Railing and guard height requirements

A guard is the barrier along an open side of a deck, porch, balcony, stair or landing that keeps people from falling. The code requires one when the walking surface is more than a set height above the floor or grade below, sets a minimum guard height, and limits the size of openings so a small child cannot slip through. Handrails, which you grip on stairs, are a separate requirement with their own height range.

Deck guards are a common inspection item: measure height from the walking surface (or the line of the stair nosings) to the top of the guard, and check the opening limit with the code's sphere test.

The International Residential Code (IRC) is a model code. It is law only where a state or city adopts it, usually with changes, so the wording below shows how the model reads in published government copies, not the rule where you live.

Bonney Lake, WA

2012 IRC

• 30 inches. R312.1.1 Where required. Guards shall be located along open-sided walking surfaces, including stairs, ramps and landings, that are located more than 30 inches (762 mm) measured vertically to the floor or grade below at any point within 36 inches (914 mm) horizontally to the edge of the open side.¹
• 36 inches. R312.1.2 Height. Required guards at open-sided walking surfaces, including stairs, porches, balconies or landings, shall be not less than 36 inches (914 mm) high measured vertically above the adjacent walking surface, adjacent fixed seating or the line connecting the leading edges of the treads.¹
• 4 inches. R312.1.3 Opening limitations. Required guards shall not have openings from the walking surface to the required guard height which allow passage of a sphere 4 inches (102 mm) in diameter.¹

Washington (statewide)

WAC 51-51 (Washington amendments to the 2021 IRC), effective March 16, 2024

• 30 inches. Guards shall be provided for those portions of open-sided walking surfaces, including floors, mezzanines, lofts in accordance with Section R333, stairs, ramps, and landings, that are located more than 30 inches (762 mm) measured vertically to the floor or grade below at any point within 36 inches (914 mm) horizontally to the edge of the open side.²
• 36 inches. R312.1.2 Height. Required guards at open-sided walking surfaces, including stairs, porches, balconies or landings, shall be not less than 36 inches (914 mm) in height as measured vertically above the adjacent walking surface or the line connecting the nosings.²