Stairs Residential Building Permits

• New stairways must be at least 36 inches wide between walls (above the handrail).
  • In a few cases (like if the new stair is the second stairway), the stairway can be 30 inches wide. This exception does not apply to outdoor stairs, like for deck.
• Spiral stairs must be at least 26 inches wide, measured at and below the handrails.
• Existing stairs. You may want to rebuild the stairway in the same location to make the stairs safer.
  • If space is limited, Portland allows stairs to measure (does not apply to outdoor stairs):
    • 30 inches wide
    • 6 feet and 4 inches for head height
    • 9 inch risers

• For new stairs
  • The riser is the vertical part of the step. For standard stairways, the riser can’t be taller than 8 inches.
  • The tread is the flat surface you step on. The tread must be at least 9 inches deep, not counting the nosing (overhang).
  • The nosing must stick out at least ¾ inch but not more than 1¼ inches.
  • Steps must be consistent. The difference between the tallest and shortest riser or tread can’t be more than ⅜ inch.

Residential stairway dimensions include headroom, step riser, step tread, and nosing.

• Headroom is measured vertically. Measure from the sloped line between tread nosings to the ceiling or any other projection.
• Minimum headroom for new stairs is 6 feet 8 inches.
• For spiral stairs, the minimum is 6 feet 6 inches.

• Exterior doors must have an interior landing at least 3 feet by 3 feet before any steps.
• Required egress door.The interior landing must be no more than 1½ inches lower than the door threshold.
• On the outside of the door, the landing can drop by up to 8 inches before another 3x3 landing is required. This is only allowed if the door doesn’t swing out over the stairs.

• Stairs with more than 3 risers must have a handrail.
• Handrails can stick out up to 4½ inches on each side.
• Handrails must:
  • Run the full length of the stairs
  • Turn back into the wall or end at a post (to prevent catching on clothing or bags)
  • Be 1½ inches away from the wall to allow a proper grip
  • Be 30–38 inches high, measured from the tread nosing
• Handrail shapes:
• • Round rails: 1¼ to 2 inches in diameter
  • Other shapes: 4–6¼ inches in perimeter, with cross-section no more than 2¼ inches

• Guardrails are required if a walking surface is more than 30 inches above the ground or floor. This applies anywhere within 36 inches of an open edge. Examples include decks, landings, or balconies.
• Guardrails must be at least 36 inches high.
• On the open side of stairs, guardrails can be 34 inches high. Measured from the tread nosing.
• Openings in guardrails must prevent:
  • A 4-inch sphere from passing through on decks, balconies, etc.
  • A 5-inch sphere on the open side of stairs
  • A 6-inch sphere between the stair tread and the bottom rail

• Winder stairs turn a corner with triangular-shaped treads.
• The narrowest part of each tread must be at least 6 inches deep.
• Treads must be at least 9 inches wide, measured 12 inches from the narrowest edge. This is known as the walkline, the part of the stairs where people usually walk.
• Steps must be consistent.
  • Risers. The difference between riser heights can’t be more than ⅜ inch.
  • Treads. At the walkline, the deepest tread can’t be more than ⅜ inch deeper than the shallowest one.

• Treads must be at least 6¾ inches deep, measured 12 inches from the narrowest point.
• Riser height can’t exceed 9½ inches.
• The stairs must be at least 26 inches wideat and below the handrails to the center pole.
• All treads must be the same size.