# Japanese Building Rules: One National Rule Book Japan builds to one national Building Standard Law, with the exact numbers set in its Enforcement Order — no prefecture-by-prefecture split. Here are the rules and the calculators that solve them. - Canonical HTML: https://www.chippy.tools/building-codes/jp/ - Publisher: Chippy Tools - Language: en - Updated: 2026-09-21 [Browse all topics](https://www.chippy.tools/building-codes/topics/)[Free web tools](https://www.chippy.tools/building-codes/tools/)[Printable references](https://www.chippy.tools/building-codes/printables/) [All countries](https://www.chippy.tools/building-codes/) [Japan](https://www.chippy.tools/building-codes/jp/) Topics Stairs - [Japanese Stair Rules: Riser, Tread & Guard Heights](https://www.chippy.tools/building-codes/jp/stairs/stair-and-guard-requirements/) Footings - [Japanese Foundation Rules: Depth, Concrete & Rebar Cover](https://www.chippy.tools/building-codes/jp/footings/footing-depth-and-concrete/) Room heights - [Japan's Minimum Ceiling Height: 2.1 m, Fixed](https://www.chippy.tools/building-codes/jp/rooms/minimum-ceiling-heights/) Ramps - [Japanese Ramp Gradients: Slope, Landings & Width](https://www.chippy.tools/building-codes/jp/ramps/ramp-gradients/) Wet areas - [Japan Wet-Room Waterproofing: Standards and System Details](https://www.chippy.tools/building-codes/jp/wet-areas/waterproofing-requirements/) Calculation guides - [Concrete Calculations: The Complete On-Site Guide](https://www.chippy.tools/building-codes/concrete/concrete-calculations-guide/) - [How to Calculate Concrete Volume for a Slab](https://www.chippy.tools/building-codes/concrete/concrete-volume-slab/) - [How Many Bags of Concrete Per m³? (20kg, 25kg, 40kg)](https://www.chippy.tools/building-codes/concrete/bags-of-concrete-per-m3/) - [Concrete for Post Holes: Volume Per Hole & Bags Needed](https://www.chippy.tools/building-codes/concrete/concrete-post-holes/) - [Concrete Mix Ratios Explained: 1:2:3, 1:2:4 & Water-Cement Ratio](https://www.chippy.tools/building-codes/concrete/concrete-mix-ratios/) - [Roof Pitch to Angle: Convert Rise/Run to Degrees & Grade](https://www.chippy.tools/building-codes/concrete/roof-pitch-to-angle/) - [Rafter Length Calculation: Run, Rise & Overhang](https://www.chippy.tools/building-codes/concrete/rafter-length/) - [Stair Rise & Run Setout: Riser, Going & the 2R+G Formula](https://www.chippy.tools/building-codes/concrete/stair-rise-and-run-setout/) - [How to Convert a Fall or Gradient: Ratio, Percentage & Degrees](https://www.chippy.tools/building-codes/concrete/fall-and-gradient-conversion/) - [Stud & Joist Spacing Takeoff: How Many at 400, 450 & 600 mm Centres](https://www.chippy.tools/building-codes/concrete/stud-and-joist-spacing-takeoff/) - [Gravel & Base Volume: Compacted Depth vs Loose-Fill Order Quantity](https://www.chippy.tools/building-codes/concrete/gravel-and-base-volume/) In this section [Browse all topics](https://www.chippy.tools/building-codes/topics/)[Free web tools](https://www.chippy.tools/building-codes/tools/)[Printable references](https://www.chippy.tools/building-codes/printables/) [All countries](https://www.chippy.tools/building-codes/) [Japan](https://www.chippy.tools/building-codes/jp/) Topics Stairs - [Japanese Stair Rules: Riser, Tread & Guard Heights](https://www.chippy.tools/building-codes/jp/stairs/stair-and-guard-requirements/) Footings - [Japanese Foundation Rules: Depth, Concrete & Rebar Cover](https://www.chippy.tools/building-codes/jp/footings/footing-depth-and-concrete/) Room heights - [Japan's Minimum Ceiling Height: 2.1 m, Fixed](https://www.chippy.tools/building-codes/jp/rooms/minimum-ceiling-heights/) Ramps - [Japanese Ramp Gradients: Slope, Landings & Width](https://www.chippy.tools/building-codes/jp/ramps/ramp-gradients/) Wet areas - [Japan Wet-Room Waterproofing: Standards and System Details](https://www.chippy.tools/building-codes/jp/wet-areas/waterproofing-requirements/) Calculation guides - [Concrete Calculations: The Complete On-Site Guide](https://www.chippy.tools/building-codes/concrete/concrete-calculations-guide/) - [How to Calculate Concrete Volume for a Slab](https://www.chippy.tools/building-codes/concrete/concrete-volume-slab/) - [How Many Bags of Concrete Per m³? (20kg, 25kg, 40kg)](https://www.chippy.tools/building-codes/concrete/bags-of-concrete-per-m3/) - [Concrete for Post Holes: Volume Per Hole & Bags Needed](https://www.chippy.tools/building-codes/concrete/concrete-post-holes/) - [Concrete Mix Ratios Explained: 1:2:3, 1:2:4 & Water-Cement Ratio](https://www.chippy.tools/building-codes/concrete/concrete-mix-ratios/) - [Roof Pitch to Angle: Convert Rise/Run to Degrees & Grade](https://www.chippy.tools/building-codes/concrete/roof-pitch-to-angle/) - [Rafter Length Calculation: Run, Rise & Overhang](https://www.chippy.tools/building-codes/concrete/rafter-length/) - [Stair Rise & Run Setout: Riser, Going & the 2R+G Formula](https://www.chippy.tools/building-codes/concrete/stair-rise-and-run-setout/) - [How to Convert a Fall or Gradient: Ratio, Percentage & Degrees](https://www.chippy.tools/building-codes/concrete/fall-and-gradient-conversion/) - [Stud & Joist Spacing Takeoff: How Many at 400, 450 & 600 mm Centres](https://www.chippy.tools/building-codes/concrete/stud-and-joist-spacing-takeoff/) - [Gravel & Base Volume: Compacted Depth vs Loose-Fill Order Quantity](https://www.chippy.tools/building-codes/concrete/gravel-and-base-volume/) [Building Codes](https://www.chippy.tools/building-codes/) Japan # Japanese Building Rules: One National Rule Book Japan builds to one national Building Standard Law, with the exact numbers set in its Enforcement Order (施行令) — and local ordinances can add requirements. Check the building type, current text and local rules for stairs, ramps, footings and room heights. This hub carries the figures straight from the Enforcement Order's articles, and flags plainly where a number (like foundation depth) is genuinely left to a further notification or structural calculation rather than fixed nationally. ## Rules by topic Find guidance for the work you are doing, then confirm the requirements for your building and location. ### Stairs - [Japanese Stair Rules: Riser, Tread & Guard Heights](https://www.chippy.tools/building-codes/jp/stairs/stair-and-guard-requirements/) ### Footings & slabs - [Japanese Foundation Rules: Depth, Concrete & Rebar Cover](https://www.chippy.tools/building-codes/jp/footings/footing-depth-and-concrete/) ### Room heights - [Japan's Minimum Ceiling Height: 2.1 m, Fixed](https://www.chippy.tools/building-codes/jp/rooms/minimum-ceiling-heights/) ### Ramps - [Japanese Ramp Gradients: Slope, Landings & Width](https://www.chippy.tools/building-codes/jp/ramps/ramp-gradients/) ### Wet areas - [Japan Wet-Room Waterproofing: Standards and System Details](https://www.chippy.tools/building-codes/jp/wet-areas/waterproofing-requirements/) ## One rule book for the whole country Japan builds to **one** national law. There’s no prefecture-by-prefecture or city-by-city technical code — whether you’re building in Tokyo, Osaka or a rural site in Hokkaidō, the same national minimums apply. Local governments can and do add their own ordinances (条例) on top — most commonly a regional frost-depth figure for foundations, or stricter fire-area rules in some municipalities — but the core technical numbers a chippy sets out on site come from one national instrument. That instrument has two layers: - **The Building Standard Law (建築基準法, “BSL”)** — the Act itself, which sets out the general duties (a stair must be safe to climb, a foundation must safely carry its loads) and a handful of numbers directly, like the natural-light and ventilation ratios for a habitable room. - **The Enforcement Order (建築基準法施行令, “the Order”)** — a Cabinet Order made under the Law that carries almost all of the actual mm and metre figures: stair rise and going, ramp gradient, ceiling height, rebar cover and more. When a chippy or a builder says “the code says,” this is usually the document they mean. ## Where the numbers come from — and where they don’t Some figures are fixed hard, nationally, with no wiggle room — a habitable room’s ceiling height, for instance, is a flat **2.1 m minimum**, no exceptions. Others are deliberately left **design-driven** rather than fixed — a foundation’s depth is set by a structural calculation against your site’s ground-bearing capacity and a further Ministry notification, not by a number printed in the Law or Order themselves. And some figures that get quoted informally turn out, once you check the primary text, to only apply to certain buildings — a stair or ramp’s rise/going/gradient limits bind every building, but the 1.1 m balcony-guard figure, for example, is scoped to larger, taller or special-use buildings and isn’t automatically part of an ordinary 1–2 storey house’s legal minimums. This hub is built to tell you plainly which is which, rather than printing a number that sounds authoritative but doesn’t actually apply to your job. **A note on steepness.** Japan’s house-stair figures — riser up to 230 mm, tread down to 150 mm — are genuinely steeper than what’s typical in European codes. That’s not a translation slip; it’s the literal, current figure in the Enforcement Order for a private dwelling stair, and it’s shown here exactly as the law gives it. Japan’s Law and Order are a single, continuously-amended text rather than a series of discrete “editions” — the official [e-Gov](https://laws.e-gov.go.jp/) law database always serves the current, consolidated version. Always confirm the current text there, or at [mlit.go.jp](https://www.mlit.go.jp/), before you rely on any figure for a live job. This page is general information for tradespeople and is not compliance, engineering or legal advice. Requirements are subject to state and territory variations and adoption timing. Always confirm requirements with your building certifier and relevant state authority. ## Page directory - [Japan Wet-Room Waterproofing: Standards and System Details](https://www.chippy.tools/building-codes/jp/wet-areas/waterproofing-requirements/index.md): Check the project spec, JASS 8 edition and bathroom system before choosing membrane details. A unit bath still needs correct site joints and connections. - [Japan's Minimum Ceiling Height: 2.1 m, Fixed](https://www.chippy.tools/building-codes/jp/rooms/minimum-ceiling-heights/index.md): The Japanese Building Standard Law sets a hard 2.1 m minimum ceiling height for a habitable room, plus light and ventilation checks, including the conditional daylight exception — from the Enforcement Order and the Law itself. - [Japanese Foundation Rules: Depth, Concrete & Rebar Cover](https://www.chippy.tools/building-codes/jp/footings/footing-depth-and-concrete/index.md): Japan's strip-footing dimensions — embedment ≥240 mm, base slab ≥150 mm thick, stem ≥300 mm high and ≥120 mm thick — from MLIT Notification No. 1347/2000, plus concrete strength (≥12 N/mm²) and rebar cover (20–60 mm) from the Enforcement Order. - [Japanese Ramp Gradients: Slope, Landings & Width](https://www.chippy.tools/building-codes/jp/ramps/ramp-gradients/index.md): The Japanese Building Standard Law figure for a general ramp replacing stairs — slope no steeper than 1/8, 750 mm width, 1.2 m landings — from the Enforcement Order, Article 26. - [Japanese Stair Rules: Riser, Tread & Guard Heights](https://www.chippy.tools/building-codes/jp/stairs/stair-and-guard-requirements/index.md): The Japanese Building Standard Law numbers for a house stair — riser up to 230 mm, tread down to 150 mm, 750 mm width — from the Enforcement Order, materially steeper than typical European figures.