Spot the Violation

FramingStairs, guards & handrailsLevel 12018 IRC

Back-door landing steps

The back door of a house with gray lap siding, seen straight on, with its top cut off by the frame. A pressure-treated wood landing sits in front of the door, and a short wood stair runs down from the landing to a concrete patio, parallel to the house wall, so the notched stringer is seen from the side. The stair has two treads, each made of two 2x6 boards, three risers in all, and no handrail. A yellow tape measure stands on the lower tread with its hook over the edge of the upper tread and reads 8 1/2. A downspout, a hose bibb, a wall lantern and a clay planter with a few fallen leaves are along the wall. 8 1/2
Back-door landing and steps to the patio

What's wrong here?

  1. The risers are about 8-1/2 in. tall, over the 7-3/4 in. maximum
  2. A handrail is required on this stair
  3. Open risers are not allowed on an exterior stair
  4. Nothing. This installation is compliant
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Show the answer and the code reference

The answer

The risers are about 8-1/2 in. high; the maximum riser height for a dwelling stair is 7-3/4 in.

Correct choice: 1. The risers are about 8-1/2 in. tall, over the 7-3/4 in. maximum

R311.7.5.1 caps riser height at 7-3/4 in., measured vertically between the leading edges of adjacent treads, and R311.7 applies the stairway rules to any stair serving a building, porch or deck, including short exterior steps like these. Short exterior runs like this one are often built by dividing the landing height into as few steps as possible: about 25-1/2 in. split three ways gives 8-1/2 in. risers. Tall risers break the walking rhythm, and they are worst on exactly the stairs people use carrying groceries, in the dark, and on ice. The treads (two 2x6s, about 10 in. nosing to nosing) and the lack of a handrail on a three-riser flight are fine.

How to fix it

Rebuild the stair with four risers of about 6-3/8 in. (25-1/2 in. divided by 4), recutting the stringer and adding a tread; that also triggers a handrail on at least one side because the flight then has four risers. Alternatively, raise the patio or add a lower step so no riser exceeds 7-3/4 in. and all risers in the flight stay within 3/8 in. of each other.

Code references

  • IRC 2018 R311.7.5.1 — Risers

    The maximum riser height is 7-3/4 in., measured vertically between the leading edges of adjacent treads, and the greatest riser height in a flight may not exceed the smallest by more than 3/8 in. Open risers are permitted if openings more than 30 in. above the floor or grade below do not pass a 4 in. sphere.

    Drills citing R311.7.5.1

  • IRC 2018 R311.7.8 — Handrails

    Handrails are required on at least one side of each flight of stairs with four or more risers.

    Drills citing R311.7.8

  • IRC 2018 R311.7 — Stairways

    Where required by the code or provided, stairways must comply with R311.7. The exceptions are stairways not within or serving a building, porch or deck; stairways leading to nonhabitable attics; and stairways leading to crawl spaces.

    Drills citing R311.7

2024 IRC:renumbered to R318.7.5.1. The 2024 IRC reorganized Chapter 3 and moved stairways from R311.7 to R318.7; secondary sources place the 7-3/4 in. maximum riser and 3/8 in. variation at R318.7.5.1 with the requirement unchanged. Not checked line by line against the printed 2024 IRC. Confidence: low

Minnesota

MN adopts this rule as writtenConfidence: medium

Minnesota adopts the 2018 IRC with Minnesota amendments as the Minnesota Residential Code (Minn. Rules ch. 1309). No Minnesota amendment to R311.7.5.1 is known. Minn. Rules 1309.0311 amends parts of IRC R311; search summaries describe a replacement for R311.7.1 that spells out which stairways are covered, including exterior stairs to grade, but the Minnesota text could not be read here. DLI is adopting the 2024 IRC as the next edition; see the 2024 IRC note.

About the Minnesota Residential Code

Why the other choices are wrong

  • A handrail is required on this stair. A handrail is required only on a flight with four or more risers (R311.7.8); this one has three.
  • Open risers are not allowed on an exterior stair. Open risers are permitted on dwelling stairs. The 4 in. sphere limit applies only to riser openings more than 30 in. above the floor or grade below (R311.7.5.1), and this whole stair rises about 25-1/2 in.
  • Nothing. This installation is compliant. Each riser measures about 8-1/2 in., 3/4 in. over the 7-3/4 in. maximum in R311.7.5.1.
Safety hazardLevel 1 · Apprentice#stair#riser height#exterior#landing

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