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How to fill screw holes in James Hardie fiber cement weatherboards?

ironbark
Building a Reputation

How to fill screw holes in James Hardie fiber cement weatherboards?

Hi, watching James Hardie videos re cladding  they recommend a two part filler for filling the holes. I recently went to Bunnings but couldn't see anything of a similar type. The worker pointed me in the direction of Agnews Multi-purpose filler and Sellys Spakfilla - Heavy duty. I've used some J.Hardie Axent trim with the cladding and fixed with the screws  commended; I'm concerned that these fillers might not cover the screws effectively? Can someone advise me please. Many thanks Jan.

MitchellMc
Bunnings Team Member
Bunnings Team Member

Re: filling holes in James Hardie cement fibre weatherboards

Hi @ironbark,

 

I'm just reading through the James Hardie Axent installation guide and note that bullet head nails can be punched below the surface and "filled with a water-proof exterior filling compound". Agnews Multi-purpose filler and Sellys Spakfilla - Heavy duty would be suitable for this purpose.  Screws must be finished flush with the board surface. I suspect this requirement is in place to prevent installers from overdriving screws into the product and compromising its integrity. An overdriven screw could cause the product to crack.

 

I haven't found the video you're referencing that recommends filler over screws, but if you can link me to it, I can certainly take a look. If you have already countersunk the screws, then the fillers recommended above will work to fill the holes and cover the screws.

 

Please let me know if you have any questions.

 

Mitchell

 

 

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ironbark
Building a Reputation

Re: How to fill screw holes in James Hardie fiber cement weatherboards?

Hi Mitchell,

thank you for that.
The video I referred to is a J. Hardie https://youtu.be/FusDQpGyYvg
The screws are/have gone into 38mm Axent trim. I countersunk the holes so that the screws are fractionally below the surface level, as I don't want the screws showing once completed.
Will the products mentioned adhere satisfactorily to the steel screw with such a small covering. That's why I was pursuing the two-part product thinking it would have more 'holding power?
Thanks Jan

MitchellMc
Bunnings Team Member
Bunnings Team Member

Re: How to fill screw holes in James Hardie fiber cement weatherboards?

Hi @ironbark,

 

I've contacted James Hardie technical, and they are perfectly happy with the screw being driven slightly below the surface and being filled over. You just shouldn't over-drive them halfway through the board, and it certainly sounds like you haven't done that.

 

They've recommended a two-part product, and Sika 1L High Strength Epoxy Repair Adhesive Concrete Fix Kit is suitable for your project. It's the next step up from something like Builder's Bog. The two-part product will have significantly more holding power than a single-part cement filler.

 

Remember your PPE when sanding and filling, including a dust mask and gloves.

 

Please let me know if you have further questions.

 

Mitchell

 

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ironbark
Building a Reputation

Re: How to fill screw holes in James Hardie fiber cement weatherboards?

Thank you Mitchell,

That's very helpful, much appreciated.

Cheers Jan 😊

MitchellMc
Bunnings Team Member
Bunnings Team Member

Re: How to fill screw holes in James Hardie fiber cement weatherboards?

No problems at all, Jan (@ironbark)!

 

Keep us updated on your project, and we'd love to see some pictures when you're done. Please feel free to reach out again if you get stuck.

 

Mitchell

 

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