Gap Filling Wood Floors

Probably the single biggest question we get asked is ‘how do you fill the gaps of my wood floor’?! It is also my single biggest frustration in terms of information that people have gathered from the internet. Many of these posts that people make are not from professionals or if they are they are giving bad advice that may look good when it is first done but won’t stand the test of time.

There are a number of different ways to fill the gaps between floorboards and other types of wood flooring. Some have better results than others depending on the application. Always bear in mind that wood is a natural product and is ‘hygroscopic’ it holds and releases moisture and therefore moves.

We have seen so many different ways in which people have filled gaps between floorboards. Everything from string and wax to concrete and just about anything and everything in between!


From years of experience in the business I am going to share with you the different types of filler that we use to fill between the gaps in all sorts of wood flooring.

I am going to try my best to keep this as short as possible as this is a subject I could get really carried away with and waffle on for pages. I would go as far to say that any other products apart from the ones I have listed are just not worth bothering with.

One of the most common floors that we sand on a daily basis is pine floors, particularly ones that are 100 + years old. These floors often have gaps and can be draughty. Remember if you have added any reclaimed pine floorboards into your wood floor make sure it has acclimatised before filling as this will affect the gap filling.

Ok so the products we use from day to day are Reclaimed pine slithers, Draughtex, Resin filler (mixed with fine dust) Gap master (Bona) and wax sticks.

Reclaimed pine Slithers

Until fairly recently the best way to fill the gaps between floorboards was with reclaimed pine slithers. The slithers are cut on an angle to form a slight V shape and then glued and hammered in between the floorboards creating a blanket of pine right across the floor. This is an industry recognised way of gap filling however as I have stated above wood can and does move through the seasons. These slithers can crack away from the joints and splinter. It does vary from house to house how much these slithers move. Sometimes they have not moved at all but sometimes the movement is significant and can lead to frustration. It doesn’t matter how much glue is used or how well they have been hammered into place because it is wood, they can move.


This is a relatively new product on the market and my personal favourite when filling the gaps between old pine floorboards. DraughtEx has been cleverly manufactured with thousands of concealed air pockets which allow the sealant to be compressed by almost 90% of its original profile. These flexible properties allow DraughtEx to be compressed into floorboard gaps much smaller than its original form by stretching it during the installation process. Once the floorboard filler is in the gap it will expand until it fills the width of the gap. Timber floors can contract and expand throughout the course of their life. These variations cause alternative floorboard sealants to become ineffective and loose and eventually drop out. DraughtEx will mimic the movement pattern of the timber and therefore remain in place retaining insulation and stopping draughts.

Another thing I really like about this product is that it mimics the natural shadow gap between the floorboards leaving the floor looking as natural as it was when laid but without the draughts. DraughtEx can also be fitted under the skirting boards.

DraughtEx is generally fitted after the floor has been re-finished but the beauty of this product is that it can be used as a quick fix to stop the draughts at any time.

Resin filler

This can be used for header joints (the point 2 boards meet at the ends) on pine floors but we mainly use it on old parquet that has gaps showing. When the floor is finely sanded, the dust from this process is mixed with the resin and used like a filling paste and in some cases the whole floor is trowel filled to ensure getting into every nook and cranny. This sharpens up the look of the floor leaving it gap free and much more pleasing to the eye. Resin is a great product as it dries very fast, its easily sanded and can be over coated with almost any finish blending in nicely with the surrounding wood.

Bona Gap master

This is a silicone free floor gap filling mastic designed to fill gaps between parquet blocks, around skirting boards and door thresholds. Based on polyurethane and acrylate it contains no solvents is odourless and can be used with all parquet finishes It retains a high degree of flexibility. This is a good product as although it can be sanded it can just be applied and allowed to dry, It fills cracks nicely but can work out very expensive if there is a large amount of filling that needs to be done.

Wax sticks

These come into their own when spot repairing damaged areas where sanding is not required. They can be blended together to form knots with any excess taken off with a sharp Stanley blade. The amount of times these have been used when a builder has dropped something on a newly finished floor the dent has been disguised as a knot. When it has hardened wax stick fills are incredibly tough

For any more help and advice please feel free to call us on 01962 733016 or email and we can get your flooring project off the ground today! 

Comments are closed.