Do Knots in Cedar Cause Structural Weakness?

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Forum topic by Furnitude posted 07-25-2012 08:55 PM 2026 views 0 times favorited 11 replies Add to Favorites Watch
View Furnitude's profile


362 posts in 2596 days

07-25-2012 08:55 PM

I’m making a set of Adirondack chairs and this is my first time to really use Western Red Cedar. If you look at the crude drawing, I’ve tried to show the location of a knot in one of the boards I’m going to use for arms. Will a knot in this location cause structural weakness? Thanks for any comments.

-- Mitch, Also blog at

11 replies so far

View Ryan Haasen's profile

Ryan Haasen

362 posts in 1490 days

#1 posted 07-25-2012 09:49 PM

Yes, I think it will, especially if it has a hollow spot.

-- Ryan

View Doss's profile


779 posts in 1353 days

#2 posted 07-25-2012 09:50 PM

Yes. If the knot is that circle and it takes up that much space, it’s going to be a problem. The knots usually fall out of WRC.

If the wood were really thick and the knot pretty shallow, possibly not. But, it looks like, in this case, that it’s going to be an issue if it gets any load applied to it.

-- "Well, at least we can still use it as firewood... maybe." - Doss

View Blackie_'s profile


4270 posts in 1601 days

#3 posted 07-25-2012 11:17 PM

I’m curious if CA wouldn’t solve that problem, I know it would keep the knot from falling out. One other thing you might try is making a western sawdust paste using wood glue and fill in the voids also blending.

-- Randy - If I'm not on LJ's then I'm making Saw Dust. Please feel free to visit my store location at

View gfadvm's profile


13939 posts in 1779 days

#4 posted 07-26-2012 01:59 AM

I learned the hard way that knots at stress points are the weak link and will fail in a load bearing situation. In my tall chairs of recycled Doug Fir, I have learned to avoid putting knots in the legs or seat slats. I’m referring to full thickness knots of significant diameter (3/4-1”).

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

View Arlin Eastman's profile

Arlin Eastman

3226 posts in 1650 days

#5 posted 07-26-2012 02:04 AM

It will cause a weak point, however, I do know of several guys that have drilled them out and put in epoxy in the hole with some ceder dust.


-- Please help me help other Vets click..> is always the right time, to do the right thing.

View Bearpie's profile


2600 posts in 2107 days

#6 posted 07-26-2012 02:53 AM

Yes, definitely it will weaken the area. could you possibly switch the board around and put the knot on the wider part of the board?

-- Erwin, Jacksonville, FL

View MonteCristo's profile


2098 posts in 1277 days

#7 posted 07-26-2012 03:39 AM

Curious that someone in Tennessee is using Western Red Cedar (WRC) which is native to my neck of the woods. This wood is weak structurally to begin with, which makes it even more important that a knot like the one you show should be avoided.

In case you aren’t familiar with WRC, it is very easy to crush so cutting motises and the like requires really sharp tooling. It is quite rot resistant but that comes at a price – depending on who you talk to it’s dust is toxic to very toxic. Some people out here even get an alergic reaction just handling it, although that is pretty unusual. Old growth WRC is a much better wood than second growth stuff, much deeper color to the heart wood and very stable with fine annual rings. Much more rot resistant too I suspect than second growth.

-- Dwight - "Free legal advice available - contact Dewey, Cheetam & Howe""

View bondogaposis's profile


3448 posts in 1440 days

#8 posted 07-26-2012 03:56 AM

I would be looking for another piece of wood for that.

-- Bondo Gaposis

View rrdesigns's profile


515 posts in 2275 days

#9 posted 07-26-2012 04:01 AM

And some ears, legs and a tail and you can use that piece for an elephant. Waste knot want knot.

-- Beth, Oklahoma, Rambling Road Designs

View tomd's profile


1954 posts in 2859 days

#10 posted 07-26-2012 04:21 AM

I would be leary of using it.

-- Tom D

View woodtools's profile


21 posts in 1378 days

#11 posted 07-26-2012 05:22 AM

A western red cedar knot as you display in the drawing has no structural value. If you were to think about your adirondack chair arm as having a hole in it the size of the knot, you will answer your own question. As with western red cedar, used in outdoor applications, the knot as described will fall out in 8-12 months
Good luckwith what will be a beautiful piece of outdoor furniture.

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