| name | floor-area-exemption-pitfalls |
| description | This skill should be used when reviewing floor-area-ratio (FAR / 容積) exemption items for buildings in Taiwan and avoiding the gap between nominal drawing dimensions and finished clear dimensions. It covers the elevator/stair lobby (梯廳) FAR-exemption clear-dimension trap and the cross-regulation 'finished clear dimension' pattern where finishing layers (e.g. stone cladding) erode the legally-measured dimension and jeopardize the use permit (使照). |
| license | CC-BY-SA-4.0 |
| compatibility | claude-code,opencode,agent-skills |
| metadata | {"audience":"architects","region":"taiwan","class":"C"} |
Floor-Area Exemption Pitfalls (容積免計項目實務陷阱)
Overview
This skill captures field-level pitfalls in Taiwan's floor-area-ratio (FAR / 容積) exemption items — the practitioner know-how that statutory text omits. Plain code lists the exemption threshold; it does not warn you that a value drawn exactly at the threshold will fail at completion. Invoke this skill when:
- Planning FAR-exempt spaces (elevator/stair lobbies, MEP rooms, etc.)
- Deciding whether drawn clear dimensions must reserve thickness for finishing layers
- FAR is nearly maxed out and any failed exemption causes an overage
- Self-checking before use-permit (使照) inspection to avoid completion-stage failures
Core Principle: Nominal Drawing Dimension ≠ Finished Clear Dimension
Many FAR (and other) exemption/compliance thresholds are checked against the finished clear dimension, but drawings often note the structural / rough nominal dimension. Finishing layers consume the difference:
nominal clear dimension − two-side finishing thickness (stone, tile, substrate) = finished clear dimension (the value the regulator actually measures)
When a threshold is "greater-than-or-equal", drawing exactly at the threshold guarantees a completion-stage shortfall. The correct practice is to reserve finishing thickness as buffer and draw above the threshold.
This is a cross-regulation recurring pattern. The elevator/stair lobby FAR exemption is the most typical and highest-consequence instance — the first card in this series.
Pitfall Card: Elevator/Stair Lobby (梯廳) FAR Exemption — Finished Clear Dimension Trap
| Field | Value |
|---|
| Regulatory basis | Building Technical Regulations (Design & Construction) Article 162, Paragraph 1, Subparagraph 1 |
| Threshold | The shared stair/elevator lobby clear depth (淨深度) must be ≥ 2.0 m (note: clear depth — measured at the finished face). Also: exempt lobby area ≤ 10% of that floor's area; balcony + lobby combined ≤ 15% of that floor's area (excess counts toward FAR) |
| Gap mechanism | nominal depth − stone-cladding/finishing thickness on both ends = finished clear depth (eroded by finishes; dropping below 2 m forfeits the exemption) |
| Drawing countermeasure | Draw nominal 2.1 m, reserving finishing thickness (≈5 cm per side, adjust to actual build-up), so the clear depth stays ≥ 2.0 m after cladding |
| Failure consequence | finished face < 2.0 m → lobby area counts toward FAR gross floor area → if FAR already maxed, overage → use permit (使照) inspection fails |
| Failure timing | Surfaces only after finishing is installed; very hard to remediate (may require demolishing finishes or altering structure) |
| Linked items | FAR gross-floor-area calculation, interior fit-out, use-permit completion inspection |
| Severity | 🔴 High (directly blocks the use permit; a late-stage, post-completion risk) |
Mnemonic: the 2 m threshold is what must be measurable after cladding; draw 2.1 m so the stone's thickness is given away up front.
Cross-Regulation Siblings (to be added)
The same "finishing layer / construction tolerance erodes clear dimension → crosses a critical threshold → blocked" structure recurs elsewhere. Each sibling files under its own regulatory home but reuses this card format and cross-links here:
| Sibling pitfall (TBD) | Likely regulatory home | Threshold direction |
|---|
| Accessible route / corridor clear width | Accessibility design | ≥ (often fails after cladding) |
| Stair clear width / tread depth | Building Tech Reg (egress) | ≥ |
| Driveway / parking stall clear dimensions | Building Tech Reg (parking) | ≥ |
| Fire door / stair-lobby clearances | Building Tech Reg (fire egress) | ≥ |
| Other FAR-exemption critical/upper limits | FAR & coverage calculation | varies |
To Verify
- Clear-depth determination for irregularly-shaped lobbies (how the "> 2 m clear depth" portion is recognized when the lobby is non-rectangular) — see National Land Management Agency interpretation (nlma 12840).
- Article 162 §1 subparagraphs 2–3 (MEP, parking exemptions) carry separate execution interpretations to review alongside the lobby exemption.
MCP Tool Examples
taiwan-building-code_search_building_interpretations(query: "容積免計 梯廳", limit: 5)taiwan-building-code_search_building_code(query: "容積率", limit: 10)
References
- Building Technical Regulations (Design & Construction) Article 162 — FAR gross-floor-area calculation and exemption items (Laws & Regulations Database)
- National Land Management Agency interpretation letters (lobby FAR-exemption review)
- Local-government building-permit and use-permit inspection rules
