Gaps in floorboards are a result of temperature and moisture variations that caused the wood to shrink. Any material used to fill the gaps must be able to expand and contract at a similar rate; otherwise, the filler can pop out or fall into the space between the floorboards. For this reason, wood putty and other standard wood fillers are not recommended. Instead, jute rope should be used to fill the gaps. This floorboard repair method was used for hundreds of years, making it an excellent option for historic homes.
Remove old wood putty and other debris from the gaps between the floorboards, using a putty knife. A painter's tool can also be used; just be careful not to damage the floorboards when using this tool.
Vacuum the floor, paying particular attention to the gaps between the floorboards. A vacuum with a hose and appropriate detail attachment is more useful for this step than a standard upright.
Dye jute rope to match the floorboards by placing rope in a bucket filled with wood stain. Allow the rope to completely dry. If you do not want to dye your rope, skip this step.
Force rope between the gaps in the wood floor, using a putty knife. Trim the rope to fit the length of the gap, using a utility blade.
Purchase different diameters of rope to accommodate the varying sizes of gaps between floorboards.
When working with wood stain, use it outside or in a properly ventilated location.