Japanese Stair Rules: Riser, Tread & Guard Heights

The requirement

For a private house stair in Japan, each riser can be up to 230 mm tall. Each tread must be at least 150 mm deep. The stair must be at least 750 mm wide. The numbers sit in the Enforcement Order (施行令), Art. 23, made under the Building Standard Law.

Two words to know first. The riser (蹴上げ) is how tall each step is. The tread, or going (踏面), is the flat part you stand on.

Yes, 230 mm is steep. It is much steeper than the usual European figures. That is not a translation error. It is the current, in-force Japanese law (Art. 23 §1, proviso). The proviso covers a single dwelling’s own private stair only. A shared stair in a multi-unit apartment block (共同住宅の共用階段) does not get that private-stair exception. Select its table row by use and floor area; 220 mm rise and 210 mm tread apply only to row (4).

There is no combined “2R+G” comfort check in Japan. Riser and tread are two separate fixed limits. Set them out on their own.

Width. A private house stair needs a clear width of at least 750 mm. That is row (4) of the general Table in Art. 23 §1, the default row for a house. Rows (1)–(3) cover school stairs, large-shop or theatre stairs, and stairs serving a large upper-floor or basement room. Check the floor-area triggers before choosing row (4). A large dwelling can meet row (3). Outdoor stairs also have their own width proviso. The private-dwelling exception sets rise and tread, not all widths.

Landing. A landing is only needed when a straight run climbs more than 4 m. The trigger sits in the same row (4) that sets the width. Where a landing is needed, a straight-run landing must be at least 1.2 m (1,200 mm) deep (Art. 24). A normal 2-storey Japanese house rises about 2.7–2.9 m. That is under the 4 m trigger. So many house stairs need no landing at all by law.

Handrails & guards

Art. 25 §1 requires a handrail, subject to §4: the first three paragraphs do not apply to stair portions no more than 1 m high. But the law fixes no handrail height anywhere in the primary text. The height figures you hear quoted are trade practice and good sense, not a legal number. A side with no handrail needs a side wall or equivalent instead (§2). A stair wider than 3 m needs a middle handrail (§3). The exception needs a rise of at most 150 mm and a tread of at least 300 mm. Check §4 as well.

There is no fixed guard height at a stair edge either. For the open side of a stair or landing, “a side wall or equivalent” is all Art. 25 §2 asks for.

The 1.1 m figure is for balconies, not stairs. Art. 126 asks for a guard-wall, fence or wire mesh at least 1.1 m (1,100 mm) high. That applies around a rooftop terrace, or a balcony on the 2nd storey or above. But Art. 117 limits where that chapter (Chapter 5 §2) applies. It lists special-use buildings such as schools, hospitals, shops, theatres and hotels. It lists buildings of 3 or more storeys. It lists buildings with a windowless habitable room. And it lists buildings over 1,000 m² of floor area. A normal 1–2 storey detached house under 1,000 m² is not on that list. So the 1.1 m figure is not a hard legal minimum for it. Build to 3 storeys, though, and the figure binds.

One last thing. The law has no baluster-gap or “sphere” rule for stairs or balconies. The gap figure people often quote comes from a separate housing standard. Following that standard is a choice, not the code.

Work it out on site

Say the floor-to-floor height is 2800 mm, and it is a private house stair.

1. Pick the riser count. 2800 ÷ 230 (the tallest legal riser) = 12.2. You cannot have part of a step, so round up to 13 risers. 2800 ÷ 13 ≈ 215.38 mm per riser. That clears the 230 mm limit with room to spare.
2. Set the tread. Try 150 mm, the minimum. For one straight flight with the upper floor as the final tread, thirteen risers give 12 goings. So the stair runs 12 × 150 = 1800 mm along the floor. That short run is one reason a Japanese stair fits a tight footprint. Got more room? A tread deeper than 150 mm is kinder on the legs.
3. Check the landing trigger. 2800 mm of rise is well under 4 m. So no landing is needed by law on this run.

Keep the full quotient for setting out; 13 rises of exactly 215 mm would finish 5 mm short. The calculator gives geometry, not a code approval.

Do it in 5 seconds

Related

• Japanese building-rules hub — how the one national Law and its Enforcement Order work.
• Japanese ramp gradients — the same Enforcement Order sets the ramp figures too, applied through the same articles.

Sources

• Building Standard Law Enforcement Order (建築基準法施行令), Art. 23 (riser, tread, width), Art. 24 (landing), Art. 25 (handrail, side-wall requirement), Art. 117 and Art. 126 (balcony/rooftop guard height and its building-scope carve-out). Read the current consolidated text at laws.e-gov.go.jp.

Read this first. Japan’s Building Standard Law and Enforcement Order are a single, continuously-amended text, not a series of discrete editions — the official e-Gov law database always serves the current version, checked here as of 29 July 2026. The figures above are for a normal single-family/detached dwelling’s own private stair; a multi-unit apartment building’s shared stair sits under stricter figures, and the 1.1 m balcony-guard figure only binds larger, taller or special-use buildings, as explained above. Local governments can add supplementary ordinances on top of the national minimums. Always confirm the current text at laws.e-gov.go.jp or mlit.go.jp before you build to these figures.