# Jointed boards cupped



## v0mich01 (Aug 7, 2018)

I've been working on a bathroom vanity counter top with my dad. We jointed the board(2×8) by running through the jointer, then cutting dados along with width of the boards, and gluing with a spline. All was well with that. Yesterday I was staining the counter before applying my sealer, and left it out in the sun to dry for four hours. In that four hours, they cupped(rookie mistake, now I know not to let it get too hot) Is there anything I can do to uncup?



  






This side is cupped worse than the other










Lesser but still cupped

I haven't applied any sealer yet(I'm planning on using spar varnish)

Sorry if this is in the wrong forum, I figured since it is a joined board/panel this would be a place to start. Please redirect me if there is a better place.

Thanks!


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## BurlyBob (Mar 13, 2012)

I had the same damn thing happen to me. Totally screwed up my plans for a project. I ended up using Oak plywood for an entertainment cabinet. I wasted almost $200 on that hardwood. I can totally feel your pain.


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## RichT (Oct 14, 2016)

You can try wrapping it tight in plastic and setting it cupped side down on two supports, place some weight in the center and leave it a couple of weeks minimum. Check it every day or two without unwrapping it to see if you're making progress and to make sure you don't wind up cupping it the other way.

If you can get it close to flat, then you'll have a shot at pulling it flat when you mount it to the vanity. There should be room for a couple of battens underneath as well which will help. Of course all of the warnings about allowing for movement apply.


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## bondogaposis (Dec 18, 2011)

Just flip it over until the moisture content equalizes.


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## clin (Sep 3, 2015)

The problem isn't that the sun heated the top, it's that it dried it out causing the top to shrink. It may just flatten out on its own if you leave it alone.

What wood did you use? You mention 2×8 which makes me suspicious that you used construction lumber for this. Construction lumber isn't dried out nearly as much as furniture grade wood. If this is the case, and the wood isn't dry to start, the whole thing may turn into a potatoes chip once it does fully dry.

Pretty much any wood will cup and warp a bit if it's moisture content changes a lot. This is especially true for flat sawn wood. So even if you build it flat, if after installation it dries out a lot more, it will likely cup and twist some. Possibly even split. Splitting may happen if in an attempt to keep it flat you screw it down tightly to the cabinet.

The internal forces caused by moisture changes in wood are huge. Swelling wood with water has been used to split rock. So if it wants to cup our twist, it will, or if held, it will split.

Regardless of all of that. Be sure to apply your sealer to both the top and bottom surface. This will not completely prevent moisture changes, but the sealer will slow the changes. By finishing the top and bottom the same, they will tend to change at a similar rate. You've already seen what happens when one side dries much faster than the other.


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## ChefHDAN (Aug 7, 2010)

> What wood did you use? You mention 2×8 which makes me suspicious that you used construction lumber for this. Construction lumber isn t dried out nearly as much as furniture grade wood. If this is the case, and the wood isn t dry to start, the whole thing may turn into a potatoes chip once it does fully dry.
> - clin


Same thought here,


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## gwilki (May 14, 2014)

I would rip it again, but into 4 pieces instead of two. Joint and plain the narrower boards, then glue them again with alternating ring directions.


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## rwe2156 (May 7, 2014)

I hate to be the bearer of bad news and even worse, to disagree with Bondo (LOL), but IME once a board is cupped like this, it is unlikely to return on its own.

You have nothing to lose trying a couple things. One is to try to re- balance the moisture by either wetting the dry side, or drying the wet side, or both. IME wetting does not work. Therefore, put the convex side up in the sun maybe 1 hour at a time and leave overnight. Repeat if there is a response.

Another less harsh way is to put some battens across the panel with *mild* clamping pressure. Place the convex side up with fan blowing across it. (This is my preferred way because its more gradually allows the stresses to even out as the board dries).

Third, you can place the board on stickers convex side up with a little weight on top in a climate controlled area for a while.

Since this is a top, keep in mind it doesn't have to be perfect, just close, any slight cup can be pulled out with installation to the cabinets. Be sure to allow for wood movement when installing. Do this by screwing rearmost and allowing expansion toward the front.

Worst case scenario, you may have to rip it apart, let the boards acclimate, and re-glue.

Good luck. Let us know what happens!!


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## RichT (Oct 14, 2016)

> I would rip it again, but into 4 pieces instead of two. Joint and plain the narrower boards, then glue them again with alternating ring directions.
> 
> - gwilki


You can see in the second photo that the rings are, indeed, alternating. The fact that they shouldn't be is another matter.


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## RichT (Oct 14, 2016)

> What wood did you use? You mention 2×8 which makes me suspicious that you used construction lumber for this. Construction lumber isn t dried out nearly as much as furniture grade wood. If this is the case, and the wood isn t dry to start, the whole thing may turn into a potatoes chip once it does fully dry.
> - clin
> 
> Same thought here,
> ...


I didn't catch that at first, but you're right. It looks like 2X lumber. Not only will it be unstable, but its surface will dent easily.


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## wormil (Nov 19, 2011)

> I would rip it again, but into 4 pieces instead of two. Joint and plain the narrower boards, then glue them again with alternating ring directions.
> - gwilki


Alternating growth rings is a very old myth that just won't die. If you don't believe me, look at the op's pictures again, they are alternated. When people talk about ripping into strips and flipping rings, I believe they have conflated the alternating growth rings myth and a technique sometimes called "rip and flip". Rip and flip is a technique for stabilizing crappy wood where it's ripped into narrow boards, turned 90°, and glued into a quartersawn panel. Rip and flip in my limited experience does not guarantee a flat panel but will give you a reasonably flat panel even from twisted wood.


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## wormil (Nov 19, 2011)

> Is there anything I can do to uncup?
> - v0mich01


You could try Bondo's suggestion although I wouldn't hold out much hope. Some people have success leaving it on the grass, convex side up. The bottom draws some moisture from the grass and the top dries in the sun which sometimes takes cup out, or makes it better. Construction lumber is only dried to around 14% moisture, something like that; while hardwoods are dried to 7-8% moisture. So this wood will continue losing moisture for some time to come and will be prone to undesired wood movement.


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## GrantA (Jul 19, 2014)

I didn't see it mentioned but so you know, you should perform the same operations on top and bottom. After jointing a face then run it through the planer, to ideally remove the same amount of material from the other face. 
With construction lumber the issues are compounded.
Also, not picking just so you know what its called - if you used a spline down the edges you didn't cut a dado, it's a groove.


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