Internal & heritage
W20
The most slender profile. Solid hot-rolled steel sections with a stepped-leg design and material up to 5mm thick — where sightlines must all but disappear, on internal screens, heritage retrofits and mild-climate openings.
Specification
The fine print.
Profile depthApprox. 22mm sightline
SightlineApprox. 22mm face
GlazingSingle, or double up to 20mm IGU
Glazing — maximumUp to 20mm double glazed unit
U-value1.2 W/m²K (20mm IGU)
Wind loadUp to Class C5 — 2000 Pa
Heritage detailSolid hot-rolled steel, 3–5mm sections, stepped-leg
Max bar length5800mm
SizingTo drawings
Compatible styles
Build it in W20.
How W20 comparesSpec by spec
| Suite | SF20 | W20 | W40 | W50 TB | M65 TB | W75 TB | FPS50 |
|---|---|---|---|---|---|---|---|
| Relative cost | |||||||
| Best for | Entry · standardised | Internal & heritage | Standard external | Thermally broken | Thermally broken | Thermally broken | Strength · security |
| Glazing | Single 6mm, or slim 20mm IGU | Single, or double up to 20mm IGU | Double, up to 27mm IGU | Double or triple, up to 37mm IGU | Double or triple, up to ~50mm IGU | Triple, 26–56mm (units to 52mm) | Single / laminated |
| Construction depth | Approx. 20mm face | Approx. 22mm sightline | 42–47mm | Approx. 50mm | Approx. 65mm | 75mm construction depth | 50mm structural (uninsulated) |
| Sightline | Approx. 20mm face | Approx. 22mm face | Stepped-leg, reads near-W20 | Matched to W40 | Slim, matched family | 27mm frame / 49mm leaf-frame | Narrow face |
| Max glazing | Single or slim 20mm IGU | Up to 20mm double glazed unit | Up to 27mm double glazed unit (insulating glass up to 30mm) | Double or triple glazing up to 37mm | Double or triple glazing up to ~50mm | Triple glazing up to 52mm | Single or laminated safety glass |
| Thermal break | — | — | — | High-density cast-in polyurethane isolator | Glass-fibre reinforced polyamide isolator | Glass-fibre reinforced polyamide isolator | — |
| Thermal (U-value) | Single-glazed | 1.2 W/m²K (20mm IGU) | 1.0 W/m²K (27mm IGU) | 1.0 W/m²K (37mm IGU) | Uf from >1.0 W/m²K | Uf from >1.0 W/m²K | Uninsulated |
| Wind resistance | Sheltered / internal | Up to Class C5 — 2000 Pa | Up to Class C5 — 2000 Pa | Class C3 (1200 Pa) inward; up to Class C5 (2000 Pa) outward | Up to Class C5 — 2000 Pa | Up to Class C5 — 2000 Pa | High / structural |
| Watertightness | — | — | — | Class 7B inward; up to Class 9A (600 Pa) outward | Up to Class 9A — 600 Pa | Up to Class 9A — 600 Pa | — |
| Acoustic | — | — | — | Up to 43 dB | Up to 44 dB | Up to 44 dB (-2;-5) | — |
| Internal / external | Internal | Internal | External | External (cold) | External (cold) | External (cold) | Internal |
Indicative figures from the system catalogues — final performance is confirmed per opening on shop drawings. Figures for SF20, M65 TB and FPS50 are provisional and to be verified.
Why steelSteel vs the alternatives
| Facada steel | Aluminium | Timber | Traditional steel | |
|---|---|---|---|---|
| Sightlines | Slimmest — 20–25mm | Bulkier — 50–90mm | Heaviest — 90mm+ | Slim, but single-glazed |
| Strength | Highest | Lower — flexes over span | Moderate | Highest |
| Thermal | Thermally broken options | Broken, but bulkier | Naturally warm | No thermal break |
| Durability | Decades, recoatable | 15–25 yrs typical | Needs upkeep | Decades, rust risk |
| Maintenance | Low — wipe & inspect | Low | Higher — reseal/repaint | Higher — rust care |
| Look | Crisp, structural | Commercial | Soft, warm | Heritage |
| Relative cost | Premium | Lowest | Mid | Premium |
A general comparison of the materials, not of specific competing products — every system differs. Figures for steel are ours; the others are typical industry ranges.
Next step
Configure your W20 and price it.
Choose a style, size, glazing, finish and hardware — made-to-measure in 50mm increments. We respond with itemised pricing, by elevation.