Last weekend we visited a friend who is fixing up an old row house in historic Baltimore. He had just refinished his floors so I really checked them out. They had random sized gaps-some as large as 1/8" and they looked great! He said when he sanded them most of the "gunk" came out from the vibrations and the rest he chiseled out with a screw driver. His gaps were empty and clean. He just vacuums instead of sweeping. Don't be too afraid of gaps!