Avoiding Warping in an Unfinished Wood Tabletop

A customer has asked for a natural-wood kitchen island table top. Here, pros discuss the risk of warping and how to minimize it. December 15, 2005

We are making a kitchen island for customer who specifies that the table top be solid wood and unfinished without any treatment. With daily use, wiping and cleaning, water gets absorbed into the wood table top and it starts to warp with a slightly bulging center. What can we do to prevent this?

Forum Responses
(Furniture Making Forum)
From contributor A:
Tell the customer what is forthcoming - warping, bowing, splitting and whatever else. Make sure to document his refusal for finishing, along with your recommendations, on the contract. The customer should at least apply a food safe finish.

From contributor B:
Wet the top and wait for the grain to rise, then sand flat. Do this at least twice. Itís not a cure-all but a little better than nothing. As contributor A said, make sure it is documented by the customer that he wanted it without a finish even after you warned him of the damage that will occur without a finish, and the dangers of food contamination in the unsealed grain due to no finish.

From contributor C:
Finish them. Even with finish on wood countertops you can have issues with warping and cracking. Using quartersawn material, laminating epoxy and using narrow laminations (i.e. 3/4" - 1 1/2" wide pieces) is the best way to make a wood countertop stay flat. I have made a few wood countertops and a few butcherblock topped islands and have found that using the above methods saves a lot of headache. When it comes to finish, everyone has his opinion on what is best. I use 3-4 coats of tung oil (on teak I'd use teak oil) and then two or three coats of polyurethane. Finish all the surfaces equally including the bottom.
If the client is concerned with the color darkening when finish is applied you can tint the top coats with an opaque color to match the unfinished appearance.

From the original questioner:
I was told that we could put two pieces of long wood slats underneath the table top to help retaining its shape. Would this work as well? Or is there anything else we can do underneath the table top to make this work?

From contributor D:
To state the obvious, you have given this top room to move with floating fasteners, correct? If not, the top will bulge (across the width) as a reaction to being trapped when it needs to expand. If there are a couple of stout battens crosswise in the cabinet to fasten to, the more likely it will stay flat.

Raw wood in a kitchen is not unusual or something to be feared, as long as it is built correctly, and maintained properly. Ditto on the narrow strips, epoxy, and some kind of finish (we suggest Walnut oil) on all sides. The homeowner or staff must also understand that more water is not better when cleaning, and standing water is not be permitted.

From contributor E:
I don't understand the panic I'm reading by professional furniture makers. It's like you've never made a solid wood top before. I've installed 2 unfinished solid maple tops in restaurant kitchens with zero problems. Go for it.

From Gene Wengert, Sawing and Drying Forum technical advisor:
The thicker the piece, the less it will warp. End grain will warp less than side grain. That is why all the old tops were end grain. Indeed, any safe food finish will not help it avoid warping. The key, as stated, is to avoid a lot of water contact.