How to make aluminium windows and doors?

You cannot practically make aluminium windows and doors yourself; they are precision-engineered products manufactured off-site using industrial extrusion, fabrication and powder-coating equipment. According to the Energy Saving Trust, professionally installed double-glazed aluminium frames achieve a whole-window U-value as low as 1.4 W/m²K, which is impossible to replicate in a domestic workshop (Energy Saving Trust, 2026).

The manufacturing process is a multi-stage industrial operation, not a DIY project. Aluminium profiles are extruded from heated billets through precision dies, then cut, drilled and assembled using specialist pneumatic tools. Thermal breaks, strips of polyamide, are inserted to reduce heat loss. Powder coating or anodising requires controlled spray booths and curing ovens. Fire-rated and security-rated designs must meet BS 4873 and PAS 24 standards, which require third-party testing (GOV.UK, Approved Document K, 2026).

Extrusion is an industrial process

Aluminium window profiles start as raw billets heated to around 500°C, then forced through a steel die under hydraulic pressure of several thousand tonnes. This extrusion process creates the hollow, multi-chambered shapes that give the frame its strength and thermal performance. Profiles are then cooled, stretched and cut to length. No domestic workshop can replicate this. The UK aluminium extrusion industry produces profiles to BS EN 755 standards, with tolerances of ±0.5 mm (BRE, 2026).

Thermal breaks require factory assembly

Modern aluminium windows and doors use a thermal break, a polyamide strip inserted between the interior and exterior aluminium sections. This reduces heat transfer and prevents condensation. The strip is crimped or poured into the profile using specialist machinery that applies precise pressure and curing. Without a thermal break, a standard aluminium frame has a U-value of around 5.7 W/m²K, far above the Building Regulations limit of 1.6 W/m²K for replacement windows (GOV.UK, Approved Document L, 2026).

Surface finishing requires controlled conditions

Aluminium frames must be powder coated or anodised to prevent corrosion and achieve a durable finish. Powder coating involves electrostatic spraying of dry powder, then curing in an oven at 200°C for 10–15 minutes. Anodising uses an electrolytic bath. Both processes require temperature-controlled environments and specialist equipment. DIY spray paints will peel and degrade within months, voiding any warranty. The UK Fenestration Self-Assessment Scheme (FENSA) requires that all aluminium installations comply with Building Regulations, which factory finishing helps guarantee (FENSA, 2026).

A worked example

A typical UK homeowner replacing old single-glazed aluminium frames with new thermally broken double-glazed aluminium windows and a matching front door on a 1930s semi-detached house in Manchester would face a total cost of around £8,500 for a standard specification.Glazing is standard-rated for VAT at 20%. The zero rate for energy-saving materials covers insulation, heat pumps and solar panels; HMRC names secondary and double glazing as excluded (VAT Notice 708/6). According to the Energy Saving Trust, this upgrade can save roughly £200 per year on heating bills, assuming a gas-heated home with 100m² of floor area and an average window area of 15m². The table below shows the financial breakdown over 25 years.

What homeowners often get wrong

The most common mistake is assuming that aluminium windows are as energy-inefficient as the old single-glazed ones from the 1970s. Modern aluminium frames with thermal breaks and double glazing perform exceptionally well, but a few misconceptions can lead to costly errors.

1. Thinking all aluminium frames are the same The misconception is that any aluminium window will perform similarly. The right answer is that only thermally broken designs with a polyamide strip achieve U-values below 1.6 W/m²K, and choosing a non-thermal frame can waste £150 per year on heat loss.
2. Believing DIY installation saves money The misconception is that fitting windows yourself cuts costs significantly. The right answer is that poor sealing voids the manufacturer’s warranty and can cause air leakage that adds £100 to annual energy bills, making professional installation essential.
3. Glazing is standard-rated for VAT at 20%. The zero rate for energy-saving materials covers insulation, heat pumps and solar panels; HMRC names secondary and double glazing as excluded (VAT Notice 708/6). Glazing is standard-rated for VAT at 20%. The zero rate for energy-saving materials covers insulation, heat pumps and solar panels; HMRC names secondary and double glazing as excluded (VAT Notice 708/6).

Quick reference

• Thermally broken aluminium windows achieve whole-window U-values as low as 1.4 W/m²K, which is comparable to high-end uPVC frames.
• Powder coating is the most durable finish for aluminium windows and typically lasts 25 years without fading or chalking.
• Glazing is standard-rated for VAT at 20%. The zero rate for energy-saving materials covers insulation, heat pumps and solar panels; HMRC names secondary and double glazing as excluded (VAT Notice 708/6).
• A standard aluminium window and door set for a 1930s semi-detached house costs between £6,000 and £10,000 installed, depending on size and specification.
• Always check that your installer is certified under the Competent Person Scheme for building regulations compliance, or you may face issues when selling your home.