Try these three easy ways to take the sag out of cabinet shelving or to support heavy shelf loads and prevent sagging.
By the DIY experts of The Family Handyman Magazine:November 2011
Install brackets in predrilled holes or drill your own with a right angle drill.
For cabinets with a center stile, build 1x2 bridges. Nail the crosspiece on top of the uprights. Then slide the bridge into place under the shelf.
For cabinets with no center stile, position the crosspiece between the two uprights. Secure with decorative screws and washers.
Stocked up on canned goods, did you? Now the shelves are sagging and you’re looking for a quick fix.
If your cabinet has a center stile, check the back of the stile and the back of the cabinet to see if the manufacturer drilled shelf bracket holes to support the center (Figure A). They’re hard to spot and often ignored by whoever installed the cabinets.
If you find predrilled holes, just buy some brackets at the hardware store and install them. That’ll support the center of the shelf. If there are no holes, you have two choices: You can drill holes or you can make a “bridge” (Figures B and C).
Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.
Avoid last-minute shopping trips by having all your materials ready ahead of time. Here's a list.