Japanese Ramp Gradients: Slope, Landings & Width

The requirement

A general ramp in Japan can be no steeper than 1/8 (12.5%). The figure sits in the Building Standard Law Enforcement Order, Art. 26 §1, item 1. It covers any ramp built in place of stairs. It applies to every building, with no size or use carve-out. So it binds an ordinary house too.

The surface has its own rule. It must be rough-finished or a non-slip material (Art. 26 §1, item 2). The Order names no numeric slip-resistance coefficient. It is a quality test, not an mm value.

Landing, width and handrail come from the stair rules. Art. 26 §2 applies the stair articles to a ramp as well. Only the riser and tread parts drop out. A ramp has neither.

• Landing: needed only where a straight run climbs more than 4 m. Same trigger as a house stair. Where one is needed, it must be at least 1.2 m (1,200 mm) deep.
• Width: select the applicable Art. 23 row and outdoor-stair proviso. 750 mm is the row (4) baseline, not a rule for every ramp.
• Handrail: apply Art. 25, including its paragraph 4 exception for portions no more than 1 m high. This article sets no numeric rail height.

This 1/8 is not the accessible-ramp figure. Japan runs a second, stricter standard for accessible design. It sits in the order under the barrier-free law (バリアフリー新法施行令, formally 高齢者、障害者等の移動等の円滑化の促進に関する法律施行令, Cabinet Order No. 379/2006). On an accessible route, the slope must be no steeper than 1/12. It can relax to 1/8 where the rise is 160 mm or less (Art. 19 §2 item 4). The same figure applies to site paths under item 7. Under Art. 13, a handrail is required on a sloping part if its slope exceeds 1/12 or its rise exceeds 160 mm. A gentle slope alone does not remove that height trigger.

The current order’s Art. 4 lists specified building uses; an ordinary private detached house is not listed. Art. 5 defines a narrower special category. Building use, size, work type and local ordinances determine which duties apply. Do not treat the Art. 4 list alone as the full legal test.

For accessible routes, Art. 19(2)(4) also sets width and intermediate landing rules. A ramp replacing stairs needs 1.2 m width; one alongside stairs needs 0.9 m. Above 750 mm total rise, provide landings at no more than 750 mm rise intervals, with at least 1.5 m depth. Site paths have separate wording in item 7, including a slope condition on that landing rule.

Work it out on site

Say you are building a general ramp up a change of level of 300 mm. It is a plain ramp, not an accessible route under the barrier-free law. How long does it need to be?

1. Apply the 1/8 limit. At 1/8, the run is 8 × the rise. 300 mm × 8 = 2400 mm (2.4 m) of run.
2. Check the landing trigger. A 300 mm rise is well under the 4 m trigger. No mid-ramp landing is required. Just level ground at the top and bottom.
3. Check the width. Keep the ramp at least 750 mm clear.

So: about 2.4 m of run at 1/8, and 750 mm wide. The slope calculator does the rise-over-run maths for you.

Do it in 5 seconds

Related

• Part of the Japanese building-rules hub — the hub, with the Enforcement Order articles that set the rules.
• Building the stairs that ramp might replace? See Japanese stair rules.

Sources

• Building Standard Law Enforcement Order (建築基準法施行令), Art. 26 (general ramp gradient and surface, and its cross-reference to Art. 23–25 for width, landing and handrail). Read the current consolidated text at laws.e-gov.go.jp.
• 高齢者、障害者等の移動等の円滑化の促進に関する法律施行令 (barrier-free law enforcement order, Cabinet Order No. 379/2006), Art. 19 §2 item 4 (accessible-route ramp gradient/width/landing), Art. 13 (general-standard ramp handrail-exemption threshold), Art. 4 (特定建築物 scope list). Value and article confirmed against MLIT’s own official checklist PDF: mlit.go.jp. The current official e-Gov order was checked for Arts. 4, 5, 13 and 19. Older checklists may use Art. 18 for the route provision; the current text uses Art. 19.

Read this first. The general ramp and accessible-route rules have separate scopes. Confirm the current national text and local additions for the building and route. These calculations do not establish an exemption or a complete accessible design.