Cracks and warping in garden furniture: normal or a defect?
A crack in your new picnic table or garden bench? Why wood cracks and warps, which cracks are normal, and when it's best to send us a photo. The Wood Guide · Care & finishing
The Wood Guide · Care & finishing
Normal or notCracks and warping in garden furniture
A crack in furniture you've just bought is a shock. Usually it is simply wood being wood. Here is how to tell movement from damage.
- Drying cracks: normal
- Four signs that are not
- What you can do yourself
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A lengthwise crack is not a defect
It is the question we get most often after delivering a piece of wooden furniture. The short answer is reassuring; the long answer helps you recognise the exception.
Wood absorbs moisture when it rains and releases it when the sun shines. As it does, it expands and shrinks — but not equally in all directions. Along the length of a board almost nothing changes; across its width all the more. On top of that, the outside dries faster than the core. That tension looks for a way out, and the result is a fine crack along the fibre.
Such a drying crack opens in dry weather and closes again when it gets damper. You see them most often in the first spring after purchase, and in furniture that moves from a dry warehouse to a wet garden.
The strength of a board lies in its long fibres. A crack between those fibres, along the length, leaves them intact. That is why a drying crack does not weaken the furniture, however long it is.
- Along the length
- normal · wood movement
- At the end grain
- normal · that is where wood dries fastest
- Opens and closes with the season
- normal
- Right across the board
- send a photo
- A finger fits in it
- send a photo
- Soft or spongy
- send a photo
To be fair: no treatment prevents small cracks completely. Not even pressure treatment — that protects against rot, not against movement. If you want furniture without a single crack, don't buy solid wood.
Why wood cracks
It moves across the width
A board can swell and shrink by a few per cent across its width, and barely a fraction of that along its length. So the difference between dry and wet weather shows mainly as gaps and small cracks across the width of the top. More in how wood moves.
The outside dries faster than the inside
Sun and wind dry the outer millimetres while the core is still damp. The outside wants to shrink, the core holds it back. That is how the fine hairline cracks of the first months appear.
End grain drinks
At the end of a board or leg the fibres lie open, like drinking straws. That is where moisture gets in and out fastest, and so that is where wood cracks first. When does wood expand explains it.
Heartwood and sapwood
A board that contains the heart of the trunk moves differently from a board from the outside. That is why one board of a table cracks a little more than another. Heartwood and sapwood.
In pictures · Normal or not?
Schematic drawing.
Normal or not?
Small cracks along the length of the board, however long. Cracks at the end grain of a beam or leg. Cracks that open and close with the season. Fine hairline cracks in the first months. Gaps between the boards that get wider and narrower. A little resin coming out of softwood in the first warm summer.
A crack that runs right across the board, from edge to edge. A crack that gets so wide you can put a finger in it. A leg or load-bearing beam that is clearly weakened or sagging. Wood that feels soft or spongy. In that case, send us a photo with a hand or folding rule in it for scale, via contact — then we can see straight away what it is about.
Warping
Warping is the same movement as cracking, only visible as a change of shape instead of a split.
Cupped or crowned
A board that dries faster on top than underneath cups. After a shower of rain it can flatten out again. A slight curve that moves with the weather is movement, not a defect.
Why thickness helps
The thinner the board, the more it crowns or cups. That is why we work with 4 and 4.5 cm boards: they keep their shape better than the 2.2 or 2.8 cm you often see. More in buying a picnic table.
A wobbly table
If a table is crooked or wobbles, look first at the ground and at the bolts. Wood settles after delivery: retightening usually solves it. A thin shim under one leg does the rest.
When sawing it yourself
If you saw wood yourself, a board can already distort after sawing because of released tension. How to deal with that: preventing warping after sawing.
Limit it, because you can't prevent it completely
- Let new furniture acclimatise firstA few days to a few weeks outdoors before you sand or oil. Freshly pressure-treated wood is still damp.
- Never into a heated roomFurniture that goes from a wet garden into a heated garage or conservatory dries out too quickly. That is where the big cracks come from. An unheated garden shed is fine.
- Not right up against a white wall in full sunIt reflects extra heat and dries the top of the table much faster than the underside.
- Legs out of the waterA few tiles under the legs keep the end grain dry.
- Oil the end grain tooIf you oil for the colour, give the ends of boards and legs an extra coat: that is where moisture escapes fastest.
- Retighten the boltsA month after delivery and then every spring. Moving wood loosens joints.
A drying crack moves with the season; a hard filler usually pops out again. If you still want to fill it, do it in a damp period when the crack is at its smallest, with a flexible exterior-grade filler. Step by step: filling cracks in wood. All maintenance by season is in caring for wooden garden furniture.
Frequently asked questions about cracks in wood
Is a crack in a new wooden garden table normal?
Usually, yes. Fine cracks along the length of a board or at the end grain of a beam are called drying cracks. They appear because wood absorbs and releases moisture, and they do not weaken the furniture.
Do cracks in wood close up again?
Often, yes. Drying cracks open in dry, warm weather and largely close when it gets damper. You see them most in the first spring and the first summer after purchase.
When is a crack a problem?
When it runs right across the board from edge to edge, when it gets so wide you can put a finger in it, when a leg or load-bearing beam sags, or when the wood feels soft or spongy. In that case, send a photo with something in it for scale.
How do I stop my garden furniture cracking or warping?
You can't prevent it completely. What helps: not putting the furniture in a heated room, not right up against a white wall in full sun, not letting the legs stand in water, and oiling the end grain too when you oil.
Should I fill a crack?
You don't need to fill a drying crack; it moves with the season and a hard filler usually pops out again. If you still want to, do it in a damp period and use a flexible, exterior-grade filler.
Wood is wood
Furniture that moves is alive. With a little care it lasts for years.
Unsure about a crack? Send us a photo — we'll tell you honestly whether it is normal.
Photos via Wikimedia Commons: Quercus — HansESchmidt, CC0 · Fraxinus excelsior — Lumbar, Public domain