I have old oak floors in an upstairs bedroom which are in good shape (no big scratches or gouges, and the boards are tight) but the old oil-based poly is very worn in places. Can I rent an oscillating floor sander and simply screen the poly rough, and the vacuum and refinish with 2 new coats of oil-based poly? If this seems ok, would it be a mistake to actually sand down a few spots in the floor that are stained before refinishing? ie: If I sand the stain down to bare oak, will that spot stand out when I re-poly ??? thx.

We are 10 months in a newly built Victorian style house with pine wood floors. The gaps between the planks widening, and the puddy/filler is falling out. This seems to be a byproduct of running the A/C (especially the heat during the winter). The builder says this is due to the planks shrinking from the water drying out, but he's not sure how to fix/fill the gaps. Questions: Is this shrinking normal with pine floors? Will the expansion/contraction happen each year as the seasons (and use of indoor heating) change? Any suggestions about how to fill the gaps for a permanent fix? All suggestion would be welcomed