# joint develops gap: why?



## harum (Nov 25, 2013)

Hello, I glued up several Maloof joints using T-88 epoxy, waited five days, then shaped and sanded them. The joints were of good fit before glue-up: no gaps and required only a few light taps to close.

However, after a few more days, three out of eight joints developed hairline gaps on one side close to where the notch to dado joint is exposed. The joints are no longer flush where the gaps are as there's a little bit of a step.

While the issue is easy to fix as it is now, my question is: why would the joints move after a week of being perfectly flush and gapless? I could think of wood movement around the joints due to the dry weather or due to exposure to a range of temperatures (50 - 80°F) while sitting in the garage; alternatively, stress inside the joint caused by curing epoxy or over-clamping during glue-up.

What should be done to avoid these gaps? They are only on small stretches of the glue lines of only three out of eight, not on all of the joints. All made from the same board from a local lumber yard.

Thanks and best wishes, h.


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## Redoak49 (Dec 15, 2012)

I built a Maloof style rocker and used T88 and did not have such problems. It would help to see a picture. Were the gaps on the top or bottom side of the joint?

My joints fit smoothly and I really clamped them and left clamps on for two days. I was very careful mixing the epoxy and getting the proportions correct.


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## PPK (Mar 8, 2016)

Sounds to me like wood movement due to temp/moisture changes. Especially happens on a joint that has wood grain perpendicular. I don't know that there's any way to prevent it after applying the finish, aside from keeping your furniture inside - hopefully the final resting place of the piece is in a climate controlled place…


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## jacksdvds (Jun 13, 2015)

> Sounds to me like wood movement due to temp/moisture changes. Especially happens on a joint that has wood grain perpendicular. I don t know that there s any way to prevent it after applying the finish, aside from keeping your furniture inside - hopefully the final resting place of the piece is in a climate controlled place…
> 
> - PPK


Just 3 of 8, same board, same temp and location. More like uneven mixing of T88 or the material at those sites having different moisture or other flaw.


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## pottz (Sep 15, 2015)

i built one over a year ago,it's kept inside where the temperature only fluctuates about 20 degrees year round and no problems to date,but temp and humidity can cause that issue.what wood did you use ,walnut ? as jack said maybe improper mixing of the epoxy.i used titebond on mine.your the first ive heard mention this problem here.


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## Axis39 (Jul 3, 2019)

It sounds like wood movement to me too. How long had the wood sat before you built?

I tend to leave wood for 'important' projects in my shop as long as I can. I've been holding onto a few select boards (which don't have specific projects yet) for years and years. Then, I moved across the country. Now, those boards may need to sit a few more years.


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## Jeff28078 (Aug 27, 2009)

It may sound like a cliche but it's not the temperature it's the humidity. Wood is a sponge and will soak up and release moisture. Woodworkers always have to account for and accept some wood movement. Unless you have a museum quality controlled environment it will move. And different pieces of wood will move differently.


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## Tony_S (Dec 16, 2009)

Did you check the moisture content of the lumber before you started the build?



> And different pieces of wood will move differently.
> - Jeff


Correct…even pieces cut from the same board.


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## harum (Nov 25, 2013)

Appreciate all the replies! Well, I moved the project from the garage inside the house and overnight all the joints went back to "perfect" as before, meaning the hairline gaps have closed and steps have dissapeared. The joints are again smooth and tight where the gaps used to be.

Looks like it does have something to do with wood movement. There's little difference though between house and garage these days in terms of the temperature and air moisture-could be due to an unusual for this time of year very dry and warm wind from the desert.

Here are the pics without gaps. The depth of the notch is 2", the width 2-3/4". The red arrow points to where the gaps and steps used to be, which is the sides of the joints. The blue line shows where the steps developed; the shaped endgrain rose a bit with respect to the face grain. Now it's flush again.



















The gaps developed only on one side of the joint and only on the shorter sides, which are 2"; never on the longer ones. Yes, the glue-ups are cross-grain (like all Maloofs?), which means wood movement problems.

To answer the questions:

No, never measured the moisture content thinking it's something beyond my control.

The wood sat for about two weeks in the garage before the joints were cut.

Could be the epoxy mixing problem, but really doubt it-I mixed for five mins, waited for a bit and then mix a bit more. The leftovers cured okay.

Both walnut and maple joints showed hairline gaps and steps, and both went back to flush and gapless.

I hope that a coat, or two, of shellac and then varnish will suppress wood movement due to moisture changes. Charles Neil suggests using shellac for endgrain to minimize wood movement, which has worked for me so far. I guess I have to move the project to the front burner or, insted, wait until the winter moisture is here.

Thanks again for the feedback! Cheers, h.


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