How to prevent cracks in a solid wood table
Solid wood shrinks in dry air. Read why the first winter is the most delicate, which humidity wood prefers and what to do if a crack appears anyway.
A shrinkage crack usually appears in the heating season, when the air indoors turns dry in a short time. With a hygrometer, the right spot for your table and gradual heating you prevent most cracks.
Quick guide
- Hang a hygrometer in the room and keep the humidity between about 40 and 60 per cent.
- Do not put the table right next to a radiator, stove or open fire, nor in full sun.
- Turn the heating up gradually in the first winter, not all at once.
Why solid wood moves
Wood takes up moisture from the air and releases it again. In humid air it swells a little, in dry air it shrinks. That is called movement, and every solid wood top does it, a lacquered one too.
Wood moves mainly across the width of the board, much less along its length. A top can therefore be slightly narrower in winter than in summer. You usually do not notice, as long as it happens gradually.
What causes a shrinkage crack
A crack forms when the wood dries faster on the outside than on the inside, or when one side of the top dries faster than the other. The wood then contracts unevenly, and the tension looks for a way out. Such a crack often starts at the end grain of the top or at a knot.
The first winter: the most delicate period
A new table comes from a workshop and has to adjust to the climate in your home. If that coincides with the heating season, the air turns dry in a short time. That is when most shrinkage cracks appear.
So turn the heating up gradually in autumn. A few degrees more per week is better for the wood than going from cold to warm in a single day.
After delivery
Remove the packaging from the top straight away and completely. Film left on one side keeps that side more humid than the other, and that causes tension.
In the first weeks, do not leave a plastic tablecloth or large placemats on the top for days. The top then dries differently underneath than around it. A fabric tablecloth that you take off regularly is no problem.
Underfloor heating
With underfloor heating the warmth comes from below, right under the top. The underside can then dry faster than the surface. Do not run the floor under the table extra warm and keep an eye on the humidity, especially in the first months.
Measuring and controlling humidity
A hygrometer costs little and shows how dry the air really is. In a heated home in winter the humidity often drops below 40 per cent, and you notice it yourself in dry eyes and static hair. For wood, a humidity between about 40 and 60 per cent is a good guideline.
How to raise the humidity
- Put a humidifier in the room and set it to the desired level.
- Hang water containers on the radiators.
- Keep plants in the room, as they release moisture.
- Air the room briefly and thoroughly instead of leaving a window ajar for hours.
Mind the spot
A table with one side facing a radiator dries faster on that side. Keep a distance from heat sources and do not place the table where the afternoon sun falls on the same part of the top every day.
Lacquered or untreated: does the finish help?
An oak top from Tulmans is stained and finished with two coats of clear matt lacquer, unless you choose untreated. Lacquer slows down the exchange of moisture, but does not stop it. A lacquered top moves with the seasons too, only more calmly.
If you choose an untreated top, you finish the wood yourself. Oil or wax does not stop the movement either. See the finishes under oak table tops.
What to do if a crack appears anyway
A shrinkage crack is part of solid wood. Repairing it makes little sense: the wood keeps moving with the seasons, the humidity and the sunlight, and a crack can close up again in summer when the wood takes up moisture.
So do not fill or glue a crack yourself. What does help is tackling the cause: bring the humidity up, keep a distance from the heating and make sure the sun does not fall on the same part of the top every day. That way you prevent further cracks.
Which wood and which top suit your home?
You choose solid wood for its warmth and figure, and you accept that it lives. If you want a top that does not move and needs no attention in dry air, a ceramic table top or a granite table top is a better choice.
| Material | Moves with humidity | What to watch |
|---|---|---|
| Solid oak | Yes | Humidity, distance from heat sources |
| Solid walnut | Yes | Humidity, direct sunlight |
| Ceramic | No | Knocks on the edge |
| Granite | No | Hot pans, always use a trivet |
If you are torn between wood and stone, read custom oak dining table and ceramic or granite table top. You can also see the tops side by side in the showroom in Maasbree, Netherlands, or browse oak dining tables and walnut dining tables straight away.