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“Jordan was absolutely amazing from start to finish, very happy with our doors and the service provided. Five stars all round!”
Sophie du Toit
Bedford · Alitherm Heritage Doors
Alitherm Heritage Doors
Authentic Steel-Look Styling, Built in Aluminium
Traditional Steel-Look Doors
Alitherm Heritage Doors
Alitherm Heritage doors are steel-look aluminium doors: the slim sightlines and industrial character of traditional steel, built in aluminium so they perform better and last longer. They’re a popular choice for period renovations, listed buildings and contemporary extensions alike.
Typical 4-week lead time for supply only
Nationwide supply & delivery
Regional survey & installation
Interest-free credit available – T&Cs apply
10-year manufacturer warranty
25-year paint finish guarantee
Made to measure
Yorkshire made since 2003
Explore Our Door Systems
Which Heritage Door Is Right for You?
Alitherm Heritage is one of four heritage door systems we manufacture. Alitherm Heritage 60 offers an enhanced thermal upgrade for refurbishment and new-build projects, Sheerline Classic has a distinctive stepped Art Deco profile, and our AluSpace internal range brings the same steel-look styling indoors.
See the Full Heritage Door Range →Compare all four systems side by side.
What Is Alitherm Heritage?
Alitherm Heritage is our original steel-look aluminium door system, manufactured to replicate the elegant, slim-profile appearance of classic steel doors, with the benefits of modern aluminium performance built in. It’s the door we recommend most often for period properties including Edwardian and Georgian homes, for retro refurbishment projects, and for the industrial-inspired exteriors that have become popular in more contemporary homes.
With authentic glazing bar options, a wide range of finishes and a U-value of 1.5 W/m²K when fitted with our high-specification double glazing, it recreates the timeless look of the original steel framework while meeting current UK building regulations.
Designed for Lasting Performance
Key Features of Alitherm Heritage Doors
Traditional steel-look detailing, modern glazing performance and secure, made-to-measure aluminium construction.
Authentic Steel-Look Styling
Ultra-slim, authentic steel-look profiles with traditional glazing bar options.
Ultra-Slim Sightlines
47mm frame depth with a 33mm sightline.
Thermal Performance
U-value 1.5 W/m²K double glazed, with a Window Energy Rating (WER) of B. U-values of 1.4 and 1.2 W/m²K are possible with certain 28mm triple-glazing options, fully compliant with the June 2022 Document L UK building regulations.
High-Performance Glazing
28mm toughened double-glazed units as standard, gasket glazed, with a wide range of glazing specifications available including enhanced thermal performance down to a U-value of 1.2 W/m²K (triple glazed with Krypton).
Advanced Security
Multipoint locking protected by an Avocet ABS diamond-grade cylinder. Its Active Cam Technology is built around a molybdenum cam 20% stronger than steel, engineered specifically to resist snap attacks.
Premium Powder-Coated Finish
Single or dual-colour marine-grade quality polyester powder-coat paint finish as standard.
Long-Term Guarantees
10-year manufacturer warranty and a 25-year paint finish guarantee.
Low-Maintenance Aluminium
Rust-proof, low-maintenance polyester powder-coated aluminium.
Made to Measure
Every Alitherm Heritage door is made to measure – available as a single or double door, opening inwards or outwards, with side or top light options. For wider openings, explore our Heritage bifold doors.
Designed with Sustainability in Mind
Cradle to Cradle Certified
Designed for a circular lifecycle, so materials can be reused or recycled rather than becoming waste.
Aluminium Steel Replacement Doors: Why Homeowners Are Switching
Our aluminium steel replacement doors give you the look you want, at a fraction of the cost and upkeep of the real thing:
The Look of Steel – slim aluminium profiles that faithfully recreate classic steel-style glazing bars and sightlines.
Modern Energy Efficiency – advanced thermal breaks and high-performance glazing to keep your home warmer and reduce energy bills.
Low Maintenance – no rust, flaking paint or constant upkeep, just a long-lasting polyester powder-coated paint finish.
Improved Security – reinforced frames and the multi-point locking system described above, for genuine peace of mind.
Traditional steel doors, by contrast, are prone to compromised insulation, condensation and corrosion over time. Aluminium doesn’t rust, rot or need repainting.
Recognition & Customer Experiences
What Our Customers Say
From a Channel 4 television feature to feedback from homeowners, discover why our heritage aluminium windows and doors make an impression.
Suitable for Listed Buildings, Conservation Areas & Period Homes
Alitherm Heritage doors have already been approved for listed building and conservation area projects by a number of local authorities, including the London Boroughs of Islington, Camden and Tower Hamlets, Watford Borough Council, Essex County Council, Leeds City Council, and Cadw, the Welsh Government’s historic environment service. Final approval always depends on your specific property and local authority, and we’re happy to provide technical drawings to support a planning application.
We also offer a free sample service to help with surveying decisions, design choices or planning applications – just call us on 01535 603909 and ask.
Alitherm Heritage Projects
Explore how our aluminium heritage windows and doors complement character properties, listed buildings and contemporary homes across the UK.
Why Homeowners Choose Marlin
As a family-run manufacturer of heritage aluminium systems in Keighley, West Yorkshire, we combine over 20 years of expertise with quality materials and a 10-year warranty for complete peace of mind.
Supply & Installation Options
Choose professional installation across our regional service area or nationwide supply-only delivery.
Supply & Install
Professional survey and installation across West & South Yorkshire, Greater Manchester, Merseyside, Lancashire, Derbyshire, Nottinghamshire, East Riding and Cheshire.
Supply Only – Nationwide
Made to measure in Yorkshire and delivered nationwide, ready for your builder or installer.
Outside our installation area? We can still supply and deliver nationwide.
Visit Our Keighley Showroom
For inspiration, help and advice, visit our showroom in Keighley, West Yorkshire. You can visit by appointment Monday to Friday 9am to 4:30pm, Saturday 8am to 12 noon, or by special arrangement outside of these times – see the largest selection of Heritage steel-look windows and doors in the UK, compare frame styles, sightlines and finishes side by side, before you decide. Just call 01535 603909 to book.
Helpful guides
IS ALUMINIUM A SUITABLE ALTERNATIVE FOR THE REPLACEMENT OF STEEL PRODUCTS?
Steel look Aluminium Windows, Doors and Internal Room Dividers and Doors look very similar to their Steel counterparts but offer several benefits of being Aluminium.
The benefits of modern, secure, thermally efficient aluminium windows with the heritage and character of traditional steel at a fraction of the cost.
Frequently Asked Questions
How long will my order take?
We aim to return all quotations within 24 hours. Once your order is confirmed, your doors are typically ready within around 4 weeks for supply only, though larger projects may take longer.
Are Alitherm Heritage doors secure?
Yes. The multipoint locking system is protected by an Avocet ABS diamond-grade cylinder with Active Cam Technology as standard, built around a Molybdenum cam that’s 20% stronger than steel and specifically engineered to resist snap attacks.
Can they be used in listed buildings or conservation areas?
Yes. Alitherm Heritage systems have been approved for listed building projects by a number of councils, including those named above, although final approval always depends on your specific property and local authority.
What information do you need for an accurate quotation?
Approximate dimensions (width x height), a basic design or layout, and your project location.
How is Alitherm Heritage different from real steel doors?
It gives you a similar slim, industrial sightline, but without the rust, condensation and heavy maintenance that come with genuine steel – while meeting current UK building regulations for thermal performance and security.
Ready to transform your home?
Get a made-to-measure quote for your Alitherm Heritage doors today. Our team will guide you through sizes, styles and glazing options to find the perfect fit for your home.
Or call us on 01535 603909 to speak with our team.
Come and explore…
Aluminium Bi-fold Doors, Sliding Doors, Contemporary Glazing, Aluminium Heritage Windows and Traditional Steel Replacement Doors
