Warping Bar top HELP!

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Forum topic by NelsonA posted 01-26-2021 12:15 PM 412 views 0 times favorited 10 replies Add to Favorites Watch
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2 posts in 35 days

01-26-2021 12:15 PM

I recently finished a bar in Red Oak in my man cave. Turned out great until the humidity dropped with the dry weather. My once flat bar top is now curling upward. I believe I know the cause but don’t know a way of fixing it without refinishing it or replacing it again.

Thr bar top is 1” Red Oak and 20” wide. About 10” overhangs the knees while sitting at the bar. I did not check the moisture of it before installing. It assumed it was dry as it was in cellophane from inside the store.

The Red Oak top is screwed from below to a sub layer of 3/4” MDF.

See pic of the assembly:

Notice the beer is at an angle but the clay bottle is not. So the bar top starts curving upward from the point that the bar top overhangs.

This warping has only occurred to the bar top on the left. The other half on the right is flat.

So I believe the Oak top has contracted as the weather has become drier. 30% humidity in my room. Since the oak top is screwed to the MDF which isn’t contracting much at all, it has forced the oak to cup upward. Any suggestions on how to fix? If I understand this correctly if I could add moisture to the top of the Oak top it would expand and straighten out again. My problem is it’s sealed so not an option.

Any help would be great. I am not a woodworker, just a math teacher that took on this project by following a similar project tutorial on the web.


10 replies so far

View jamsomito's profile


628 posts in 1436 days

#1 posted 01-26-2021 12:58 PM

Yeah that’s a shame, it came out looking great! Unfortunately there’s not much you can do like you said. The best prevention is use wood that’s been properly dried, acclimated to the space it will live in, and properly milled. Even then it’s going to move with a changing environment – wood is a porous, organic material and that’s just the way it is.

Adding mositure to a face will help temporarily, but it will resume it’s current shape after it dries out again. Finishing both sides of the piece can slow moisture intrusion, but it won’t stop it.

I’d say now that the wood has acclimated to the space it would be pretty safe to mill it flat again and reuse it, but then you’re losing thickness,and like you said you’d have to refinish it.

If it’s not bad, I’d leave it or maybe try some self-leveling epoxy as a top? Depending on how much you need it could get pricey but might be an option.

View bondogaposis's profile


5950 posts in 3361 days

#2 posted 01-26-2021 01:21 PM

The problem is the MDF, it is stable while the wood is not. The wood is drying from the top surface and there is no air circulation to the underside of the wood top so it is not drying equally. To avoid in the future either use wood that is thick enough without the MDF or use plywood for the bar top. I would just leave it for now and see how bad it gets, then you will have to decide whether it can be salvaged or make a new top.

-- Bondo Gaposis

View Ruscal's profile


73 posts in 188 days

#3 posted 01-26-2021 02:26 PM

4 taps in the basement. Now that is a hobby!

-- Have a hobby? You should have a business.

View northwoodsman's profile


510 posts in 4756 days

#4 posted 01-26-2021 02:34 PM

After a couple beers it will go away and you won’t notice it.

-- NorthWoodsMan

View Lazyman's profile


6640 posts in 2397 days

#5 posted 01-26-2021 02:59 PM

Did you finish the underside? With what? Did it cause the base to distort with it? Did you attach the top so that it allows seasonal movement?

Instead of adding moisture to the top, I would try to equalize by removing moisture from the bottom. Try putting a lamp or two with halogen bulbs inside the base for a few days and see if that helps to equalize the MC and flatten it back down. You could just use a small space heater on low too. If that helps, add some additional and stronger or at least more attachments to the base and of course they need to allow for movement. If the base is strong enough that it doesn’t distort along with it, you may be able to pull it flat again with just better attachments, even without equalizing the moisture, but I would try to get it as flat as possible first. If it is also distorting the base, you will need to strengthen it.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

View Woodmaster1's profile


1656 posts in 3596 days

#6 posted 01-26-2021 03:01 PM

Try putting a cleat on the wall and drawing it down.

View NelsonA's profile


2 posts in 35 days

#7 posted 01-26-2021 04:25 PM

Thanks for the advice.

Here are my responses to most questions about my project:

It has bent enough that milling it down may not be an option. It would be so thin on the outer edge that the bar rail may not attach correctly.

I agree that the MDF is the problem as it did not contract and the Oak top did. Now the MDF is curved as it was secured with screws (no movement was allowed).

I did not seal underneath.

Epoxy may not work in this case since the top is not a true cup but more of a flat surface that curves up on the end. Epoxy would just pour over the inside of the bar.

Is there any chance that a humidifier would reintroduce moisture enough to get it to bend flat again? Or when the wet season comes back? I’m assuming not.

I did put some heaters underneath (facing towards the MDF) to dry it out. It did not work.

It may make things worse but I thought about removing the screws that secure the MDF to the Oak top. This would only be where the bar top overhangs the knees when sitting. Then try to add moisture (spray bottle perhaps between the two pieces. Of course this could cause it to get worse.

View Ruscal's profile


73 posts in 188 days

#8 posted 01-26-2021 04:58 PM

Can you completely unscrew the oak from the MDF? It might take the tension off and allow things to flatten (or not). You probably should have screwed it from underneath with an oversize hole in the MDF that the flat head screw could “float” in to let the oak move.

-- Have a hobby? You should have a business.

View Lazyman's profile


6640 posts in 2397 days

#9 posted 01-26-2021 05:16 PM

I didn’t look at all of the pictures and didn’t realize that it was just the overhang that seems to have bent up. I don’t think that there is really a way to fix that without removing the top. Since it is the overhang, you have nothing to draw it down to but if you remove it, you may be able to flatten it using some cauls and clamps. You may find that laying it top down on some concrete with some heat on the bottom for a day or 2 may cause it to flatten some on its own and make the clamping easier. Once flat, you can try adding some battens across the width. Normally I would recommend routing a dado wide and deep enough to embed one wing of an angle iron and screw the other wing to the underside of the top but with it being only 3/4” thick that probably won’t work. (Probably should have used 1.5” thickness for the top.) Instead I would use C-channel, open side down. You can use angle iron but it will hang down lower than the C-channel. Drill elongated holes in the channel to allow for seasonal movement. You also need to make sure that attachment to the base allows for movement too. Make sure that you round and smooth the ends where someone might bump up against the channel. Not sure exactly how far apart to space the battens but I would probably start with 16-18” just to over engineer a bit. After flattening, I would also apply a finish to the bottom to minimize differential moisture loss.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

View wildwoodbybrianjohns's profile


2654 posts in 557 days

#10 posted 01-26-2021 07:17 PM

Can you do to the bottom whatever finish you did to the top, and as many coats? I would start there. And now you know, always do both sides, finishing, exactly the same.

-- WWBBJ: It is better to be interesting and wrong, than boring and right.

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