I’m frequently asked about nasty-looking vertical cracks in wood deck posts. Is this a problem? Is the deck going to fail? How big of a crack is too big of a crack?
It’s called Checking
The appropriate term for these so-called cracks is “checking”. This happens when big wood timbers quickly dry; the outside dries faster than the inside and it shrinks, which splits the wood apart. For a good, long explanation of this process, check out Wood Science Consulting. The good news is that this is rarely a problem. If the checking was so severe that it split the post in two, we’d have a problem. But I’ve never seen that happen in all my years of inspecting.
In short, this frequently happens with big wood timbers, it doesn’t affect the integrity of the post, and nothing needs to be done about it. Just call it character.
Also, the same applies to wood beams found in old basements.
But it’s ugly
I see this so often that I hardly give it a second glance; it’s typical and normal. But some people really don’t like the look of checking, and they want to do something about it. I’ve seen people caulk and paint their posts, and it makes the checking less noticeable for a while… until the caulk splits.
If you want a more long-term solution, consider wrapping your deck posts. It’s what all the cool kids are doing with high-end decks. You can buy a kit like the ones shown below, or you can make your own with white PVC or composite boards.
