Hospital Clearance & Headroom Rules (HOSP-CLR)

Healthcare environments require generous clear vertical dimensions to accommodate suspended medical imaging equipment, operating ceiling tracks, laminar air flow canopies, and mobile IV drip stands. Headroom bottlenecks under structural transfer beams or MEP distribution ducts represent severe coordination failures.

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1. HOSP-CLR-001: Hospital Structural Soffit & Beam Headroom Clearance

Statutory Standard & Intent

• Standard: NHS Health Building Note 00-04 Section 3.4 and HTM 03-01 (Ventilation).
• Intent: Enforces a minimum continuous habitable clear height of $\ge 2.40\text{ m}$ ($2,400\text{ mm}$) from finished floor level (FFL) to the underside of any downstand structural beam, concrete transfer drop panel, or structural soffit.

Vertical Calculation Methodology

For every structural beam or slab drop element in the structural partition (WRSH_Structural.ifc), BIM Checker computes the true vertical elevation above the resolved Storey Finished Floor Level (FFL):

$Z_{\text{headroom}} = \text{BBoxLow.z} - Z_{\text{StoreyFFL}}$

$\text{Compliance Condition}: \quad Z_{\text{headroom}} \ge \text{EffectiveThreshold}$

• Storey Elevation Grounding: Headroom is evaluated strictly against official building storeys. If storey datums are missing from the model, the audit surfaces an Insufficient Information warning to preserve data integrity.
• Intelligent Vertical Discrimination: Vertical columns, risers, and structural supports are automatically distinguished from horizontal transfer elements to eliminate false headroom violations.
• Context-Aware Spatial Adaptation:
  • Clinical & Habitable Spaces: Enforces statutory $\ge 2.40\text{ m}$ per NHS HBN 00-04.
  • Plant Rooms & Mechanical Penthouses: Automatically adapts threshold to $\ge 2.00\text{ m}$ per BS EN ISO 14122 (Plant / Walkway Headroom).
• Validation Geometry: Emits HEADROOM_CLEARANCE_ZONE (3D spatial bounding envelope highlighting the breach volume in red).

Client-Configurable Parameters

{
  "nominalThreshold": 2.40,
  "plantHeadroom": 2.00,
  "unit": "m",
  "comparisonOperator": ">="
}

What Must Be in the iModel (Revit & IFC Data Requirements)

• Revit: OST_StructuralFraming elements must have valid 3D geometry and be associated with the correct level constraint. Foundation beams below ground floor must be categorized as OST_StructuralFoundation so they are not mistaken for habitable downstand beams.
• IFC: IfcBeam, IfcMember, or IfcSlab with valid Representation (solid sweep or BRep geometry).

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2. HOSP-CLR-002: Overhead MEP Ceiling Drops & Service Duct Headroom

Statutory Standard & Intent

• Standard: NHS HBN 00-04 and HTM 03-01 (Heating and Ventilation Systems).
• Intent: Healthcare HVAC air supply ducts, exhaust ducts, medical gas manifolds, and cable tray containment racks must not drop below the statutory ceiling height threshold of $\ge 2.40\text{ m}$ ($2,400\text{ mm}$).

Cross-Discipline Coordination Hotspots

Overhead MEP drops are particularly prevalent in:

• Corridors: Where ducts from multiple plant rooms converge into major ceiling plenums.
• Floor Level Transitions: Storeys with restricted slab-to-slab dimensions (e.g. Level 7A where slab height is restricted to $3.0\text{ m}$, leaving only $600\text{ mm}$ for structure and services).
• Beam Penetrations: Where large rectangular ductwork crosses underneath deep downstand steel beams.

Client-Configurable Parameters

{
  "nominalThreshold": 2.40,
  "plantHeadroom": 2.00,
  "unit": "m",
  "comparisonOperator": ">="
}

Defect Message

"Overhead MEP Element 'HVAC Supply Duct 600x400 [0x20000005a12]' on Level 7A drops to an elevation of 2.18 m above FFL, violating NHS HBN 00-04 required clear headroom of 2.40 m (clearance shortfall: -0.22 m)."

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Pre-Flight ECSQL Diagnostic Query

Inspect lowest MEP and beam elevations across your iModel:

SELECT 
  e.ECInstanceId AS elemId,
  e.UserLabel AS label,
  ec_className(e.ECClassId, 's.c') AS ecClass,
  e.BBoxLow.z AS bottomZ,
  e.BBoxHigh.z AS topZ
FROM bis.GeometricElement3d e
WHERE (
  ec_className(e.ECClassId, 's.c') LIKE '%Duct%'
  OR ec_className(e.ECClassId, 's.c') LIKE '%Beam%'
  OR e.UserLabel LIKE '%Duct%'
  OR e.UserLabel LIKE '%Beam%'
)
ORDER BY e.BBoxLow.z ASC
LIMIT 50