Gap Filling: Resin or Timber Slivers?
The two main methods, and why gaps can return
Most period floors develop gaps over the years as boards dry, shrink and shift. Apart from the draughts, gaps collect dirt and can spoil the look of a freshly restored floor. 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
With this method, a clear resin is mixed with fine dust collected from sanding your own floor, creating a paste that matches the timber. It is spread across the floor, worked into every gap and sanded smooth once it has hardened. It is ideal for narrow gaps, small cracks, splits and nail holes.
Blends well, since the filler contains your own timber.
Efficient and affordable for larger areas.
Suits narrow gaps rather than wide ones.
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. Once dry, they are planed and sanded flush with the boards. Being real timber, slivers accept oil or lacquer like the surrounding boards. It is labour-intensive, so it is priced higher than resin filling.
Why gaps can come back
This is the part many people do not expect: wooden floors are never completely still. Timber absorbs moisture in humid summer months and releases it when the heating is on in winter, so boards swell and shrink with the seasons. On top of that, the building itself moves slightly, and joists flex as people walk across the floor.
Because of this, any gap filler, resin or timber, can crack, shrink, loosen or work out over time. It is a normal characteristic of timber floors rather than a fault in the work. That is why gap filling is excluded from our service guarantee, while the sanding and finishing themselves remain covered. We make sure you know this before any filling is booked.
Tips for better results
Try to keep humidity and temperature reasonably stable.
Fix loose boards before filling so they move less.
Match the method to the gap size.
Insulation beneath the floor can reduce draughts and movement.
When gaps are filled
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 allows us to check each gap closely and choose the right method for it, rather than treating the whole floor the same way.
Draughts and energy efficiency
Filling gaps is not just cosmetic; it can also make a room more comfortable. 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.
The essentials at a glance
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.
All wooden floors move with seasonal humidity and structural movement, so any filler can crack or loosen in time.
Because of this natural movement, gap filling is excluded from our service guarantee.
Stable heating, secure boards and good ventilation under the floor all help filler last longer.
Choosing a method
For floors with mostly narrow gaps, resin is usually the practical, affordable choice. For wider gaps, slivers tend to look better and hold up better. Many floors benefit from a mix of both. Find out more about our gap filling service, or ask us to assess your boards during a free survey in Epping.