Thread: Merbau outdoor table top cupped

Water made it bend up - water might make it bend down.

At the outset, let me say I have no experience here - just a theory I saw put in practice in a video once.

Here's my idea - and someone will likely tell me that I'm bonkers! But unscrew the board from the table. You then need to find a way of stabilising it and bracing it to "force" it straigh - you might use steel square tubing (or similar material) either side of the board in many places, and a lot of clamps. Sort of like the material you use to show it's cupped. Once you have these stabilisers, you put them in place and apply no force yet. Then subect the board to water (probably preferably steam) to *gently* force it back to an uncupped state. You begin tightening your stabilisers bit by bit, apply more steam/water, and gently force the board back to straight.

Once you have it straight again - let it dry with the stabilisation (clamps and square tubing) on it. Once dry, seal it well!

Hi MM,
Thanks for the suggestion. I have considered trying to coax it flat using moisture. I have two concerns about doing it though. Firstly, it could be VERY slow, and secondly, the board might return to being cupped when exposed to the sun again.

Have you considered rotating the table 180 degrees?

It 'could' be that, that side of the table gets exposed to more weather (sun/rain) than the other - just a thought.

Interestingly, the board has cupped in the opposite direction to the growth rings than what would be considered normal. A backsawn board such as this will normally cup in the opposite direction of the curve of the growth rings. This board has cupped with the rings. Why? greater tensions placed on the timber than its own inherent qualities ie Uneven drying. Being an outside table prevailing conditions will have the capacity to over rule a board's normal performance. Particularly if the timber is exposed with a high moisture content. The surface most exposed to the elements will dry quicker than the other causing shrinkage. As the shrinkage is fighting against the natural forces created by the annual/growth rings, the board begins to crack from the ends to release tension. This,in turn, allows the board to cup in the opposite direction to that which it would follow naturally.
In short; too wet to go outside initially. If the timber had been too dry, it would have cupped the other way as moisture would have been absorbed to reach equilibrium.
Replacement would be one option, or rip the board, reverse one of the pieces and glue with epoxy.

Rip the offending board in half. Redistribute the three good boards with the two narrower pieces from the ripped board between them. It won't be perfect, but the cupping will be far less noticeable and you will have a better chance of flattening them without it being so obvious.

Being outside like that in all weathers is a big ask for a wood table. Soaking wet one day then baked in the sun the next. Unless the cupping was so bad the table was no longer functional then I would be inclined to just live with it. Any fix you do will only be temporary if the table is still exposed to the elements. The best fix would be some cover for it.
Regards
John

Thanks all. The wood was quite green when I made the table and, as suggested, that particular board hasn’t aged well.

I may just buy another board and let it dry in my workshop for 12 months or so before swapping it for the cupped board. This time I’ll make sure the growth rings are orientated correctly. In the meantime I’ve got nothing to lose by cutting slots in the bottom and trying to coax it back to flat.

I take the point about an exposed outdoor table being subjected to endless wet/dry cycles, but good quality (i.e durable) cover would be quite expensive.