If you have an older home with original hardwood floors, you may wish to restore or repair the old floors rather than install new ones. Gaps between floorboards are a common problem with older hardwood flooring. Left in a state of disrepair, gaps can catch shoe heels, allow drafts into the home and capture dirt and dust between the boards, making it difficult to clean. Before refinishing the floors, you can solve the problem by caulking between the floorboards to close the gaps and make the floor safe, draft-free and easier to maintain.
Remove all debris from the cracks with a screwdriver, putty knife or other hard tool that will fit in the gaps. Try not to scratch the rest of the floor when cleaning the cracks. Vacuum away debris as removed to prevent from knocking it back into the cracks.
Insert foam backer rods into the gaps that are large enough to support the rod. The foam backer rod will reduce the depth of the gap between the floorboards and will prevent drafts.
Apply urethane caulk on top of the backer rod to fill the remaining gap. Use a caulk gun for efficient application. Be careful when caulking that you do not get caulk on the flooring. Urethane caulk can be purchased in different woodlike colours, so choose a colour that matches the stain on the floor or is slightly darker.
Smooth the caulk into place with a wet finger. Try to keep the caulk level with or barely below the level of the floorboards, similar to the way grout sits between ceramic tiles.
Allow the urethane to dry completely before refinishing or cleaning the floor. Refer to the caulk manufacturer's instructions for drying time, but actual drying time will vary depending on the depth of the caulk and the temperature and humidity in the room.
If you do not have a steady hand, mask the wood planks on each side of the gap before caulking.