Author Topic: Is this acceptable quality? Cupping & cracks in timber table top  (Read 1710 times)

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Offline eddomak

  • Posts: 307
Hi,

My friend is seeking general advice as he purchased a solid timber American Oak custom table top with an oil/wax finish and after only a few months he sees some problems developing.

1) cupping / bowing of the top as a whole - in the below photo where a straight/level board has been put on top you can see a gap where the table seems to have bowed/cupped quite a bit
307161-0


2) Crack in a single board - the photo above shows a crack which has developed in the grain, and below is a close up.
Cracked Grain.jpg
307163-1

3) Crack along join line - a crack in the join line between boards to make the panel has developed
Cracked Join.jpg
307165-2

The manufactuerer's response was to quote from their maintenance page:

"All the timber we use in our furniture is pre seasoned and ready for a long hard life. Splits andcracks may develop as it responds to the environment and these are not to be considered afault or flaw and will not compromise the construction of any furniture we make."

I am not an experienced woodworker but thought that issues 1 & 2 might be symptomatic of not letting the wood stabilise or dry out prior to creating the tabletop panel, and that issue 3 should not really happen if glued well in the first place.

I was hoping for some of your experience whether these types of problems would be typically expected and/or acceptable in a commercial product made from this material? For me it seems strange that tables that are decades (or even centuries) old can remain straight and crack free, whereas this is only months old.

Thanks in advance for your help.

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Offline kcufstoidi

  • Posts: 849
Re: Is this acceptable quality? Cupping & cracks in timber table top
« Reply #1 on: November 24, 2019, 08:15 AM »
The flaws you are seeing are a result of them using wood that wasn't properly kiln dried and prepared. You can also see this if the table was built in the NE and shipped to the much drier parts of the country where the relative humidty is much lower. The check is a result of the wood drying after construction. The glue failure at the glue joint is indicative of the same problem. The bowing can be attributed to seasonal change but looks more like a poorly designed table IMHO. The disclaimer is a butt cover because of their on going problems, as always buyer beware.

Offline RKA

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Re: Is this acceptable quality? Cupping & cracks in timber table top
« Reply #2 on: November 24, 2019, 10:01 AM »
The check I’m more likely to understand, depending on the price point of the product.  The more stable you want the wood, the more the product will cost.  If it was a premium product, I would expect them to take reasonable measures to ensure the wood is stable and stand behind it if a problem develops. 

But the glue line failure I’m not so sure about.  If it did dry and shrink after assembly wouldn’t you expect the crack to form adjacent to the glue line and not on it?  My expectation is if it was properly glued and assembled, that long grain glue joint would be stronger than the naked wood fibers next to it.  Is that an incorrect assumption?  Or maybe it’s possible that on board wasn’t completely straight and that part of the joint was weak from the start?
-Raj

Offline SRSemenza

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Re: Is this acceptable quality? Cupping & cracks in timber table top
« Reply #3 on: November 24, 2019, 10:59 AM »
The attachment method to the base / legs also matters. The top needs to be allowed to move with humidity changes no matter how well seasoned the wood.

The top side and bottom side also need to be "sealed" in the same way to keep moisture change even between the top side and the bottom side.

Since the bottom side currently has more moisture than the top side. I would be curious to know what the finish is like on the bottom side.

Seth


Offline Michael Kellough

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Re: Is this acceptable quality? Cupping & cracks in timber table top
« Reply #4 on: November 24, 2019, 12:05 PM »
Unacceptable.

If the wood truly was adequately pre-seasoned it wouldn’t split, nor would the joint open.


Offline ChuckM

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Re: Is this acceptable quality? Cupping & cracks in timber table top
« Reply #5 on: November 24, 2019, 02:22 PM »
The attachment method to the base / legs also matters. The top needs to be allowed to move with humidity changes no matter how well seasoned the wood.

The top side and bottom side also need to be "sealed" in the same way to keep moisture change even between the top side and the bottom side.

Since the bottom side currently has more moisture than the top side. I would be curious to know what the finish is like on the bottom side.

Seth

I'm more in tune with the above analysis. The lumber is probably not seasoned enough for the destination conditions, but even if well seasoned, allowing for wood movement should have been a must, which includes putting the same number of coats of finish on both sides.

If it's a high-end table, the vendor should take it back, let it sit to get used to the shop humidity, flatten the table, fix the crack with a bowtie, put a new finish, and double check the mounting system to make sure wood movement is catered for. If that is too much work for both parties, the vendor should offer a discount.

Offline kcufstoidi

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Re: Is this acceptable quality? Cupping & cracks in timber table top
« Reply #6 on: November 24, 2019, 03:28 PM »
The check I’m more likely to understand, depending on the price point of the product.

The check developed because the wood wasn't properly dried to between 6 and 8% especially if it developed after purchase. I see this very regularly with low grade products done by people that don't understand how important proper drying is.

  The more stable you want the wood, the more the product will cost.  If it was a premium product, I would expect them to take reasonable measures to ensure the wood is stable and stand behind it if a problem develops. 

The whole design is a perfect example of someone that doesn't understand wood. The price of the product whether premium or not should not be dictated by the stability of the wood, thats a given unless Billy Bob doesn't no shite from shinola.


But the glue line failure I’m not so sure about.  If it did dry and shrink after assembly wouldn’t you expect the crack to form adjacent to the glue line and not on it?  My expectation is if it was properly glued and assembled, that long grain glue joint would be stronger than the naked wood fibers next to it.  Is that an incorrect assumption?  Or maybe it’s possible that on board wasn’t completely straight and that part of the joint was weak from the start?

There is no direct shot of the overall table top to make any direct assumptions of the failure. Improper drying can cause all kinds of distortions, improper joint preparation, inadequate glue or poor clamping could contribute to that failure. Spin the wheel. The disclaimer also says alot about the company and was probably put in place to combat their poor techniques and multiple previous failures of the same sort. Just because they are in business doesn't mean they are any good at what the produce.
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« Last Edit: November 24, 2019, 03:32 PM by kcufstoidi »

Offline eddomak

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Re: Is this acceptable quality? Cupping & cracks in timber table top
« Reply #7 on: November 24, 2019, 06:49 PM »
Thanks once again to all of you for your wisdom and replies. I haven't been on FOG for quite some months (as I haven't had much time to do projects) but it is considered and careful replies like this that make me appreciate you all the more. Thankyou again!

Well, the American Oak has been shipped all the way to Australia, assembled in one state and shipped to another, so that is quite a lot of climate change not to mention the current change of seasons.

I also mentioned to my friend about how the top needs to be fixed to the base in a way that allows for movement, and we'll look a bit more into this.

Without going too far into judgement as to skill/craftmanship, when I look at that vendor's site it seems a lot of the furniture has a simple aesthetic and design (nothing wrong with that), and some of it may be more "rustic" (eg turned log stools), so perhaps there was less need to understand the finer points of wood movement etc.



Offline Dogberryjr

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Re: Is this acceptable quality? Cupping & cracks in timber table top
« Reply #8 on: November 24, 2019, 07:15 PM »
How are people discerning the method of attachment?  Did I miss a photo?

Offline mcooley

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Re: Is this acceptable quality? Cupping & cracks in timber table top
« Reply #9 on: November 24, 2019, 07:21 PM »
I too would need to see more images of how the top is attached.

Offline SRSemenza

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Re: Is this acceptable quality? Cupping & cracks in timber table top
« Reply #10 on: November 24, 2019, 10:57 PM »
I don't think people are discerning the method of attachment, they are suggesting that it is something that can affect the top due to wood movement.  More like something to check.

Just like I would like to know what the bottom side finish is like. Another possible reason for the warping.

Seth

Offline Jiggy Joiner

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Re: Is this acceptable quality? Cupping & cracks in timber table top
« Reply #11 on: November 25, 2019, 02:59 AM »
Not sure of the consumer laws in your country but, I wouldn’t accept that. It’s almost certainly going to get worse, and without some kind of remedial work, poses some hygiene issues amongst other things.
Looks like the timber is acclimatising to it’s current environment.


Offline Oldwood

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  • Alberta, Canada
Re: Is this acceptable quality? Cupping & cracks in timber table top
« Reply #12 on: November 25, 2019, 11:10 AM »
I think it is poor work. The check was probably in the board before the table was constructed and not noticed. The ends shrink and crack when they are dried and these cracks need to be cut out before gluing up. It is hard to do when you pay high prices for hardwood but if you have other projects where you can use the cut offs you can minimize the loss of material. The fact that there is only one crack makes me think this was a preexisting condition.

We built nothing but solid wood doors for a about 15 years and depending on how fast the oak was dried we had to cut back the ends by 6 to 18" before the milling process. These cracks can be hard to spot and you need to have good lighting and look closely to see them sometimes. If left they tend to open up later.

The open glue joint is a concern. It is impossible to know what the problem is there. There are a long list of things that could cause this and a lot of them would get worse as time passes.

As has been said it is not possible to see from the photos how the top is attached and not allowing the wood to move could cause problems.

I think both the check and bad glue joint could be repaired  but the rest of the glue lines may be a concern depending on the cause of the problem. The oil wax finish makes this a lot easier.
Real knowledge is to know the extent of one's ignorance.
Confucius

Offline Svar

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Re: Is this acceptable quality? Cupping & cracks in timber table top
« Reply #13 on: November 25, 2019, 12:13 PM »
I also think it's poor work. If something like that happened to my work within few months, I'd take it back and fix it.
Rip it along glue line(s), re-join and re-glue. That will take care of glue failure and cupping.
The check is right on the edge of a solid piece. Because of that it can be glued back after ripping.

Large slab apron-less tables like this often get a metal angle or u-channel brace on the underside to add stiffness.
« Last Edit: November 25, 2019, 12:29 PM by Svar »

Offline HarveyWildes

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Re: Is this acceptable quality? Cupping & cracks in timber table top
« Reply #14 on: November 25, 2019, 12:32 PM »
...
I think both the check and bad glue joint could be repaired  but the rest of the glue lines may be a concern depending on the cause of the problem. The oil wax finish makes this a lot easier.


I use oil/wax finishes a lot.  I live in Colorado, so once the wood gets down to about 6% moisture content, it stays there.  However, I have done oil/wax finished boards for high moisture applications like bathroom counter tops.  For those applications, I rub in a lot of coats (15-20) to isolate the wood from the moisture as much as possible.  In general, I'm a bit scared of oil finishes when there is a lot of change in relative humidity.


I know there are other factors involved oil finishes, like the % of solids in the oil, whether the finish is rubbed with wet/dry sandpaper so that wood dust fills the grain, and so on.  I generally mix some poly varnish in with the oil and wet sand with 600 grit or higher.  If I want a better finish, I rub in more coats and sand to finer grits.


If this is a commercially produced table, I'd be wiling to bet that the oil finish was applied with just the final look in mind.  As @Oldwood mentioned, an oil finish is (relatively) easy to repair, although you still have a account for changes in the color of the wood over time due to UV, sanding and buffing patterns, and so on.


As others have mentioned, I'd be surprised if these issues didn't get worse over time, particularly if you have big seasonal swings in relatively humidity, either due to natural weather patterns or to heating/cooling systems that only kick in during certain times of the year.  In my experience, day/night swings in humidity don't affect wood much.


As an aside, I'd be interested in a thread on how people have fine-tuned their oil finishing techniques over the years, either with specific products or specific techniques.


Offline Oldwood

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  • Alberta, Canada
Re: Is this acceptable quality? Cupping & cracks in timber table top
« Reply #15 on: November 25, 2019, 01:09 PM »
Svar
I also think it's poor work. If something like that happened to my work within few months, I'd take it back and fix it.
Rip it along glue line(s), re-join and re-glue. That will take care of glue failure and cupping.
The check is right on the edge of a solid piece. Because of that it can be glued back after ripping.

Large slab apron-less tables like this often get a metal angle or u-channel brace on the underside to add stiffness.

I agree that would be my reaction to this also. The very least would be to rip out the one joint that is open and redo it and epoxy repair or inlay the check. I would only do this if I knew for certain the other glue joints were not going to show the same problems. Cutting out the check would be more work but probably a more undetectable repair.
Real knowledge is to know the extent of one's ignorance.
Confucius

Offline usernumber1

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Re: Is this acceptable quality? Cupping & cracks in timber table top
« Reply #16 on: November 25, 2019, 02:40 PM »
how much did your friend pay for this?

i'd fix and accept whatever wood shrinkage and cracks, but their own glue line failed in #3 - that is not acceptable, that is literally all on them and they failed gluing two boards together

Offline ChuckM

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Re: Is this acceptable quality? Cupping & cracks in timber table top
« Reply #17 on: November 25, 2019, 03:30 PM »
Glue line failures typically happen at either or both ends (first). That's why I always glue the dominoes even if they're just for alignment purposes.

Offline mcooley

  • Posts: 247
Re: Is this acceptable quality? Cupping & cracks in timber table top
« Reply #18 on: November 25, 2019, 06:36 PM »
Ditto gluing the dominoes. Easy enough even if you think you don't need them other than for alignment. It only takes a second.

Offline demographic

  • Posts: 549
Re: Is this acceptable quality? Cupping & cracks in timber table top
« Reply #19 on: November 25, 2019, 06:43 PM »
Did your mate buy this using a credit card? Often some way of seeking redress via a complaint through the credit card company even if the seller claims "its all normal and nuffink to see here guvnor".

Offline eddomak

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Re: Is this acceptable quality? Cupping & cracks in timber table top
« Reply #20 on: November 26, 2019, 09:00 PM »
Thanks all again for your replies. My mate is also watching this thread  :) , so hopefully he can get some ideas here.

I had also asked about the base prior to posting and here are the photos for those who are as curious as I am:
307344-0

307346-1

I can't tell if the holes for the bolts into the top are elongated or oversized to allow for movement, but he had been advised to "not tighten too much" (which doesn't really say much at all).

Offline ChuckM

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Re: Is this acceptable quality? Cupping & cracks in timber table top
« Reply #21 on: November 26, 2019, 09:31 PM »
 "not tighten too much" could mean avoiding over stripping the holes, or allowing the top to move in elongated holes. The only way to tell if the holes are elongated is to unscrew one bolt to check, which is a problem easy to fix compared to others.

Offline Oldwood

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  • Alberta, Canada
Re: Is this acceptable quality? Cupping & cracks in timber table top
« Reply #22 on: November 27, 2019, 10:55 AM »
From looking at the photos it looks like there is no accommodation for wood movement. I would put one or two fasteners in the middle of the panel that have no slots to fix the panel and route slots for the other bolts and washers.

It does not look to me from the photos that this fastening method is the cause of the check or glue joint failure but it could be contributing to the bowing. 
Real knowledge is to know the extent of one's ignorance.
Confucius

Offline Svar

  • Posts: 1910
Re: Is this acceptable quality? Cupping & cracks in timber table top
« Reply #23 on: November 27, 2019, 11:09 AM »
As I've mentioned before, large solid wood tables without apron benefit from having steel braces underneath.
Something like this: http://www.akroydfurniture.ca/blog/Entries/2012/7/25_Steel_Brace_for_Underside_of_Live_Edge_Table.html
Particularly if you have large humidity fluctuation, or the table might be moved from one contrasting climate to another, or the finish is not air tight.

It could be a wooden cleat or batten too, as in traditional trestle table. Sometimes cleat is dovetailed into the top, and dovetail edge is concealed. Hafele even sells very clever concealable metal dovetail batten for solid wood tables: https://www.haefele.de/en/produkt/dovetail-batten-for-solid-table-tops-straightening-fittings/64110903/?MasterSKU=0000000d0000b81a00050023

This particular one could have had a batten on top of the legs extending 80% of the width of the table without being visible and preserving the overall aesthetic. The minimalist approach they took might work, but it's a gamble.

Ditto gluing the dominoes. Easy enough even if you think you don't need them other than for alignment. It only takes a second.

Gluing dominos is unlikely to prevent cracks, as the underlying problem is excessive tension, rather than week joint. If you add domino, but tension is not addressed you'll still end up with a crack, just not in the joint but few centimeters away.
« Last Edit: November 27, 2019, 12:16 PM by Svar »

Offline mcooley

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Re: Is this acceptable quality? Cupping & cracks in timber table top
« Reply #24 on: November 29, 2019, 05:46 PM »
Definitely would prefer elongation as opposed to just oversized holes for that dimension of top.