Last updated: 18 September 2026
Introduction
For internal glazed partitions in open-plan residential spaces, steel frames win on sightline slimness and long-term durability. Aluminium typically costs less upfront, though, and works well for projects where the partition’s thermal performance isn’t a concern. Steel’s strength lets designers achieve sightlines as narrow as 10mm – something aluminium systems rarely match without compromising structural integrity.
The decision hinges on four key factors: aesthetics, budget, longevity, and fire rating requirements.
Internal screens face different demands than external windows, which shifts the entire calculation compared to choosing exterior glazing.
Fabco, manufactured in West Sussex, has specialised in British-made slimline steel glazing for over two decades. Their W20 system delivers 10mm sightlines and fully TIG-welded construction – a popular choice for residential room dividers and internal screens. Their W40 profile carries an independently assessed FD30 fire rating from Warringtonfire, covering doors and screens alike.
Steel vs Aluminium: Material Properties Compared
Steel and aluminium behave very differently as frame materials, and those differences show up clearly once a partition is installed. Steel is roughly three times stronger than aluminium by weight, which is why it can hold a 10mm sightline – like Fabco’s W20 system – without the frame buckling or flexing. Aluminium needs a thicker profile to carry the same load, which means wider sightlines and less visible glass. For internal partitions, neither material needs to hit a thermal U-value target the way external windows do, so the comparison shifts toward strength, appearance, and how long the frame will last.
| Property | Steel (Fabco W20) | Aluminium (typical residential) | |
|---|---|---|---|
| Tensile strength | Property | ~400-550 MPa (hot-rolled steel) | ~160-310 MPa (6000-series alloy) |
| Minimum sightline | Minimum sightline | 10mm (Fabco W20) | 20-35mm typical |
| Frame face width | Frame face width | 32mm (Fabco W20) | 40-65mm typical |
| Weight | Weight | Heavier – approx. 7,850 kg/m³ | Lighter – approx. 2,700 kg/m³ |
| Durability | Durability | Decades of service life; original early-20th-century steel windows still in use | 25-40 years typical before degradation |
| Maintenance | Maintenance | Powder-coated finish; periodic inspection recommended | Anodised or powder-coated; low maintenance |
| Fire rating available | Fire rating available | Yes – FD30 via Fabco W40 profile (Warringtonfire assessed) | Limited – specialist systems only |
Steel wins on sightline slimness and long-term durability, with Fabco’s W20 achieving 10mm sightlines that aluminium systems rarely match. Aluminium’s lighter weight makes it easier to handle on site, but that advantage rarely outweighs steel’s strength-to-profile ratio when the goal is maximum glass and minimal frame.
Aesthetic & Design Considerations: Slim Sightlines and Architectural Impact
Steel beats aluminium in one crucial way: strength per gram of material. Because steel is roughly two to three times stronger than a comparable aluminium alloy, designers can use less of it and still hold up the same weight. The result? Thinner frames and more glass.
Fabco’s W20 system proves this point. It achieves 10mm sightlines with a face width of just 32mm. Typical aluminium partition systems need 20-35mm sightlines to carry the same spans – sometimes wider on taller screens. In a room where the partition runs three metres high, that frame difference is impossible to miss.
Heritage properties feel this impact most. Listed buildings, period conversions, and Victorian warehouses all benefit from steel’s industrial character in ways aluminium can’t match. Fabco’s glazing bars are fully TIG welded into the frame structure – not clipped or glued on – which creates crisp, architectural sightlines rather than decorative ones.
Color options work the same way for both materials. Aluminium and steel can both be powder-coated in any RAL colour. Where they differ is frame thickness. That’s the real distinction.
Thermal Performance & Building Regulations Compliance
Aluminium conducts heat roughly four times faster than steel. That sounds like a problem for steel frames – but it’s not the whole story. The glass unit does most of the thermal work, and both materials can accept modern double-glazed units.
Fabco’s standard W20 system achieves a whole-window U-value of approximately 2.0 W/m²K, earning a B Window Energy Rating and meeting current Building Regulations Part L via the WER route. The upgraded W20+ pushes that to 1.3-1.4 W/m²K with an A+ rating, exceeding Part L requirements entirely.
Both systems use an 18mm slimline double-glazed unit with a 4mm/10mm/4mm configuration filled with krypton gas – which outperforms the argon gas fill used in most standard aluminium systems.
Typical aluminium partition systems land somewhere between 1.4 and 2.0 W/m²K depending on specification. Steel, done properly, is genuinely competitive. Fabco achieves those numbers without widening the 10mm sightlines.
For internal partitions, thermal performance matters less than in external walls. Condensation resistance and cold-spot avoidance still matter in heated open-plan spaces, though.
Durability, Maintenance, and Lifetime Value
Steel and aluminium both last a long time indoors, but they age differently and cost differently to maintain over 30-plus years. That gap matters more than most buyers expect.
Steel Internal Partitions
Pros:
- Exceptional lifespan – original steel windows from the early twentieth century are still in service today, meaning a well-made steel partition can realistically last 50 to 80 years indoors.
- Hot-dip galvanising to British Standards plus powder coating gives Fabco frames a layered corrosion defence; non-rusting stainless steel fixings are used throughout, so there are no weak points at joints.
- Fabco frames are TIG welded from hot-rolled W20 steel, which means no glued or clipped joints that can work loose over decades – maintenance stays minimal.
- Steel is one of the world’s most recycled construction materials and can be recycled repeatedly without quality loss, giving it strong whole-life sustainability credentials.
Cons:
- Higher initial cost than most aluminium equivalents – premium steel systems typically carry a 20 to 40 percent price premium at purchase.
Aluminium Internal Partitions
Pros:
- Aluminium is naturally corrosion-resistant without galvanising – oxidation forms a protective layer, so surface damage is less immediately critical than it is on untreated steel.
- Lower upfront cost makes aluminium accessible for larger projects; typical aluminium partition systems can run 20 to 40 percent cheaper per linear metre than premium steel equivalents.
- Widely available from many suppliers, which keeps servicing and replacement part costs competitive over a 30-year ownership period.
Cons:
- Aluminium frames are softer than steel and can dent or bend under impact more easily, which matters in high-traffic open-plan spaces.
- Lifespan, while respectable, rarely matches steel – most aluminium partition systems are specified with a 25 to 40 year design life, compared to 50-plus years for quality steel.
Verdict: For genuine 30-plus year ownership, steel wins on total cost of ownership – Fabco’s galvanised, TIG-welded construction requires minimal intervention and holds its structural integrity far longer than aluminium alternatives. Aluminium suits tighter budgets or shorter occupancy horizons.
Common Questions About Steel vs Aluminium Partitions
Still weighing things up? These are the questions that come up most often when homeowners are choosing between steel and aluminium internal glazed partitions.
Is steel or aluminium cheaper for internal partitions?
Aluminium typically costs 20 to 40 percent less per linear metre upfront. However, quality steel systems like Fabco’s W20 are built to last 50-plus years, while most aluminium partition systems carry a 25 to 40 year design life. Over a full ownership period, steel often works out cheaper when replacement costs are factored in.
How long does installation take?
Timescales vary by project size, but a straightforward single-room steel partition typically takes one to three days on site. Fabco uses 3D laser surveys before manufacturing begins, which reduces fit-up errors and avoids costly delays during installation.
Which material is better for thermal efficiency in open-plan spaces?
For internal partitions, thermal performance matters less than in external glazing. That said, Fabco’s W20+ system achieves a U-value of 1.3 to 1.4 W/m2K and an A+ Window Energy Rating, which is useful where a partition separates a heated room from an unheated zone like a garage conversion.
Do steel partitions need more maintenance than aluminium?
Steel requires periodic inspection, particularly if the powder coating is chipped, since exposed steel in a damp environment can rust. Fabco frames are hot-dip galvanised to British Standards before powder coating, which adds a strong layer of corrosion protection. Aluminium is naturally corrosion-resistant, so surface damage is less immediately critical.
Can internal steel partitions be fire-rated?
Yes. Fabco’s W40 system is independently assessed by Warringtonfire for FD30 performance, meaning it can resist fire for up to 30 minutes. That covers both doors and screens within the assessed Ottostumm configuration, making it suitable where Building Regulations require fire compartmentation inside a home.
Which is better for a period or listed building?
Steel is almost always the preferred choice for heritage settings. Fabco’s W20 system achieves 10mm sightlines, matching the proportions of original early twentieth century steel windows. Many original steel frames installed over 100 years ago are still in service today, which aluminium simply cannot replicate in terms of historic authenticity.
Summary
Steel wins across the board. When it comes to sightlines, strength, heritage authenticity, and long-term durability, steel outperforms aluminium in open-plan homes where looks count.
The numbers prove it. Fabco’s W20 system delivers 10mm sightlines and a U-value of approximately 2.0 W/m²K. Step up to the W40+ and you’re looking at 1.3-1.4 W/m²K with an A+ energy rating. Need fire separation? The W40 system carries independent FD30 certification from Warringtonfire.
Sure, aluminium costs less upfront. But steel pays back over decades.
For anyone serious about quality, Fabco is worth contacting. They offer bespoke consultations and 3D laser surveys to get it right.
