I run a dance in a an old, rather worn, building. By old, I mean 1840s Greek Revival. I'm not sure how old our dance floor is, but the nail heads are rectangular and many stick up a bit, which makes me think they are wedge-shaped cut nails.

The floors have seen a lot of use. There are a lot of gaps and cracks, and a few places where some of the tops of the boards have had pieces of the surface break off. I'm concerned about people possibly tripping or stubbing toes, and also concerned that since some of the top long-side edges of boards are missing, that damage could snowball as boards "erode". The place is a not-for-profit with no money for renovations.

Are there any putties or fillers I could use to level the surface and fill some of the gaps? Bonus points if if looks at all decent and if it won't cause major problems for doing real historic restoration work later.

Whatever we use would have to be slippery enough to dance on, and tough enough to hold up to people dancing on it. A little sanding on the broken parts to prep the surface would be ok, but I don't think we could handle the complexity or expense of sanding the entire floor.

Thanks for any help!

Unfortunately if the boards are cracking and breaking off at the seams this usually means that the floor has very little top layer left. So it is likely that they could not even be sanded and refinished. However, that is hard to say for sure without seeing the floors. Also, I am not really aware of any putties that will stick into larger cracks like this.