Article - September 15, 2010
This article was inspired by a question from Steve. He writes:
“I am building a large bookcase and don’t want to add any more support than necessary. Everything will be made from 3/4″ plywood. My plan is to mortise the shelves into the sides of the cabinet and screw the shelves to the back panel. Will that be enough support for a 76″ long shelf?? Will I have problems with sagging??”
The wider a shelf is, the more likely it is to sag. This can make an incredibly attractive bookcase look absolutely dreadful. Screwing the shelves into the back is a great start and will provide a significant amount of support along the length of the shelf. Another similar option would be to install a thicker back panel and rout a dado for the entire back of the shelf to sit in. If that’s not an option you could simply glue in a ledger strip under each shelf.
Here’s another cool option: attaching strips of wood to the shelf itself. A common implementation of this technique involves trimming out the front of the shelf with a 1 – 1 1/2″ wide piece of solid stock. This trim piece will give the shelf a lot of extra support and also give you enough material to rout a decorative profile, which is a nice bonus.
Whenever I have to decide how much support to give a shelf, I start by checking The Sagulator. This is a great online resource for calculating how much deflection to expect using different materials under different loads. Simply fill out the online form and the program tells you how much sag to expect. You just need to decide how much sag is acceptable. The author of the website gives a very helpful tip: “The eye will notice a deflection of 1/32″ per running foot.” You can even factor in the effect of a solid piece of trim at the front of the shelf.
With a little planning and the help of a handy online calculator, sagging shelves will be a thing of the past!
I’m curious what handy tips you guys have for supporting really wide shelves.
The Wood Whisperer is proudly sponsored by brands that Marc trusts. Thank you for making this possible.
Copyright © 2006-2020 The Wood Whisperer Inc. The Wood Whisperer, The Wood Whisperer Guild, TWW, and TWW Guild are trademarks of The Wood Whisperer Inc. All rights reserved. Designed and developed by Underscorefunk Design
This site uses affiliate links. Given this, please assume that any links leading you to products or services are affiliate links that we will receive compensation from. However, there are millions of products and services on the web, and I only promote those products or services that I would use personally. The Wood Whisperer abides by word of mouth marketing standards and holds integrity in the highest regard. Should I ever be compensated to write, I will make full disclosure. I always give honest opinions, findings, and experiences on products. The views and opinions expressed on this blog are purely our own. Any product claim, statistic, quote or other representation about a product or service should be verified with the manufacturer, provider or party in question. All content on The Wood Whisperer is copyrighted, and may not be reprinted in full form without my written consent.