# Dado joints separating one year later



## JohnnyBoy1981 (Mar 15, 2017)

I built this decorative bench a year ago. I had just started trying woodworking, and I didn't really have any idea what I was doing. I tried using dado joinery for the first time, but I had to use an old router I rescued from a pawn shop and free hand it (at that time I thought a 'jig' was an Irish dance or something). I reinforced parts of the bench with wood screws since I didn't really trust my work. I tossed three coats of a red indoor/outdoor paint on it (which is starting to fade already) and set it outside my house on the north side of the house absorbing the cold winds.

I noticed this year that the dado joints are beginning to separate. I can't recall if I used wood glue in them or not, but I think so. Is this happening because of wood movement? Humidity levels? And can I do anything to fix it? The bench still holds my weight, and seems sturdy, it just looks tacky now.


----------



## Loren (May 30, 2008)

Take a look at the orientation of the growth
rings on the part that's separating.


----------



## wormil (Nov 19, 2011)

Hard to be sure through the paint but it looks like the grain is oriented the wrong way in the small dividers, they shrank.


----------



## papadan (Mar 6, 2009)

Squirt some glue into the openings and shoot a few big screws to pull it back together.


----------



## bondogaposis (Dec 18, 2011)

It looks like you used construction lumber and now the boards have dried and shrunk. Can you draw the joints tight w/ clamps? If so, glue and screw like papadan recommends.


----------



## wormil (Nov 19, 2011)

To clarify, the end pieces have grain oriented vertically, the dividers are oriented horizontally so they shrank in different directions. You could try forcing them together but I believe that would be a mistake. I would leave it alone and chalk it up as a learning experience.


----------



## JohnnyBoy1981 (Mar 15, 2017)

Here's a close up of one of the two vertical dividers in the middle of the bench. The sides have the vertical grain pattern too. The horizontal top and bottom boards have horizontal grain direction. How should I have done this differently? In what direction does a piece of wood expand and contract?


----------



## papadan (Mar 6, 2009)

To me it just looks like you forgot the glue or your glue was not waterproof for outdoor use. Can you take a picture of the whole bench for us.


----------



## Loren (May 30, 2008)

wood cups opposite the growth rings. Probably
the top board is oriented so it's cupped upward
with repeated sun and moisture exposure. The
board edges would cup the other way if it were
flipped over and the joints probably wouldn't
open up that way.


----------



## 000 (Dec 9, 2015)

I would just drown it in glue and clamp it closed and forego the screws so that you don't have to deal with screw holes.


----------



## HorizontalMike (Jun 3, 2010)

At this point I am going to suggest clamping it and installing wood screws to hold it together. IMO, the mixed orientation calls for screws. I don't think you have room to put plugs over the screws either.

Just my 2-cents…


----------



## RichT (Oct 14, 2016)

Another issue with the grain running vertical in those panels is that you screwed into end grain. Screws don't hold well like that. Going into the long grain along the side of the board is better, since the screw threads bite into the grain and hold better.


----------



## Unknowncraftsman (Jun 23, 2013)

Looks like the wood bowed up and away.
Just normal wood movement.


----------



## wormil (Nov 19, 2011)

Nevermind my post, like I said, was hard to see. 


> Here s a close up of one of the two vertical dividers in the middle of the bench.
> - JohnnyBoy1981


----------



## JohnnyBoy1981 (Mar 15, 2017)

> To me it just looks like you forgot the glue or your glue was not waterproof for outdoor use. Can you take a picture of the whole bench for us.
> 
> - papadan


Here's a pic of the entire bench as it stands now:


----------



## JohnnyBoy1981 (Mar 15, 2017)

I need to read some more of my beginner's woodworking books, I guess. So would I look at the end grain of each board, and cut them (if possible) so that any expansion would go inwards or toward places where two boards connect thereby driving them together?


----------



## papadan (Mar 6, 2009)

Well Hell, I thought you had a bench to sit on. LOL Glue and screw and repaint!


----------



## wapakfred (Jul 29, 2011)

I think Loren identified it, although there are probably several possibilities. Like someone suggested, call it a learning experience, In looking at the overall design it doesn't appear to be weakened by that separation.


----------



## JohnnyBoy1981 (Mar 15, 2017)

> Well Hell, I thought you had a bench to sit on. LOL Glue and screw and repaint!
> 
> - papadan


Ha! I might have slightly exaggerated things when I called it a bench. It's more of a glorified stool!


----------



## Ruewood (Jun 15, 2017)

I guess, like others have mentioned, to clamp them closed with some glue, but they will probably seperate again, if you used construction grade lumber I.E. Home Depot/Lowes,its usaully the worst quality and high in moisture content. Maybe even look at it as a chance to start again, new and improved with knowledge youve gained


----------



## patcollins (Jul 22, 2010)

Putty and paint can make a wood worker what he aint.

What is that toenail looking thing in the one joint?


----------



## JBrow (Nov 18, 2015)

JohnnyBoy1981,

I know I am a couple of months behind in my post, but perhaps this analysis, if correct, is helpful.

My guess is that increased humidity after assembly is the cause. The top of the bench features wood grain running from right to left. The dividers feature grain running from top to bottom. As moisture enters the wood, the bench top and hence the width of the dados will not increase or decrease in width to any great extent. However, the dividers will increase in width as moisture enters the wood. While the top constrains swelling of the wood fibers in the dividers, the wood fibers at the point where the dividers engage the dado can swell. But the swelling may be uneven since the fibers of the dividers in the dado are constrained by the dado. The result could be a slight tapering of the dividers at the joint, where the wood of the dividers just outside the dado are wider than in the dado and thus push against the shoulders of the dado. This could cause the divider to begin separating from the dado. As wood fibers are released from the confines of the dado, they too swell and cause a little more separation.

It appears to me that you may have glued the joint. There seems to be some material in the first posted pic that runs from the corners of the dado to the center of a divider. In any event, this glue joint would likely have been a weak glued joint. The long grain of the top would have been glued to the end grain of the dividers at the bottom of the dado and the long grain of the dividers would have been glued to end grain of the top on the shoulders of the dado.

This problem may have been averted had the dividers been rotated 90 degrees; the end grain of the dividers exposed at the front of the bench. The glue would have had long grain purchase with the bottom of the dados.

A mechanical joint like a sliding dovetail joint could have added some strength to the joint and perhaps, even with the as-built orientation of the dividers, may have resisted the separation.

I have no good or even bad ideas on how to fix this bench.


----------



## JJohnston (May 22, 2009)

> This problem may have been averted had the dividers been rotated 90 degrees; the end grain of the dividers exposed at the front of the bench. The glue would have had long grain purchase with the bottom of the dados.


I don't know if that would have been any better. You'd have had the crossgrain expansion and contraction of the large horizontal pieces being constrained by being glued to the longitudinal grain of the divider, and the horizontal pieces may well have cracked lengthwise.

JohnnyBoy - wood expands and contracts the least in the longitudinal direction (essentially none, and all movement is a percentage of the dimensions of the piece, so I don't think your problem is shrinking of the [short] vertical dividers). It expands and contracts most in a direction tangential to the rings, and somewhere in between in a direction radial to the rings. It also cups so the rings tend to straighten out (if your end grain looks like a smile, the wood will take on the shape of a frown, and vice versa).

Try this: put a straightedge on the horizontal pieces above and below the dividers, across their width, and see if they're still straight in that direction.


----------



## JohnnyBoy1981 (Mar 15, 2017)

JBrow,

Thanks for your thourough analysis of the situation. When I made this thing, the concept of building to accommodate wood movement was foreign to me. I pay more attention to it now, but I must confess sometimes it's difficult for me to predict how the wood might move on a piece, or how to assemble a piece so it doesn't twist itself apart!

I pulled the pieces of the bench back together with wood screws, pocket holes and some wood glue. It hasn't become warped again, but I did some cosmetic damage to it. I don't know if I'll try to repair it, start over, or scrap it and move on. My friends and neighbors liked it quite a bit, but I'm not married to it. I almost hate to redo it, and would rather move on to something new.


----------



## JBrow (Nov 18, 2015)

JohnnyBoy1981,

Not that this info is particularly helpful for this project but it may be for a future one; JJohnston is correct that a cross grain joint glued entirely along its length can result in wood failure due to expansion and contraction. This problem can be averted by applying glue for a distance along the joint of no more than 3". The glue could be applied from one edge toward the center of the dado, allowing expansion and contraction of the bench top from the glued edge outward toward the opposite edge. The other option would be locating the 3" glued area at the center of the bench top, allowing expansion outward toward both edges of the bench top.


----------



## RichT (Oct 14, 2016)

I highly recommend Charles Neil's Cases and Bases course. It's an eight-disk video set covering the concepts behind what JBrow just suggested, plus lots more. It's pretty much a PhD level course in cabinet making taught by a real master in a clear, easy to understand style. I've been a serious woodworker for decades, and I learned countless tips and techniques from it. You will never again be in doubt about how movement will affect your project and how to construct it to account for that movement.


----------



## JohnnyBoy1981 (Mar 15, 2017)

Thanks Rich,

I'll look into that course. My birthday is coming up!


----------



## sawdustdad (Dec 23, 2015)

wood movement due to moisture changes is a powerful force. Not many joints can resist these forces. Outside structures are especially challenging. All in all, I'd say you did a credible job on this bench, despite the separated joints.

What you are seeing is why teak is favored for outdoor furniture as it oily and does not as readily absorb moisture and warp. Also, the paint you applied probably held moisture in and aggravated the wood movement.

For that project, I'd have used a trestle style base, avoiding the large flat pieces of wood. Some wedged through tenons would allow you to tighten up the base as it moves due to moisture. The flat top (seat surface) should be quartersawn to minimize inevitable warpage.

Maybe you'll be inspired to make another?


----------



## JohnnyBoy1981 (Mar 15, 2017)

Maybe. I'm approaching this hobby trying to learn from my mistakes. I'm finding it difficult to do so! I'm a bit impatient, wanting to be good at woodworking now and not later. Those are unrealistic expectations, and I keep reminding myself of that.

I'm working on the finish of another project now, and while my friends and family look at pics of it I posted on Facebook and say they love it the way it looks, my critical eye sees all the mistakes I made. I needed to sand more carefully, I didn't apply pre-stain conditioner (I'm using soft wood), I let the gel stain goop up in places, etc.

It takes time to learn this stuff, and then practice it. But I still want to feel like I'm good at woodworking, and only time and making mistakes will help that.


----------



## RichT (Oct 14, 2016)

We've all been there, JB. One good tip is to get over the compulsive need to point out errors. Maybe you don't have it, bit I did. It took me ages. What cured me was an article pointing out how insulting it is to someone who just complimented your work to basically be told they are stupid because they missed all of the errors. Nowadays, I'm happy to just smile and say thanks. One of these days I'll build something flawless - nah, not likely 

You've got the right attitude, and I'm sure you'll continue to excel.


----------



## JohnnyBoy1981 (Mar 15, 2017)

That article has an interesting point of view. Never thought of it like that. I'll keep that in mind. Thanks!


----------

