Floor finishing advice - Pine boards


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Established Member
30 Apr 2023
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Hi all

My next project involves our flooring.

So the original floorboards in our house are pine, our plan is the sand these, theb stain and seal with Fiddes hard wax oil (already have the oil and stain).

My question however resides in how to seal the gaps between the tongue and groove? Where over the years people have required access under the floor there are also areas where the tongue has been cut off to allow boards to be removed. So I'll need presumably a slightly different approach where I have larger gaps without a tongue to sit on?

My original plan was slithers, but that is a lot of work/effort that I will do if I have to. But would prefer something simpler.

Any wood caulks that would do the job? Rubber strips worth trying? I've seen resin/saw dust mentioned but I'd have to find an alternative solution where the boards have been removed in the past due to no tongue.

Any advice would be appreciated! Especially recommended products.

There is a range of compressible round foam strips that tilers will use to push into the gap between tiles that hve not been cemented in place. The foam is pushed in towards the bottom of the tile which means the grout doesn't fall through. That would let you use glue/dust.

Or wood slivers whcih is wha I'd go for
Am I right in thinking that the standard tongue and groove joint doesn't actually need anything additonal to seal it if the tongue and groove is in tact?
Or should I seal up everything regardless?
There's no need to fill gaps, some people like to as they think it looks better. If you decide to I would avoid caulking and filler as they will age and stain differently to the wood .
Am I right in thinking that the standard tongue and groove joint doesn't actually need anything additonal to seal it if the tongue and groove is in tact?
Or should I seal up everything regardless?
If the tongue and groove is intact then I'd not do anything else as Jones suggests.

Be wary if anyone suggests mixing up sanding dust and glue/PVA/D4/whatever. In theory it sounds as if it should match the wood already there since that's where the sanding dust has come from. In practice, chances are it will be much lighter because the stearate/fixing compound in the sanding disc/belt wears off and into the sanding dust. DAMHIKT.
I'd recommend using wood filler and sawdust to address the gaps, especially in areas without a tongue to support them. By mixing wood filler with sawdust collected during the sanding process, you can create a custom filler that closely matches the wood, which works effectively for medium-sized gaps. If you're uncertain about the process, seeking the opinion of a professional is also a good idea. You can find professional insights and recommendations in sources like BuildDirect reviews, for example.
Tal, do you want a wood finish? About 30 years ago I painted our dining room floor. I could not afford posh floor paint as money was short, so I did the following.
- belt sand floor and spot fill nail holes.
- spot prime knots etc with blocking primer.
- two coats acrylic primer undercoat in one day.
- caulk all gaps.
- three coats of emulsion, in one day.
- two coats of acrylic floor varnish, in one day.

It worked a treat and looked marvellous.

just bear in mind the floorboards need to be able to expand and contract if you do fill it in, I would not touch it, air needs to be able to flow through the building, gaps in floorboards can help prevent mould.
Thanks all.
Yeah I would like an oiled wood finish.

All posts taken on board. I think I will cut my own slithers from some spare pine floor boards just to fill the gaps where the tongue has been removed (I have a few hatches cut into various areas of the floor from when I had the place rewired) that need repairing etc.
I will leave the majority of the floor in tact and won't bother with filling the gaps.
Less work is always a good outcome :)

I do need to insulate the floor (from within the crawl space) at some stage as well. But was saving that until the floor had been completed. So expect some more questions soon....