plywood bookshelves

Hi all,
I am planning a couple of bookshelves to be made from a 1/2 inch plywood, 35x11 inches in size; some shelves will be fixed in 1/4 inch deep dadoes in the sides of the bookcase and others will be "floating", supported by pins inserted in 1/2 inch deep holes. The shelves will only be supported on the sides; not along the length. Should I worry about the sag of the plywood? What's a good length of the shelf that can sustain a load full of books without additional lengthwise support? Thanks! Vlad
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Yes - you might sag, especially with books. Consider doing both of the following:
Upsize your shelf to 3/4 plywood - quite a bit stiffer
Trim the front with a piece of oak about 3/4" wide by 1" or 1-1/4" high. You can route or roll the edges for appearance. It will give you a little more edge stiffness.

in
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I would strongly second RonB's comments. A 36" wide shelf that's only 1/2" thick is bound to sag, especially if not supported along the length. Upgrade to 3/4" plywood at the very least. Wouldn't be surprised to see even the 3/4" sag if you don't use the oak/hardwood trim piece at the front edge of the shelf.
If you have access to it, Andy Rae's "The Complete Illustrated Guide to Furniture & Cabinet Construction" has lots of useful info relevant to what you're asking about.

in
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

My son has a creative punker friend who is only 17, he made a set of (adjustable) shelves from 3/4 rough slabs and barb wire and nothing else. They are suspended from a ceiling beam. Ouch! They actually look pretty good.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

1/2" plywood will sag to much for a 35" wide shelf full of books. Unless you use 3/4" ply or add some kind of bracing or stiffener, you probably should keep the length around 12" or so for 1/2" plywood.
--

Larry Wasserman Baltimore, Maryland
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
http://www.woodbin.com/calcs/sagulator.htm
: Hi all, : : I am planning a couple of bookshelves to be made from a 1/2 inch plywood, : 35x11 inches in size; some shelves will be fixed in 1/4 inch deep dadoes in : the sides of the bookcase and others will be "floating", supported by pins : inserted in 1/2 inch deep holes. The shelves will only be supported on the : sides; not along the length. Should I worry about the sag of the plywood? : What's a good length of the shelf that can sustain a load full of books : without additional lengthwise support? : Thanks! : Vlad : :
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
How about an inch wide strip of 3/4 ply supporting the shelves lengthwise both at the front and at the back of the shelf? Would this help? Vlad

plywood,
in
pins
the
plywood?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Why not a nice dadoed vertical strip up the middle front? Looks nice, less work.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

yes. 35" span with books and half-inch ply will most likely sag

Depends on the books. How many copies of Lehninger's Principles of Biochemistry are on them?
I rarely go over 32" with 3/4" plywood. Dunno for 1/2". (Even 32" and 3/4" will sag some, about 1/32nd to 1/16")
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

A 35" span will require 3/4" ply, plus a 1.5" lip on the front to prevent sagging. Rabbet the lip and secure with carpenter's glue and biscuits or finishing nails. If you want super-strong shelves, put a lip on the back as well as the front. Half inch ply is just not practical for heavy loads.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Your shelf will sag about 0.30 inch over a 35" length. Anything over .09" would be noticeable, according to the Sagulator:
http://www.woodbin.com/calcs/sagulator.htm
You'll do well to follow the many suggestions to upgrade the shelf thickness and add stiffener(s).
http://mywebpages.comcast.net/wgoffeney/Woodworking/Woodworking.htm
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Site Timeline

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.