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I have a maple bench that recently decide to crack. I'm not sure what's the cause. I'm guessing wood expansion due to humidity changes. Anyway, I've decided to look around for solutions on fixing the crack. The crack itself is pretty small, a finger nail barely fits in the opening. Here's some pictures:

Top of the bench Top of the bench

Close-up of the top Close-up

Under the bench enter image description here

Ideally, I would like to close the gap. In the end, I'm not sure which one is the best approach. I've considered the following:

  • Bowties; although it doesn't seems to close the gap.
  • Dutchman; a patch wouldn't be that bad, but requires a lot of precision!
  • Re-gluing; by carving the crack in a V shape from under the bench, adding glue and then clamping.
  • Wood filer; would probably require sanding the whole top, staining and varnishing again. I would like to avoid that.
  • Staining the crack with a tiny brush; makes the crack less visible but wouldn't close the gap.

Anyone have experiences on fixing these cracks?

UPDATE: I went ahead and stained the crack as per @HenryJackson's answer. It is a lot less visible. I will leave it as-is for now. (It's not making me crazy... yet!)

Stained Crack

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It looks like the crack occurred right where the horizontal support ends. No matter how you fix the crack, make sure to replace that horizontal support (or sister it) with something that extends the whole length of the bench. Otherwise it will probably crack again if someone sits on the end! –  longneck Mar 28 '13 at 18:36
    
@longneck I find it odd that it cracked there. Although, it didn't crack when someone was sitting on the edge. It cracked in the middle of the night. As you suggested, once fixed, I will probably sister it to help with the support. –  Maxime Morin Mar 28 '13 at 18:57
    
The wood has actually contracted due to lower humidity now. When the humidity increases again the crack will probably close up on its own and it could even blow out the ends. As Henry describes below, allowances need to be made for expansion and contraction cycles in solid wood. There would have been less chance of cracking if the grain had been run the long direction of the bench instead of the short direction. –  JayL Mar 30 '13 at 7:42
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2 Answers 2

up vote 4 down vote accepted

This looks like a crack caused by the wood drying and shrinking. Likely caused by dry winter air, although it's also possible that the wood wasn't properly dried before the bench was assembled. (Humidifying your whole house can help with cracks like this, but wood is a natural material and nothing will preserve it perfectly forever.)

It also doesn't help the way the bench is put together: ideally wood furniture should be capable of a little wood movement. When wood absorbs moisture it expands perpendicular to the grain; when it dries out it contracts perpendicular to the grain. (Wood also expands and contracts in the direction of the grain, but usually it is small enough to ignore.) The way this bench is constructed with that large surface of wood, there's no way for a little natural shrinkage without a crack like this.

Unless it's driving you crazy, my recommendation would be to stain the crack and then just leave it. You could try using pocket screws from underneath like HerrBag suggests, but if you try to close the crack tight there's a decent chance that you'll just get another crack somewhere else next winter when the wood shrinks again.

(I disagree with longneck's comment that this is caused by lack of structural support underneath: the crack probably happened next to the support because the support was holding the wood together and resisting shrinkage there. If you say it appeared in the middle of the night, that reinforces my suspicion.)

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Thank you for your answer, I did as you recommended and I'm satisfied. The crack is a lot less visible. –  Maxime Morin Apr 6 '13 at 17:40
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Do you have a straight enough crack to cut the crack out, joint the edges (perhaps with bisquits) and re glue with side-to-side clamping. This would minimize refinishing (possibly none).

Pocket screws from the underside(alternating pull direction, every 4-6") or cauls glued/screwed to the underside and tightened with countertop joining. hardware. Some woodworking glue may help just before tightening down, but a wax woodworking crayon rubbed in afterwards may survive seasonal stresses better over time.

Did you humidify this winter? Setback thermostats and low humidity wreak havoc on old wood.

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The crack isn't straight enough to cut out without losing at least an inch, but it's a possibility. (I don't want a diagonal cut and I somewhat fear the weakness this joint might create. It's a bench for two after-all.) I definitively like the idea of adding pocket screws to help solidify if I re-glue it. As for the winter, since this is a new house, we did not humidify to help the house dry up. The bench/wood is fairly new too, less than a year old. –  Maxime Morin Mar 28 '13 at 18:04
    
All large tables are joined edge to edge. The difference is to use sliding joints to allow across the grain movement. Slotted holes are aligned perpendicular to the grain. –  HerrBag Mar 28 '13 at 20:15
    
The bench can be fastened along one long edge, if it can move as a unit back and forth from the other. –  HerrBag Mar 28 '13 at 20:17
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