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How to maintain Merbau deck?

I replaced my 23-year-old, 12m deck with new marabou slates in June 2023, and then in October 2023, I treated them with Cabots Merbau Aquadeck Exterior Decking oil. Throughout the process, I was continuously getting advice from the experts at Bunnings.

Now, I feel it’s time to give the deck a bit of a refresh, especially since the heavy traffic areas have gotten quite dirty. I’ve attached some current photos for you to take a look at. Could you please let me know what steps I should take now and what materials would be best to make the deck look brilliant again?

Thanks so much!

Syed

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Comments

JacobZ

Hi Syed (@smhasnain),

While your deck still looks great, it looks like it's time for a maintenance coat of oil to have it looking brand new.

Start by giving your deck a good clean with Cabot's Deck Clean and a Long Handle Deck Scrub Brush. Check out How To Clean a Deck for some guidance.

Once clean, the process is much the same as what you did initially. Apply 1-2 coats of the Cabot's Merbau Aquadeck Exterior Decking Oil with an oil applicator and a paint brush. Check out How To Oil Your Deck for guidance on this process.

Let us know how you go and if you have any questions along the way, please don't hesitate to reach out.

Jacob

smhasnain

https://www.workshop.bunnings.com.au/discussion/comment/51117#Comment_51117

Hi Jacob,

Thank you for your prompt reply. I am wondering if you could also explain the difference of using Aquadeck oil over water based stain (Merbau) on my slates. Can i apply any of this on cloudy day when ambient temperature is less than 20degree. Thanks

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/87694#Comment_87694

Hi @smhasnain,

Aquadeck, and more specifically, Cabot's Merbau Aquadeck Exterior Decking Oil is a decking oil with merbau coloured water-based stain added.

If you were to use just a stain, you would have to apply another product over the top. It's just easier to use the oil and stain combo, so I'd suggest sticking with it.

You can apply your oil on any day where the temperature is between 10-30 degrees, but if there is rain forecast, I would put it off till the weather clears.

Let me know if you have any further questions.

Jacob

smhasnain

https://www.workshop.bunnings.com.au/discussion/comment/109404#Comment_109404

Thank you very much for your valuable advice and guidance.

I have cleaned the deck and attached some images for your reference. I’ve noticed that certain areas of the boards appear to have darker, more brownish patches compared to the rest of the surface. I would appreciate your advice on how to address this inconsistency in colour. Should I scrub these areas further or consider using sandpaper to achieve a more uniform appearance?

Additionally, I have a few other questions:

Do the boards require further cleaning before applying the finishing product?
Is it necessary for the boards to be completely clean and free of residue before application?
I have some leftover products from a previous project: approximately 3L of Aqua Deck Merbau and 1L of a water-based Deck and Exterior Stain. Can these two products be mixed and applied together, or should they be used separately? I’d like to understand which approach is more effective, cost-efficient, and likely to deliver the best results.

I would greatly appreciate your expert advice on the above points. Thanks

EricL

https://www.workshop.bunnings.com.au/discussion/comment/122049#Comment_122049

Hello @smhasnain

In its current condition if you were to oil it now, there is the possibility that some sections will be darker than others due to the stain of the old oil still on the surface. It's also possible that some sections will not absorb the oil properly because there are still sections of your deck that are sealed with the old oil. In order to get a uniform finish, I suggest sanding the entire surface back to wood. This will remove all the unevenness of the surface and bring you back to the original surface of the wood.

Once the decking panels have been sanded and cleaned properly, you can then make your plans on staining its surface. Please do not mix stains as they are not compatible with each other and will produce an unreliable finish. I suggest using only one product for your entire deck, I recommend visiting your local store and looking at the oil and stain sample board in the paint department so that you'll have a better idea of what the finish colour will look like.

Here are some handy step-by-step guides:

If you need further assistance, please let me know.

Eric

smhasnain

https://www.workshop.bunnings.com.au/discussion/comment/130093#Comment_130093

Hi Eric,

Thank you so much for your valuable advice — I really appreciate it! I’ll go ahead with the hand sanding using 200-grit sandpaper on the boards that show signs of old oil before applying a fresh coat to the entire deck. Is this ok? I’ll also avoid mixing stains as you recommended.

Just one quick question: I have about 3 litres of Cabot’s Aquadeck in Merbau left over from around 4 years ago. Would it still be okay to use on the boards, or would you recommend buying a new tin of Aquadeck?

Thanks again for your help!

Best regards,

syed

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/135129#Comment_135129

Hi @smhasnain,

I think you'll find the grit would be 240, as I haven't seen 200 before. If 240-grit doesn't remove the previous coating, you can try using 180-grit.

I suspect three-year-old oil might be at the end of its usable life. The pigments have likely sunk to the bottom of the can, and it might be difficult to get them into suspension again. I'd recommend buying some new oil as you don't want to go to the effort of sanding and have old oil ruin the finish.

Mitchell

smhasnain

https://www.workshop.bunnings.com.au/discussion/comment/138473#Comment_138473

Hi,

I recently purchased brand-new Aquadeck Merbau and applied two coats on my deck after using grate 240.

However, I am not entirely satisfied with the outcome.

Could you please review the appearance of the deck after the two coats, and compare it with the previously submitted photos taken after the pressure wash but before coating?

I would also appreciate any suggestions on how I might further enhance the sharpness and overall appearance of the deck.

Thank you very much for your assistance

EricL

https://www.workshop.bunnings.com.au/discussion/comment/140713#Comment_140713

Hello @smhasnain

Thank you very much for sharing those pictures of your newly revamped deck. Looking at your first pictures and these new ones, your deck freshly sealed deck looks much better. I suggest putting on an extra coat to make it a bit darker.

Let me call on our experienced members @Dave-1 and @Nailbag for their recommendations.

If you need further assistance, please let us know.

Eric

smhasnain

https://www.workshop.bunnings.com.au/discussion/comment/142334#Comment_142334

Thanks Eric for your prompt reply. I will wait for Dave and Nailbag’s recommendations before taking further steps.
Just for the sake of curiosity, if i opt to put another coat, Will i need to wait for warm sunny weather in Melbourne?.

Thanks.

EricL

https://www.workshop.bunnings.com.au/discussion/comment/143492#Comment_143492

Hello @smhasnain

It's best to apply the next coat in the morning when its not too hot and there is no sign of rain for the next few days. I don't recommend coating the decking surface when its too hot or when its in direct sunlight.

If you need further assistance, please let me know.

Eric

Dave-1

https://www.workshop.bunnings.com.au/discussion/comment/144371#Comment_144371

Good Evening @smhasnain

Do you have any pics of the deck after you sanded it? I am just wondering why that darker area is on the steps. I think it has come up nicely and as @EricL has suggested another coat will belnd it more so (it will also darken it)

I would dispose of the old oil you have been asking about as @MitchellMc has said the materials would have seperated and hanging out on the bottom of the can 🙂 Never worth using something after going to the effort to sand a deck.

I am a little confused as to the grit of the sandpaper you have used tho, I used a belt sander with a brit of 36 to sand back my deck.

Hardwood deck restoration Step 2 will show the sandpaper I used.

Dave

Nailbag

https://www.workshop.bunnings.com.au/discussion/comment/140713#Comment_140713

Hi @smhasnain

I suspect the issue causing your unhappiness is probably in the areas where the more weather blackness thats was deep in the boards grain. Your choices here are:

1. Sand those specific boards much deeper back to raw merbau to remove the blackness. Boards in this bad of condition I always start with 180G then move to 240G. But this would be very labour intensive and replacing the few worst ones would be a consideration. However it will take several coats of oil on just those boards to match them back with the rest colour shade wise..

2. A similar suggestion to @EricL but only apply oil with a brush to the non-blackened boards first to darken them. This will help blend all the boards to the same colour. When I repair badly weathered decks I use this approach, but then apply another coat over the the top to even them out. In some cases the final top coat would be a clear so not to darken the boards further.

Bottom line is that this shows the importance of regular oiling and not letting the boards get to a state where the old has faded to grey. Once you get this lot sorted, make a note to give 1-2 fresh coats at the start of every summer.

Nailbag

Jacob-Hawkins

Hi Syed,

I've come across this exact situation many times. Water-based stains (like all coatings) wear off unevenly — partly due to UV, but mostly from foot traffic, as you noted. The results you've achieved are about as good as you can get without fully sanding everything back and starting fresh.

The water-based product forms a semi-transparent film on the surface. When some areas still have it intact and others are worn off, applying more just stacks the coating unevenly — creating a patchy look with darker, heavier sections where it's layered.

As others have said, adding more coats can help make it look more uniform, but it will also make the timber darker, more opaque, and hide more of the grain. That’s the cheapest and easiest option.

If you want to get the original look back, I’d recommend sanding it all back. Grab a belt sander with 36- and 80-grit belts. Start with the 36 to quickly remove the coating and blackness, then switch to 80. Finish off with an orbital sander using 80 or 120 grit (depending on the coating you're planning to apply).

In future, try to recoat just as the original layer begins to fail — usually at the first sign of patchiness. That way, you’ll maintain the colour and consistency without needing to start from scratch. Depending on UV exposure and wear, you might get several seasons before needing a full restoration.

P.S. Belt sanders have the added benefit of making your arms slightly longer!

Let me know if I can clarify anything.
Cheers, Jacob

Before Sanding - Worn from UV & Foot TrafficAfter Sanding - Ready for any coating

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/54925#Comment_54925

Hi @Jacob-Hawkins,

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

I trust Syed (@smhasnain) and our other readers will appreciate the fantastic advice you have offered.

Thank you for sharing your knowledge.

Jacob

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