Warped workbench top

[Matt635]

Hi, wood movement question…

I bought a workbench about four months ago and the top was flat when it arrived. I gave it two coats of polyurethane varnish top and bottom. There is now a noticeable amount of movement on the surface, see the photos. My question is how to recover it. Is it ok to hand plane it back to flat or will it then go the other way when it gets warmer?

It’s kept in a shed so I know not a very stable environment for humidity.

ps the seller had already replaced the original top when it bowed, but as this has happened a second time I’m now wondering if it’s something I’ve done wrong.

 

[rogxwhit]

It looks to me as if the bench top might have aprons front and maybe back too that are deeper than the main width of the top?

In the light of the above - if I'm right - and studying your first image - I suspect that the design is suspect in the circumstances, in the way that the top is attached to the end cleats and maybe the bench frame too.

Can you do an image from underneath?

I don't think you've done anything wrong, in fact sealing it top & bottom should help if anything. I wonder if the construction could be modified?

It's reasonable to think of planing it - but it's ever likely to move seasonally to some extent. An unheated shed is a challenging location - damp in winter & an oven in summer.

I'm too far away to come round & do some brainstorming.

The placement of the shed may be an issue too - does it get full sun?

 

[thetyreman]

it's going to move as it acclimatises to the environment, unfortunately damp sheds are not ideal, in other words there is not much you can do to stop it, except maybe try a de-humidifier when it's very damp.

 

[Matt635]

It looks to me as if the bench top might have aprons front and maybe back too that are deeper than the main width of the top?

In the light of the above - if I'm right - and studying your first image - I suspect that the design is suspect in the circumstances, in the way that the top is attached to the end cleats and maybe the bench frame too.

Can you do an image from underneath?

I don't think you've done anything wrong, in fact sealing it top & bottom should help if anything. I wonder if the construction could be modified?

It's reasonable to think of planing it - but it's ever likely to move seasonally to some extent. An unheated shed is a challenging location - damp in winter & an oven in summer.

I'm too far away to come round & do some brainstorming.

The placement of the shed may be an issue too - does it get full sun?

Thanks. Images from underneath below. I did wonder if the fixed end panels limit the sideways movement of the wood on the main top too much.

Shed is in part sun part shade. I do heat it when I’m in there when needed, and have a dehumidifier, but that is only the few hours a week when I’m out there.

 

[Jacob]

ps the seller had already replaced the original top when it bowed, but as this has happened a second time I’m now wondering if it’s something I’ve done wrong.....

Design fault. That's why it happened again.
From photo the top looks thin and not well braced. Plane it flat today and it will be bent again by tomorrow.
I wouldn't worry about it too much. See how your woodwork goes.
There's currently a bit of a fetish about flattening everything, which is best ignored.
I wouldn't have applied finishes anyway - it's not what you want on a workbench
PS looking again at the photos - it's a total bodge job. Sorry to be bearer of bad news! Can you get your money back?

 

[Adam W.]

It'd be difficult to produce flat work on a bench like that.

Could you remove the strips underneath by the stool, which hold the end pieces and see if it flattens out, or will the bench collapse without them?

The reason I ask is because the top plate has swollen up, but the strips haven't increased in length and this has made the top bow upwards.

 

[rogxwhit]

Ah! It'll keep on behaving extremely, unless you re-structure it somehow. Adam has the gist of it above. Undo those screws that hold the top to the frame. They're a cross-grain nightmare. Discard them. The task is to engineer a way to locate the top without them. The top needs to 'float' - but stay supported.

It's all do-able as far as it can be. Not to say a complete elimination of problems will occur, but a major hurdle can be crossed.

Chock blocks on top of the leg-frames could locate & support the top without fixing it.

I can't see how the end cleats are fixed - possibly it might be best to do away with them, I don't know yet.

Anyway, once the compromises in the structure have been addressed, only then is the time to plane the top level. Not before.

Ignore Jacob's negative persona. ;-)

 

[Jacob]

Ah! It'll keep on behaving extremely, unless you re-structure it somehow. Adam has the gist of it above. Undo those screws that hold the top to the frame. They're a cross-grain nightmare. Discard them. The task is to engineer a way to locate the top without them. .....

The task is to rebuild the bench. See it as a useful pile of wood but it might be better to start afresh.
The useless ornamental vice is another detail. This is fantasy woodwork.

 

[Adam W.]

I think what Jacob means is that it's a good start, but it needs a few minor adjustments to get it to its optimal working condition.

 

[Jacob]

If you can't get your money back I'd strongly recommend trying to use the bench as it is, with first project being to make a proper bench.
With either a Record vice, or if fashion dictates then a wooden leg vice. The mechanism you have could make a leg vice, but is near useless as it is.
Love him or loathe him Paul Sellers bench is one of the best - basically his version of the universal design which used to be found in every school, training establishment, industrial woodwork shop, and all the books, before fashionable "modern" woodwork kicked off.
https://paulsellers.com/2022/08/workbench-make-it/

 

[Matt635]

Thanks All for your constructive comments. Looks like its a more major rebuild. I'll take the advice on board and look at more significant adjustments.

At the time I weighed up building my own or buying one ready made, and as the costs came out similar I opted for convenience. Lesson learned.