Spatial Planning

Spatial Planning

Section 1: Floor Plan Archetypes

The floor plan archetype determines nearly every downstream design decision — structural grid, facade rhythm, servicing strategy, daylight penetration, and occupant experience. The ten canonical plan types below cover the full spectrum of building configurations from narrow residential slabs to deep-plan commercial towers.

1.1 Single-Loaded Corridor

Diagram description: A linear building with habitable rooms on one side only and an open corridor or gallery on the other, typically facing a courtyard or exterior view.

• Typical plan depth: 6–9 m from corridor wall to exterior facade
• Structural grid: 6–8 m bays perpendicular to corridor, 3–4 m bays parallel
• Daylight characteristics: Excellent — all rooms have direct exterior exposure on at least one side; corridor receives borrowed light or is open-air
• Circulation efficiency: Low — corridor serves rooms on one side only, yielding high circulation-to-usable area ratio (NTG penalty 5–10%)
• Best-fit building types: Tropical housing, student residences, hospital wards, hotels in warm climates, gallery-access social housing
• Exemplar buildings: Robin Hood Gardens (Alison & Peter Smithson, London, 1972); Park Hill (Jack Lynn & Ivor Smith, Sheffield, 1961)

1.2 Double-Loaded Corridor

Diagram description: A linear building with habitable rooms on both sides of a central corridor, creating a deeper floor plate.

• Typical plan depth: 12–18 m total (two 6–9 m room depths flanking a 1.5–2.4 m corridor)
• Structural grid: 6–8 m bays perpendicular, 3–5 m parallel
• Daylight characteristics: Good in rooms; corridor is typically windowless and requires artificial lighting or periodic breaks with glazing
• Circulation efficiency: High — corridor serves rooms on both sides, achieving 78–85% NTG in residential, 80–87% in hotel
• Best-fit building types: Hotels, residential apartments, dormitories, hospital departments, budget office buildings
• Exemplar buildings: Unite d'Habitation (Le Corbusier, Marseille, 1952); Trellick Tower (Erno Goldfinger, London, 1972)

1.3 Central Core

Diagram description: A floor plate organized around a central vertical core containing stairs, elevators, risers, and often toilets, with usable space radiating outward to the perimeter facade.

• Typical plan depth: 9–15 m from core face to facade (18–30 m total floor plate dimension)
• Structural grid: 9 m x 9 m or 10.8 m x 10.8 m typical for office; 8.4 m x 8.4 m for residential
• Daylight characteristics: Good at perimeter (within 6–8 m of facade); deep zones beyond 8 m require artificial lighting; core zone is dark
• Circulation efficiency: Excellent — shortest average travel distances, compact service distribution. NTG 75–82% for office
• Best-fit building types: Office towers, mixed-use high-rises, commercial buildings over 10 storeys
• Exemplar buildings: Seagram Building (Mies van der Rohe, New York, 1958); Swiss Re (Foster + Partners, London, 2004)

1.4 Side Core

Diagram description: The vertical core is positioned at one end or one side of the floor plate, freeing the remainder for uninterrupted usable space with maximum facade access.

• Typical plan depth: 12–18 m from core to far facade
• Structural grid: 9–12 m clear spans common to maximize open floor plate
• Daylight characteristics: Excellent — core does not obstruct perimeter daylight; deep floor plates still need supplementary lighting beyond 8 m from facade
• Circulation efficiency: Good — slightly longer travel distances than central core; single direction of egress requires careful code compliance (max 45 m travel distance IBC sprinklered)
• Best-fit building types: Speculative offices (lettable floor plates), creative workspaces, laboratories, buildings on narrow urban sites
• Exemplar buildings: Lever House (SOM, New York, 1952); One Angel Court (Fletcher Priest, London, 2017)

1.5 Point Tower

Diagram description: A compact, typically square or circular floor plate with a central or offset core, rising as a slender tower. Small floor plates (400–800 m²) with high perimeter-to-area ratio.

• Typical plan depth: 6–10 m from core to facade
• Structural grid: Radial or 6–8 m orthogonal grid
• Daylight characteristics: Excellent — high perimeter-to-floor-area ratio ensures most space is within 6 m of facade
• Circulation efficiency: Very high — compact core serves 4–8 units per floor in residential, or open-plan office. NTG 75–82% residential
• Best-fit building types: Residential towers, boutique office towers, landmark/iconic structures, slender urban infill
• Exemplar buildings: Barbican Tower (Chamberlin Powell & Bon, London, 1976); Aqua Tower (Studio Gang, Chicago, 2009)

1.6 Courtyard Plan

Diagram description: Building mass encloses or partially encloses a central open courtyard, creating inward-facing as well as outward-facing rooms.

• Typical plan depth: 6–12 m building depth around 15–40 m courtyard dimension
• Structural grid: 6–8 m bays; loadbearing masonry or frame
• Daylight characteristics: Very good — dual-aspect units possible; courtyard provides sheltered daylight source. Courtyard must be min 1:1 width-to-height ratio for adequate light at lower floors
• Circulation efficiency: Moderate — circulation wraps around courtyard, adding length but creating social/amenity corridor
• Best-fit building types: Low-to-mid-rise housing (3–8 storeys), institutional (schools, monasteries, museums), hotels, mixed-use urban blocks
• Exemplar buildings: Palazzo Farnese (Antonio da Sangallo/Michelangelo, Rome, 1534); Beurret & de la Croix housing (Valerio Olgiati, 2014)

1.7 Atrium Plan

Diagram description: A large internal void (atrium) rises through multiple storeys, with occupied floors opening onto galleries or balconies surrounding the void. The atrium is typically top-lit or side-lit.

• Typical plan depth: 6–12 m from atrium edge to exterior facade; atrium 10–30 m wide
• Structural grid: Long-span (12–15 m) to clear atrium void; 6–9 m in occupied wings
• Daylight characteristics: Excellent at upper levels; diminishes at lower floors of deep atria. Atrium acts as light well. Glazed roof or clerestory essential
• Circulation efficiency: Good — atrium acts as orientation device and social condenser; galleries double as circulation and informal meeting space
• Best-fit building types: Corporate headquarters, shopping malls, hospitals, museums, civic buildings, hotels
• Exemplar buildings: Bradbury Building (George Wyman, Los Angeles, 1893); Commerzbank Tower (Foster + Partners, Frankfurt, 1997)

1.8 Free Plan

Diagram description: Structural columns are set back from the facade on a regular grid, with non-loadbearing partitions freely arranged on each floor independently. The floor plan has no fixed interior walls tied to structure.

• Typical plan depth: Variable — 12–20 m common
• Structural grid: Regular grid (Dom-ino: 5 m x 5 m); pilotis or columns at ground; flat slabs
• Daylight characteristics: Dependent on floor plate depth and window placement; facade is free from structural constraint enabling floor-to-ceiling glazing
• Circulation efficiency: High — absence of loadbearing walls allows optimized corridor placement per floor
• Best-fit building types: Modernist villas, flexible office space, galleries, retail, adaptable-use buildings
• Exemplar buildings: Villa Savoye (Le Corbusier, Poissy, 1931); Farnsworth House (Mies van der Rohe, Plano, 1951)

1.9 Open Plan

Diagram description: A large, unpartitioned floor plate with minimal internal walls or divisions, typically with perimeter structure or long-span trusses enabling column-free interiors.

• Typical plan depth: 18–30 m or more; limited only by daylighting (8 m effective daylit zone from each facade)
• Structural grid: Long-span: 12–18 m (steel) or 9–12 m (concrete). Post-tensioned slabs common
• Daylight characteristics: Moderate — perimeter zones well-lit, deep core zones require artificial light. Atriums or lightwells mitigate this
• Circulation efficiency: Very high — minimal dedicated corridor space; NTG 82–88% achievable
• Best-fit building types: Trading floors, tech offices, co-working spaces, warehouses, exhibition halls, large retail
• Exemplar buildings: Willis Faber & Dumas (Foster + Partners, Ipswich, 1975); Centraal Beheer (Herman Hertzberger, Apeldoorn, 1972)

1.10 Hybrid Plan

Diagram description: Combines two or more plan archetypes within a single floor plate or building — for example, a central core office tower with an atrium zone and a double-loaded residential wing.

• Typical plan depth: Variable — responds to mixed program
• Structural grid: Transitional grids at junctions; transfer structures where grid changes
• Daylight characteristics: Varies by zone — each archetype zone retains its own daylight characteristics
• Circulation efficiency: Moderate — junctions between plan types create circulation complexity; careful wayfinding needed
• Best-fit building types: Mixed-use developments, large civic buildings, university buildings, transport hubs, hospital complexes
• Exemplar buildings: Linked Hybrid (Steven Holl, Beijing, 2009); De Rotterdam (OMA, Rotterdam, 2013)

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Section 2: Circulation Design

Circulation consumes 15–30% of gross floor area depending on building type. Efficient circulation design directly impacts NTG ratio, user experience, code compliance, and emergency egress.

2.1 Primary Circulation

Lobbies:

• Main entrance lobbies: min 3.0 m clear height, typically 4.5–6.0 m for commercial
• Lobby area: 0.5–1.0 m² per person served in peak 5-minute arrival period
• Elevator lobbies: min 1.5 m depth in front of elevator doors; 2.4 m preferred for office towers
• Residential entrance lobbies: min 6 m² (BS 9991), concierge desk adds 4–6 m²

Corridors: Minimum corridor widths by building type and code:

Dead-end corridors (IBC 1020.4):

• Unsprinklered: max 6.1 m (20 ft)
• Sprinklered: max 15.2 m (50 ft)
• Group I-3 (detention): 15.2 m max regardless
• Exception: single-exit dwelling units per IBC 1006.3.4

Travel distance limits (IBC Table 1017.2):

• Unsprinklered: 60 m (200 ft) for most occupancies; 23 m (75 ft) for H-1/H-2 hazardous
• Sprinklered: 76 m (250 ft) for most; 30 m (100 ft) for H-1/H-2
• Common path of egress: 23 m unsprinklered / 23 m sprinklered for most; 30 m for B/F/S/U occupancies (sprinklered)

2.2 Stair Design

IBC Requirements (Chapter 10):

• Minimum width: 1118 mm (44 in) for occupant load >50; 914 mm (36 in) for ≤50
• Riser height: min 102 mm (4 in), max 178 mm (7 in)
• Tread depth: min 279 mm (11 in)
• Riser-tread relationship: 2R + T = 600–640 mm (optimum 630 mm)
• Uniform risers within a flight: max 9.5 mm (3/8 in) variation
• Maximum flight height without landing: 3.66 m (12 ft)
• Landing depth: min equal to stair width, need not exceed 1220 mm (48 in)
• Headroom: min 2032 mm (80 in) measured vertically from nosing

Handrail requirements (IBC 1014):

• Height: 864–965 mm (34–38 in) measured from nosing
• Graspable: circular cross-section 32–51 mm (1.25–2 in) diameter or equivalent
• Extensions: 305 mm (12 in) beyond top riser, one tread depth + 305 mm beyond bottom riser
• Both sides required for stairs ≥1118 mm wide
• Intermediate handrail required when stair width exceeds 1524 mm (60 in) with no handrail within 762 mm (30 in)

Accessible stairs (ADA/IBC 1009):

• Max riser 178 mm, min tread 279 mm
• Nosing: max 38 mm projection, radius max 13 mm, angled max 60 degrees from horizontal
• Tactile warning strips at top landing of exterior stairs

Stair capacity:

• IBC capacity factor: 7.6 mm (0.3 in) per person for stairs (IBC Table 1005.1)
• A 1118 mm stair serves: 1118 / 7.6 = 147 persons per storey
• For phased evacuation (BS 9999): stair capacity = stair width (mm) / 5.2 mm per person = flow rate per minute
• Typical stair flow rate: 60–80 persons per metre width per minute (downward)

2.3 Elevator Design

Cab sizes (EN 81-70 / ASME A17.1):

Waiting time targets (CIBSE Guide D):

• Premium office: 20–25 s average waiting time
• Standard office: 25–30 s
• Residential: 40–60 s (up-peak less critical)
• Hotel: 30–45 s
• Hospital (bed): 60–90 s (dedicated bed lifts)
• Quality of service: >90% of passengers served within target wait time

Elevator quantity estimation (rule of thumb):

• Office: 1 elevator per 2,500–3,500 m² GFA per zone
• Residential: 1 elevator per 60–90 units (min 2 per core)
• Hotel: 1 elevator per 100–150 rooms
• Hospital: complex traffic analysis required; typically 1 bed lift per 100 beds + visitor/staff lifts

Elevator speed by building height:

• Low-rise (≤10 storeys): 1.0–1.75 m/s
• Mid-rise (10–25 storeys): 2.5–4.0 m/s
• High-rise (25–50 storeys): 5.0–7.0 m/s
• Supertall (50+ storeys): 8.0–10.0 m/s (sky lobbies with express + local)

2.4 Escalator Design

• Standard width: 600 mm (single file) or 1000 mm (two abreast)
• Inclination: 30 degrees (standard), 35 degrees (compact, lower capacity)
• Speed: 0.5 m/s (standard), 0.65 m/s (high traffic)
• Capacity: 600 mm @ 0.5 m/s = ~4,500 persons/hour; 1000 mm @ 0.5 m/s = ~6,750 persons/hour
• Horizontal run at top and bottom: min 800 mm (0.8 m) flat steps
• Headroom: min 2300 mm vertical clearance
• Rise: typically 3.0–6.0 m per escalator (single storey); structural opening ~1.6 m wide x 6–12 m long
• Escalator pairs (up/down) require structural opening 3.5 m wide minimum

2.5 Emergency Circulation (Egress)

• Minimum 2 exits required when occupant load >49 (IBC 1006.2.1) or building >1 storey
• Half-diagonal rule: two exits must be separated by distance ≥ 1/2 the maximum diagonal of the floor (IBC 1007.1.1); 1/3 diagonal if sprinklered
• Exit discharge: directly to public way or through exit passageway; max 50% through building interior if sprinklered (IBC 1028.1)
• Areas of rescue assistance: required at each stair for buildings without full sprinkler system; min 760 mm x 1220 mm clear space per wheelchair
• Protected corridors: fire-rated 30/60 minutes depending on building height and sprinkler status

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Section 3: Core Design

The vertical core is the organizational spine of any multi-storey building. It concentrates vertical circulation, fire escape routes, and service risers into a compact zone that repeats floor-to-floor.

3.1 Core Types

Central Core:

• Location: geometric center of floor plate
• Max floor plate efficiency: shortest average travel distances
• Typical for: office towers, commercial high-rises
• Core area: typically 20–28% of gross floor plate for office towers
• Advantage: equal facade access on all sides
• Disadvantage: deep floor plates can exceed daylight limits; inflexible for tenant subdivision

Side Core:

• Location: one end or one side of floor plate
• Typical for: speculative office, labs, creative workspace
• Core area: typically 18–25% of gross floor plate
• Advantage: uninterrupted usable floor plate, flexible tenant layouts, views unobstructed
• Disadvantage: longer travel distances to far end; potential egress code issue if single core

Dual Core:

• Location: cores at both ends of a long floor plate
• Typical for: long-span buildings, hospitals, large floor plates >2,500 m²
• Core area: 2 x 12–15% = 24–30% of gross floor plate
• Advantage: meets travel distance limits on long floor plates, redundancy in egress
• Disadvantage: duplicated elevator lobbies, additional shaft space

Distributed Cores:

• Location: multiple small cores across a campus or large floor plate
• Typical for: campus buildings, shopping centers, hospitals, airports
• Core area: varies; each core typically 50–150 m²
• Advantage: local servicing, short travel distances, incremental construction
• Disadvantage: total core area exceeds consolidated core approach; more risers to coordinate

3.2 Core Components

Every core typically contains:

1. Stairs: Min 2 per building >1 storey (IBC 1006.3). 1-hour fire rating for buildings ≤4 storeys, 2-hour for >4 storeys (IBC 1023.2). Pressurized to 50 Pa positive in tall buildings.
2. Elevators: Passenger, goods, firefighter. Shaft: 2-hour fire rating (IBC 3006.2). Machine room or machine-room-less (MRL).
3. Service risers:
   • Electrical: 600 mm x 400 mm min per riser for typical office floor; increases with building height and load
   • Data/telecoms: 400 mm x 400 mm min; separate from electrical for EMI
   • Water (potable + fire): 300 mm x 300 mm min; wet riser diameter 100–150 mm
   • Waste (soil + vent): 150 mm dia soil stack per bathroom group + 100 mm vent
   • HVAC: vertical ductwork risers 600 mm x 1200 mm typical for office floors; or AHU per floor eliminating vertical duct risers
   • Gas: where applicable, in fire-rated enclosure
4. Toilets: Typically adjacent to core for riser access; stacking is essential
5. Lobby/waiting area: Elevator lobby min 1.5 m depth; 2.4 m preferred for commercial
6. Refuse/recycling chute: 500 mm dia min, fire-rated enclosure, ground floor collection room

3.3 Core Dimensioning by Building Type

Residential tower (20 storeys, 8 units/floor):

• Single stair per core (where code allows, e.g., UK for <11 m above ground) or 2 stairs
• 2 elevators (1 x 13-person + 1 x 8-person)
• Core area: approximately 40–55 m² per floor
• Core as % of floor plate (600 m² GFA): 7–9%

Office tower (30 storeys, 1,500 m² floor plate):

• Central core with 2 stairs (each 1200 mm wide min)
• 6–8 elevators in 2 banks (low-rise + high-rise zones for >20 storeys)
• Core area: approximately 300–400 m² per floor
• Core as % of floor plate: 20–27%

Hospital (8 storeys, 3,000 m² floor plate):

• Dual cores at building ends
• 2 stairs per core + 2 bed elevators + 2 passenger elevators per core
• Core area: 2 x 150–200 m² = 300–400 m²
• Core as % of floor plate: 10–13%