Crafting ideas - Parchet

Solid wood flooring - how to repair gaps between elements

For those who have solid wood floors Coming out of winter - when the heating in your home turns off - can come with surprises. That is, with the appearance of gaps between floor elements.

It can happen with a new floor, but also with an old one that is supposed to have long since reached equilibrium in terms of drying. And yet, these gaps occur. And besides being unsightly, they also collect dirt or become a nest for mites. What can we do about it?

How spaces appear between elements

Let's first clarify why gaps appear when talking about old wood that is supposed to be dry. Because there is a large variation in humidity. The very low humidity causes the wood to get out of equilibrium under normal temperature and humidity conditions and to give up its own moisture to the environment.

Given the usual humidity in our homes of 40-60%, equilibrium moisture content of wood should be between 8 and 12%. In winter the house is heated and the heat supplied by the radiators is dry.

Opening the windows does not bring humidity either because the winter and the outside humidity is low. The frost causes the humidity to freeze, making the air dry. That's why we feel our nostrils dry out inside the house and why logs stored outside under sheds crack outside.

The low humidity inside causes the wood to lose its moisture content and thus decrease in size. The phenomenon is true for all solid wood objects, including furniture. That's why doors don't always stay closed, boards start to show edges or cracks, furniture creaks and gaps start to appear between elements in parquet.

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Before you start repairing the gaps between the floor elements

These spaces are of two kinds and it's good to figure out what you're dealing with before you start any repairs. Some are spaces seasonal that occur in winter.

But in spring, when the dry heat stops, the interior moisture level is restored and the wood returns to its original size. The appearance of these gaps is normal and should not be repaired because the wood will crack and remove the material used for repairs or the flooring will swell.

The second type are spaces permanent. These are actually the ones that need fixing. They can occur for many reasons and the process is irreversible. The main reasons are:

  • Wrong drying of the flooring. The flooring had higher than normal humidity and the drying continued after installation.
  • Insufficient acclimatisation time before installation. Before fitting the wood should be allowed a few days (7-10 days) to acclimatise to the new conditions and rebalance, avoiding noticeable variations.
  • Incorrect fitting of one element relative to the neighbouring element can lead to gaps that do not disappear when the humidity returns to normal.
  • Mounting on an un-dried or insufficiently dried screed. Flooring that is continuously in the sun can also have these problems.

Repairing these spaces can be done in several ways. Regardless of the method, the place is thoroughly vacuumed of dust beforehand so that the materials used have adhesion or get in very accurately.

If there are traces of dried adhesive, they are sanded off and removed. It is recommended that repairs are made during periods of high atmospheric humidity (April, October) and only after you have ensured that the defects are not seasonal.

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Repair methods

One method that applies to small spaces is grouting. It can be made with homemade putty or purchased materials. The easiest and most effective putty you can prepare yourself is from wood dust and aracite adhesive (PVA). Use wood dust not sawdust because the mixture will be coarse. The mixture should have the consistency of a paste. For natural wood, the mixture can be used as it is or it can be stained with a water-based stain to bring it to the colour of the floor.

Apply with a plastic spatula to avoid scratching the floor. Put on a larger amount because it will dry less. After drying (24 hours for safety) sand lightly to bring level. Use a fine abrasive sponge to avoid damaging the rest of the flooring. Then wipe with linseed oil or wax (which you polish) to remove the sanding effect.

You can also use special glues (acrylic or epoxy) that you can find commercially available in different colours. You can also use them if the spaces are a bit bigger because they don't crack when drying. Apply and level as above.

However, it is not a long-term safe solution. Repeated movements of the wood in winter, leading to seasonal gaps, can cause the grout to pull away from the edges of the elements and the gap to reappear.

A recommended method for large spaces is to usewooden shackles of the same essence and colour as the parquet. Cut it to size slightly larger than the space and knock it out. Adhesive can also be used for safety.

Knocking is done with a wooden hammer or a small piece of wood (if using a regular hammer) to avoid making marks on the floor. Leave it until the next day (if glue is used), then level it by planing and finish it.

In the past it was used stringto close the gaps between the floorboards. It is still used to repair floorboards in old houses without altering their charm. Before fitting, the space is thoroughly cleaned of old dirt and the string is painted. Only natural twine (jute, hemp, cotton) is used because synthetic twine cannot be dyed.

After painting, the rope is left to dry for 24 hours and then forced into the free space. Choose twine that is larger than the space. Use a sharp-edged tool - a spackle or even an expired card - to secure it.

A modern variant of using string is to use gaskets. Elastic round laces or V-rings (which fold in the middle) can be used. They must also be fitted by force. The materials can be found in DIY or specialist shops.

If the spaces are large and numerous, the floor should be re-laid (re-fitted), but first the reason for the defect must be found so that problems do not recur. Also make sure there are no seasonal defects. In this case, when the humidity returns to normal, the floor will swell.

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How to reduce or even avoid the occurrence of the defect

First,avoiding the causes that lead to its occurrence. It's good to call in a specialist for the installation of the flooring because he knows what and how to do it so that there are no problems in the future. Don't forget to acclimatise the flooring before fitting!
The installation of parquet is done when the house is warm and the humidity is normal. Fitting at low temperature and humidity can lead to the opposite effect, i.e. swelling.
Another way is choice of laminate flooring. It's much more stable, and the look is the same. Laminate flooring is a thick veneer of solid wood glued to one or three such thick veneers glued perpendicular to each other. In both cases the perpendicular gluing of several layers results in stabilisation of the wood, and its dimensional variation becomes insubstantial. It is also recommended for underfloor heating.
Last but not least, it is recommendeduse of humidifiers to maintain perfect humidity in the home. Ideally, each room where solid wood flooring is installed should have its own humidifier.
I hope you find this information useful and can use it if you have problems with solid wood flooring. If you have any queries, questions or additions, please leave them below in the space provided.

About the author

Mihaela Radu

Mihaela Radu is a chemical engineer but has a great passion for wood. She has been working in the field for more than 20 years, wood finishing being what defined her during this period. She gained experience working in a research institute, in her own company, as well as in a multinational. She wants to continuously share her experience with those who have the same passion - and more.


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  • Good evening, I also have the parquet floor in the appearance shown by you. I disinfected with Spirt, then with Domestos, after drying I vacuumed very well and put putty of commercial wood joints. Now some cracks have appeared again and I haven't even laid the carpet yet because in January I took the carpet to the wash, because some black spots appeared on it, and then I realized that they were coming out of the parquet. I bought Bochemit and I've already given it 2 times but there are still some tiny black insects, which then get on the bed, get under my clothes and in my hair. I brought someone in and they gave it a universal cold mist.It stopped and they appeared again. I think it's some wood but not cavities because you can't hear them gnawing, more like little black dots even on new furniture and some round shapes on the table paint. Can you please give me some pointers? Thank you very much!

    • Hello!
      I'm sorry you have such problems. It is difficult to identify the insect without a photo. Outside specialist sites even recommend an enlarged photograph, taken under a microscope, for identification. In my opinion they are mites that thrive on moisture. It is possible that the screed you have fitted was not dry enough or there is a source of moisture. Such insects grow very well in a damp environment. With the treatments you have solved the effect but not the cause. You should discover the nest (a wet, rotten wood).
      Another insect that stays on wood is the woodpecker. It is hardy and has hidden nests. However, it does not roam around in very large groups. You can check by crushing one. It gives off a bad smell at the time.
      Again, one cause may be dampness, which is beneficial to insect development, or heavily egg-infested wood that will need to be removed.
      All the best!

  • Hello.
    I have a 2bed apt - apx. 30 sqm. of parquet floor that is badly damaged. Therefore please advise me, if and how I can recondition the parquet (oak) plank by plank. Some boards are damaged and need to be replaced, others straightened (recalibrated) being more uneven areas, the space between the slats is f. large in some areas of the room now and cannot be just grouted and sanded.
    The right thing to do would be to recalibrate one blade at a time.
    I am looking for help, someone or a company in the V area of the country as close as possible to TM that can do this operation.

    • Hello.
      I think it's far too hard and time-consuming a job to redo lamella by lamella. In my opinion, the flooring should be re-laid by a specialist and slats added to complete the surface (possibly replacing those that can no longer be saved). After that the whole floor is scraped to bring it to the same level and remove the damaged layer. There are companies that rent machines, but I advise you to work with a specialist. After scraping, sanding and sanding, apply parquet varnish, 2-3 coats, with drying and sanding in between. There are also water-based varnishes and this gets rid of the unpleasant smell in the house. At the end apply a coat of floor wax which you can polish with polish for gloss. Waxed floors are much easier to maintain.
      For more details you have the link below.
      Unfortunately I don't know anyone in the western area who could help you. But there are Facebook groups and if you say what you want, you will definitely find someone.
      All the best!

  • Hello,

    I was pleased to discover that there is also a concern for wood. I mention that I am a beginner, but passionate about wood 🙂
    On the other hand, we face the opposite problem: the multi-layered flooring was installed last year. I think the humidity was very low in the house (20% if the hygrometer at Lidl is to be believed). The flooring was in the house for a month before we installed it. Now, when the humidity rises above 50% the floor rises in the middle of the hallway (the hallway is very long - 14 m and relatively narrow) next to a door.
    As if it had no room to expand lengthwise. Anyway, it rises where the width of the hallway is minimal.
    The floor is on the sponge, not glued.

    • Hello!
      This is a common phenomenon when air humidity rises or after flooding. Probably not enough room under the plinth to expand. The floor doesn't stick all the way into the wall. That area is hidden by the skirting and the wood can "reset" to changes in humidity. If the variation is large and the flooring swells, as in your case, the flooring should be re-floored. That is, remove a piece (if there are small pieces of flooring) and reposition so that the pattern is continuous and a small space remains under the skirting board for such movement. It is advisable to call in a floor layer.
      The movement of the flooring also depends on the type of flooring used. The maiputin moves the laminate.
      All the best!

  • Hello,
    I have oak flooring installed in 2007 ,2 years ago it was scraped grouted and varnished with water based varnish by a company, my pb is the same as in the picture, between the joints remained hole or the old grout started to jump. They gave me the people who did my work and a repair putty for me to add in the places where the gaps appear, which I did and only now that one has cracked and is extremely unsightly in places it sticks to the socks/drawer. I called the company as I have a warranty ,I was told that the wood is working and that it may be from dry air ( I don't dispute that it is so I bought humidifiers and use them ) and they told me that what they can do is to come with a gel in places where there are problems ( I mention that they are pretty much everywhere ) this gel will go between the joints after which they will lacquer. I wanted to get another opinion, I mention that the floor was impeccable until two years ago, when there was no varnish in some parts of the rooms and I decided to do a reconditioning that frankly now leaves something to be desired.
    Thank you in advance.

    • Hello!
      From my point of view the cause would be the following: the old flooring was very dry. Certainly in the house the humidity was low and the lack of varnish made the moisture of the wood drop even more. At the time of the intervention with water-based varnish, the wood absorbed the water from the varnish and the humidity increased, the wood increased its volume. After the repair the wood returned to its old condition and started to lose moisture and shrink. This is how the gaps between the pieces of parquet appeared.
      Certainly a big influence has been the dry over-winter heat. The park will certainly recover over the summer, so I don't think it's a good idea to do anything now. Let the winter pass and let the heat go, then do the repairs. I think there will be a lot less work.
      If a lot of spaces remain, the floor must be beaten up again. You cannot putty the entire surface. If only a few gaps remain, they can be repaired with epoxy putty, with hardening (it does not shrink and is very resistant) or wood wedges can be beaten into the gaps.
      Good luck!

  • Hello,

    After this grouting, especially as it requires sanding, is it necessary to varnish the parquet?
    The floor in my apartment has been fixed to stop scratching with a scraper , scraped , grouted (bona) and varnished with water based varnish in 2018 but small gaps have appeared between the boards and I have no way to move all the furniture in the house to varnish it and would like to know if I start repairing it.
    Thank you,

    • Good evening!
      If you use touch-up putty, there is no need. As far as I know Bona also has putties suitable for such repairs.
      It is possible that the gaps are temporary. In winter, because of the dry heat, the humidity inside drops, the wood loses moisture and decreases in size. When the humidity returns to normal, so does the flooring and the gaps disappear. Therefore, if gaps have appeared during this period, I recommend leaving them until spring to see if they disappear. If not, seal them then.
      All the best!


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