# Riverside Twin Towers — Design Narrative & Specifications

**Two crowns on the Mekong**
Mekong Riverfront, Phnom Penh, Cambodia · 11.5°N
Concept / Feasibility master plan — **NOT for construction**
Date: 2026-06-14 · Drawn by: Integrated design team (architecture · urban · structural/MEP · interiors · sales)

| Headline figure | Value |
|---|---|
| Parcel | 94 m × 20 m = 1,880 m² |
| Towers | 2 × gateway crowns leaning toward each other — T1 162 m · T2 172 m (sculpted glass) |
| Above-grade GFA | 35,204 m² (FAR 18.73) |
| Programme | 18-floor Grade-A office + 120-key 5-star hotel (T1); 144 residential units (T2) |
| Storeys | T1: 37 · T2: 43 |
| Parking | 205 stalls across 3 basements (~90% of estimated demand) |

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## 1. Concept Story

The site is a thin ribbon of land between the city and the Mekong — 94 metres of river frontage, only 20 metres deep. Rather than fight that geometry, the scheme makes it the entire architectural idea: **two slender towers, set at the east and west ends of the parcel, each turned fully to the water.** The towers rise as a matched pair — *"two crowns on the Mekong"* — and are read as one composition across the riverfront skyline.

Between them, a 20 m gap is held open as an **arrival plaza and atrium void**, framing a clean slot of sky and river view straight through the building from the street. Just above the retail podium — ≈ 22.6–31 m above the ground (Level 6–7) — the two towers are stitched together by an inhabited, planted **Garden Bridge**: a two-level shared lounge and café with a green roof, a low green seam across the slot. Higher up, the two **sculpted glass crowns lean toward one another** to resolve the pair into a single gateway over the river.

Each tower terminates in a **sculpted glass crown**: in the western tower (T1) a sky restaurant, bar and spa beneath a glass parapet; in the eastern tower (T2) a stacked sky-amenity world of infinity pool, sky bar and signature restaurants. By night the crowns and the podium's media façade carry the project's identity along the river edge.

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## 2. Site Response

**The parcel.** 94.0 m of frontage running east–west along the river edge, 20.0 m deep north–south, river to the **north**, street to the **south** — 1,880 m² in total. It is, by any measure, a slender riverfront parcel, and the masterplan is explicit that **the 20 m depth is the primary design driver.**

**From parcel to buildable envelope.** Applying the assumed setbacks — 5.0 m to the river, 2.0 m to the street, 4.0 m to each side — leaves a buildable rectangle of **86.0 m long × 13.0 m deep** (1,118 m²). That 13 m residual depth is the pivot of the whole design.

**13 m drives single-loading.** A 13 m plate is too shallow to support a conventional double-loaded corridor (rooms on both sides of a central hallway) at any sensible quality. So the scheme commits to **single-loaded plates**: a 9.0 m river-facing zone of primary habitable rooms (Y 5–14), and a 4.0 m back zone (Y 14–18) holding the 1.6 m corridor, the twin-stair core, lifts, risers and back-of-house. The payoff is unambiguous and becomes the project's core sales promise: **every habitable room — 100% of units and offices — faces the river.**

**Raised ground / flood datum.** The finished ground floor and podium sit on a raised datum **+1.5 m** above the assumed Mekong flood level. The riverside arrival is lifted clear of flood risk while still reading as a generous, water-facing ground plane.

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## 3. Massing & Vertical Stacking

**Two plates and a void.** Two identical slender tower plates — each **33.0 m wide × 13.0 m deep (429 m²)** — sit at the ends of the parcel. T1 (west) occupies plan X 4–37; T2 (east) occupies X 57–90. The **20 m central gap** (X 37–57) is left as arrival plaza and atrium void, crossed low (≈ L6–7) by the planted Garden Bridge. A 2-level podium (5.0 m floor-to-floor, 1,040 m² plate) fills the base across the full envelope, with a riverside **arrival notch** (X 42–52, Y 5–9) cut into its north face as a grand entry. The two towers carry **separated cores** — coreWest and coreEast, 48 m² each — so the office, hotel and residential populations never share a core.

### Tower 1 (West) — Business & Hospitality · 37 storeys · structural top 152.6 m, crown 162.0 m

| Level | Use | Floors | z₀–z₁ (m) | F-to-F |
|---|---|---|---|---|
| L3–L20 | Grade-A office | 18 | 10.0–85.6 | 4.2 m |
| **L21** | **Hotel sky-lobby / transfer** | 1 | 85.6–91.6 | 6.0 m |
| L22–L36 | 5-star guestrooms + suites | 15 | 91.6–147.1 | 3.7 m |
| L37 | Sky restaurant / bar + spa (crown) | 1 | 147.1–152.6 | 5.5 m |
| CROWN | Sculpted glass crown — leans toward T2 | — | 152.6–162.0 | 9.4 m |

**Why office-low / hotel-upper.** Three reasons drive the stack:
1. **Views & branding** — the hotel takes the upper third where river-and-skyline views command the strongest 5-star room rates, and where the crown can carry the hotel's signature sky restaurant/bar/spa as a visible brand beacon.
2. **The L21 sky-lobby transfer** — locating hotel arrival at L21 (a generous 6.0 m level) creates a clean break between the two populations: offices operate below on their own lift group; hotel guests are shuttled express to a dedicated sky-lobby where ballroom, meeting and all-day dining sit, then dispersed upward to rooms. This is the natural place to make a **structural transfer**, since office and hotel plates carry different column rhythms and loads.
3. **Operational separation** — day-time office traffic and 24-hour hotel traffic are decoupled vertically and never cross.

### Tower 2 (East) — Residential · 43 storeys · structural top 155.7 m, crown 172.0 m

| Level | Use | Floors | z₀–z₁ (m) | F-to-F |
|---|---|---|---|---|
| L3–L40 | Apartments (every unit river-facing) | 38 | 10.0–139.2 | 3.4 m |
| L41 | Residents' sky club, lounge, gym, sky-garden | 1 | 139.2–144.7 | 5.5 m |
| L42 | **SKY CROWN** — infinity pool + sky bar | 1 | 144.7–150.2 | 5.5 m |
| L43 | **SKY CROWN** — signature restaurants | 1 | 150.2–155.7 | 5.5 m |
| CROWN | Sculpted glass crown — taller, leans toward T1 | — | 155.7–172.0 | 16.3 m |

T2 runs as a **full-residential stack** — 38 typical apartment floors — capped by a three-level **sky-amenity crown** (residents' club, infinity pool/sky bar, signature restaurants). Putting the amenity at the very top gives every resident a shared destination with the best views in the project and lets the crown do double duty as both lifestyle asset and skyline sculpture.

**The 20 m plaza void & the garden bridge.** The central gap stays open as a 20 m-wide slot of plaza, atrium and view, kept clear up the full height so the gateway reads straight through. It is bridged low, twice: a **podium link** at L2 (z = 5.0 m) carries retail across the gap, and just above it the inhabited **Garden Bridge** spans the slot at z 22.6–31.0 m (≈ L6–7, 2 levels, 520 m²) as a planted shared lounge and café.

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## 4. Façade & Materials

**Glazing.** A high-performance curtain wall in **bronze and river-blue glass** (palette: bronze #C9974C / #B8863B, river #2C6E8F / #173B4F, glass #9FC6D8 / #5E93AE), echoing the river surface and a Mekong sunset (sunset warm #F2C078, glow #E8804B). The glass is specified as high-performance to manage solar gain at this latitude while keeping the 100%-river-facing rooms fully glazed to the view.

**Solar control tuned for 11.5°N.** At 11.5° north the sun tracks high and close to overhead, with intense low-angle exposure on the east and west elevations and a strong southern path. External shading is therefore differentiated by orientation:
- **East / West / South** — the harsh exposures — receive the heaviest external shading (deep horizontal and vertical fins) to cut direct gain.
- **North (river)** — receives soft, indirect river light and is left most open, maximising the glazed river view that is the project's whole premise.

This is the architectural expression of the single-loaded plan: the building turns its glazed, lightly-shaded face to the river/north and its more solid, shaded faces to the sun.

**Podium media façade.** The L1 riverside frontage carries a **media façade** — the project's primary night-time identity along the promenade, integrated with the double-height lobbies and retail/F&B.

**Crown lighting.** The two sculpted glass crowns (T1: 152.6–162.0 m; T2: 155.7–172.0 m) are lit as the skyline signature — the "two crowns on the Mekong" reading at distance and after dark.

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## 5. Structure

**Slender-tower lateral system.** Both towers are extremely slender (≈33 m plate carrying up to 172 m of height). Lateral stability is provided by a **reinforced central core working with the perimeter frame in an outrigger-type system** — the core resists the bulk of wind and seismic shear, while perimeter columns engaged through outriggers control overturning and drift on the slender axis. The plate is set on an **8.25 m structural grid** (33 m plate / 4 bays), with the back-zone core (coreWest / coreEast) acting as the primary shear element.

**Podium transfer for the hotel sky-lobby.** In T1, the office floors (L3–L20) and the hotel floors (L22–L36) have different planning grids and loadings. The **L21 sky-lobby** — a generous 6.0 m transfer level — is the structural changeover, where loads from the hotel stack above are transferred onto the office/core structure below. The podium itself (2 levels, 5.0 m floor-to-floor) is the transfer zone between towers and basement.

**The garden-bridge link.** Spanning the 20 m void low — at z 22.6–31 m (≈ L6–7) — the two-level **Garden Bridge** is a clear-spanning ~520 m² truss between the two towers. Because it sits low, where both towers are still very stiff, differential movement between them is modest; even so it is detailed with a **slide-bearing / movement joint at one end** so it carries gravity and occupancy loads without rigidly coupling the towers. *(Final span articulation and bearing strategy to be confirmed by the structural engineer-of-record.)*

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## 6. MEP & Vertical Transport

**Separated lift groups (the core logic).** Because the towers carry distinct populations on separated cores, vertical transport is zoned by use:
- **T1 — office group** serving L3–L20 from the ground lobby.
- **T1 — hotel group**: **express shuttle lifts** from the ground arrival straight to the **L21 sky-lobby**, then local hotel lifts L21→L36 to rooms and the L37 crown. Guests and office tenants never share a car.
- **T2 — residential group** serving L3–L40 plus the L41–L43 sky-amenity crown, with express service to the top-of-tower amenity.

**Services strategy.** Primary plant, the substation, water tanks and loading sit in the basements — **B1** (z −4 to 0, 4.0 m) carries retail/hotel valet, loading, MEP plant and the substation; **B3** carries the water tanks. Floor-to-floor heights are set per use to carry services and reach within them: retail 5.0 m, office 4.2 m, hotel 3.7 m, residential 3.4 m, amenity/crown 5.5 m. The single-loaded back zone (4.0 m deep, Y 14–18) consolidates risers, corridor and core, giving every floor a clean vertical services spine behind the habitable river-facing rooms.

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## 7. Sustainability

- **Solar control** — orientation-tuned external shading at 11.5°N (heavy E/W/S, open N) plus high-performance bronze/blue glazing, cutting cooling load while preserving the river view.
- **Rainwater harvesting** — basement water tanks (B3) anchor on-site rainwater capture and storage.
- **Flood resilience** — raised ground floor / podium on a **+1.5 m** datum above the assumed Mekong flood level; basements designed for a riverfront water table.
- **EV-ready** — **30%** of parking stalls provisioned EV-ready, with EV-priority bays part of the parking mitigation strategy.
- **River-breeze cross-ventilation** — the sky-amenity crown levels and the planted Garden Bridge are positioned and configured to draw the river breeze, allowing naturally cross-ventilated shared amenity space.
- **Open space** — a 0.30 green-space / public-realm target at grade; the scheme reports 45% open space against 55% site coverage.

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## 8. Phasing

The slenderness that complicates the towers simplifies the construction logic into a clean sequence — and the programme split lets cashflow lead.

1. **Substructure & shared base** — excavate and build the 3 basements (B1–B3, z −10 to 0) to the lot lines, then the 2-level podium and **both tower cores** brought up together off the common base.
2. **T2 residential first (cashflow)** — race the **eastern residential tower** up first. Residential is the fastest-absorbing, pre-sellable product (144 units, 100% river-facing), generating early sales revenue to fund the rest.
3. **T1 office / hotel** — follow with the **western business & hospitality tower**, including the L21 sky-lobby transfer and the hotel stack, which carry longer lead times (operator fit-out, brand standards).
4. **Bridge & fit-out** — install the low **Garden Bridge** across the gap, then complete interior fit-out, the podium media façade and the sculpted crown lighting.

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## 9. Constraints & Assumptions Register

Every figure below is an **input assumption or a value computed from inputs**. The scheme is designed to re-derive if any input changes — these are deliberately exposed, not buried. All require verification before any move beyond concept.

| # | Item | Value (from masterplan) | Basis | Who must verify |
|---|---|---|---|---|
| 1 | River setback | 5.0 m | Assumed riverfront promenade relief | Phnom Penh municipal code + riverbank authority |
| 2 | Street setback | 2.0 m | Assumed minor street relief | Phnom Penh municipal code |
| 3 | Side setbacks (E / W) | 4.0 m each | Assumed side relief → 13 m buildable depth | Architect-of-record + municipal code |
| 4 | **FAR / plot ratio** | **18.7** (computed 18.73) | Consequence of two 162–172 m towers on a 1,880 m² plot — **HEADLINE item** | Plot-ratio / FAR ceiling per municipal code |
| 5 | **Height limit** | **175.0 m** (assumed ceiling; tallest crown 172 m) | Assumed height ceiling above the T2 crown | Height ceiling incl. CAAC aviation (Phnom Penh Int'l ~7 km) constraints |
| 6 | Flood datum | +1.5 m | Raised GF/podium above assumed Mekong flood level | Local flood datum + river setback line, riverbank authority |
| 7 | **Buildable depth** | **13.0 m** (20 m − setbacks) | Drives single-loaded, 100%-river-facing plates | Architect-of-record (confirm once setbacks fixed) |
| 8 | Parking provision | **205 stalls** provided vs **228** estimated required (**~90%**) | Illustrative blended demand (1 stall per unit / 100 m² office NLA / 2.5 keys); mechanical stackers on B2/B3 | Municipal parking standard; shortfall mitigation (off-peak sharing, valet densification, EV-priority bays, off-site/valet contingency for the ~10% gap) |
| 9 | EV-ready | 30% of stalls | Sustainability provision | Architect-of-record + utility |
| 10 | Green / open space | 0.30 target (45% reported) | Public-realm / open-space target at grade | Municipal open-space requirement |
| 11 | Parking ratio basis | 1.0 stall per (1 unit \| 100 m² office NLA \| 2.5 keys) | Illustrative blended demand | Municipal parking standard |
| 12 | Above-grade GFA / FAR base | 35,204 m² ÷ 1,880 m² | Σ of computed use GFAs (basement 4,500 m² excluded from FAR) | Architect-of-record (area methodology) + authorities |
| 13 | Garden-bridge structural concept | 20 m clear span, inhabited, LOW at z 22.6–31 m (≈ L6–7) | Slide-bearing movement joint between the two towers | Structural engineer-of-record |
| 14 | L21 / podium transfers | Hotel sky-lobby transfer at L21; podium transfer | Office→hotel grid change; tower→basement | Structural engineer-of-record |

**General verification note.** All of the above must be confirmed by the **architect-of-record** and the relevant **Phnom Penh municipal authorities and riverbank authority** (and CAAC for aviation height), with structural items confirmed by the **structural engineer-of-record**, before this concept advances toward any statutory or construction stage.

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> **CONCEPT — NOT FOR CONSTRUCTION.** This document and its figures constitute a concept / feasibility master plan only. Every number is an input assumption or is computed from inputs and is subject to verification by the architect-of-record and competent authorities. It is not a basis for construction, contract, sale, or statutory approval.