IKOSI-One Pavilion — Investment Pitch

Structural Logic

Geometry as Structure

The icosidodecahedron is one of only thirteen Archimedean solids — the rarest class of convex polyhedra, each vertex-transitive with two or more types of regular polygon faces. It possesses 30 vertices, 60 edges, and 32 faces (20 equilateral triangles and 12 regular pentagons). IKOSI-One uses a uniform 6-metre edge length throughout its entire exoskeleton, meaning every structural member is identical in specification.

At pavilion scale the geometric logic is even more potent: 360 metres of CHS tubular steel — 7.46 tonnes of circular hollow section — spans a 16.52-metre building across four occupied floors. The near-spherical form distributes wind loading with no flat facades — the estimated drag coefficient of 0.65–0.75 is roughly half that of a conventional square tower.

The solid has 32 faces, but only 31 become bespoke cassettes: the base pentagon is the ground slab. The 31-panel envelope (20 triangular, 11 pentagonal) is a set of sealed, pre-fabricated units with integrated thermal performance, waterproofing, and structural attachment — enabling rapid on-site assembly onto the pre-erected steel frame.

Structural Efficiency
7.46 tonnes of tubular steel — 360 m of CHS — for a 16.52m, 4-storey building. Homogeneous load distribution across all 60 members — no eccentric joints.

One Joint, 120 Times
Every member is full-penetration welded to a stub cast into its node — the same joint at both ends of all 60 members, 100% ultrasonically tested.

Wind Performance
Cd 0.65–0.75 vs. 1.1–1.3 for rectilinear buildings. No stagnation pressure on any facade — reduced cladding and structural loads.

Capital Expenditure

Financial Overview

The total build cost of £3,496,158 (Scenario C — CLT core and CLT floors) reflects a proof-of-concept prototype — a first-of-kind pavilion where every cassette, node, and connection detail is bespoke. At £5,271/m² gross slab area (£7,491/m² on 466.7 m² usable) this sits at the premium end of pavilion construction, but Ikosi Architecture projects a 30–40% reduction in volume production through standardised tooling and repeat fabrication.

The largest cost centres are the exoskeleton frame (£597k) — the 30 cast nodes, 60 CHS members and the CLT core — and the bespoke façade cassettes (£595k), now led by the 11 ETFE pentagon cushions that form the pavilion’s primary daylighting. Together these constitute the geometric identity of the building.

Switching the central spine from a reinforced-concrete cylinder to a CLT decagonal core — with CLT floors at F1–F3 — saves £269,644 (−7.2%) against the Scenario A baseline of £3.77M, while cutting mass and embodied carbon. A 20% contingency (£583k) reflects genuine prototype risk on a novel-form assembly.

£2,547k Construction (A–I)

+£366k Design Fees

+£583k Contingency (20%)

£3,496k Total Build Cost

Market Context

Pavilion Benchmarks

Project	Total Cost	Cost / m²	Notes
UK Expo 2025 Osaka Pavilion	~£7.0M	~£8,750/m²	National pavilion, temporary, fully serviced exhibition programme
IKOSI-One Pavilion	£3.50M	£5,271/m²	← OUR PROJECT — proof-of-concept icosidodecahedral pavilion (gross slab basis)
Serpentine Pavilion (typical)	~£1.5M	~£7,500/m²	Single-storey temporary pavilion, ~200 m², Kensington Gardens
Antepavilion (typical)	~£100k	~£3,300/m²	Small-scale experimental structure, ~30 m², Hoxton

40% Below Expo Rate
At £5,271/m² gross IKOSI-One costs materially less per square metre than a typical national expo pavilion, while delivering 4 occupied storeys and a permanent-capable structure.

3× The Space
At 466.7 m² usable across 4 floors, IKOSI-One provides over twice the usable area of a Serpentine Pavilion within a compact pentagonal footprint of just 62 m².

Volume Production Path
The proof-of-concept premium of 30–40% is recoverable in series production. At volume, unit cost is projected at £3,000–3,200/m² gross — competitive with bespoke commercial pavilions.

Engineering Innovation

Materials & Technology

Cast Steel Nodes

Thirty degree-4 junction crowns — each a precision-cast steel sphere with four CHS stub connections. Factory-applied intumescent coating to R60 fire rating.

∅580mm cast steel sphere
≈183 kg per node, 5.49 tonnes total
4 integral cast stubs per node
Intumescent DFT 30–60mm (factory applied)
Aluminium node collars with EPDM gaskets

CHS Tubular Members

Sixty identical circular hollow section members at 6m length, each full-penetration welded at both ends to a stub cast into the node.

Ø139.7mm OD, 6.3mm wall thickness, S355
6m uniform length (all 60 identical)
360m total CHS, 7.46 tonnes of tubular steel
Full-penetration welds to cast stubs, 100% UT
Intumescent coating to R60 standard

Bespoke Cassettes

31 sealed, pre-fabricated facade panels (20 triangular, 11 pentagonal — the base pentagon is the ground slab). Each uniquely oriented — parametric BIM + CNC fabrication ensures precision fit to the steel frame.

11 pentagonal ETFE cushions (daylighting)
15 double-glazed triangles + 5 apex PV triangles
U-value 0.25–0.30 W/m²K target
Elastomeric gaskets + silicone sealant (Class 100)
Parametric BIM (Rhinoceros/Revit), 20–25 yr lifecycle

Environmental Performance

Circular Economy

Reversible Where It Can Be

The steel shell is welded: each of the 60 tubes is full-penetration welded to stubs cast into the 30 nodes, and it is recovered as steel at end of life. The CLT core and floors are screw-fixed and fully reversible. The node fabrication method (cast vs fabricated) remains under review at Stage 2.

Minimal Material

7.46 tonnes of tubular steel for a 16.52m building. The icosidodecahedral geometry achieves the lowest surface-to-volume ratio, minimising both embodied carbon and cladding material.

Carbon-Negative Core

The CLT decagonal core replaces 117 tonnes of concrete with 15 tonnes of timber — removing 18 tonnes of CO₂ from manufacture and storing a further 24 tonnes of atmospheric carbon in the wood. A net swing of 42 tonnes from a single decision.

Wind Efficiency

The spherical form eliminates flat facades. Cd 0.65–0.75 halves stagnation pressure compared to rectilinear buildings, reducing structural steel weight and cladding fixings throughout.

Embodied Carbon — RICS WLCA, Scenario C

213 tCO₂e Whole-Building A1–A3
(457 kg/m²)

122 tCO₂e Including Biogenic
(261 kg/m²)

−42 tCO₂e Net Core Swing
(CLT vs. RC)

68% Cladding Share
of Total Carbon

Swapping the reinforced-concrete core for a CLT decagonal core removes 18 tonnes of manufacturing CO₂ and stores a further 24 tonnes of atmospheric carbon in the timber — a 42-tonne net swing from one design decision. Whole-building embodied carbon (Scenario C, with CLT floors and apex PV) is 213 tCO₂e at A1–A3, or 122 tCO₂e once biogenic sequestration is counted. The aluminium-framed cladding is now the dominant element (68%) and the primary Stage 2 reduction target.

Delivery Programme

Programme Overview

Weeks 1–2 Site Prep & Foundations
(5 Pad Footings)

Weeks 1–14 Node Fabrication
(Off-Site, Parallel)

Weeks 3–8 RC Core Construction
(Slipformed)

Weeks 15–22 Steel Frame Erection
(3-Phase Assembly)

Weeks 22–30 Cassette Cladding
& Fit-Out

Node Fabrication

14 Weeks

Off-site, parallel to ground works

On-Site Assembly

12–16 Weeks

Frame + cladding + fit-out

Total Programme

~30 Weeks

Fabrication start to handover

Enquiries

IKOSI-One is a proof-of-concept for a new class of mathematical architecture — a welded steel frame with reversible timber and cladding, structurally efficient at any scale.

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