Warping Beech Worktop. Solutions

[twm.bwen]

Hi there, I have a beech worktop that is starting to rise in the middle and thus push the sink up at one end and not drain.

I realise that usually the worktop is fixed from underneath to the units to stop this, but the bowed area left of the sink is above a corner unit so there is no upright to tie the worktop down to.

So i was thinking of bringing it back to flat by fixing some sort of batten underneath to screw up through. The trouble is what meterial.
It needs to be shallow enough to not be seen but strong enough to takew the bow out of the 40mm worktop. (ie stonger then the forces in the worktop)

do you thik 2x2 pine would do it/ I was even thinking of an aluminium level (stong box section).

The other issue is that the fixings need to hold to the worktop. Its seriously dense beech so do you think a No 10 with correct pilot should do it?
Thanks in the vain hope that anyone replies to this random query

 

[big-all]

my first thoughts are

can you easily push the top flat!!!!
if you have more than token resistance yout likely to get splitting

was /is it propely sealed or do you think the water has enterd the top!!!!

have you thought about not using the top for a week or so and seeing if it goes down as it dries out!!!

 

[oilman]

do you thik 2x2 pine would do it.........

Definitely not. You would have to be thinking of a board, edge on, of something like beech and 4 to 6 inches deep to restrain the top.

I was even thinking of an aluminium level (stong box section).

Again 4 to 6 inches deep. You might get away with a carbon-fibre channel an inch or so deep but the cost....................

 

[Scrit]

I agree with Big-Al. Leave it to dry out and see what happens. If, as I feel is likely, it doesn't change anything then the worktop is scrap IMHO. The cost of getting it out and taking corrective action is probably more than the cost of a replacement top. If you do replace it make sure that the new top is acclimatised to the room first and well sealed before installation - then keep oiling it and make sure that the top is wiped dry when it gets wet. And as for trying to hold it down - the only way to straighten laminated staves which have bowed is to rip saw them, reglue (adding extra material to compensate for the loss on the rip saw), reglue then plane and thickness - hence easier to replace. A 3 metre x 40mm thick worktop some 600mm wide will support my 85kg with little over 12mm deflection (we tried this recently) so I don't see a few #10 screws making a lit of difference. Sorry

Scrit

 

[twm.bwen]

Thanks for all the replies, but doesn't sound gooddoes it.
I think I've also painted the wrong picture, so please see my added drawing

I put the top down before xmas and sealed it under and over with danish oil before doing so. It had been laid flat inthe same bulding for a few weeks.
As mentioned the presence of a corner unit will not allow the top to be fixed from below on that section and has no upright to fix it to.

I thought block wood avoided warping my alternating grains, which is part of the reason I got it (£135 from Timbmet)
I can push it down slightly by hand (total warpage is about 3mm)

What could it seal it with other than danish oil, which doesn't seemed to have worked?
Thanks
Tom

 

[Scrit]

I put the top down before xmas and sealed it under and over with danish oil before doing so.

OK, then, did you check it was flat before installing by putting a straight edge across it? Oh, and how many coats of oil went on? (3 or 4 on all sides with a bit extra in the end grain I hope) I am also beginning to suspect that the top might have been slightly bowed to start with. Did you check it before installing? This is always a necessity with any wood product

As mentioned the presence of a corner unit will not allow the top to be fixed from below on that section and has no upright to fix it to.

I don't like leaving long worktop runs unsupported, especially at the outer ends, so I generally batten the wall on one side or other of the corner unit and attach the worktop to the batten when installing the top (or at least support the top on a bed of silicone atop the batten). After the units are in place this may be difficult to achieve so you may need to consides something like fixing a piece of Dexion to the wall instead.

I can push it down slightly by hand (total warpage is about 3mm)

I suspect that may be because the back edge of the worktop is unsupported and the worktop is possibly in wind as well as bowed. If you look inside the corner unit is there a gap between the top of the cabinet and the worktop, or can't you see that because the unit has a solid top? If there is a gap at one end and none/less at the other then your top is in wind (i.e. it has a twist in it).

If the top is merely bowed across the width it's just possible that you may be able to anchor it to the top of the cabinet using angle brackets and screws - remember to open out the holes in the brackets so that expansion is catered for. Preferebly use angle plates with slots as opposed to holes.

Once secured if the sink is removed it should be possible to hand or power plane the bow out of it, finishing with a belt sander. Remember to plane and sand with the grain, never across it. Keep offering-up the sink until it sits flat. Finally reseal the top (3 to 4 coats) and replace the sink.

f a customer asked me to do this I'd have to point out that the chances of success are not high and that the only sure-fire way to sort the problem is to install a new top.

Scrit

 

[oilman]

What could it seal it with other than danish oil, which doesn't seemed to have worked?

It will be difficult now as you have danish oil on it which will impede penetration of alternatives.

I would use tung oil. Danish oil is tung oil with driers and it dries too fast to allow the oil to penetrate adequately. About 7 to 10 coats of tung oil (one a day) would do to start on bare wood, then keep on oiling as much as you like.

Wooden bowls are often finished with a glossy finish. Fine until a piece of fruit leaks onto it, then the finish is penetrated and the wood is stained. If tung oil had been used, the wood would have been ok.

 

[twm.bwen]

Thanks for all the replies,

I can no longer be sure it wasn't slighly cupped when I installed it, be it has certainly got worse as It pushed the sink up!

but I thought that the point of staved board was that the grains could be alternated so as to stop warping.
Anyway,

I am going to have to make a custom unit underneath that incorporates 3x2's edge on to clamp then screw it to. I have little other choice but to try.

Would No12's have a betterchance of holding? What about coach screws?
Also what are the strongest screwswhen it comes to torque and hold?

And considering it is probably moisture that caused any existing warp to increase what should I do, try and appl;y some steam when clamping?

I have managed to take out about 1/3 to 1/2 of the bend with just 2x2 and no10's so I hope it will mostly come out if it is clamped first then more substantial fixings used.

Failing that I could use pan head coach bolts from the tops and pretend its some kind of custom trivet!

Let me know hat you think,
Thanks
Tom

 

[Scrit]

....but I thought that the point of staved board was that the grains could be alternated so as to stop warping.

That always assumes that the grain is alternated. Is it? There are actually two differing schools of thought on this one - and the other one says have all the grain arch upwards so the the top will bow upwards evenly and can be secured by fixing to a cross batten to limit movement, although I've never seen worktops done this way. Neither method is meant to resist continual soaking. However, commercial worktops are made from thin staves for purely economic reasons and I doubt that they check grain orientation so assiduously. Have you checked the grain orientation?

And considering it is probably moisture that caused any existing warp to increase what should I do, try and apply some steam when clamping?

To steam bend 2in timber normally requires the timber to be immersed in a steam box for 1-1/2 to 2 hours, so I doubt a small amount of steam will make any difference at all as it won't penetrate very far

I am going to have to make a custom unit underneath that incorporates 3x2's edge on to clamp then screw it to. I have little other choice but to try.

Did you know that wood expands and contracts across the grain far more than with the grain? If your battens are rigidly fixed to the underside with no provision for movement, e.g. slotted holes or larger holes with undersize screws and washers, then the stresses in the top should it continue to move may cause joint failure. You may get away with it, but that's only a maybe. Having written that it now raises the question in my mind of how you fixed the tops to the units in the first place. Rigidly, or did you allow for wood movement?

Let me know what you think

Tom, as my time has to be paid for, by now I would have simply taken out the top and replaced it as that would have been a far cheaper alternative. A minor bow I would have possibly planed out, assuming that I was satisfied that the top had stopped moving. Having got some of the warp out, and hopefully resealed it, you are now running the risk of splitting the top if you continue to try to screw it down, especially if you screw it rigidly with no provision for movement. Wood is a natural material and moves - it is not inert like metals and plastics. If the top has not yet stabilised and you continue to add additional stresses you are going to push it nearer to a joint failure, more so if you try to fix it rigidly. Assuming it's stabilised, that your solution accomodates any future movement and that the bow is only a few millimetres I'd seriously consider getting out the hand planes and belt sander and correcting it that way.

Scrit