Rafter

A rafter is a single length of framing lumber, typically running from a ridge board at the peak down to a top plate on the exterior wall, and a whole roof is framed with many of them set at even spacing, commonly every 16 or 24 inches.

Building a roof with rafters is called stick framing, because each piece is cut and set in place on site rather than arriving as a finished assembly. That makes rafter framing more labor-intensive to build than a factory-built alternative, but it also leaves an open, usable attic space underneath, since there is no internal webbing running through the middle of the roof cavity.

Rafter size and spacing are not arbitrary. A structural calculation, based on the roof's span, its pitch, and the snow and wind loads it needs to withstand, sets both the lumber dimension and how far apart the rafters can sit before the roof deck between them starts to flex.

Over decades, rafters can weaken from a source most homeowners never see: a slow leak that keeps a section of wood damp for years. Wet lumber loses strength gradually, and a rafter softened by hidden moisture can start to sag under a load it once carried without issue.

Rafters can also be undersized from the start, a shortcut sometimes taken on older additions or informal builds, and a roof framed with rafters too small for its span or its climate load can show a visible dip long before it fails outright.

For a homeowner, rafters generally stay out of sight until a leak, a renovation, or a sagging roofline brings them into the conversation. A soft or spongy feel underfoot in the attic, or a visible dip in the roofline from the street, is worth having looked at, since it usually points to a rafter or the decking above it rather than the shingles themselves.