They may sag, and I would provide a strongback along the front
edege......You will be amazed how much this helps with rigidity. Strongback
like a 1x2 or 1x3.....
I also dado the shelves and glue into the sides and make sure to cleat or
nail the back.
Glue all members.....
jloomis
"Jeff D." wrote in message
...
I'm building a wall of storage shelving for my 45 record collection (appx.
20,000). The records are stored 200/box and each box is 16x8x9, weighing
15lbs. Will 3/4" plywood shelving 4 feet long support this load without
deflecting, each shelve will be loaded to 75lbs with supports on the ends
only.