Frameless Shelf Spans

      Cabinetmakers discuss the span limits of 3/4-inch shelf material, and share tips on mid-span supports and a stiffening valance. December 28, 2005

I'm replacing a 42" wide upper framed cabinet with a new frameless cabinet design. It is 12" deep. It has two doors that will be full overlay. Can I really span 42" with 3/4" melamine and not have the base shelf of other shelves sag? I could use a 3/4" back to provide more support, but is that enough?

Forum Responses
(Cabinetmaking Forum)
From contributor A:
Use two 21", and you will have no call back for saggy shelves.

From contributor B:
42" is too long a span for ordinary shelves. Either put a center panel in it, or use two 21" cabinets. No matter what you use, the lady of the house will put a huge pile of heavy plates right in the center, so you better be prepared for it.

From the original questioner:
Is 36" too long? What about is the max span? I don't want a callback for saggy shelves or saggy bottom.

From contributor C:
For 3/4" thick man made materials I wouldn't span much more than 32", for natural 3/4" wood you can get away with about 42 inches. It also depends on the depth of the cabinet. The deeper the cabinet the more length you can have, to a certain point of course. I would stick with the 32/42 rule.

From contributor D:
I agree with all answers so far. The only thing I would do is follow your suggestion to use minimum of 1/2" or 3/4" back and drill it to match and use shelf supports on the back also. In fact, I would use two rows on the back so the real span would be divided by 3 or 4, i.e. 42" is reduced to 13" maximum.

From the original questioner:
I would drill the 3/4" back for the movable shelves, but what about the bottom shelf - it is just attached to sides and back. Is that okay to span 42?

From contributor D:
That bottom is going nowhere. It is fixed on all sides. Also, you haven't mentioned a center stile, but if you have one then it is really only 21" because the center stile supports it even more. That said, if you could get the customer to approve a center partition, which you hold back so doors close over it, that would solve all your issues.

From the original questioner:
Customer doesn't want center stile. So the bottom of the upper cabinet (which is the bottom shelf) is 42 x 12 connected on 3 sides (actually 2 sides and a back). Will that hold a stack of plates in the middle without sagging? If so, then I can run 3 columns of shelf pins for the moveable ones. If 42" is too wide for the bottom and I put a stile in, would just pocket screws to top and bottom be the right way?

From contributor B:
I should have mentioned before that you should have a valance glued to the front edge of the bottom panel to provide the strength you need, and provide a space under the cabinet for task lighting. I usually use about 2-1/4" x 1" thick stock for this valance. This will easily hold that dreaded stack of plates. You could also use a smaller valance on the shelves, which in combination with the aforementioned pins set in the back panel, will handle any reasonable load she puts on them. I have done this many times in this situation, and have never had a problem. Any shelf larger than 42", in my opinion, needs a torsion box construction with slotted standards.

From contributor D:
I like contributor Bs valance. Raise the floor the height of that valance 1-1/4" so you have a recess for lighting, and use biscuits and Roo Glue for joints into sides, floor etc. Do the same for shelves on front edge. 1-1/4 will give you a 1/2" lip on the bottom and hide shelf pins, plus it looks good. Run edge full and shelf into it. Use L-shaped biscuits and Roo, and dont forget to edgeband the edges of that 1-1/4 piece.

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: Knowledge Base

  • KnowledgeBase: Cabinetmaking

  • KnowledgeBase: Cabinetmaking: Custom Cabinet Construction

  • KnowledgeBase: Cabinetmaking: Residential Cabinetry

    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