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How to prevent Merbau board ends from splitting?

First time deck builder have starting installing the top Merabu boards and noticed that some on the end have started to crack. I have pre-drilled holes and installed with deck screws. Is it a common issue with the Merabu boards or maybe are my drill holes too small for the screws? Any advice would be appreciated.

regards

Rick

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Jewelleryrescue

Hi @rick6947

It couldnt hurt to make the drill size the same as screw diameter or a tad larger as the screw head will hold the boards down no need to put alot of pressure on the wood decking side ways this includes doing pre counter sinking each hole, The screw head is a wedge shape head and can spilt the wood like your seeing. Merabu boards is a pain for this and splintering.

Gravity holds the deck boards in place and the screws hold them in location and stops side to side movement mostly with a little bit of down force from the screw.

You can buy drill bits with a counter sunk head built in so drilling is a one step operation. Strickly time saving and a conviniance but worth while on a huge deck. You can also use two drills like me one drill bit the other a counter sink rose. I have that gear configuration so I use it.

Ok the 10 million dollar question is fixing those cracks. I would squirt some Aquadhere EXTERIOR from its bottle as deep into the cracks as possible then extract the offending screw allowing the crack to close. So if you use wedge shaped pegs you can gently place them into each side of the deck plank like a mini clamp pushing crack closed more with out having to unscrew whole length. May have to pull a couple pegs apart for there wegdes if this works for you. or clamp planks closed gently for 24 hours.

Once glue dried re drill hole and do a counter sinked hole and place screw back in holding the decking. As it seams it is multiple cracks.

I would re drill and countersink all of the screws installed to take that pressure of the boards as they are constantly expanding and contracting in the weather .

This is a good use of you drills torque control setting a medium firm screw in not a pile driver.

Get that deck sealed asap after fixing it helps them resist weather effects,

By the way you deck looks great top work I hope i help today

EricL

https://www.workshop.bunnings.com.au/discussion/comment/25234#Comment_25234

Hello @rick6947

That's excellent recommendations coming from @Jewelleryrescue. Just a friendly reminder to measure your drilling distance when drilling into decking boards and that's 15mm from the edge of the board and 20mm from the top. Splitting often occurs when the pilot hole is too small and the screw is placed in too tight. When the board contracts it pulls on the screw and this constant push-and-pull cycle is what caused the timber to split.

Just to add to the suggestions made, I recommend drilling larger pilot holes and moving the mounting screws a bit further in. I propose checking the rest of the screws on the deck making sure that they have not bonded to the decking panel.

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

Eric

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