Filling Gaps Between Floorboards: Resin vs Slivers
The two main methods, and why gaps can return
Gaps between floorboards are especially common in older homes, where boards have shrunk and moved over many decades. They let in cold draughts from under the floor, trap dust and crumbs, and can make an otherwise beautiful floor look tired. Filling them is a popular part of a floor restoration, but it helps to understand how each method works and what it can and cannot do.
Method one: resin filler
Resin filling uses a clear binder mixed with the fine dust from your own floor, so the colour matches closely. It is spread across the floor, worked into every gap and sanded smooth once it has hardened. It works best on fine gaps, cracks and holes rather than wide openings.
Good colour match because it uses your floor's own dust.
Quick and cost-effective across a whole room.
Best for gaps of a few millimetres.
Can crack or fall out as boards expand and contract.
Reclaimed wood strips
Wider gaps are better filled with slivers: tapered strips of matching timber glued and fitted into place. After the glue sets, the strips are trimmed and sanded level. Because the slivers are wood, they take the finish in a similar way to the floor and can look very natural. The work is slower and more skilled, so it costs more than resin.
Seasonal and structural movement
It is important to understand that wood is a natural material that moves throughout the year. Boards take in moisture in damp weather and dry out when the heating is on, expanding and contracting as they do. Structural movement in joists and the building adds to this, particularly on suspended timber floors.
Because of this, any gap filler, resin or timber, can crack, shrink, loosen or work out over time. This is not a sign of poor workmanship; it is simply how wooden floors behave. That is why gap filling is excluded from our service guarantee, while the sanding and finishing themselves remain covered. We will always explain this before you decide.
Tips for better results
Try to keep humidity and temperature reasonably stable.
Fix loose boards before filling so they move less.
Choose slivers for wider gaps; resin for fine cracks.
Insulation beneath the floor can reduce draughts and movement.
The order of work
Gap filling is normally carried out as part of a full sanding and finishing project, rather than on its own. We begin by sanding the floor to level the boards and strip off the old coating. After that, gaps are cleaned and filled, and the floor is sanded again once everything has set. This means the repairs are sanded flush with the boards and take the finish in the same way as the rest of the floor.
Done at the right point in the process, gap filling blends in far better. It also gives us the chance to look at each gap and pick the best approach for its size and position.
Draughts and energy efficiency
Beyond the look of the floor, filling gaps can make a room feel noticeably warmer. Older homes frequently have ventilated spaces under the floor, letting cold air rise up between the boards. Closing those gaps reduces draughts and helps keep heat in the room, although it is important that the void beneath the floor remains properly ventilated to prevent damp.
Key points to remember
Resin filler made with dust from your own floor suits fine gaps, small cracks and holes best.
Reclaimed timber slivers are stronger and more natural-looking in gaps wider than a few millimetres.
Seasonal and structural movement affects every timber floor, so all fillers can eventually crack or work loose.
That natural movement is the reason gap filling is not covered by our service guarantee.
Stable heating, secure boards and good ventilation under the floor all help filler last longer.
Our recommendation
If most of your gaps are narrow, resin is often the best value. Where gaps are wider than a few millimetres, slivers give a stronger, more natural finish. Plenty of floors are best treated with a combination. Find out more about our gap filling service, or ask us to assess your boards during a free survey in Enfield.