but this isn't really necessary unless you want to.

Let me know if you have any further questions.

Jacob

[teddybear]

Thanks so much

[teddybear]

Hi would you know whats the amount of time after applying a coat of aqaudeck before rain would affect it?

[JacobZ]

Hi @teddybear,

AquaDeck generally needs around 4 to 6 hours of drying time before it can handle light rain, depending on temperature and humidity. For the best result, try to apply it when no rain is expected for at least 8 hours. That will give the coating enough time to start curing properly. If rain does arrive earlier and the surface still feels tacky, you may need to lightly sand and recoat once it’s fully dry.

Let me know if you have further questions.

Jacob