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I would like to screw this solid wood tabletop (the long one in the back, it's beech wood)

enter image description here

onto this steel frame.

enter image description here

The slab's dimensions are going to be 200 x 80 cm. I read that "wood moves", so I would have to screw the table top on in a way that allows for movement.

The problem is that none of the methods that I've read about that allow for movement are compatible with the screw holes facing up in the frame. enter image description here

How can I solve this? Should I worry about movement for this type of tabletop at all or can I just screw it fixed?

Here's another photo of how the wood is supposed to look after it's been oiled: enter image description here

Ashlar
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Zoltán
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  • I should point out that the holes are a bit wider than the screws I got with the frame, so there is some 'wiggle room', which I guess allows some wood movement. – Zoltán Mar 31 '17 at 21:49
  • Your first picture shows a slab of oriented strand board (OSB). This type of wood slab will not expand and contract. like solid wood. It is unclear if the butcher block slabs in plastic wrap are the same type of veneered wood on OSB of solid wood glue-ups. Please clarify. – Ashlar Mar 31 '17 at 21:50
  • If the table is in a steady temperature and humidity environment year round such as an air conditioned apartment the movement might not be much of an issue. – Ashlar Mar 31 '17 at 21:54
  • @Ashlar sorry for the confusion. I mean the large slab behind the OSB, it's made of beech wood, but I don't know what this type of material, where the slab is glued together of smaller blocks is called. Glulam perhaps? – Zoltán Mar 31 '17 at 21:58

5 Answers5

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The over-sized screw holes will certainly allow the table top to expand and contract without splitting.

Even if the changes across the grain take up the slack allowed by the larger holes, the frame itself will likely flex enough to allow for the wood movement without splitting.

I think the whole project is a winner - go for it.

Ast Pace
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We use very few screws in our solid wood countertops - we installed a commercial 27' x 9' L-shaped shaped bar with only two hold-down screws some years back. But when we do, we bore a 1/2" hole in the member to which it will be attached, and use a black #2 screw and washers to attach it. We also lubricate on the bearing side of the washer. Overkill? Yeah, but call backs are expensive, and we don't get them.

So anyway, I would be inclined to bore those holes out and use a smaller screw.

Benchwerks
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It should probably be ok. You can try it out and see if it is too flimsy for your use.

If the screws are too creaky, you can add angles.

enter image description here

Treow Wyrhta
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Nothing to worry about those solid wood tabletops. They have been heat treated which means; unless you soak them into water, nothing (significant) happens to your table.

borgs
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  • I'm at the Milgram checkpoint for badges and have to downvote somebody. Sorry about that.

    I would agree with you, if one were simply going to suspend this Buche top in midair. Buchenholz is stable as you say, but the problem comes when you have to attach it. That's what all the discussion above is about.

     – Benchwerks Apr 03 '17 at 20:40
  • well you can't change facts by voting :) real life issues :) – borgs Apr 03 '17 at 20:44
  • Please feel free to reciprocate when you need to :) – Benchwerks Apr 04 '17 at 02:47
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    You're completely wrong here. Solid-wood tops, whether a single piece or made up from multiple pieces glued together. "Heat treating" doesn't change wood's response to changes in humidity, air-dried and kiln-dried wood still absorbs and loses moisture through the year, expanding and shrinking across its width. – Graphus Apr 05 '17 at 08:43
  • @Graphus : There is actually a form of heat-treatment which does stabilize wood (and make it rot-resistant). See http://www.woodlinkuk.com/Thermo%20wood.htm (however the table top in the picture has not been treated like this). – Martin Bonner supports Monica Apr 05 '17 at 13:14
  • Hey Martin - Ive used a "heat treated" poplar as a lower-budget walnut. Nice stuff. Not for the discerning client, but it works for folks who want "stain grade" in that color. Little more expensive for me, but I'm glad to trade the drudgery of applying stain. Its incredibly light, so its not suitable for tops, and it drinks finish. – Benchwerks Apr 05 '17 at 22:09
  • You seem to think the iron legs for this table are "rigid". Iron itself can also move, extend; Especially with temperature. So as i said nothing significant will happen, since the tiny movements of wood will be tolerated by legs and screws, because they also have the capacity to move. Furthermore, (besides being heat treated) this wooden table top is also laminated which also minimize the movement. But anyway, the owner will decide what to do and I hope he/she shares the future progress about this table :) – borgs Apr 06 '17 at 05:59
  • @MartinBonner Yes I'm aware of thermally-modified wood (called variously torrefied, toasted, roasted, caramelised) but it supposed to, at best, reduce movement by 50%, not remove it entirely. Which for beech leaves a little over 12mm which is not insignificant, and as you say the pictured top hasn't been treated that way anyway :-) – Graphus Apr 06 '17 at 06:53
  • @borgs The ability of the legs to flex is an open question. You're guessing as are we all but everyone else is guessing it can't flex enough. "besides being heat treated" it's not, as the colour alone indicates. "this ...top is also laminated which also minimize the movement" As I said, no, it doesn't. Glue-up or not the movement hasn't been minimised. It could be, but it would require careful selection and placement of each and every piece, which is definitely not done on these. And that's not a guess, you can tell from the face grain even if we couldn't from the random colouring!. – Graphus Apr 06 '17 at 07:04
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Should I worry about movement for this type of tabletop at all or can I just screw it fixed?

Yes, you always have to consider wood movement with components made from solid wood. And the larger the pieces are the more important this is because the total movement is greater.

In addition you have a greater concern because this is European beech, Fagus sylvatica, because it is subject to greater changes in dimension that many other woods — double that of some pines, triple that of iroko! So the this top could change width by more than 2cm (an inch for Imperial users) between the wettest part of the year and the driest part of the year in a climate with wide swings in humidity.

The problem is that none of the methods that I've read about that allow for movement are compatible with the screw holes facing up in the frame.

I hate to say it but I think that's because that leg framework just isn't designed for a solid-wood top. The movement here could easily exceed the small amount of play of those screws in those holes (in fact I think this is likely based on my guesses of the dimensions), which would at least begin to work the screws loose after a few cycles of expansion and contraction. In extreme cases this type of strain can snap screws in half before they pull free.

It's not too difficult to work around the problem however. If I were doing this I'd lengthen those holes slightly* to make them into short slots oriented 90° to the long sizes of the top. Then I'd install the screws with washers underneath their heads to spread their load and allow them to slide more easily.

*Using a carbide burr in a drill or a round hand file, depending on how tough the steel was.

Graphus
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