This a 3 year old (lightly used) weather exposed swing set.

Should I be concerned about the cracks?

outdoor swing set

  • You did not indicate if the cracks are on the bottom side of the beam or only the top. That would be useful information here. Also, can you probe one of the cracks with a long thin probe and let us know how deep the deepest crack is. What are the dimensions of the beam?
    – Itsme2003
    Commented Apr 16, 2020 at 17:36

4 Answers 4


This is typical of wood movement. The wood will eventually start to rot because of the "pockets" created by the cracks. Those will hold water, expediting the rot that will occur over the years.

Cedar is rot resistant, but with these cracks it will quicken the inevitable. If a well formed metal cap can be added to the length of the top which would be preferred so it can be fastened on the sides, or covered with a peel and stick waterproofing, so the movement of the wood will not affect the covering. This is another preferred fix, since a metal cap is a nice harbor for insects, depending on how close it is set to the wood.


It is not stress from the weight of the swings nor is it because the wood is cedar

It happens to all species of wood and he cracking was caused by sun drying not structural issues such as overloading.

Wood expands and contracts on the sun dried side and the sun also has an aging affect on the wood making it more hard and brittle (less able to tolerate expansion and contraction cycles). This causes the wood to tear apart in the weakest places which is the softer spring growth layers that are in between the strong fall growth rings (lines on the edges of the boards).

Is it an issue that you need to fix?

No and yes.

No, in that it does not yet need to be replaced. It is not a structural issue right now (I suspect that the cracks don't come anywhere close to going through the entire beam). It likely won't become a structural issue ASSUMING that it doesn't also get further weakened by wood decay (rot) that is likely to occur in the cracks.

Yes, it that it is necessary to fix the situation by protecting the wood from further damage. Do this by protecting it from both moisture and the sun's rays. This can be done in many ways including such things as metal flashing, brush on sealant, or a rubberized roofing member.

Suggested Action

I suggest cleaning the debris out of the cracks and then covering the top of the wood beam with a rubberized roofing material to prevent moisture from rain and the drying rays of the sun from getting to the top surface of the wood. This material should be available in most home improvement stores

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  • 5
    If water gets in any way other than coming straight down (dew, seasons of high humidity, storms with strong winds and semi-horizontal rain) then a waterproof rubbery layer on top will make it rot much worse. I would use a good treatment for any existing rot then coat with a sealant or exterior-grade polyurethane. Commented Apr 16, 2020 at 0:02
  • by what process would water get in? Polyerethane will soon crack and you're have the condition that you say it is the solution to. You solution does not address the very cause of the problem, sun exposure
    – Ack
    Commented Apr 16, 2020 at 0:09
  • 2
    That's why I said exterior-grade. Not the rigid stuff you'd use on floors. Commented Apr 16, 2020 at 0:14
  • 3
    If it was that long ago, you were not using modern formulations. Commented Apr 16, 2020 at 0:51
  • 3
    It was during the age of the dinosaurs. This has the merit of being another approach, how about you post it as an answer?
    – Ack
    Commented Apr 16, 2020 at 0:56

This is known in the lumber and construction industries as "checking", and it's normal. Wood contracts about its circumference as it dries.

As long as it's parallel to the wood grain it's generally not a concern in the short term.


Weathering of the member certainly was the initial cause of this cracking. As the wood expands and contracts with the seasons, the countersunk washers remained (relatively) the same size and thus the wood split. The fact that the member is splitting along the bolt line leads me to the suggestion that this should be replaced.

  • agreed. If this was isolated to just a couple spots I would think "no big deal" but it appears here that it's happening along almost the entire length of the post in line with the bolts. Only a few sections along the length are solid all the way through, and I am guessing the same thing is happening on the other side. The directions of the forces that would be applied when it's under load do not help, either.
    – Z4-tier
    Commented Apr 16, 2020 at 20:36

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