Crittall-Style Doors and Glazing for Extensions
Steel-framed Crittall-style doors and windows for extensions - costs, genuine vs replica, thermal performance, and design ideas.
The Crittall look - slim black steel frames with large glass panes - has become the defining design feature of UK kitchen extensions. Whether you're building a side return, rear extension, or simply adding character to an open-plan layout, Crittall-style glazing transforms the aesthetic from standard to striking.
But the price range is vast, and the choices are confusing. Here's what you need to know.
The Options: Steel vs Aluminium vs Budget
Genuine Crittall (Hot-Rolled Steel)
Manufactured by Crittall Windows Ltd - the original company, operating since 1884. Their modern Homelight and Corporate ranges use thermally broken steel profiles with the slimmest sight lines available.
- Sight lines: 20–25mm (the thinnest on the market)
- Cost: £3,000–£6,000 per door/screen installed
- U-value: 1.5–1.8 W/m²K (double-glazed, thermally broken)
- Finish: Hot-dip galvanised + polyester powder coat (any RAL colour, but black is classic)
- Maintenance: Repaint every 8–12 years
- Lead time: 8–14 weeks from order
Best for: High-end extensions, listed buildings, period conversions, maximum visual impact.
Premium Aluminium Replicas
High-quality aluminium systems engineered to replicate the Crittall look with slimmer-than-standard profiles.
- Sight lines: 30–40mm (wider than steel but narrower than standard aluminium)
- Cost: £1,500–£3,500 per door/screen installed
- U-value: 1.4–1.6 W/m²K
- Finish: Polyester powder coat (no repainting needed)
- Maintenance: Virtually none
- Lead time: 4–8 weeks
Brands: Mondrian by Aluco, Origin OW-70, AluK BSC94, Schuco Jansen Janisol
Best for: Most extension projects - 80% of the look at 50% of the cost.
Budget Steel-Look Aluminium
Standard aluminium doors with a stepped or welded glazing bar to suggest the Crittall style. Wider profiles but much cheaper.
- Sight lines: 40–55mm
- Cost: £800–£2,000 per door installed
- U-value: 1.2–1.6 W/m²K
- Finish: Powder coat
- Lead time: 2–4 weeks
Best for: Budget projects where the look matters but perfection isn't required.
Cost Comparison: External Doors
For a typical rear opening (2.4m wide × 2.1m high):
| Configuration | Genuine Crittall | Premium Aluminium | Budget Aluminium |
|---|---|---|---|
| Fixed screen + single door | £4,000–£6,000 | £2,000–£3,500 | £1,000–£2,000 |
| French doors (pair) | £5,000–£8,000 | £2,500–£4,500 | £1,200–£2,500 |
| 3-panel bifold | £8,000–£15,000 | £3,500–£6,000 | £2,000–£3,500 |
| Fixed screen (no door) | £2,500–£4,000 | £1,200–£2,500 | £600–£1,500 |
Compared to standard aluminium bifolds (£3,000–£6,000 for the same opening), Crittall-style doors are a premium - but they're also the single most impactful design choice in a kitchen extension.
Where to Use Crittall-Style Glazing
1. Rear Extension Doors
The most common application - replacing the traditional bifold or sliding door with Crittall-style French doors flanked by fixed glazed panels. This creates a wall of glass with the elegant grid pattern as a design feature.
Typical configuration: Two fixed side panels + central French doors Cost: £3,000–£8,000 depending on specification
2. Side Return Glazing
In a side return extension, Crittall-style glazing can form the roof-to-floor glass wall that floods the narrow space with light. Because the side return wall is often shared with the neighbour, glazing is limited to the roof and the rear - making the roof glazing line a perfect place for a Crittall-style framework.
3. Internal Partitions
Crittall-style internal screens are transformative in open-plan spaces:
- Kitchen-to-hallway screen - separates cooking smells while maintaining light flow
- Home office partition - visual separation with borrowed light
- Utility room screen - hides laundry while keeping the space connected
Internal screens don't need thermal glazing, reducing cost to £1,000–£3,000 per panel (1.2–1.5m wide × 2.4m high).
4. Shower Screens
Crittall-style shower screens and wet room dividers are a popular bathroom upgrade. A framed glass shower screen costs £300–£800 for a steel-look aluminium version.
5. Glass Links
When connecting a new extension to the existing house (especially on listed buildings), a glazed link creates a visual break. Crittall-style framing gives this link architectural presence.
Design Considerations
Grid Pattern
The signature Crittall look is a grid of rectangular panes divided by glazing bars (also called astragal bars). Options:
| Pattern | Look | Cost Impact |
|---|---|---|
| No bars (plain glass) | Modern minimal | Cheapest |
| Horizontal bars only | Contemporary industrial | +10–15% |
| Full grid (horizontal + vertical) | Classic Crittall | +15–25% |
| Asymmetric grid | Architect-designed | +20–30% |
For replicas, bars are typically applied to the glass surface (stuck-on or clip-on) rather than being true divided lights. Genuine Crittall uses welded steel bars that are part of the frame structure - more authentic but more expensive.
Colour
Matt black (RAL 9005 or similar) is the classic choice and accounts for 80%+ of Crittall-style installations. Other popular options:
- Anthracite grey (RAL 7016) - softer than black, matches many modern window frames
- Dark bronze - warmer tone, suits period properties
- White - traditional for original Crittall in some period settings
- Dual colour - black outside, white inside (aluminium replicas only)
Threshold Details
External Crittall-style doors need a weather-resistant threshold. Options:
- Low threshold (20mm step) - standard, meets Building Regulations Part M for accessibility
- Flush threshold - level access for accessibility, requires excellent drainage detailing
- Raised threshold - most weather-resistant but creates a step
Crittall and Thermal Performance
The historic weakness of steel windows - poor insulation - has been solved by thermal breaks. Modern Crittall and replica products insert a polyamide strip between inner and outer steel/aluminium sections, dramatically reducing heat transfer.
| Product | U-value | Building Regs Compliant? |
|---|---|---|
| Original Crittall (single-glazed, no break) | 5.0+ | No |
| Modern Crittall (double-glazed, thermal break) | 1.5–1.8 | Yes |
| Premium aluminium replica (double-glazed) | 1.2–1.6 | Yes |
| Standard aluminium door (double-glazed) | 1.2–1.4 | Yes |
All modern products meet Building Regulations Part L requirements. The Energy Saving Trust recommends checking U-values before purchase - lower is better.
Installation
Crittall-style doors and screens are typically installed by the manufacturer's approved installers or specialist glazing contractors. Key points:
- Structural opening must be prepared by your builder with an appropriate lintel or steel beam
- Tolerance is critical - steel frames have very little adjustment compared to uPVC. Openings must be square and correctly sized.
- FENSA registration - external doors and windows must be installed by a FENSA-registered installer (or inspected under Building Regulations)
- Lead times - genuine Crittall takes 8–14 weeks from order. Plan around your extension build schedule.
Tip: Order doors and screens before construction starts so they arrive when the opening is ready. Delays on glazing are one of the most common causes of extension overruns.
Next Steps
- Decide steel vs aluminium - visit a showroom to compare sight lines and feel
- Choose your configuration - French doors + fixed panels is the most popular and cost-effective
- Get 3 quotes - from Crittall directly, an aluminium replica supplier, and a budget option
- Coordinate with your architect - the door specification affects the structural opening design
- Order early - 8–14 weeks lead time for genuine Crittall, 4–8 for replicas
- Budget within your extension costs - use our free calculator for the overall project
- Check our glossary for terms like sight line, thermal break, U-value, and astragal bar
Frequently Asked Questions
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