How to fill floorboard gaps before hard wax oil?

I’ve finished staining our hardwood floor but there’s a few big gaps that need repairing. I bought selleys no more gaps for timber floors, and the colour match is great. My question is whether it will affect the feast watson hard wax oil I was planning to seal with? I’m getting conflicting advice. Is there a way to patch test? Thanks!

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MitchellMc

Welcome to the Bunnings Workshop community @ilovelucy8383. It's sensational to have you join us, and many thanks for your question about coating and filling timber floorboards.

I’ve checked the guidance from both Feast Watson and Selleys, and in general these two products are compatible. Hard Wax Oil can be applied over Selleys No More Gaps Timber Floors without causing issues, so there is no real concern about the oil reacting with the filler itself. The real consideration is not the chemistry, it is the way fillers behave on a floor.

Selleys specifies that the product is suitable for gaps up to 3 millimetres in trafficable areas. Anything wider than that is likely to fail simply because the filler will not have enough strength or flexibility to cope with movement. It is also important to think about where the gaps are located. Filling a split or a stationary defect within a single board is fine, although filling between boards is generally not recommended. Floorboards expand and contract, and although the Selleys filler has some flexibility, the Feast Watson Hard Wax Oil is rigid once cured, so movement at those joints can lead to fine cracking along the coating line. That is why flexible fillers and non-flexible coatings can be a poor match when used between boards that move seasonally.

If you can share a couple of photos, it will help us understand whether these gaps are within boards or between them, and how much movement they are likely to experience. Once we can see the size and location of the gaps, we can give you clearer guidance on the best way to repair them before you apply the Feast Watson finish.

Please let me know if you have any questions.

Mitchell

ilovelucy8383

Thanks for the quick reply. Here’s some photos. Ignore the skirting boards! Is it necessary to fill the gaps at all? The previous filler seems to have disintegrated and is crumbling, so I’m trying to decide whether I need to chip it out and start over, or just ignore the gaps and seal it.

I’m a total novice, so learning as I go. Not sure what the consequences are if I do a half-baked version versus ‘doing it properly’. Appreciate the advice.

MitchellMc

As these gaps are between the floorboards @ilovelucy8383, it means you need to be a little cautious. Any floorboards that move seasonally can cause issues with the finish. Even if you fill these gaps with Selleys No More Gaps, there’s a chance that continued movement could lead to the Hard Wax Oil cracking along the joint. Because the oil cures as a rigid coating, it doesn’t flex with the timber, so areas with movement are always a little unpredictable.

The same consideration applies if you used a non-flexible filler instead: the filler itself might crack rather than the topcoat, but you would still see cracking in those areas. Essentially, gaps between boards are always tricky because of natural timber expansion and contraction. If the appearance of fine hairline cracks is a concern, it’s worth weighing whether to fill the gaps at all or to monitor how the boards move over time before applying the Hard Wax Oil.

Mitchell

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