Nearly all homeowners share one common problem - lack of storage space. Regardless of the size of their house, it seems there is never enough room to store everything.

This is true especially for condominium owners and apartment dwellers. Somehow, the longer you live in the same place, the worse the problem gets. Fortunately, easy-to-build shelving systems offer an effective, inexpensive remedy for the do-it-yourselfer.Shelving materials are available at lumber yards and home centers. Shelves are most commonly made from particleboard, plywood or solid lumber and are either 3/4 or 11/2 inches thick.

Edge treatments are often applied to shelves for appearance. They can conceal exposed plywood edges, add rigidity and increase the shelf's load capacity, or simply create a decorative detail to dress up the room.

The exact shelf design you choose is determined by the weight of the items being stored and the look you desire. But remember, you might also want to store heavier items in the future, so it's always better to overbuild the shelves slightly to prevent sagging and possible collapse.

The maximum span for each shelf between supports varies with the load and the material. As a general rule, 3/4-inch particleboard 10 inches wide can handle a load of 30 pounds per linear foot with supports 24 inches apart. You can stretch this span to 32 inches for 3/4-inch plywood. If the shelf is reinforced with 3/4-by-2-inch-wide stiffener along the front edge and a 3/4-by-2-by-6-inch-long support cleat under the rear of the shelf at the middle, you can increase these spans by 50 percent.

Be sure to handpick the boards carefully to avoid loose or oversized knots that would weaken the shelves. Note: If the pine is to be painted, first seal each knot with shellac to keep it from showing through.

Particleboard is the most economical shelving material and is often used under a plastic laminate. The disadvantage of particleboard is that it's heavy and tends to sag if it isn't supported properly.

When the look of fine hardwood shelves is desired, choose hardwood-veneer plywood. This cabinet-grade plywood is less expensive and lighter than solid hardwood, and it's warp-free. Also, extra-wide plywood shelves are made easily without having to edge-join several boards together. Conceal the plywood's exposed edge with veneer tape, trim or a molding.

Shelves can be installed as permanent fixtures in the cabinet or as separate components that can be adjusted or removed, if necessary.

Large cabinets or cabinets without backs often have several adjustable shelves and one fixed shelf. This fixed shelf adds rigidity and strength to the assembly. Fixed shelves for small, lightweight cabinets can be attached with simple butt joints using glue and screws.

However, for a much stronger assembly, you should use dado joints - slots in the end supports - to install permanent shelves.