taiwan-stair-railing-ramp

name	taiwan-stair-railing-ramp
description	This skill should be used when checking stair dimensional compliance for buildings in Taiwan — minimum stair-and-landing width, riser height, tread depth by building-use category, and the critical handrail-encroachment rule (clear width must remain >= 75 cm regardless of handrails), per Taiwan Building Technical Regulations (Design & Construction) Article 33, Chapter 2 Section 7 (Stairs, Railings, Ramps, Articles 33-39). Railings (Art. 38), handrails (Art. 37) and ramps (Art. 39) are stubbed for later completion.
license	CC-BY-SA-4.0
compatibility	claude-code,opencode,agent-skills
metadata	{"audience":"architects","region":"taiwan","class":"C"}

Taiwan Stair / Railing / Ramp Compliance (建築技術規則 §33–39)

Overview

This skill evaluates stair geometry compliance under Taiwan's Building Technical Regulations (Design & Construction), Chapter 2 "General Design Principles", Section 7 "Stairs, Railings, Ramps" (Articles 33–39). It should be invoked when:

• Determining the minimum required stair / landing width for a building
• Checking riser height (級高) and tread depth (級深) limits
• Resolving whether a handrail eats into the legally required width
• Classifying a building into the correct Article 33 use category

Current scope: Article 33 (stair dimensions) is fully documented. Articles 34/37/38/39 (exemptions, handrails, railings, ramps) are stubs — see Section 4.

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Section 1: Article 33 — Width / Riser / Tread Table

Minimum dimensions depend on the building-use category. Pick the matching row.

#	Use category (用途類別)	Stair & landing width	Riser (級高)	Tread (級深)
1	Stairs for children (elementary schools etc.)	>= 140 cm	<= 16 cm	>= 26 cm
2	School halls, hospitals, theaters, cinemas, dance halls, markets, department stores, assembly halls, amusement venues, etc.	>= 140 cm	<= 18 cm	>= 26 cm
3	Floors where any single floor's habitable area > 200 m², or a basement floor > 200 m²	>= 120 cm	<= 20 cm	>= 24 cm
4	All other buildings (incl. ordinary residences / 住宅)	>= 75 cm	<= 20 cm	>= 21 cm

Residences fall into category 4 — the 75 cm baseline.

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Section 2: The Handrail-Encroachment Rule (the part people get wrong)

Article 33 proviso (verbatim):

「樓梯及平臺寬度二側各十公分範圍內，得設置扶手或高度五十公分以下供行動不便者 使用之昇降軌道；樓梯及平臺最小淨寬仍應為七十五公分以上。」

Translated mechanism:

1. The table width (140 / 120 / 75) is the nominal stair-and-landing width.
2. A handrail (or a <=50 cm assistive lift rail) may sit within 10 cm on each side of that nominal band — i.e. the handrail is allowed to be counted into the nominal width, not added on top of it.
3. But in every case the actual clear (net) width must stay >= 75 cm.

interface StairWidthCheck {
  nominalWidth: number;          // cm — required by Article 33 category
  handrailEncroachLeft: number;  // cm — handrail projection into the band (<=10)
  handrailEncroachRight: number; // cm — (<=10)
}

function clearWidth(s: StairWidthCheck): number {
  return s.nominalWidth - s.handrailEncroachLeft - s.handrailEncroachRight;
}

// Compliant only if BOTH conditions hold:
//   each encroachment <= 10 cm  AND  clearWidth >= 75 cm
function isCompliant(s: StairWidthCheck): boolean {
  const encroachOk = s.handrailEncroachLeft <= 10 && s.handrailEncroachRight <= 10;
  return encroachOk && clearWidth(s) >= 75;
}

Why 75 behaves differently from 120/140

• Category 4 (75 cm): the clear-width floor (75) equals the nominal width. Any handrail encroachment would push clear width below 75 → fails. So a handrail must sit outside the 75 → the 75 is effectively a clear dimension and the structural opening = 75 + handrails. (Practitioner rule of thumb: "75 是有效淨寬， 扶手突出後不足 75 就不行".)
• Categories 1–3 (120 / 140): plenty of slack. 120 − 10 − 10 = 100 >= 75, so handrails on both sides may be counted into the nominal width.

Caution: 90 cm outdoor stairs are not "always count the handrail"

Outdoor direct stairs may be reduced to >= 90 cm (separate provision). But 90 − 10 − 10 = 70 < 75 → you cannot discount handrails on both sides; at most one side (90 − 10 = 80 >= 75). The real test is always "clear width after handrails

= 75 cm", not the width tier.

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Section 3: Related Article 33 notes (verify exact text before relying)

• Outdoor direct stairs (戶外直通樓梯) may be reduced to >= 90 cm.
• Stairs >= 3 m wide generally require an intermediate handrail, unless riser <= 15 cm and tread >= 30 cm. (Commonly cited with §33/§37 — confirm placement when Section 7 is fully built out.)

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Section 4: Stubs — to be completed

Article	Topic	Status
§34	Cases where Art. 33 width does not apply	TODO
§37	Handrails (扶手) — height, continuity, intermediate rails	TODO
§38	Railings / guards (欄杆) — height, anti-climb	TODO
§39	Ramps (坡道) — slope, surface, width	TODO

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Cross-references

• Accessible stairs / accessible handrails → taiwan-accessibility (raw/建築法規/無障礙設計/). Do not duplicate here; link there.
• Means-of-egress stairs (直通樓梯 / 特別安全梯) and evacuation → raw/建築法規/消防安全/.
• General spatial / circulation planning → spatial-planning (raw/建築設計與規劃/設計理論/).

MCP Tool Examples

• taiwan-building-code_search_building_interpretations(query: "樓梯寬度 第33條", limit: 5)
• taiwan-building-code_search_building_code(query: "樓梯", limit: 10)

Source

• 建築技術規則建築設計施工編 §33 — 全國法規資料庫 https://law.moj.gov.tw/LawClass/LawSingle.aspx?pcode=D0070115&flno=33