tread

The tread is the horizontal surface of a stair or ladder where your foot lands. In a staircase, it spans the full width between the stringers (the angled support beams) and extends from the inner edge to the outer edge, typically 10 to 11 inches deep in residential construction, though commercial stairs often run 12 to 14 inches. The tread is what absorbs the wear and tear of foot traffic, so its material and condition determine both safety and durability.

Treads are manufactured or fabricated to match the riser height above them. Standard residential riser height is 7 to 7.75 inches, and building codes in most jurisdictions specify that tread depth and riser height must be uniform throughout a staircase; inconsistency is a serious trip hazard. The tread's front edge may project slightly beyond the riser below it, a feature called overhang or nosing, which typically measures 1.25 inches and allows the toe room on the step below.

Materials and finishes

Treads are built from wood, steel, concrete, rubber, or tile depending on the application and environment. Wooden treads in homes are typically solid hardwood or plywood with a finish coat; commercial and industrial stairs often use steel plate or stair nosings (metal or rubber edge strips) bolted to steel or concrete structures. Rubber or cast-in-place nosing materials increase grip and reduce noise while extending the usable life of the edge, which takes the most damage.

Slipperiness is the primary failure mode. A wet tread becomes dangerous quickly; outdoor stairs and those in kitchens or wet rooms must have anti-slip surfaces either cast into the material, applied as tape or coating, or built into the nosing itself. Worn treads lose their texture and grip over time. Cracked, splintered, or delaminating wooden treads are structural and safety concerns that require replacement.

The term tread appears in other contexts: on a tire, it is the patterned rubber surface that contacts the road; on a track or athletic facility, it refers to the walking or running surface itself. In stairs specifically, treads work in concert with risers (the vertical faces) to form the complete step. A staircase without risers is called open or floating, and each tread must be reinforced to cantilever or support itself independently.