Keeping solid doors flat

      Techniques for preventing warpage of solid wood cabinet doors. June 14, 2000

A customer of mine is requesting that I build her kitchen cabinet doors out of 3/4-inch solid oak panels with routed edges.

I expressed my concerns to her about the panels warping, but she still wants them, so I am planning on the following to ensure the doors remain as flat as possible:

1. Ensure that the moisture content of the wood is consistent throughout all boards used, about 9 percent.

2. Rip all boards down to 3 inches or less, and alternate growth rings when gluing up.

3. Apply three heavy coats of lacquer to ensure an adequate seal.

My question: Is there anything else I should do to keep the doors flat? Here in Minnesota we have extreme temps and humidity/dryness so I need to take all precautions.

I've sold doors like that for years, and was intimidated by them at first. I've had few problems, though.

My lumber's usually at around 6 percent when I glue up, but settles to around 8 percent here in Oregon. I often use boards from 5 to 8 inches wide and don't alternate growth rings, but rather assemble for color. I've always had doors finished ASAP, ensuring that the end grain is sealed as well.

No matter how you construct, if a door is exposed to harsh direct sunlight it will cup to some degree. (In the shop you can turn it around and it will cup the other way.) Keep your doors as narrow as possible, especially if they may lay in the sun's way.

We used to put an 1.75-inch-wide batten across the back of the door, usually about 2 inches shorter than the width of the door. We used three screws, and NO GLUE.

We always did this after finishing and really never had any problems.

The moisture content (MC) in Minnesota is closer to 6 percent than 8 percent. So go for this drier MC. Double-check it with a good MC meter (costing over $250).

Alternate the lumber end for end and top for bottom, both.

Do not use a cleat on the back side, unless you also allow for the screws to move as the door changes MC (slotted holes and pan head screws with washers).

Use 6 percent MC lumber (this is key, so I repeat it), especially in Minnesota.

Spar varnish will provide more moisture barrier than many lacquers. Coat all sides, edges, faces, etc.

Buy a portable relative humidity (RH) measuring device at Radio Shack for under $30 and measure the humidity in the home in question, or in your own home. If you see the RH is about 30 percent, then 6 percent MC is what you need. It is possible that the RH may be under 25 percent, but in the summer, it will be a little higher.
Gene Wengert, forum moderator

Would you like to add information to this article?
Interested in writing or submitting an article?
Have a question about this article?

Have you reviewed the related Knowledge Base areas below?
  • KnowledgeBase: Cabinetmaking: Cabinet Door Construction

  • KnowledgeBase: Cabinetmaking: General

  • KnowledgeBase: Finishing: General Wood Finishing

  • KnowledgeBase: Wood Engineering: General

  • KnowledgeBase: Knowledge Base

    Would you like to add information to this article? ... Click Here

    If you have a question regarding a Knowledge Base article, your best chance at uncovering an answer is to search the entire Knowledge Base for related articles or to post your question at the appropriate WOODWEB Forum. Before posting your message, be sure to
    review our Forum Guidelines.

    Questions entered in the Knowledge Base Article comment form will not generate responses! A list of WOODWEB Forums can be found at WOODWEB's Site Map.

    When you post your question at the Forum, be sure to include references to the Knowledge Base article that inspired your question. The more information you provide with your question, the better your chances are of receiving responses.

    Return to beginning of article.

    Refer a Friend || Read This Important Information || Site Map || Privacy Policy || Site User Agreement

    Letters, questions or comments? E-Mail us and let us know what you think. Be sure to review our Frequently Asked Questions page.

    Contact us to discuss advertising or to report problems with this site.

    To report a problem, send an e-mail to our Webmaster

    Copyright © 1996-2016 - WOODWEB ® Inc.
    All rights reserved. No part of this publication may be reproduced in any manner without permission of the Editor.
    Review WOODWEB's Copyright Policy.

    The editors, writers, and staff at WOODWEB try to promote safe practices. What is safe for one woodworker under certain conditions may not be safe for others in different circumstances. Readers should undertake the use of materials and methods discussed at WOODWEB after considerate evaluation, and at their own risk.

    WOODWEB, Inc.
    335 Bedell Road
    Montrose, PA 18801

    Contact WOODWEB

  • WOODWEB - the leading resource for professional woodworkers

      Home » Knowledge Base » Knowledge Base Article