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W40.
Genuine hot-rolled Swiss steel, three to five millimeters thick — one of only three systems on the market still made this way. Equally at home restoring a landmark or drawing the line in a new build.
Why W40
Built for timeless
architecture.
W40 pairs genuine hot-rolled steel with contemporary glazing . Its slim sightlines and authentic steel character make it equally at home in a historic renovation or a modern residence — the reason architects specify it by name.
Authentic hot-rolled steel
Drawn through dies under heat, not extruded or cold-formed. The grain, density, and restrained patina belong to the material itself — never an applied finish.
Ultra-slim sightlines
Solid sections just 3–5 mm thick carry far more glass and far less frame — the delicate steel lines that only true FerroFinestra can hold.
Interior & exterior applications
One system for the whole envelope — partitions and doors indoors, casements and window walls out — detailed and finished to a single standard throughout.
Anatomy
Designed around light.
Every millimeter has a purpose.
Solid hot-rolled steel, overlapped and finished on both sides, sealed with non-shrinking gaskets. Concealed hardware accepts modern tilt-and-turn or historical fittings without ever thickening the line.
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01.
Hot-rolled steel, Montanstahl — Switzerland.
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02.
Wall thickness of 3 – 5 mm, internal and external overlaps.
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03.
Self-adhesive, anti-shrinkage glazing gaskets.
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04.
Low-E insulated glass, up to 31 mm thick.
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05.
Concealed hardware — modern and classic styles.
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06.
Nine opening modes, inward and outward.
Four beads of detail.
The bead is the smallest line in a steel window — and the one architects read first. Four profiles, historically faithful to contemporary.
iv. Provenance
Since 1880.
Made the same way for more than a century. Unlike extruded aluminum, W40 begins as genuine hot-rolled steel — its distinctive texture, density, and strength are part of the material itself, not an applied finish.
The technique gave us the Crittall windows of London, the great glasshouses of Paris, the original steel curtain walls of New York. W40 is rolled today in Maserada sul Piave, using a process largely unchanged since the late 19th century.
Finish
Your finish.
Your personality.
Raw Steel — left to speak.
The steel speaks for itself. The rolling marks, subtle variation, and rich patina remain visible beneath a protective clear coat — specified for interior partitions and gallery walls where the material is the detail.
Powder Coated — in any RAL.
A multi-stage powder-coat applied through Tiger Coatings, our certified European partner. Any RAL standard, any custom-matched color — matte, satin, or texture. Warrantied against fade, chalk, and adhesion failure.
vi. For the Specifier
The numbers,
on demand.
Everything an architect needs, tucked away for everyone else. Open a section, or pull the files straight into your drawing set.
Frame depth — 40 mm
Face width, fixed light — from 25 mm
Face width, vent meeting — from 55 mm
Section wall thickness — 3–5 mm
Side-hung vent, max height — up to 2,400 mm
Single leaf door, max height — up to 3,000 mm
Vent weight per leaf — up to 120 kg
Insulated glazing unit (IGU) — up to 31 mm
Single glazing — from 6 mm
Low-E & laminated — supported
System type — Non-thermal (steel)
Recommended use — Interior & temperate exterior
Thermally-broken alternative — Ottostumm W50-TB
Compatible Collections
Designed
using W40.
Proven designs from our signature collection, drawn in W40 and built to your dimensions, finish, and hardware. Start here, or bring your own opening.
Choose the Right Profile
Not sure which
system fits?
Three steel systems, three jobs. W40 is the authentic hot-rolled choice; specify up when thermal performance or scale demands it.
| Compare | W40Ottostumm · Swiss-Italian You are here |
OS2-75Secco Sistemi | WelserAustrian Steel |
|---|---|---|---|
| Best For | Authentic hot-rolled steel — residential & heritage projects | Highest thermal performance, large exterior glazing | Commercial storefronts & interior systems |
| Material | Solid hot-rolled steel | Thermally-broken steel | Non-thermal steel |
| Thermal Break | No — non-thermal | Yes — high performance | No — non-thermal |
| Sightline | Ultra-slim (3–5 mm) | Slim, insulated | Slim |
| Application | Interior & temperate exterior | Exterior, all climates | Interior & light exterior |
ix. Why BlackFramed
Specified through
one partner.
Original European profiles, engineered and supported in North America — with a single point of contact from first sketch to final install.
Original European profiles
Fabricated under official Ottostumm | Mogs license — never a copy.
North American support
Local project management, lead times, and service you can reach.
Shop drawings
Fully detailed drawings prepared and reviewed for every opening.
Custom engineering
Non-standard sizes, spans, and configurations engineered to fit.
Project management
One team coordinating fabrication, finishing, freight, and site.
One point of contact
From specification to installation — never handed off.
x. Specification
Let's build with W40.
Tell us about your opening and we'll recommend configurations, prepare shop drawings, and provide indicative pricing within 48 hours.
