Parapet

A parapet is the top of an exterior wall carried up past the roof surface. On a flat or low-slope desert home it does the visual work: ducts, condensers, and solar all disappear behind one straight line. That is why the form runs through so much North Scottsdale and Paradise Valley design, and why the National Park Service describes Pueblo Revival buildings as having "flat roofs with parapeted walls."

Drainage is the trade-off. With a wall in the way, water cannot run off an eave, so the roof must be drained on purpose. Under IRC Section R903.4, unless a roof sheds over its edges, roof drains go at each low point. Water leaves through scuppers, openings cut through the parapet, or canales, the Southwest version that throws water clear of the wall.

Section R903.4.1 adds a backup: where the perimeter rises above the roof so water gets trapped if the primary drains clog, the code requires secondary overflow drains or scuppers. In a monsoon cell that is not paperwork. Blowing dust packs a scupper, rain follows, and a parapet roof becomes a shallow pool held back by wall flashing.

So a parapet is won or lost at the cap and the inside corner. R903.2 requires flashing that keeps moisture out of joints in copings and at parapet wall intersections. R903.3 requires the wall to be capped, or coped, with noncombustible weatherproof material at least as wide as the wall. IIBEC notes the coping should slope back toward the roof so runoff does not stain the wall.

Height is the other decision. A taller parapet screens taller equipment, but it is still wall, so its top usually counts toward measured building height. A parapet is not a fascia and not an eave, which sit at or below the roof plane. For example, settle how tall a Paradise Valley parapet must be to hide rooftop units before elevations get drawn against the height cap.