How to seal period floorboards after sanding?

[ImaBuilder]

Planning to sand our old floorboards, ground floor. There’s a crawling space underneath.

Gaps are 2-4mm wide and there’s some areas of damage, I’ve attached an example.

I understand how to sand but there’s so many options on how to seal. I’m assuming I need to allow for breathing.

Would love to hear your experience and advice

Do you mean seal the wood or fill the gaps in-between the boards?

Ronseal Floor Oil. Really easy to apply, and much better than varnish.

You can fill the gaps between floorboards with a sort of papier-mâché using dampened twisted lengths of newspaper to stop draughts.

Good question. I think seal the wood with oil and fill the gaps/ potholes with something.

Maybe the paper mache @DogInATent suggests is a great option! thank you

I use Osmo poly-x oil. In Satin. It goes on really easily and can be patched up in future if needed.

I definitely wouldn’t use paper-mache for the gaps. It wouldn’t last and would be messy and give a poor finish.

I’d use Bona master gap filler as long as the gaps aren’t too big. If the gaps are over about 12mm you might want to repair them first or use slithers of wood. You can buy them online. You can sand and stain the bona master gap filler if needed but I always choose a suitable colour to start with. There are lots to choose from.

There are other ways to fill the gaps but I think the gap filler is the easiest and most effective for a DIY person. There are other brands but I haven’t used them.

We had ours sanded professionally and they used osmo oil to seal.

@MoreNotLess @MissAtomicBomb1 thanks for your replies!

What made you go for an oil? I’ve ordered Ronseal floor varnish because I also would like to change the pine colour…. Is the oil you mention new and better? Do you stain in a colour before the oil?

Also the sanding is HARD! Lots of bitumen to wade through

Don’t oil it, the previous owners of our house did. It just traps dirt, gets scraped easily etc, it’s not good. Use a floor varnish, it will ptoetect them way more,

https://www.tikkurila.co.uk/kiva-30

Excellent varnish they do it in Matt or semi Matt. It is non yellowing.

If you go to this website page... Scroll to the bottom for the guide on how to insulate a suspended floor, it will show you how to name your floor air tight and insulated without compromising the breathability
https://www.ecologicalbuildingsystems.com/product/solitex-plus#installation-guide

I've used caulk in the gaps but when the wood expands and contracts in the heat bits can drop or need re-doing. Some parts may be too wide - it's a labour or love. Agree with the varnishing over oil - oiled ours last time and it looks dirty and feels less protected.

Fill the gaps with thin bits of soft wood, sand flat carefully, then varnish.

I picked up 5 litres of Bona traffic floor sealer for £6 at our recycle centre, in shops at over £120 so have used that last month....yet to see how it goes...dont use any polyeurathane stuff...its gloopy and goes yellow.

This isn't true of all oils. If you use a suitable oil it will be extremely hard wearing. Floor varnishes are a good option too. Oil, such as Osmo Poly x oil, are easier to apply and are easier to touch up if they get damaged.
It's equally easy to stain/colour oiled or varnished floors.

Sorry my experience is that oil is no where near as effective and hard wearing as oil.

@ImaBuilder we chose oil as we didn't want a shiny polished look. It's less hard wearing than varnish but very easy to fix any patches where marks or scapes may appear. With varnish you would ideally need to redo the whole thing.Thats what we were told by the company we used.

Just to add we've had no issues with the oiled floor in our lounge. Probably wouldn't go for one in a hall or high traffic area though.

https://www.draughtex.co.uk/
we used this for filling the gaps, you don't glue it in, just push it down and because its spongy it fills the gaps

Yes, floors need re oiled every two years, more often in high traffic areas and will need buffed with a fine grit sandpaper before hand. Where has varnish needs to be done every decade.

Don’t use varnish. It’s not breathable and you must allow surfaces to breath.

Suggest contact SPAB ( society for the protection for ancient buildings )
The Listed buildings property group are also good ( even if your buildings not listed OP )

Ps Beeswax and canuba wax blend is often recommended but I’d talk to SPAB or LBPG

I've nothing against varnish and for some types of wooden flooring it's my first choice but I still think OP should go with oil. It's not my experience that are oiled floors need re-oiling every 2 years. None of the ones I have or that I've done do.