Possible to fix "checked" / split cedar posts?
August 25, 2017 8:04 AM   Subscribe

I had some fencing put in last year, and a number of the posts have "checked"--i.e., split. Depending on the weather, the cracks are really big--up to 1/4" wide. Installer was unmoved. Is it possible to reduce the checking--i.e., glue together when the cracks are smaller? Or will future changes of humidity cause the cracks to open again?

My concern with gluing is that the forces at work were clearly strong enough to split a cedar post--and that's likely enough to overpower any glue I'd use (or the glue will hold and the wood will split alongside).

This is in cedar that was intended to remain unpainted. I could, if push comes to shove, patch with an epoxy and paint the fence, but that's a bit of a hassle.
posted by Admiral Haddock to Home & Garden (8 answers total)
Best answer: That's what wood does. Especially untreated. Glueing will never work. 1/4" seems small, IMO. If you wanted unchecking poles you should have used PT or outdoor wood 4x4's. The checking is cosmetic and won't affect the fence structurally.
posted by humboldt32 at 8:25 AM on August 25, 2017

Best answer: The splitting happens because wood shrinks and swells with changes in humidity and it shrinks and swells more tangentially than radially, so something has to give. As humboldt32 says, it's not a structural problem, which is a good thing because there's really nothing you can do about it.

A good reference is Understanding Wood by Bruce Hoadley.
posted by Bruce H. at 8:38 AM on August 25, 2017 [2 favorites]

Best answer: Gluing won't hurt anything; give it a try.

I'd use Titebond III, and clamp or screw in some long wood screws with a big washer to act as a clamp. Either way remove the clamp after a couple hours.
posted by gregr at 9:46 AM on August 25, 2017

Best answer: In reinforcement of what's already been said: for practical purposes there's nothing you can do about this. With 1/4"-wide cracks I'll guess that many or all of these posts include the very center of the tree. When wood "moves," i.e. shrinks and expands due to changes in moisture content, the rate of dimensional change is different in different directions. The length of a given stick will change very little. Dimensions measured perpendicular to the annual rings, along lines between the center of the tree and the bark, will change moderately. Dimensions tangential to the annual rings will generally change the most. As a result, a chunk of wood that includes the center of the tree will behave like a pie whose individual slices get smaller and pull apart from each other as they shrink. This is why checks nearly always radiate out from the center of the tree.

There are chemical treatments that can control such movement, but they are far too expensive to be practical in this sort of application.

Lumber that does not include the pith / tree center, instead being cut closer to the bark of a large tree, will be less prone to checking, but such lumber is also significantly more expensive and more difficult to procure.

Even if you had high-grade, carefully-dried lumber, a fence that gets exposed to frequent wetting and direct sun is going to degrade over time no matter what you do. Moisture content will change faster at the surface than at the core, and this will create mechanical stresses that will eventually be relieved by some degree of cracking.

I'll disagree with the above comment that glue won't hurt anything. Glue won't work, and it will be (or become) an eyesore, because it won't behave like the surrounding wood. Its texture will be different, it will fall out in chunks, etc.

What you have is a perfectly normal and reasonable fence. I suggest you learn to love it.
posted by jon1270 at 9:53 AM on August 25, 2017 [4 favorites]

Response by poster: Thanks, all! I figured as much. I understand the posts are still sound--but the checks happen to be on the very posts that frame the gate I use daily, and are three feet long starting at the very top, so it's harshing my suburban perfection vibe.

But perfection is not for us mere mortals, or suburban dads, so I will let it go.
posted by Admiral Haddock at 10:19 AM on August 25, 2017

... or garden structures.

Post a photo. I bet it's lovely.
posted by humboldt32 at 11:43 AM on August 25, 2017

Are the posts set in concrete? If not you could rotate the post to put the checked side on the side you can't see.
posted by Mitheral at 9:17 PM on August 25, 2017

That'd be pretty impractical with a gate and fence attached to it.
posted by humboldt32 at 9:20 AM on August 26, 2017

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