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Accounting for Wood movement in joinery

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Forum topic by Eric_S posted 10-06-2009 06:04 PM 6292 views 1 time favorited 25 replies Add to Favorites Watch
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Eric_S

1551 posts in 2654 days


10-06-2009 06:04 PM

So I’m getting ready to start designing nightstands and since I’m new to woodworking I’m a little confused on wood movement in regards to joinery. I understand wood moves more across its width, and some species more than others. I also understand that quarter sawn is more stable than rift, and rift is more stable than flatsawn.

What I am confused about though is joinery. I keep watching online videos from finewoodworking and wood whisperer and whenever they do mortise and tenons or dovetails or any other joints, they are always very tightly cut so that the joints are strong, yet I always hear to account for wood movement. So is it always necessary? How do I make a mortise and tenon that allows for woodmovement while still keeping a strong/tight joint? Same for lap joints and pretty mucha ll other joints. Can anyone help me on this? I want to make sure I design the joints correct the first time. I live in Indiana.

Eric

-- - Eric Noblesville, IN


25 replies so far

View mstenner's profile

mstenner

57 posts in 2613 days


#1 posted 10-06-2009 08:00 PM

The short answer is this: when two pieces of wood are joined with opposite grain directions, but only over a SHORT DISTANCE, then you don’t need to worry about it. What’s a short distance? A few inches (typical joinery sizes) are fine. I’ve heard 12 or 18 inches tossed around. For example, if you’re putting a breadboard end on a table, you typically only glue it in the middle and use pegs/dowels that can move on the ends. If it were only 10 inches long, you could probably just glue the whole thing.

Note that dovetails are almost always done so that the cross-grain directions of the two pieces are in the same direction. That is, a drawer might get taller or shorter but the boards will do that together. The change in thickness of a 1/2” drawer side will be completely insignificant.

-- -Michael

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Eric_S

1551 posts in 2654 days


#2 posted 10-06-2009 08:43 PM

Thanks mstenner, that helps a bit and makes perfect sense.

I found this article on finewoodworking for online subscribers (14 day free trial) http://www.finewoodworking.com/fwnpdf/011165044.pdf that shows how to do mortise and tenons and other joints to account for woodmovement. He is showing tenons of less than 5” wide being pinned and glued only at the top. Really? Is this truely necessary? This article is whats causing my confusion.

-- - Eric Noblesville, IN

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mstenner

57 posts in 2613 days


#3 posted 10-06-2009 08:55 PM

Yeah, that seems a little extreme to me. Maybe extra care is taken there because it’s such a stressed joint. Perhaps the wizened old graybeards can shed some light on the middle ground. I’ve seen in many cases people recommending gluing the entirety of a 3” tenon. Realistically, the “middle ground” is probably the sort of territory where either approach will work.

-- -Michael

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Eric_S

1551 posts in 2654 days


#4 posted 10-06-2009 09:07 PM

The tenoned joint he shows is from a bed headboard so maybe it does take extra stress? So realistically I should be fine gluing up the entire joints in a nightstand except for the top? I still havent’ decided if I’ll do frame and panel sides yet or slab. Also in that article, it shows the bottom of a slab chest loosely sitting in a groove similar to a frame/panel and resting on the aprons. Would I need to do this for the bottom of a nightstand that would probably measure 30” x 15-20”.

-- - Eric Noblesville, IN

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Dan Lyke

1510 posts in 3584 days


#5 posted 10-07-2009 02:54 AM

I have no actual empirical evidence to back this concern up, but my guideline is that I become concerned about wood movement with more than 2 or 3 inches of cross-grain joint. In thinking about it this is probably way too conservative, because many people make their tenons 2 inches wide, but there’s no way I’d go five or ten inches with a glued cross-grain joint unless I knew specifics about how that wood will expand and contract, and for 4 inch wide frame pieces I’d make the tenon smaller than that and only glue the tenon..

-- Dan Lyke, Petaluma California, http://www.flutterby.net/User:DanLyke

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scottishrose

110 posts in 2625 days


#6 posted 10-07-2009 11:14 AM

I’m a newbe to woodworking myself, but if you are designing side tables and you are putting panels in a stile and rail type frame allow a bit of room and only glue the stiles and rails. You might want to take into consideration where you live and the time of year you are building it. For instance I live near Seattle where the winters are damp and summers are dry so while building in winter the wood is more swollen so put stain or color on the hidden part of the panel before glueing up so it doesn’t show in summer when it gets dry. That is the opposite that one would do say in Minnesota where it gets very cold and dry in winter and humid in summer. In either case you have to leave room for panel movement and gluing just the joints lets the panel move freely with the change in humidity.

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Wes Giesbrecht

155 posts in 2270 days


#7 posted 06-16-2011 05:24 AM

I see a lot of projects posted on LJs that I’m sure are doomed to failure and often wonder if a person should point it out to the newbies or not. What’s the protocol?

Don’t want to sound like a crotchety old know it all but hate to think that some newer woodworkers might make the same mistakes several times before learning the hard way, over time.

If we’re talking about fine woodwork, as in furniture etc., I would never expect a cross-grain joint of most solid wood types, of more than 3 or 3 1/2” across max, to hold for more than a few years at best and perhaps not very long at all at worst.
Certainly there’s a difference between a very dense wood like Eastern Maple and a softer more porous wood like poplar or Western Maple but…. all wood moves seasonally. I would never do a cross-grain joint of 4” with just glue and expect it to hold longterm. If it’s a tenon, break it up into two smaller ones.
Cross grain edging on a table or tray or breadboard… use a breadboard joint. Some sort of movable mechanism for the panel to expand and contract, like dowels in a slot, and glue only the center 3”.
There are metal fasteners specifically for this purpose where they can be hidden, under a tabletop for instance.

Spend some time in an antique store and study the traditional ways of furniture building. There’s good reasons for all those techniques and short cuts can lead to disaster down the road.

-- Wes Giesbrecht http://www.wesgiesbrecht.com/index.htm

View Lee Barker's profile

Lee Barker

2170 posts in 2310 days


#8 posted 06-16-2011 06:10 AM

Good answers. Oh, and a good question, Eric! How about this:

Pick a number for yourself, based on this sample and or others, and build two nightstands. While you’re at it, make a dummy piece with several widths of joint involved both smaller and larger than what you decided on, and take it in the house and stick it under the bed. (Maybe do this in several species, too.) Or wherever, just so it’s a heated place. In a year, drag it out and take a look at it. You’ll become the local expert on Area Wood Movement.

Meantime, relax and build the nightstands. That’s a great project—door and drawer, but nothing overwhelming. Have fun. Let the anxiety fly out the window and just dance with the plan and the tools and the wood.

Kindly,

Lee

-- "...in his brain, which is as dry as the remainder biscuit after a voyage, he hath strange places cramm'd with observation, the which he vents in mangled forms." --Shakespeare, "As You Like It"

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rsdowdy

105 posts in 2655 days


#9 posted 06-16-2011 06:10 AM

I don’t know about the protocol, but if I posted a project, I would really like corrective input into the project. If the corrective input is severe, then I would perfer it in a personal email/mail/note to me with a kind critisim to the viewing public so I won’t look so much like a left shoe. Oh, what am I talking about, if the shoe fits then let me have it, but this is what I try to do in other things I am more profecient at than woodworking. A gentle helpful reproach, and if something is muderous, I would send a a personal mail stating they might want to delete their post and here are the reasons why, and if they want more help, please email me. Like our pastor has said, if you see a problem and open your mouth, congratulations, you have just volunteered to fix said problem.

Royal

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gargey

457 posts in 235 days


#10 posted 08-09-2016 09:25 PM

I think wood movement is overblown.

Don’t glue/screw table tops, or mismatch length & width in other LARGE scale or EGREGIOUS applications.

Evidence of exploding furniture is sorely lacking.

View Aj2's profile

Aj2

684 posts in 1257 days


#11 posted 08-09-2016 09:42 PM

Every woodworking project should start with.This is what I am going to make.What wood will I use and do I have enough.Plus extra for back up since we never know for sure how certain parts of a plank will behave until we start cutting into it.
What jointery will I be useing is my wood right for this build.
Color, weight, durable
So I think it’s a good sign when someone’s asking these questions at the beginning of any build.Being sensitive to how to work wood is what separates us from junk furniture that’s sold to the majority.

Aj

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Wes Giesbrecht

155 posts in 2270 days


#12 posted 08-09-2016 09:46 PM

Gargey: There is absolutely no aspect of wood joinery that is as non-understood as wood movement.
I’ve repaired everything from high end guitars to solid wood furniture of all kinds that have had failed joints,
not necessarily because of improper builds, but simply as the result of wood movement.
Look in the dumpsters behind apartment buildings and you’ll find tons of evidence of exploding furniture.

If you live in a desert it’s of little consequence but if you live near the coast, as I do, it’s a huge issue that needs always to be considered when planning a build.

-- Wes Giesbrecht http://www.wesgiesbrecht.com/index.htm

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gargey

457 posts in 235 days


#13 posted 08-09-2016 10:18 PM

Wes & Aj2,

There is no shortage of poorly built ANYTHING these days. Most of the exploded furniture behind apartment buildings is likely due to poor build quality (materials and joinery) rather than a lack of consideration for wood movement; good luck finding solid wood in most of it.

I’m not suggesting that we should disregard the phenomenon of wood movement. It deserves consideration. I am suggesting that the OP (and others) should not freak out about small scale grain mismatches if the joinery is otherwise well considered. By and large it will not matter (in the opinion of gargey). It is common for people to learn something new, and then get carried away…

..

Wes, you mentioned failed guitars… For the culprit to be wood movement, in your opinion, can you describe what joint failed? I’m just curious. I assume it would have to be some plainly face-glued piece glued cross-grain, with no other fastening (i.e. not a great joint)? How can you be sure that heat, water, impact, were not contributors? Sincere questions.

View Wes Giesbrecht's profile

Wes Giesbrecht

155 posts in 2270 days


#14 posted 08-09-2016 10:40 PM

Heat and water, as you put it are not just contributors, they are the very real cause.
It’s called weather and has nothing to do with projects left out in the rain.

On a bright and clear sunny day here on the coast, the humidity can be 95%.
Warm are hold more moisture than cold air.
In the winter, it could be raining and relative humidity is only 40%.

Unless you have a system of humidifiers and dehumidifiers like they do in guitar factories,
the moisture content of the air is constantly changing and even wood projects with a heavy varnish on them,
will contract and expand in response to those changes.
Like I said, if you live in a desert, this isn’t a factor.

I fixed and older, good quality classical guitar just yesterday.
The fretboard had let loose for about 10 inches from the headstock towards the body.
Rosewood on mahogany, both pieces running the same direction obviously.
The mahogany neck (still no wear thru the varnish after 40 years) had expanded
slightly more than the the fretboard.
Only a tiny bit but nevertheless, enough to cause the joint to fail.

In antique stores you see all kinds of failures even tho the guys who built the furniture, knew what they were doing.
No glue, can hold a joint forever if the wood is moving at slightly different rates.
It doesn’t have to be cross grain to fail.
Virtually all chairs built with round mortise and tenons (rungs) will fail eventually because the hole expands and contracts into an oval shape and so does the rung.

I’m a retired, ticketed joiner. Also used to teach joinery at a trades college.

-- Wes Giesbrecht http://www.wesgiesbrecht.com/index.htm

View BulldogLouisiana's profile

BulldogLouisiana

214 posts in 599 days


#15 posted 08-09-2016 10:49 PM



Wes & Aj2,

There is no shortage of poorly built ANYTHING these days. Most of the exploded furniture behind apartment buildings is likely due to poor build quality (materials and joinery) rather than a lack of consideration for wood movement; good luck finding solid wood in most of it.

I m not suggesting that we should disregard the phenomenon of wood movement. It deserves consideration. I am suggesting that the OP (and others) should not freak out about small scale grain mismatches if the joinery is otherwise well considered. By and large it will not matter (in the opinion of gargey). It is common for people to learn something new, and then get carried away…

..

Wes, you mentioned failed guitars… For the culprit to be wood movement, in your opinion, can you describe what joint failed? I m just curious. I assume it would have to be some plainly face-glued piece glued cross-grain, with no other fastening (i.e. not a great joint)? How can you be sure that heat, water, impact, were not contributors? Sincere questions.

- gargey

I too doubt wood movement caused the furniture to be thrown out behind most apartment buildings. Mainly because doesn’t wood movement only really effect solid wood? On this forum, I’d hope wood movement is more of an issue. It’s possibly given too much consideration, but I’m not experienced enough to have a real opinion.

-- There are 10 types of people in the world. Those who understand binary and those who don't.

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