What is the best way to build large shelves?
Well, you don't want the edge of the plywood showing across the front. So a nosing of hardwood that will match your nearby woodwork or furniture would suffice at probably 1.5" depth. Rabbit 3/4" (plywood thickness) out of the back of the top edge, leaving about 1/4 or 3/8 to flush with the top surface of the plywood. This will give you a professional decorative edge across the front edge, and hardwood will be strong enough to keep the bow out of the shelves if you don't go crazy loading them up. Be sure the hardwood goes all the way to the wall (mitered) on both ends. This will mean you have to hold the side supports short by the thickness of the hardwood, and likely angle and bevel their ends back for aesthetics.
If you DO need to put a lot of weight on these shelves, you can back up the hardwood underneath the shelves with a 3/4 x 3/4 piece of angle iron, running the full length of the front. 3/4 will hide behind the hardwood.
The side suports do not have to be all that big because you will be screwing (and gluing?) them to the two walls of the corner. 1.5" deep and 3/4 thick will be fine... and will not hang below the front nosing too much.
If this is to carry a lot of weight out in the laundry room or garage, just throw up a 2x4 under the front edge. Miter it to match your ends.
"True eloquence consists in saying all that is necessary, and only that which is."
François Duc de La Rochefoucauld
Last edited by Willie T; 01-29-2009 at 10:39 PM.