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Table Top Curve/ Warp1/24
I had a custom farm table made from red oak recently and after 3 days in my house it has bowed/ warped 3/16"... now at 7/16"
The red oak was air dried for about 20 months prior to milling. It seems the bottom (flat image) has dried more rapidly than the top (image with the X)
The finish on the table is tung oil with a clear coat on the top. 2 coats tung oil on the bottom, 3 on the top.
The glass shown was on the table (photo 3, right side up) after about 24 hours, then removed. The table warped about 3/16 of an inch, then once the glass was removed, it continued to what is now 7/16. I took the table off the base and flipped (image 1 & 2) it to see if gravity would help and put the glass back to give it some weight... it did not. This is why you see a few different photos of the table on the base.
Now for my question:
If you need more photos I can e-mail them. Thanks for your help and feedback in advance.
I see 3 issues:
1. the cross grain cleat on the ends of the table top are inhibiting the oak panel's abiltity to shrink or swell with humidity changes. Remove the cleats and most of the cupping on the top will probably go away. If the cleats were installed just to make the top look thicker, they should have matched the grain orientation of the top.
2. you stated that the clear coat was only applied to the top side. To keep solid wood panels stable, an equal amount of finish should be applied to both sides.
3. the glass on top of the wood is also causing the moisture transfer from humidity changes to be unequal. On a veneer top this wouldn't be an issue.
You don't show a photo of your barn door, but I imagine it has the same finish on both sides and no glass.
Your builder needs to redo the top, because it ain't gonna get better...
As Duster points out, the cross-grain cleat on the end is the main problem.
Additionally, if "air dried" means in equilibrium with exterior conditions, the lumber should have been dried further to match its intended use.
The maker should redo the top after reviewing proper construction related to predictable moisture related wood movement.
Your questions, answered:
1. Cross grain construction inhibiting the free movement of wood across grain is the direct result of not using a professional woodworker of good reputation. This is typically caused by a drive to save money, and asking the wrong person/people to do something they are not qualified to do.
2. Have the builder rework the top correctly and for no cost to you. But first, insist he learn his errors and know how to correct them. If he refuses, find a professional shop to do the work.
1. 20 months air drying sounds good, but what is the moisture content of the wood? It can be used with as high as 12-14% MC, but the construction details are even more important. The top will move more than a kiln dried top as it reaches the EMC- equilibrium moisture content. Movement is OK, as long as it is understood and accommodated by the builder.
2. Do away with the glass top. That solution was from a time (60 yrs ago) when nitrocellulose finishes were so soft they had to be protected. Have a professional finisher spray a catalyzed varnish or lacquer designed for such an application. It will be very durable. Keep in mind that wood tables will age and not be perfect surfaces. They will reflect the life and activities of the household, as they should.
Since the builder shows no regard for wood movement, he may have glued and screwed the base to the table top, adding to the issue.