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) sits under a stricter row. There the riser can be at most 220 mm, and the tread must be at least 210 mm.

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

BSL Enforcement Order Art. 23

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. None of those rows apply to a dwelling.

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

Every stair must have a handrail (Art. 25 §1). 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 mid-span handrail too (§3).

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.

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 mm per riser. That clears the 230 mm limit with room to spare.
Set the tread. Try 150 mm, the minimum. Thirteen risers means 12 treads. 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.
Check the landing trigger. 2800 mm of rise is well under 4 m. So no landing is needed by law on this run.

The calculator does the rounding for you and keeps every riser even.

Do it in 5 seconds

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.

Frequently asked questions

What is the maximum riser and minimum tread for a house stair in Japan?

Riser no more than 230 mm. Tread no less than 150 mm. That is Enforcement Order Art. 23 §1, the proviso for a dwelling's own private stair. Yes, that is steeper than most European codes, and it is the real, current figure. A shared apartment stair is stricter: riser up to 220 mm, tread at least 210 mm.

Is there a combined 2R+G comfort check, like in some other countries?

No. The Enforcement Order sets riser and tread as two separate fixed limits. There is no combined walking-line formula. Set out straight to the 230 mm and 150 mm limits.

How wide does a private stair need to be?

At least 750 mm. That is row (4) of the general Table in Art. 23 §1, the default row for a normal house stair. Rows (1)–(3) cover school stairs, large-shop or theatre stairs, and stairs serving a large upper-floor or basement room. None of those apply to a dwelling.

Is a handrail mandatory, and how high does it need to be?

Yes. Every stair needs a handrail (Art. 25 §1). But no handrail height is fixed in the primary text. A side with no handrail needs a side wall or equivalent instead. A stair wider than 3 m needs a mid-span handrail too. Quoted height figures are trade practice, not a legal number.

What guard height applies to a stair, and does the 1.1 m balcony figure apply to my house?

The Order sets no guard height for a stair edge. Art. 25 §2 asks for a side wall or equivalent. The 1.1 m figure (Art. 126) is for rooftop terraces and balconies from the 2nd storey up. Art. 117 limits it to bigger or special buildings. A normal 1–2 storey house under 1,000 m² is outside that. At 3 storeys it binds.