Ledger strips are structural support elements used in timber construction and cabinet making. Typically a ledger strip is a square length of timber attached horizontally to a vertical surface to support one end of a shelf or joist. The joists or shelves are then supported on their opposite ends by a second ledger strip or another sort of support mechanism. A critical part of ledger strip installation is the correct number, type, and spacing of the fasteners used to attach the strip. Nails or screws generally attach ledger strips to the uprights, and a safe average for fastener numbers and spacing is to position one fastener below each joist.
The ledger strip is a common cabinet making and timber frame construction method of supporting horizontally orientated surfaces such as shelves, floors, and decks. The strips are generally square in cross section and located at either end of the construction element they support. When used in the timber construction industry, ledger strips are generally attached to a ledger board. This is a flat length of timber anchored to a wall or frame that serves to evenly spread the load of the joists it supports. There are a number of ways of attaching the joists to the ledger board including joist hangers or ledger strips.
Joist hangers are pressed steel frames sized and shaped to accept standard sized floor joists. These frames are screwed onto the ledger board, and the joists slide into them for support. The ledger strip is a simple, square timber strip screwed or nailed onto the ledger board on top of which the joists rest. The joists may have no profiles cut into them and simply rest on top of the strip, thus butting up against the ledger board. They may also have a square profile cut out of their ends to match the size of the ledger strip which then rests on the ledger strip offering more secure joist placement.
Ledger strips are often found in cabinet making and shop fitting as an alternative for pegs or brackets to support shelves and cabinet tops. These strips are simply nailed or screwed into place at the shelf position and the shelf board placed on top of them. In both cases, the correct fastener types and their spacing is critical to the integrity of the ledger strips. Although the types of fasteners and their spacing differs from job to job, it is generally accepted that joist bearing ledger strips feature three fasteners at each joist position with one placed directly below the joist. Ledger strips that support shelving should have one fastener on either end and one, evenly spaced, for every 25% of the remaining length.