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Discussion Starter · #1 ·
Here is a question about working with green oak timber.
A friend of mine, experienced at timber framing and working with green wood in general, was explaining to me that over time, oak will elongate as it dries. I have never heard of any timber expanding longitudinally as it seasons, but my friend swore that he was absolutely sure of this and that it was common knowledge among green woodworkers. For example he claimed that traditionally, tenons were always left shorter than the depth of the mortice, to allow for later stretching. Has anybody else ever heard of it? Can you explain why it might happen? I am currently building with green oak and need to know if this is a known occurrence or a load of rubbish. Thanks!
 

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Welcome aboard rsk. I have never heard of it myself. Wood simply does not expand over time unless it takes up more moisture than what it had when you put it in service.
In timberframing, when you use it green which is what you are asking, you would practically have to submerge it to get it to expand.
Wodd, in service, will vary in mnoisture content and contract and expand with respect to this but over all, over the years in a somewhat stable environment, wood is going to reach EMC and until it does, it is going to shrink.
longitudinal shrinkage is quite minimal, but longitudinal expansion is a new one on me. I have to plead ignorance on it. I simply have never heard such a thing.
 

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Red oak? http://www.woodfinder.com/woods/red_oak.php

White oak ? http://www.woodfinder.com/woods/white_oak.php

I dry my share of wood, I wish it would grow as it dried :laughing:, more bft= more money.

Maybe in this case he means it shrinks less for length than it does in width ? "For example he claimed that traditionally, tenons were always left shorter than the depth of the mortice, to allow for later stretching." The tenons are left longer because the width of the tenoned post will shrink more and the tenon would stick out since it did not shrink as much ?

I am not a timber framer, I am speaking without any knowledge of the practice. But rest assured wood does not grow after you cut it :no:.
 

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Hey George.....it's shrinkage again!!!

Daren is spot on with his reasoning about the lenth of tenons. As the element containing the mortise dries, it tends to reduce in size and if your tenon is a matched length, as the mortise element dried it would create a gap at the joint. This even creates the illusion that the tennonned element was growing as it dried. Additionally, would you want to be the guy that hand chiseled a mortise that was too shallow originally to accept the tennon? That's not something you want to find out 15 or 20 feet off the ground.

Ed
 

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Discussion Starter · #5 ·
ok, thanks for the replies. I'll get back to my mate and get some more details on what on earth he thinks he's on about
 
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