The engineered steel kit. A complete structure.
Every member is welded, primed and cut to length off site. On site it bolts together — no cutting, no welding. The same portal-frame concept scales from a small studio to a wide-span home simply by stepping up the steel.
- Structural steel
- AS 4100
- Wind rating
- 50 m/s design speed
- Scope
- Footings to a complete structure
Off-site fabrication, engineered to code.
Welded and primed in the factory, engineered to AS 4100, AS/NZS 4600 and the AS/NZS 1170 series. Three size tiers cover the full span range, and the scope runs from footings to a complete structure, including internal wall framing, windows, doors and cladding.
Off-site fabrication
Every frame member welded, primed and cut to length in the factory before it reaches site.
Engineered to code
AS 4100 structural steel, AS/NZS 4600 cold-formed steel, AS/NZS 1170 series structural and wind actions.
Three size tiers
Perimeter PFC size steps up with module width — see the tier table below.
Scope
Footings through to a complete structure, including internal wall framing, windows, doors and cladding.
Enseam cladding
Lysaght Enseam 265 mm vertical profile, one system for both roof and wall.
Base system and primary structure.
| Component | Spec |
|---|---|
| External perimeter | PFC 180 / 200 / 230 (Grade 250, AS/NZS 3679.1), sized to module width |
| Base subframe | Boxspan 150×50 @2mm cold-formed steel |
| Post-to-base detail | 75×180×12mm baseplate, 10mm stiffener, 4× M20 anchor bolts |
| Portal frames | 150 or 180 PFC (span-dependent), 35° gable, Grade 250 |
| Eave beams | 125 PFC, continuous |
| Apex connection | 75×180×10mm plate, Ø18 bolts |
| Purlin / eave connection | 10mm plate, 2× M16 bolts |
| Welds | 6mm fillet, AS/NZS 1554 |
| Shop finish | Primed; galvanising optional to AS/NZS 4680 |
| Roof purlins | Lysaght C15019 Cee @488mm centres |
| Wall framing | Cold-formed 45×100@600mm c/c, double stud at openings |
| Roof & wall cladding | Lysaght Enseam, 265mm vertical |
| Structural bolts | Grade 8.8, M12 min, AS/NZS 1252 |
Footings to a complete structure.
Every kit goes up in the same order — footings, portal frame, purlins and bracing, then the Enseam cladding. Portals always land at 4m max centres.
01 / 12
Footings and base beams
The footings are set, then the 200PFC base beams are bolted down to form the perimeter the whole frame is set out from.
Step 1 of 12
Sequence shown is diagrammatic, single bay at 4m portal spacing. From the Structural Kit System supply specification.
Same concept, bigger steel.
The portal frame concept is identical across every tier — only the perimeter and portal PFC sizes step up with module width.
| Tier | Module width | Perimeter PFC | Portal PFC |
|---|---|---|---|
| T1 · Standard | Up to 3,000mm | PFC 180 | 150 PFC |
| T2 · Mid | 3,000-3,500mm | PFC 200 | 150 or 180 PFC |
| T3 · Wide | 3,500-4,500mm | PFC 230 | 180 PFC |
Beyond the documented tiers, the kit is also supplied as a 5.0 m or 6.0 m clear open span on 300 PFC portals, in lengths from 9.5 m to 15.5 m. These widths are kit supply only — a finished building wider than 4.5 m cannot be moved on a road — and the internal layout is drawn with you rather than selected from a plan set, because nothing inside the perimeter is load bearing.
Sourced from the Structural Kit System supply specification, June 2026. The 5.0 m and 6.0 m open-span widths sit outside that document and are current Arc supply direction. Module length is variable up to an 8,000mm standard bay, extended by combining bays; multi-module layouts run side-by-side via a shared central portal or independent frames. Figures presented here are specific to the Kit System supply spec and are separate from the PFC width bands quoted on the main Proof section of this site.
Built to code, not to guesswork.
| Structural steel | AS 4100 |
| Cold-formed steel | AS/NZS 4600 |
| Structural actions | AS/NZS 1170 series |
| Wind actions | AS/NZS 1170.2 — 50 m/s basic design wind speed |
| Residential live load | 1.9 kPa floors / 0.25 kPa roof |
| Roof dead load | 0.15 kPa minimum |
| Welding | AS/NZS 1554 — 6mm continuous fillet |
| Bolting | AS 4100 + AS/NZS 1252, Grade 8.8 M12 min |
| Galvanising | AS/NZS 4680, where specified |
Structural Kit System supply specification, June 2026. Portal spacing is always at 4m max.
Included. Not included.
Included
- ＋ PFC perimeter base frame
- ＋ Boxspan floor subframe
- ＋ Portal frames with welded cleats
- ＋ 125 PFC eave beams
- ＋ C15019 Cee purlins
- ＋ Cold-formed wall framing
- ＋ 265mm Enseam roof and wall cladding
- ＋ Aluminium windows and doors
- ＋ All structural connections and hardware
- ＋ Shop prime coat
- ＋ Fabrication drawings (IFC set)
- ＋ Internal fit-out, supplied through Arc Elements
Not included
- － Concrete pier or footing construction
- － Internal linings and insulation
- － Electrical and plumbing rough-in
- － Crane and erection labour
- － Building approval / CDC documentation
- － Site preparation and access
Structural Kit System supply specification, June 2026, page 5.
Need documentation and approval before the kit ships? Start with Arc Studio, or fit it out with Arc Elements once it's up.
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