Custom aluminium windows - bring your project to life

26th May 2026

Off-the-shelf window frames create specification problems that surface late in a build. The standard uPVC range does not suit the elevation. The timber option adds cost and a maintenance commitment. The standard aluminium finish is too bulky for the glazing ratios the architect had in mind.

Choosing bespoke aluminium windows from a manufacturer that makes to order changes that. Dimensions, colour, thermal specification, and lead times become variables the tradesperson controls, not constraints to work around.

Specifying custom aluminium windows right from the start delivers three practical advantages:

• Slim profiles that increase the glazed area per opening.
• Thermal performance backed by Document L certifications, building regulations.
• A colour range that covers every property type, including conservation areas.

Getting those decisions right early saves time and money and avoids difficult conversations later.

Slim Frames Let More Light into the Room

Aluminium's strength-to-weight ratio is what makes the difference here. Because the material is so strong, frames can be narrower than uPVC equivalents while holding larger panes of glass, which means more glazed area per opening and a cleaner line on the elevation.

For extensions and new builds where the brief asks for light and openness, it’s both a styling preference and a structural advantage built into the material itself.

Our Colour Range Works with Any Property

Most aluminium window suppliers offer a standard RAL range, and the gap shows up quickly on period properties and conservation area window projects. Off-the-shelf anthracite grey is rarely the right answer for a listed building or a Victorian terrace.

A good bespoke manufacturer carries colour collections designed for the full range of property types. Our colour range includes warm Cotswold tones for traditional and listed building work, contemporary shades in the Naturals collection for modern builds, and anodised effects for commercial and contemporary residential projects. The MAXi4 Heritage profile is specifically designed for Victorian, Art Deco, and conservation area work, available in the full colour palette with finishes that echo the original steel window aesthetic without the corrosion risk.

Our collections are shown in full at our Fordingbridge showroom, where colour samples and finished frames are available to review in person before specifying.

Made to Measure at Our Hampshire Factory

Off-the-shelf windows create fitting problems. A bespoke window made to the exact opening dimensions does not.

Every window in the full window range is manufactured on demand at our Hampshire facility, with full control over materials, tolerances, and lead times from design through to fabrication. Products are assembled and quality-checked before they leave the factory, with no field adjustments required and lead times as short as 5 days on prime product lines, backed by 24-hour order confirmation.

For tradespeople who want to check product specs before committing to a specification, our aluminium windows FAQ covers tolerances, lead times, and ordering in detail.

Why Aluminium Window Frames Last Longer Than You Might Expect

Modern aluminium window frames use a polyamide thermal break, a layer of insulating material that sits between the inner and outer parts of the frame. This prevents heat transfer through the metal, which is how aluminium window frames meet Document L requirements [1].

The thermal break technology delivers measurable performance across the full range:

• B energy ratings as standard, with A-rated upgrades available.
• Dimensional stability that holds the seal between the frame and glazing year-round.
• A service life of up to 45 years, which puts the initial cost in a different light.

Aluminium's service life is one of the arguments that holds up under scrutiny. How long aluminium windows actually last and what affects that figure is worth walking a client through when they're comparing options.

Energy Performance You Can Put a Number To

Specifying energy-efficient windows is one thing. Being able to show a client the certification is another.

Aluminium windows built to Document L requirements carry a Window Energy Rating. Both the MAXi2 Flush Casement and the MAXi3 Standard Casement carry WER certification, along with Air 600Pa, BS 6375, PAS 24, Water 1050Pa, and Wind 2000Pa ratings. For a contractor advising a client on compliance or a developer writing a specification, those numbers matter more than a vague performance claim.

U values sit alongside WER ratings when it comes to compliance conversations. The question of what a U value means in practice is one that comes up regularly on both residential and commercial specs.

The Right Specification Makes the Whole Project Easier

Specify the wrong window, and you find out late. There might be a frame that needs trimming on site, a colour that does not suit the conservation officer, certifications that fall short of Document L. Get the specification right at the start and those conversations do not happen. Custom aluminium windows give a project the foundation it needs rather than a problem to manage around.

Alimax manufactures bespoke aluminium windows and doors from our Hampshire factory, supplying trade professionals across Dorset and Hampshire for over 30 years. Every window is made to order, delivered on-site fully assembled, and backed by 24-hour order confirmation and lead times as short as 5 days on prime product lines.

To discuss your next project or request a quote, get in touch with the team on 01425 205465.

External Sources

[1] GOV.UK, Ministry of Housing, Communities and Local Government (MHCLG), Department for Levelling Up, Housing and Communities (DLUHC), Ministry of Housing, Communities & Local Government (2018 to 2021), Statutory Guidance, Conservation of Fuel and Power: Approved Document L (2023): https://www.gov.uk/government/publications/conservation-of-fuel-and-power-approved-document-l