Best screws for Merbau decking - colour coded?

Hello @GeoffMS

Welcome to the Bunnings Workshop community. It's a pleasure to have you join us, and thank you for sharing your question about the best-coloured screws for Merbau decking.

I agree with your choice of using the Buildex 10-8 x 65mm Climacoat Treated Pine And Hardwood Decking Screws - 100 Pack for the treated decking panels. It's an ideal screw as it's designed to be used for decking panels. It has a subdued colour and should blend in when you stain your deck. My best suggestion is to make sure that the pilot holes you drill are big enough to prevent the decking panel ends from splitting. I suggest having a look at the P&N 10G Quickbit TCT Cut Smart Countersink Drill Bit to make pilot hole drilling convenient.

In the interest of safety please make sure to wear gloves, safety goggles and a dust mask when drilling into your decking panels.

If you have any other questions we can help with, please let us know.

Eric

Hi @GeoffMS,

I just wanted to confirm that these screws are fine for your hardwood Merbau decking. They're just stipulating that they are also fine for treated Pine since some screw types are not.

Mitchell

Thankyou @EricL and @MitchellMc for your quick replies and confirmations.

Eric, I agree in using the Countersink drill bit - time saving for sure.

On the screws again ....

1) Thinking, would the 65mm be a little over kill? Would the 50mm be ok?

2) The bit in the Cut Smart Countersink drill kit doesn't seem to be very long. I'm worried that the pilot hole wont go far enough through the 19mm Merbau and then into the h3 treated pine joists -- therefore creating the possibility of shearing off screw heads due the 'toughness' of the treated pine (maybe wrong, but just a slight worry in my head 🙂 )

3) Would these screws be that little bit better (I could get away with black) https://www.bunnings.com.au/buildex-10g-x-50mm-black-decking-screws-50-pack_p0284271 compared to the 1st suggested Buildex climacoat deck screws?

Thanks again.

Geoff

https://www.workshop.bunnings.com.au/discussion/comment/25436#Comment_25436

Hi @GeoffMS,

50mm screws will be fine. For countersinking, we also have the P&N 4 Piece Quickbit Pilot Drill / Countersink Bit Set. Once again, the drillbit appears short, but it can be adjusted to drill slightly deeper. It's actually the Merbau being a hardwood that is more of a concern, and you'll be pre-dilling completely through that. The Pine is a softwood, and even if you didn't pre-drill it at all, it isn't likely to cause the screw heads to shear off.

The black Buildex screws would certainly be a viable option.

Please let me know if you have further questions.

Mitchell

https://www.workshop.bunnings.com.au/discussion/comment/75401#Comment_75401

Thank you @MitchellMc for your advice.

I've never completed such a job, especially on this scale and on my own, so advice from yourself, Eric and staff at my local Bunnings (Seaford SA) store

(and youtube) has certainly given me more confidence - my wife was especially worried though 😅

We never used the spa, so it was decided we try and make better use of the area.

A couple of progress photos before final touches of noggins, deck lights and decking.

https://www.workshop.bunnings.com.au/discussion/comment/101439#Comment_101439

Looking good @GeoffMS! I can't wait to see your finished results.

Mitchell

A question on whether to screw down Merbau decking boards over all joists or every other joist.

My joists are 450mm (or there abouts) apart and wondering if I should have to screw down the decking boards into each joist - or is every over joist ok?

Sort of answering my own question here as I'm thinking if I screw into every other joist, then there is a possibility of possible bounce/movement on the joists that are not screwed down (especially if the level is slightly out).

https://www.workshop.bunnings.com.au/discussion/comment/25638#Comment_25638

Hi @GeoffMS

You are absolutely correct, the reason the decking panel is fixed into every joist is to prevent it from moving and twisting. It also adds stiffness to the entire decking assembly.

If you need further assistance, please let us know.

Eric

https://www.workshop.bunnings.com.au/discussion/comment/75501#Comment_75501

Thanks for the confirmation @EricL .

ok, getting to the stage of putting the noggins in place.

I have enough wood to do 2 rows of noggins - probably not needed, but I might as well use it up.

I was looking at hiring the Paslode FrameMaster-Li Powervent for about $46 (24hrs).

My dilemma is the nails ..... I'll probably require about 200-250 nails (75 x 3.06mm) at most.

Obviously, the galvanized nails are better for the anti-corrosion factor at a cost @ $92 for a packet of 1,000 nails. (couldn't find if there ware smaller quantity packets available).

For the 200-250 I need, it seems a little steep (so about $138 total).

But seeing it is just for noggins and that the deck is under cover of a pergola, would the Bright D head nails be sufficient (considering the are corrosive)?

At $30 for a 1,000 packet, it's a far more reasonable cost ($76 total) to the galvanized nails .....

Time is not a factor and am half thinking to just hand nail or screw in the noggins - cheaper again, but time consuming.

Just not sure which way to go 🤔

https://www.workshop.bunnings.com.au/discussion/comment/25668#Comment_25668

Hi @GeoffMS,

How many noggins do you need to install? My preference would be to install them with Climacoat screws and a drill driver.

Galvanised nails wouldn't be the best choice for treated Pine as they react with the treatment. You should never use galvanised fixings for structural elements on a deck. Bright nails are not suitable for exterior use as they have no coating and will rust away over time. Stainless steel would be the best choice in treated Pine, but you'll struggle to find nails in a 75mm length. You'd likely need to use joist hangers and shorter nails.

Please let me know if you have further questions.

Mitchell

https://www.workshop.bunnings.com.au/discussion/comment/75519#Comment_75519

Hi @MitchellMc and thanks for your reply.

Thanks for the advice about the Galvanised nails - I didn't realise they can react to treated pine.

And also about the Bright D nails - knew they would corrode over time, but thought 'they're just for noggins, so be might ok' - so they are a no-go too 😁

To answer your Q.... Minimum noggins required would be 10, but have plenty off cut wood so thought I'd use it up and do 20 noggins + some small noggins at 2 ends where the deck framing will be (so about 10) = about 30 in total.

Your recommendation for the Climacoat screws seems the way to go - same ones that I will be using to screw decking onto joists (except shorter).

https://www.workshop.bunnings.com.au/discussion/comment/101530#Comment_101530

Since the noggins are an afterthought @GeoffMS, you could use the bright or gal nails it's just not a great building practice. Expect a limited life span on the fixings, and the noggins should not be considered a structural element.

Mitchell

https://www.workshop.bunnings.com.au/discussion/comment/117719#Comment_117719

Well it took a bit of time by myself but I happy with my achievement 😁

Your recommendation @MitchellMc and @EricL to use the Buildex 10-8 x 65mm Climacoat treated pine/hardwood deck screws was a great choice, together with smart cut countersink was a time saver. No broken or burred screws and the smart cut countersink bit completed the 800+ drill holes easily and without breaking.

One last bit of advice needed please ...... To secure the bottom skirting board (Porta 92 x 18mm 2.7m Moulding White Pine FJ Primed Bullnose)

to cement fibre wall sheets, I was going to use liquid nails but the skirting boards (4) all have a bow, so will be an issue to keep hard against each other - and straight.

So looks like I need to screw the boards to wall.

I presume these will do (although I don't need 200 - maybe 30-40) Macsim 8G x 30mm Fibre Cement Screws Galvanised - Jar 200.

And any thought on a drill bit to go through the cement fibre?

Thanks.

https://www.workshop.bunnings.com.au/discussion/comment/127322#Comment_127322

Hi @GeoffMS

Thank you very much for posting that photo of your decking project, it looks awesome.

If you are drilling into cement sheet, I suggest using Kango 3mm x 90mm Masonry Drill Bit. The masonry drill bit is small but it will do the job. This will guarantee that the screw will be able to travel through the cement sheet and will anchor itself nice and tight.

I recommend placing some heavy objects on the skirting board and leaving it overnight to possibly remove the bow. Make sure to drill countersunk pilot holes on the skirting board to prevent the timber from splitting.

Plese remember to wear personal protection such as gloves and goggles when working on your skirting board.

If you need further assistance, please let us know.

Eric

https://www.workshop.bunnings.com.au/discussion/comment/133473#Comment_133473

Thanks @EricL for your reply/suggestion.

I'll give your suggestion on some heavy objects on top of the skirting boards to hopefully even out the bows 😁

Any thought on the screws?
Macsim 8G x 30mm Fibre Cement Screws Galvanised - Jar 200 (200 is too many for my needs although not expensive) Any others that could do the job?

Thanks again.

https://www.workshop.bunnings.com.au/discussion/comment/137268#Comment_137268

Hi @GeoffMS

The screws should work well with the cement sheets, my only suggestion is to make sure that the countersink in the timber moulding is deep enough so that the screw heads sit flush with the surface of the moulding.

Eric

Jason

https://www.workshop.bunnings.com.au/discussion/comment/127322#Comment_127322

It's looking awesome @GeoffMS. Very well done.

When you are finished I hope you can hit the Share a project button and document the steps you took. I'm sure other Bunnings Workshop community members would be really interested and inspired to see more detail and the finished result.

All the best,

Jason

cathalm88

https://www.workshop.bunnings.com.au/discussion/comment/25431#Comment_25431

Hi Eric,

I am starting a very similar project but note that the countersunk drill bit you linked above isn't available anymore. What else can I use? thanks

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/90979#Comment_90979

Hi @cathalm88,

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

This Kango 10G Adjustable Countersink Drill Bit Set is more or less the same thing as the one @EricL mentioned above.

Let me know what you think and if you have any further questions, please don't hesitate to ask.

Jacob

https://www.workshop.bunnings.com.au/discussion/comment/111445#Comment_111445

Hi @JacobZ thanks for the recommendation. I had to login in a different profile this morning as was having issues getting signed in but all sorted now and back to my original profile.

I am only installing maybe 14 lengths. I am replacing lengths I had to pull up to fix some rotted timber below at a landing that is fully weather exposed. So it is a small section of deck. The lengths to be installed are 1160mm. The width of the existing lengths is approx. 65mm with some small variances. This deck is probably 25 years old hence the rotted timber below.

The countersunk drill bit you linked is likely to cost almost as much as the timber itself. Is there any other option or is the countersunk bit essential?

I have attached an image of the existing planks. I have been having a hard time confirming the timber but I am thinking its merbau. What are your thoughts?

I have also attached an image of the landing where I have removed the old lengths and the old rotted beam. The other issue is because the existing planks are 65mm I can't readily source 65mm at least not from bunnings. I've measured it and the total width to be replaced is 1335mm. This was 19 planks of 65mm plus the gaps.

As bunnings only have 90mm and 140mm merbau decking I am thinking I can use 14 x 90mm planks with 5mm gaps and this measures perfectly to 1335mm. What are your thoughts on my plan of going with the 90mm merbau?

Once I install the new lengths on the landing there is also going to be major contrast with the rest of the deck which has been painted a light navy or grey colour as you can see in the photos. My plan would be to sand back the entire deck and oil it. I have read that you should allow new merbau timber to leach its tannins for maybe 3-6 months before oiling? If this is the case then its likely there will be a period of time that the new landing and old deck wont be uniform looking. Hopefully once I have applied the same oil to the new landing then it will start to look more uniform.

Thanks in advance.

https://www.workshop.bunnings.com.au/discussion/comment/123151#Comment_123151

Hello @Cathalm8

If it is Merbau, its certainly has provided outstanding service to last 25 years. I propose using the same timber to patch up your deck. The countersunk drill bit is to prevent pinching the surface of the decking panel especially if you are using bugle head screws. There is a more affordable counter sunk drill bit which is the Starborn No.10 Smart-Bit Flat Head Countersink Drill Bit.

In regards to using 90mm decking panel, I propose installing it with a picture frame to make it stand out. Instead of blending it in, I propose making it a feature and draw out a positive feature rather than trying to hide it. I've placed an image below to give you an idea of what it might look like. Just keep in mind that you'll need to slightly modify the decking frame to accommodate the picture frame feature.

Your analysis of the contrast and oiling is spot on! But given enough time and seasoning you'll be able to sand the surface and oil it to get a uniform finish.

Let me call on our experienced members @Dave-1, @AlanM52, @diy_hausdesigns and @Remarka6le for their recommendations.

If you need further assistance, please let us know.

Eric

Dave-1

https://www.workshop.bunnings.com.au/discussion/comment/130823#Comment_130823

Good Morning @Cathalm8

Making a repair look like what was originally can be an interesting exercise. Generally I say its on the plus side of bringing whatever back to how you want it to look.

The timber looks like merbau, and also looks very good for lasting 20 years 😲 My deck is 15 years and I think I used spotted gum and jarah and its still going strong.

Sizzing, for an area such as your repair and making it look consistant, I would be very tempted to rip the width from 90mm down to the 65mm so it stays consistant.

Aging it before oiling is a definite, letting it bleed out some of the colour (water will want to stain)

Sanding back your existing deck, now thats a job and a half. Doable yes, hard work and painstaking even more so. Here is when I did some long overdue maintence on my deck at the start of this year Hardwood deck restoration The hardest points I see for you is between the boards and the stairs as in removing the old paint.

If you install the new boards and then start on the sanding, maybe by the time the fine bits have been done you will have that bedding in time for the new boards?

Dave

https://www.workshop.bunnings.com.au/discussion/comment/135548#Comment_135548

Thanks for the response mate. I could be putting myself in for a world of pain. I feel like iam already committed at this stage though because I think i need to put down new boards anyway as the ones ive taken up are pretty beat. I was going to rent the floor sander from bunnings and the edge sander as well to do the egdes.

My main concerns are that there is some cupping / high lips on the edges of the boards. Not sure how to deal with that.

Also as you say the paint in between the boards, how the heck do i remove that?? After sanding I was thinking of oiling it with cutek extreme cd50 and a light colour tone to hopefully show off the timber. Ive already punched down alot of the nails. Yes whoever installed the deck installed with what I think ate 1.6mmx65mm otter head nails. Not ideal!

And yes the stairs, steps, posts, rails and side of the deck would also need sanded which will take a lot of time.

I have already sanded back a small portion of the main deck to try and identify the timber. I think its merbau but might be spotted gum.

So yes its a big undertaking and I may have to pull the pin because I may not have the time with a 2 kids under 4 running around! Also I do not have a pile of DIY experience!

But my priority now is to get that landing fixed up as quick as I can.

Ive attached a few more photos of the existing deck..

WhatsApp Image 2025-09-11 at 11.36.00_d8a1de22.jpg

https://www.workshop.bunnings.com.au/discussion/comment/138751#Comment_138751

You’re right in thinking this is quite a big undertaking, and with two little ones around, it’s worth carefully considering how much time you can realistically put into it @Cathalm8. You could always do it in sections as time allows.

Unfortunately, there’s no really effective way to remove paint from between the deck boards. A detail sander might let you get into a few corners, but once paint gets into those gaps, it’s almost impossible to get rid of completely. That’s why painting a deck is usually a permanent decision and not something that can be easily reversed.

As for the cupping and high lips, sanding can help to even things out if the issue is minor, but you’ll need to take care not to sand the boards too thin. If the cupping is severe, replacement is often the only practical fix. Flipping the boards would sometimes be an option if they were screwed down and the undersides were unpainted, but since yours are nailed, that’s not really feasible.

When it comes to identifying the timber, Merbau and Spotted Gum can look quite similar once they’ve weathered. Sanding back a larger test area should give you a clearer idea. Once you’ve got the surface prepared, finishing with a natural decking oil will really help highlight the natural grain and protect the boards going forward.

Mitchell

https://www.workshop.bunnings.com.au/discussion/comment/130823#Comment_130823

Thanks @EricL . I was wondering is the counter sunk drill bit adjustable? Or does it matter? I will be using 19mm hardwood. Having sanded back more I actually think that the timber is spotted gum now. I have attached another photo. I can more readily source 64-68mm spotted gum as well.

WhatsApp Image 2025-09-23 at 2.47.46 PM.jpeg

https://www.workshop.bunnings.com.au/discussion/comment/135552#Comment_135552

Hello @Cathalm8

Yes, the Kango brand that JacobZ recommended is adjustable, but the Smart-bit is fixed in position. Countersinking too deeply is also not recommended as they act like water reservoirs and damage the surface of the decking panel. Should you decide to invest in this tool, I strongly suggest testing it on decking off cuts in order to get an idea how it works. I propose visiting your local store and having a long chat with the senior tool specialist about countersinking tool bits and its advantages.

Eric

https://www.workshop.bunnings.com.au/discussion/comment/130823#Comment_130823

Hi @EricL is the https://www.bunnings.com.au/starborn-no-10-smart-bit-flat-head-countersink-drill-bit_p6360119 suitable to use for the following screws https://www.bunnings.com.au/buildex-10g-x-65mm-10-tpi-rapiddrive-treated-pine-climacoat-screws-50-box_p0417602 for fixing down 19mm spotted gum to treated pine frame below?

Thanks