Are aluminium windows worth the extra cost over uPVC?

For extensions and contemporary properties, yes — aluminium's slim sight lines maximise glazed area, the colour range (via RAL powder coat) is superior, and the 40-year lifespan versus 25–30 years for uPVC makes aluminium more cost-effective over the property ownership horizon. For standard replacement windows in a non-conservation-area mid-terrace, coloured uPVC delivers 80% of the visual result at 60% of the cost. The exception is front elevations in conservation areas — here the planning authority will typically require timber, making aluminium irrelevant.

Can aluminium windows be installed in a conservation area in London?

On extension elevations (rear, side) not visible from the public highway, yes — most London conservation area planning policies permit contemporary aluminium frames on clearly contemporary addition buildings. On front elevations or original openings in the main house within a conservation area, the planning authority will usually require timber to match the original character. Always confirm with the planning department before ordering — a pre-application query (free in most boroughs) will give a definitive steer.

How long do aluminium windows last?

Aluminium window frames last 40+ years with normal maintenance (wipe-down, occasional hardware lubrication). The sealed glazing unit (double or triple glazed) typically lasts 20–25 years before seal failure causes condensation between panes — at that point the glazed unit can be replaced without replacing the frame, at approximately £80–£180 per unit. Powder coat finish: most manufacturers guarantee 10 years for standard RAL colours; higher-performance coatings (Qualicoat Class 1 or Qualicoat Class 2) can extend this to 20 years.

What is the difference between slim-profile and standard aluminium windows?

Standard aluminium window frames have a face width of 60–80mm — visible from both inside and outside. Slim-profile systems (Schüco AWS 57, Reynaers CS 38, Senior Alitherm 47) have a face width of 35–50mm, maximising the glazed area and giving a more minimal aesthetic. Slim-profile systems are typically used in contemporary extensions, Crittall-style multi-pane windows, and high-end residential projects. They cost 20–40% more than standard profiles. For conservation areas where a contemporary aluminium window is acceptable, slim-profile is strongly preferred by planning officers as less visually dominant than a wide-profile frame.

Aluminium Windows Cost London 2025 | Builderr

Aluminium window cost by type and size

Aluminium window cost in London varies significantly by window type, size and specification. Casement window (600mm × 900mm, double-glazed, white powder coat): £400–£700 supply only; £600–£1,000 installed. Casement window (1,200mm × 1,200mm, double-glazed): £600–£1,000 supply; £900–£1,500 installed. Tilt-and-turn window (1,000mm × 1,200mm): £700–£1,200 supply; £1,100–£1,800 installed. Fixed light (1,200mm × 600mm, over-door or clerestory): £350–£600 supply; £500–£900 installed. Crittall-style steel-look aluminium window (1,000mm × 1,500mm, multi-pane): £900–£1,800 supply; £1,300–£2,500 installed. Full house replacement — 3-bed Victorian terrace (10 windows, mix of casements and fixed lights, including scaffold): £8,000–£16,000 installed. Extension glazing package — 3m × 2.1m bifold doors + 2 fixed lights + 1 rooflight: £6,000–£12,000 installed. Premium suppliers include Senior Architectural Systems (SAA), Schüco, Reynaers, and Smart Architectural Aluminium — all offer extensive colour options via RAL powder coating.

Aluminium vs uPVC vs timber — which is right for your project?

The three main window frame materials each have distinct use cases in London. Aluminium: most appropriate for contemporary extensions (bifolds, sliding walls, Crittall-style multi-pane windows), new-build replacement windows in modern properties, and conservation areas where a non-timber contemporary frame is acceptable to the planning authority. Slim sight lines (25–35mm face width) maximise glazed area — important for extensions seeking maximum natural light. Powder-coat colour range is effectively unlimited (RAL colour chart); anthracite grey (RAL 7016) and black (RAL 9005) are the most popular extension finishes in London. Lifespan: 40+ years with minimal maintenance (no painting, just periodic wipe-down). uPVC: most cost-effective option — best for mid-market residential replacement windows in non-conservation-area properties. Modern coloured uPVC (foil-wrapped anthracite, black, grey) has narrowed the aesthetic gap with aluminium significantly. Not accepted by most conservation area planning departments. Lifespan: 25–30 years before seal failure becomes common. Timber: mandatory for listed buildings and many conservation areas (matching original Victorian/Georgian sash profile). Highest U-value potential with slim glazing units; draught-proofing and secondary glazing can bring heritage timber to near-modern thermal performance. Most maintenance-intensive (5–7 year repaint cycle). Lifespan: 60+ years with proper maintenance.

Aluminium windows in conservation areas and listed buildings

Conservation area planning policy on aluminium windows varies significantly by London borough. Contemporary aluminium: accepted in most conservation areas for new extension elevations (rear and side) that are not visible from the public highway, provided the frame profile is sufficiently slim and the colour is sympathetic (usually dark — anthracite, bronze, or black). Not accepted for front elevations in most conservation areas — front elevation windows must match the original material (typically timber). Crittall-style aluminium (multi-pane, slender profiles): popular in conservation areas as a contemporary reference to original steel-framed Crittall windows found in many 1930s properties and industrial conversions. Well-received by conservation officers when used on extensions, less so as replacement windows in original openings. Listed buildings: Listed Building Consent (LBC) is required for any window replacement in a listed building. Aluminium replacement windows are almost never approved in Grade II or higher listed buildings — original timber sash or casement windows must be repaired or like-for-like replaced in timber. Slim-profile aluminium secondary glazing (Selectaglaze, Secondary Glazing Specialists) is LBC-approved in most cases as it does not alter the primary window.

What to include in an aluminium window quote

A complete aluminium window installation quote from a London contractor should itemise the following. Supply and fabrication: frame system (specify the manufacturer and profile series — e.g., Schüco AWS 65 or Reynaers CS 68), colour and finish (RAL code), glazing specification (double or triple, U-value, glass type — toughened, laminated, solar control, low-e), hardware (handle, locking, hinge grade). Installation: removal and disposal of existing frames, lintels and structural work if new or enlarged openings, draught-sealing, cill fitting, internal plaster returns (making good around new frames), and window board (internal windowsill) fitting. Access: scaffold or scaffold tower hire for upper floors. FENSA registration (required for all replacement window installations in England — the contractor must notify the local authority and issue a FENSA certificate confirming Building Regulations compliance). Guarantee: most manufacturers offer a 10–25 year frame guarantee and 5–10 year sealed unit guarantee. Check guarantee terms — powder coat guarantees are typically 10 years for standard colours.

How Much Do Aluminium Windows Cost in London?