Is Wood Movement a Myth? Analyzing 30 Years of Data

[@katzmosestools]

Support What we do at the Katz-Moses Tools Store: KMtools.com Free Formula, Data and Tables to Calculate Wood Movement* shop.kmtools.com/3mSMMXr *The Forest Service's Forest Product Laboratories, Wood Handbook - Wood as an Engineering Material (508 Pages of Awesome)* www.fpl.fs.fed.us/documnts/fplgtr/fpl_gtr190.pdf *Moisture Metter* amzn.to/3ESeXvR

[@Lincolnstww]

I can't express enough how much I appreciate going through all the effort so you could drop the mic on Turdburgler - I love a good grudge. Great value add video as always dude.

[@CeeJayThe13th]

Why don't you do the same topic but do it with your signature humor?

[@Lincolnstww]

@@CeeJayThe13th I think Jonathan has covered this perfectly.

[@MrLelo337]

Awesome book that gives you step-by-step photos kzbin.infoUgkxTNB_zFBSnTo_O1PqfVUwgi7ityw0JlKt and directions to make every day project. I can see myself making a few of these projects and giving them as housewarming and holiday gifts!

[@BlackHoleForge]

I worked with my father in the construction industry for several years. Understanding how your material reacts to the weather it's just part of building. I was told to always leave 1/8 to 1/4 of an inch on the outside edges of the room to allow for the expansion and contraction of the wood during the winter and summer months. I was told to do the same thing when we're making cabinet faces. Make the dato grooves deeper on the sides of the frame, so the panel in the center can expand and contract properly. An old wood worker told me that back in the day they used tack cut nails to deal with it. They use them because they could Bend with the expansion. He said if someone didn't account for the expansion and also use screws, after time to screw could just snap off, because screws are hardened.

[@charleswestwooddesign4320]

I want to say thank you! - Around 2 months ago I bought your shop apron (bought from the UK and arrived in less than a week and at a frankly incredible price for the excellent quality)... but the story... the reason for buying it is that I was upgrading to a professional table saw and my previous little site saw had given me a kickback once on some dowel and left me with a mean little bruise. The thank you comes in 4 days ago however, I was ripping large lengths of 6x3 walnut. On one of them, the weight tilted the stock about half a millimetre and bam, the saw splintered the wood and flung it back into me, practically lifted me off my feet and threw me on the floor. It left me winded beyond belief with a large black and blue bruise on my upper stomach and a graze on my arm where the splintered end glanced off the apron and cut me across the forearm. I can say with absolute certainty that without the apron absorbing the blow and the thick material in the way, I'd have a broken rib or two and possibly even have been punctured by the 6 foot splinter that broke off. This is the biggest endorsement I can possibly make for the product. Not only is the quality incredible for the price, it genuinely could save your life in your workshop. So many of us work alone, often out in the garage or workshop or even out away from anyone, we need to be safe and your apron kept me safe! So thank you! I can't wait to buy literally everything else you make!

[@toddulery]

Jonathan, this is really great stuff. What a great reference to have. Really appreciate all the time you put into videos like this. Cheers!

[@JamesRibe]

In a climate with extreme high and low temperatures like Minnesota, you could be looking at 65% RH in summer in buildings with lots of air leakage and no dedicated devices for humidity management.

[@katzmosestools]

I think you misinterpreted something I said or I didn't make it clear enough. You're talking about relative humidity. What makes wood move is "absolute humidity." Minneapolis, MN for example (+/- 2.7%) has less EMC (equilibrium moisture content) swings than Santa Barbara CA (+/- 3.2%) where I live. Heating your house does not affect absolute humidity (to a point) because although the moisture can absorb more moisture it doesn't. Ever get nose bleeds when it becomes heater season? This is because you massively raise relative but not absolute humidity and your skin dries out.

[@theeddorian]

Movement in North America tends to be seasonally opposite on the East and West Coasts. In California summers are dry and wood shrinks, while the winters run somewhat more humid. There are occasional failures where a piece of furniture has serious problems with movement for unknown reasons. We moved a mahogany gun cabinet from Southern California to the northern state and for some reason the doors twisted into pretzels. Coast versus interior also can be considered.

[@williamweatherall8333]

One thing I think is worth thinking about is that in like New England or Canada, we have massive swings in humidity INSIDE even if the outside ones aren’t that big because of the effects of heating our houses.

[@katzmosestools]

I think you misinterpreted something I said or I didn't make it clear enough. You're talking about relative humidity. What makes wood move is "absolute humidity." Bridgeport, CT for example (+/- 2.7%) has less EMC (equilibrium moisture content) swings than Santa Barbara CA (+/- 3.2%) where I live. Heating your house does not affect absolute humidity (to a point) because although the moisture can absorb more moisture it doesn't. Ever get nose bleeds when it becomes heater season? This is because you massively raise relative but not absolute humidity and your skin dries out.

[@williamweatherall8333]

@@katzmosestools I don't think I misunderstood you. You were talking about the absolute humidity of the wood right? You mention exactly what I was referring to in your comment about nose and skin; the physics is the same for the drying of skin as for wood (kilns are usually hot to massively reduce the RH, right?). We massively reduce the relative humidity each winter, because we are heating air that has an RH of at most 100% at -20°C. The same air at room temp will be like 5% relative humidity. And we often aren't starting with saturated air. This means that the equilibrium will drive towards dryness for wood in our houses. What I'm driving at here is that the forestry study did outdoor air which has lower swings in RH, which will lead to less flux in the absolute humidity of the wood. Know what I mean? Yes, they are measuring absolute humidity of the wood, but that is dependent upon the RH of the environment. In California, where you have perfect weather, outside and inside are basically equivalent RHs, but up here it's different. 😜

[@katzmosestools]

@@williamweatherall8333 what city do you live in?

[@williamweatherall8333]

@@katzmosestools Calgary AB

[@williamweatherall8333]

@@katzmosestools anyway, you could probably use Colorado's data for it, but given that they stipulate that the wood is outside (see the top of the graphic at 12:00), it's not really useful for furniture. Ask anyone there when their drawers stick. It's not in the winter, even thought EMC on the chart seems to be equivalent through the year.

[@ohiomp7606]

Love seeing the science behind things! I see this mostly impacting something like hardwood flooring, where not accounting for seasonal expansion could cause the flooring to buckle.

[@laroseauxboisrosewoodwoodw8585]

Finaly someone says the truth about wood movement 🙏 30 plus years ago when i’ve learned that wood at 6 to 8% will only move 1mm or 1/16” . So thank you 👍🏼🇨🇦

[@fab186]

I'm a chessboard maker and I learned about wood expansion on my 3rd board. Thankfully #2 was my close friend so he wasn't an unhappy customer when the frame popped open due to the panel expanding

[@TheSnekkerShow]

Chess boards are how I learned this the hard way as well.

[@cuebj]

Reading this with feet up on coffee table with chess board (¼" × 2" x2") white oak and red rauli, walnut surround with white oak inlay on ¾" plywood with walnut base and legs. Made at school 50 years ago, no machinery. Apart from reglueing a leg top that got bashed so it cracked, it's as good as newly made by 15-year old me. No noticeable movement. Still stands without wobble. Survived hot, dry, central heating, sunlight through windows. Proud of it

[@fab186]

@@cuebj sounds lovely! Congrats! What region are you in?

[@CeeJayThe13th]

@@fab186 I learned that this was possible with an endgrain cutting board so similar idea. I left the wood in my shop for a few weeks at each stage hoping that that might help stabilize it somehow (and because I'm lazy and also work a full time job with weird hours). It only spent a couple weeks in my grandma's kitchen before one square on the edge popped. It turns out that exposing wood to the elements in my garage is no match for the wild swings in temperature and humidity in a southern kitchen. My poor grandmother was beside herself over it because she was so proud of the cutting board I made her. But, I just had my grandfather put a little super glue in the crack and a year later there's not been another single issue.

[@mm9773]

And if you were a cheese board maker, you would have learned even more about wood expansion ;-) But you’re right of course, it doesn’t have to move much at all to pop a frame. A lot of chess boards, even eye-wateringly expensive, handmade ones, are made using veneers on a base plate made from sheet material that doesn’t move.

[@badger2897]

I agree the topic is brought up a bit too much, for most pieces it isn't an issue. Honestly its a matter of how long you want the piece to be in use for. I restore antiques and while most pieces will be fine for decades eventually the wood will move into the least stressed position which is usually twisted for plain cut boards. It also becomes more complicated, for example when the environment inside a cabinet is different from the outside. Ultimately if you want something to last as an heirloom, the timber selection / orientation need to be well thought through.

[@nathanmather5954]

Good video but I'm not sure it really makes a lot of sense to use outdoor EMC. In MI the chart says EMC is higher in JAN than in JUL, but indoors will likely be dryer in winter because of heating. Do you know of any stats for indoor humidity ranges?

[@bboeckman]

Swear to God it is videos like this that keep me coming back and supporting your channel. I'm only ever a hobbiest, making things for side profit and fun, but knowing the care and effort you out into this is just brilliant. I love your videos. Keep it up!

[@tofuscramblegames5165]

One of the things I love the most about your videos is that you talk about things that you don’t really have to. Going into the level 10 nerd numbers was arguably not necessary to give us the basic info, but I really loved hearing it and know it took a lot of time and effort. Keep it up John

[@MattsTAW]

Jonathan, great stuff, as always. As an engineer, I enjoy your data-driven approach to explaining things, as opposed to a lot of guys who use the "anal extraction method" without any support or justification. I appreciate all your efforts. Keep the good content coming.

[@katzmosestools]

Great channel name. I chuckled

[@richardgoebel226]

Another source book that I have found very helpful is "Understanding Wood" by R. Bruce Hoadley. The revised edition was printed in 2000 by Taunton Press. I found my copy in a used book store. I don't know if it is still in print but it is a bit thinner than 508 Wood Handbook.

[@codacreator6162]

My first projects were desks built from constructed lumber. The mistake I made was not acclimating my wood before the builds. The result was a 1/4” shift on one edge. Won’t make that mistake again. And that’s what it’s all about, right? Thank you for taking the time and doing the research for this most thorough explanation. It really puts things in perspective. 😎

[@jasoncarroll2328]

This a great man, I have noticed a difference in the furniture I built in San Luis Obispo, CA and the furniture I’ve built in Al where I now live, which is in line with the data you’ve shared. I feel like the biggest factor for wood movement has way less to do with humidity and way more to do with milling lumber and allowing it to release the stress in the wood through that process before final dimension and assembly. I have process that I go through to combat this phenomenon, I think a good follow up for this topic would be on properly processing wood for use as it relates to movement realized in milling and dimensioning. That would be amazing!

[@totallynottrademarked5279]

I think most people forget that these practices came from a time when houses were drafting messes. So in summer furniture would be sitting in 80+% humidity and in winter sub 45% reguarly. In a modern home with less than 2% air leakage when it was built this is not an issue. So long as you don't lose power reguarly.

[@VeretenoVids]

So, in other words, my 1910 house with no a/c. 😂

[@hotbam37]

I only use lumber doing remodels in bathrooms. I really appreciate the tip on looking at which side the grain is on. I never knew there was a difference. Thanks

[@nicklarson801]

Hmm. I figured since I live in the desert (Utah), that we wouldn't have much movement. But according to that chart there is a 7.8% humidity difference through the seasons. That means a 36" wide walnut desk will grow over a half an inch throughout the year. That is surprising.

[@mr.smitty1993]

People: Freaks out about wood movement. Me: Laughs in lumber mill dry kiln operator.

[@miketaylor9979]

What an awesome contribution to the woodworking community. Can't believe you read 500 pages on wood movement. You're a true wood geek.

[@ramonartful]

Yeah man…fantastic video. I love reaching behind my two benches…in the summer and winter to see how much they’ve moved. One is Ambrosia Maple , the other one is Walnut. They move, but not bad.

[@katzmosestools]

Thanks my brother. I thought you might like this one. Cheers

[@moderntouchfurniture]

Great video Jonathan, and another reference sheet for my notebook. We never want to get that embarrassing call from a customer complaining about that beautiful dining table you made for them just cracked, or is pulling apart. My takeaway here, plan for the worst case variance on large projects, and don't sweat it so much on the small ones. I'm downloading that pdf now.

[@danagrindle9779]

Great video and information. How would the moisture content changing impact a wooden cup? I’m looking for the best way to choose What type of sawn wood, flat or quarter, and layout pattern to reduce the possibility of cracking, especially if I want to burn/char the inside of the cup a.k.a. probably zero moisture on the inside without risk of cracking.

[@TheZooloo10]

This has gotta be the most informative video about wood movement I've ever seen. even the two simple examples of how to deal with wood movement with he table end and the checking were suuuper useful.

[@redial5249]

Thank you for explaining wood movement as a normal person not a mathematician with a science course in the middle . hitting a sub here , thanks again .

[@FridayWorkshop]

A buddy of mine wanted a planter box made. He brought over cedar fence boards that had been rained on for days. They were dripping wet. Honestly only the top that had mitre joints moved. I was surprised that the whole thing didn’t get crooked.

[@MrErViLi]

Awesome information. Question. Wood movement is from moisture movement into and out of the wood. If the wood is completely sealed with a waterproof finish, why does the wood still move? Even with a good lacquer finish wood still moves. Would an epoxy coating prevent wood movement?

[@purv989]

Betteridge’s Law: any headline that poses a question can be answered with “no.”

[@looopy2u]

How would you go about applying this to flooring? Solid and engineered for example?

[@spycedezynuk]

If you allow sufficient gaps at the perimeter for lateral expansion/ contraction under the skirting board or trim you shouldn’t have a problem.

[@troyclayton]

Very cool, thanks. Too many people who work with wood don't think about movement. I was on site in a new home when we heard what sounded like an extension ladder going down in the great room. Turns out the fir ceiling on the giant 3 season porch, installed in the dead of winter (New Hampshire), exploded one wet spring day. A section like 8 feet wide and 12 feet long came crashing down as the boards ripped free from their brads. The aftermath was a sight to behold. The GC wasn't impressed, I was glad it had nothing to do with me.

[@charlesthomas9294]

Wow. My uncle worked for Forest Products Labs (in Madison) for decades. He used to tell me all the crazy stories about the wood testing they'd do. Like firing 2x4"s through brick walls and such.

[@dcuccia]

This was so helpful, thank you. The one thing I was hoping for was a figure of merit for when I don't have to worry about my rigid piece cracking, which I assume is species- and grain orientation-dependent. E.g. if given the math I expect a 3/8" dowel joint mating two pieces of Red Oak ~1/2" from exposed end grain to strain by 1/16th can I just glue it up and move on, or is it likely to crack?

[@christobar]

Shout out to the good people at the Forest Products Laboratory Madison WI!

[@davidmorton8170]

Where wood movement inevitably comes up though, is when people fail to acknowledge it at all, binding end grain and long grain. The most common failures are breadboards glued all the way across, or cutting boards with a trim all the way around the board that traps the grain. In these situations, a tiny amount of movement may still be enough to cause a crack. So allow for the movement with smart techniques, but don’t sweat exactly how much.

[@mm9773]

Yes. A friend of mine has a cutting board that is built like a bread board, and after a few years of use, the middle section sticks out, it’s about a quarter of an inch wider than the bread board ends. It was made using the proper technique, so nothing has cracked, but of course it doesn’t look right anymore. Perfect illustration of wood movement.

[@jamesmellis8766]

I really enjoy how you show the details around your topics. You have become my favorite channel to follow. I have a question around finished wood. Does wood move as much once it has been sealed or finished with something such as Lacquer, poly or paint? It would seem that the wood would be less able to absorb moisture once it has been finished and thus less movement. Thoughts?

[@katzmosestools]

That was a layer of complexity I didn't want to get into because I didn't have exact data. I believe and have heard that film finishes also eliminate transfer. Good question

[@jamesmellis8766]

@@katzmosestools thank you for the quick reply. I have asked some seasoned woodworkers this question and get very different answers. I live in an area and see a lot of old work and I don't see many movement issues. I often wondered if it was the finish they used that may have helped keep moisture out. Thanks again for your thoughts.

[@roderik1990]

It might, but honestly I don't think most finishes are enough to significantly prevent or reduce seasonal wood movement. Some moisture will still end up diffusing through the surface.

[@katzmosestools]

@@jamesmellis8766 I will say this, That lacquered table I used in the video reads much lower in moisture content than comparable walnut in my shot that is bare wood.

[@jamesmellis8766]

@@katzmosestools interesting. So here is what I do not understand about the whole movement process. Does moisture need to get inside the grain tubes to cause the wood to expand or just getting between the grain cause expansion? Correct me if I am wrong but doesn't the mills paint the end of wood with something to prevent the wood from absorbing moisture once it has been dried? It seems like there has to be a process to reduce the woods ability to absorb moisture. Do we need to stick it in a vacuum bag to pull the finish/sealer into the wood? Are there any finishes with a small molecules that can penetrate deep enough to minimize moisture absorption?

[@wakeupcall8188]

G'day mate I have 2 questions Im building kind of kitchen top but for outside. It is undercover, no direct sunlight but still european winters and hot summers will have some influence. So it will be 2.5m x 700mm x some 40mm thick in beech wood So im thinking to put 4 x 14mm rods through with nuts on every glue joint to prevent splitting and banding but What about wood movement in that case And second question is what would be best finish in that environment. Thanks

[@karl_alan]

It's good to know about. I have only had two issues with wood movement, both of which I glued a panel into place instead of allowing it to float & in both cases, the panel split along the grain.

[@michaelswain328]

You really got me with the “I’m not that stupid” shtick 😂 This video was a really helpful video as a new woodworker.

[@jecheesecake]

Way more informative than that “Samurai” guy. He tried to make the case that wood never moves, he had no data and thus his video made no sense. Measuring moisture content and using humidity data for your region makes so much more sense. After having a shaker panel door in a bathroom crack, as well as a dining room table, it helps to get a process to account for this. Thank you.

[@TimberBiscuitWoodworks]

Thank you Jonathan for the highlight on the email! And this video is awesome, you did great explaining wood movement. It’s good to know that I’m not in danger of blowing the house up.. at least not from wood movement. 😂

[@robohippy]

Well, pretty sure that kill/kiln dried wood is at 6 to 8% when it comes out of the kiln. Let it sit in your shop for a year or so, and it will be the same MC as the rest of the wood in your shop. Also, quarter sawn wood does not cup or bow like rift sawn wood does as the relative humidity changes.

[@stevecall5744]

What movement occurs in wood that is sealed with multiple coats of finish? For example, table with four or five coats of polyurethane? Unless you assume the finish is water permeable, any finish has to dramatically reduce any movement from changes in atmospheric humidity.

[@lorihawk9046]

This is very helpful thank you. I’m making an ottoman tray (as large as 32 x 32). The tray panel is made from quartersawn white oak. According to the information in this video, the seasonal movement across this panel would be roughly 1/16, so 1/32 on each side. But the problem is the tray panel includes brass accent pieces inlaid about 1.3 inches in from each of the 4 sides. The brass strips are 1/8 inch deep and 1/4 wide and there are 2 that go across the grain and 2 that go along the grain. In your opinion, could this cause the tray to warp over time?

[@alwayslearning3426]

So in the example given, worst case scenario, the 40” table will move 1/8”. That’s 1/16 over half the table and a bit less than that at the location of the outboard tenon I don’t elongate holes in my tenons and have never had a problem. I guess your data back’s that up. Thanks for the proof!

[@robertanderson2223]

Hi Jonathan and followers, I am planning on making a tea box out of Cherry. Dimensions, 15" along the length of the grain and 8.75" along the width. I was planning on having a solid top versus a veneer over MDF. Do you foresee any shrinkage issues with this size? My concern with using a veneer is color and grain matching with the sides. I was planning on making the whole thing from on board. What thickness would be best?

[@ds1848bp]

I don't quite understand the relevance of these figures. The data you give regarding variation in temperature /relative humidity matter only to the outdoors. Indoors, where most of what you would build would be, the situation is much different. In a cold winter climate, the indoor RH can swing dramatically across seasons, and wood movement will absolutely be noticeable and significant, even in a little jewelry box. Maybe in socal it's not a big deal since the temperature is always the same, but in the north it's not uncommon for the RH in a home to swing from sub-20 in the dead of winter to 60+ in the heat of the summer. Maybe you shouldn't freak out about it but at the same time it shouldn't be downplayed either. It's most pronounced in big pieces which also happen to be the most time-consuming and expensive to make - and the last thing you would want to see is all your kitchen cabinet doors you built and installed over the winter warping a summer or two later - - something which does indeed happen!

[@willstutely]

First…awesome video, and awesome resource you highlighted. Second…I’m confused by the EMC on the chart being higher in the winter months… any thoughts?

[@joshrosen6604]

Why doesn’t the middle dowel point have room for movement? On the table you made?

[@billvojtech5686]

I installed solid wood doors with panels in my apartment. I finished them in the summer when it was hot and humid. I did use the AC except when the finish was being applied and drying. They looked fine. When winter came, the panels shrunk and a sliver of wood at the edge of the panels became visible. Then summer came and the sliver of raw wood was hidden again. Other than only finishing in winter, or touching up the finish in winter, what can be done?

[@landonsharrett20]

Pre-finish all of your pieces, avoid the glue surfaces.

[@billvojtech5686]

@@landonsharrett20 I didn't build the doors, they came pre-assembled.

[@jeffhreid]

Good video. I have seen cracked carcasses and split tops due to wood movement especially in old pieces. It’s worth considering especially in cross grain situations

[@mulletthehunter7163]

Interesting! I once went back to snag a tulip fronted kitchen I fitted on the coast in Devon England and the 2.5mm door gap on each side had become zero door gap. I trimmed 2.5mm off each side, added 2 coats of paint and left. Less than a year later I had to go back cos the door was too tight to open. Took another 2.5 off each side... that's 10mm!!

[@thodgson13]

My only critique is that you didn't cut in Charlie's "he created a reasonable doubt" sound byte from always sunny at 1:05.

[@chriszen4128]

Great and informative video. What about the tables with slabs and epoxy? Does one have to worry about movement?

[@walter5401]

Hi Jonathan how would wood move in a half lap join?

[@homer009x]

I live in Montreal, canada. Looking up my location, EMC is highest in winter and lowest in spring, which blows my mind. Always thought wood shrank and got dry in winter! Although this holds true for outdoors only, indoors the effect is opposite.

[@katzmosestools]

Same in Minnesota. I just looked it up to reply to a guys comment. Crazy

[@luisssyou]

14:18 was the best part! I love you take the time to explain things with research, Loved the video!

[@cindyhammack68]

What would happen if you moved from low humidity (Colorado) area to a high humidity place (Central Texas)?

[@TheThreatenedSwan]

How did they account for this historically in fine furniture?

[@katzmosestools]

The same way they do now. Planning and accounting for it

[@wiktorjachyra1869]

Great video but how about things like tables....if you have let's say a dining room table that you built with multiple glued pieces that made it into one large piece how do you prevent it from deforming then across the surface.....this happened to my cousins island so I wanted to know

[@Pauken11]

Love watching your videos, Jonathan. Lots of good information, and you make me laugh.

[@BrentDaughertyMe]

So unless you have a humidifier/dehumidifier then the absolute humidity, which is what matters for wood movement, is roughly the same indoors and outdoors?

[@katzmosestools]

Very rough and general yes. Keep in mind AC actively cools by removing moisture from the air

[@dutchswan4009]

How does that pinless moisture meter compare to more expensive ones? It’s difficult to justify the high price of a Wagner when I won’t use it much.

[@ChickenDinnerz]

So what you're saying is if a 40inch dining table will only change 3mm over the year if left outside, then inside we could probably say half, or 1.5mm. Is it really worth considering wood movement at all???

[@russstaples6125]

When I started woodworking, 35+ years ago, I put breadboard ends on a table but I used glue instead of pins. Cracked to poop. Learned my lesson.

[@jhonnygaulke1335]

How thick is a desk surface?

[@gasserjoshua7448]

Excellent video! The equation accounts for an overall width of a panel but I am curious if making the same panel with 6” boards vs 8” would render slightly different result. The assumption being that smaller boards are considered more stable or maybe it doesn’t matter. Thoughts?

[@saucyonePR]

Man this went over my head. Clear enough to follow but something I never payed attention too because I figured it wasn’t a really big deal. 95% of the furniture I build for myself is for indoor climate controlled environment so this video really opened my mind to this concept of wood movement. Thank you! Love this channel!

[@davidstevenson9633]

Hi from Australia love your vids mate I’ve ordered your apron from your site and can’t wait for it to arrive thanks for the great content and any hater’s out there just don’t watch the vids if you can’t handle real content

[@egbluesuede1220]

I've been pretty serious about woodworking as a hobby for about 5 years, and I would agree with what you started your presentation with. Wood movement scared the hell out of me and I was sure I needed decades of experience to master this aspect of wood. I even took a class to learn about wood before I made many projects. For new wood workers.....just start cutting! Give it a go! Until you get to larger furniture projects, it really doesn't matter. Yeah, wood is organic and it will change, but if you really nerd out like my man here.....it ain't enough to worry about. Just do it!

[@xdacunha]

Thank you for all the work you put into this videos! Great content as always

[@DIYDuBItYourself]

Interesting to know that rift to flat sawn’s coefficient is around double. Thanks JKM for the good info!

[@seanlandsman7516]

Does someone know in that handbook where the chart for humidity data is? I can’t seem to find that.

[@seanlandsman7516]

Found it: page 13-4

[@leedobson30]

Techy but helpful and a little bit gutsy to dive deep - well done

[@tbc5790]

This is amazing. I did have some problems with a dovetailed jewellery box made from maple and the inside tray was made from cherry. I finished this project in the summer of Qatar (in the middle east and it was soo humid), then it was shipped off to Dubai and a month later the tray got stuck. Because it was soo humid in Qatar I thought that it would very slightly shrink, but the wood was dry, so if anyone knows why it moved could you tell me? After watching this video I love that I can calculate the movement in tables etc. Thank You Very Much Mr. Katz Moses.

[@thecanadiantradesman7916]

Best description of wood movement yet. Thanks

[@freds4703]

Not fine woodworking, but I saw contractors install about 100 ft of brand new, kiln dried, red oak tongue and groove wainscoting along a wall in a church. Left no room for wood movement. Not too long after, when the wood equilibrated with the RH in the church, the wainscoting had pushed a short steel stud wall about 9 inches. Ouch! The carpenters said that the architects had not specified leaving any space for expansion and contraction. It adds up over 100ft!

[@randymajor2000]

Awesome video demonstration and discussion on wood movement . Haven’t had an explosion yet but maybe I can make it happen one day

[@EternityForest]

It seems similar to "exact constraint" in machine design! What they do is look at all the degrees of freedom something has and try to have exactly one constraint per degree. Three points define a plane, so a 4 legged table is an "overconstraint" which is why it has to be just right or it wobbles. It's not the same exactly, woodworkers *want* to get things just right, wheras product design is a lot about avoiding the need for precision in the first place where possible, but it's the same idea. Two boards with one screw have two degrees of freedom. The screw constrains both axes of sliding. Adding another screw constrains rotation but also constrains the same two sliding axes. Now they're overconstrained, and you'd have probably if they expand at different rates, but if you had a peg in a milled slot replacing one screw, you wouldn't have 2 constraints on the long axis, and it could expand freely. The "bendiness" of the wood also can be treated like a degree of freedom, every place it's going to bend is it's own degree Woodworkers seem to have figured this all out, but if you're new and not a pro woodworker(I'm sure not!!) looking at degrees of freedom seems useful.

[@robertwittman9793]

Im a newbie woodworker, and at a glance, the data doesn't seem too far apart between species. If we are talking 1,000ths of an inch per inch, couldn't you just account for the worst case scenario (like .005 per inch?) for wood movement in ALL your projects? I mean does it really matter if you allow for more than necessary movement?

[@kuffyswoodwork]

Thank you for nerding out on this for us. I was taught to allow for 0.5-1% movement depending on how much room I had available. It's never failed me, and it seems it corresponds nicely with your own numbers at roughly 0.3%. Cheers 👍

[@metzessible1271]

So if you're shipping a piece to a client in another part of the country, would you make the calculations based on where they are? What about international clients?

[@mistaqil]

Do you have plans available for that farm house table? I love to buy it. Plan on making one soon.

[@Cadaver1actual]

Great video and great tips Johnathan. Thanks for the data sheet. Also on a side note, I’m loving my apron. My hips can’t take a belt anymore so this is a great alternative. Super fast shipping to the uk.

[@zloungeact]

"Can't take a belt"?

[@victorhopper6774]

this is my experience i made a beautiful bread box and 3 years later it moved 2 miles to the east and then 2 years after that it moved 16 miles to the west and than 9 years later it and the ball and chain moved somewhere making me happy.

[@mrlukones]

Im from Brazil and i work building cabinets, wardrobe, etc. But we only use basically laminated mdf, don't you guys in the usa have that? i only see u guys using plywood and a little bit of mdf and paint to cover both, and i find that a lot more work, and you need 2 types of skills, as a painter and a "woodworker/carpinter" (im not sure what u call someone that builds furniture with only mdf or plywood, not wood it self.) i say all this because its really common for us to use laminated mdf, we have a LOT of colors, and wood Appearance on those laminated mdf. ty for your time.

[@seanhollandcanada]

Beautifully nerdy. I love it.

[@MaydaysCustomWoodworks]

Not to toot my own horn too much, but I'm quite experienced with wood movement. I invented some thin and stable water resistant end grain cutting boards. It took a ton of experimenting on wood movement and it's effects on certain wood products and glues... Anyways. I had no idea that there was all this data and formulas for figuring out wood movement. That could have probably saved me a lot of time if I piggy backed off of their research lol. Very well done video!

[@JkCanvas]

Great video and answers a lot of my questions. Thank you sir for making this very understandable especially for a knuckle dragging mech turned woodworker.

[@onjofilms]

I went over and checked the data. I feel much better about my OSB jewelry boxes not cracking now.

[@katzmosestools]

🤣🤣

[@collapse99]

Really great content, Jonathan. It's a dense topic but you made it approachable. Thanks, man!

[@rob_sykes]

Jonathan, this is probably the most useful video I have seen on wood movement. Thanks!

[@Lorddanielrushton371]

Thank you Jonathan. Always good to have the sience from it. I appreciate your diligence. Plus its always a good day when you videos drop.

[@KuntaKinteToby]

Thank you for your continued epic contributions to the woodworking community!

[@sgsax]

Love it when you back up your info with science and facts. You should do one on the perils of static discharge on dust collection next. 😁 Thanks for sharing!

[@katzmosestools]

We're shooting that next month with the slowmo camera

[@VITO-Wood-and-Goods]

Such a great explanation. Thank you for taking the time and point this out and make it easy for everybody.