Just moved into new house and kids had a bath last night, they always manage to splash plenty of water onto floor (carpet) the water then appeared through the living room ceiling (argh) on inspection, I lifted carpet and found existing wood (board) flooring (not laminate) had gaps at the biggest points some 1/4 - 1/2" wide.
What can I use to fill these gaps in with(drying time and movement to take into consideration) until a new bathroom & floor is saved for.
Ive seen this many times, its very easy to fix what you need for a proper fix is wood glue, length of timber floor board.
1/ measure the widths of the gap and transfer them to the new section of floor board and now mark out the length of gap onto the floorboard you should now have an exact replica of the gap on the new timber,
2/ cut the shape out of the new board keep the cut as tight to your pencil marks as possible, we want a tight fit.
3/ Appliy wood glue to the edges of the board.
4 / Insert the newly cut board in to the gap, now this should be a tight fit so give it a tap with a hammer untill flush.
5/ now run a line of wood glue around the out line of your repair smooth out with a cloth to seal the join, if the fit is not great and has a slight gap around the edges fill in with some quick grip.
Job Done !!!