Filling gaps in boards before sanding

I want to sand the floor in our back room to use as the kids playroom. It's 6x3m with 100mm Cypress Pine boards. There was carpet glued on it and I've pulled this up and scraped off the remaining glue and foam backing.


The boards have been varnished and are in reasonable condition but need a clean up. I was going to hire a sander for half a day just to take the old layer of varnish off. I was thinking 60grit to start.


There are a few gaps between some of the boards ~3mm. I can feel them if I walk barefoot. These larger gaps have some old brittle filler in there, it's has shrunk and cracked, filled with the carpet glue and crud. If I go to the trouble of digging this out, should I re-fill these gaps? What do I use?


Also, what are the options for varnish? I'd prefer water based and was going to ask at Bunnies, but I trust the advice here a bit more.:)

Cheers.

Hi there Milar, I have had a number of old floors done and I always ask that question too. The response has always been that it is possible but it will only look good for a while, as the boards expand and contract the filler will crack and fall out etc.

There are some neat ideas around and probably some newer better products but it sounds like a pretty old floor, so the gaps just add character. :)

On my last floor I actually put some clear silicone into some of the larger gaps after it was finishied just to stop drafts and dirt. This worked well for me but if you were using a high gloss finished and there was lots of light in the room it probably wouldn't be a good idea.