Does uPVC have any place in a London renovation?

Very limited — uPVC is appropriate only for outer-borough non-conservation properties where budget is the dominant constraint and the property has no period character. uPVC fails on three fronts in central London: (1) conservation officers reject it in all CAs and Article 4 areas; (2) buyers in prime postcodes consider uPVC a downgrade from timber/aluminium and discount property values 5–8% on a fully uPVC-glazed period house; (3) uPVC lifecycle is shorter (15–20 years vs 30+ for timber/aluminium) and disposal is environmentally problematic. Builderr does not specify uPVC on any renovation in CAs, Article 4 zones, or properties valued above £750k.

Can I mix timber on the front elevation and aluminium on the rear?

Yes — and this is the dominant spec across central London renovations in conservation areas. Conservation officers typically focus on the front-of-house (street-facing) elevations; rear elevations facing only the rear garden are usually accepted with aluminium or other contemporary materials. Builderr's standard approach in a CA: timber sash restoration or like-for-like timber on the front; aluminium for new rear extension elements; conservation officer informally consulted before submission to confirm acceptability. Westminster, Kensington and Chelsea, Camden, and Islington conservation officers commonly accept this split.

How long is the lead time for aluminium vs timber windows in London?

Aluminium (Reynaers, Schuco, AluK fabricated by UK fabricators like IDsystems, Express Bi-Folding Doors, Sunfold Systems): 8–12 weeks from order to delivery, typical. Schuco direct: 10–14 weeks. Bespoke colours or special configurations: 14–16 weeks. Timber (Mumford & Wood, George Barnsdale): 12–16 weeks for sash replacement; 14–18 weeks for bespoke configurations. Heritage timber for listed buildings (3D-scanned, bespoke replication): 16–24 weeks. Plan windows on the critical path for renovation projects — they are typically the longest single lead-time item.

Are aluminium windows more secure than timber?

Both can achieve PAS 24 (the UK security standard for windows). Aluminium systems (Reynaers, Schuco) routinely include PAS 24 hardware as standard — multi-point locking, security hinges, laminated glass. Timber sash windows can achieve PAS 24 but require specification (Mumford & Wood Conservation Plus and George Barnsdale High Security ranges). Standard residential timber sashes are less secure than modern aluminium casements due to the inherent linear sliding action — adding key-locking sash stops and laminated glass to original sashes raises security to acceptable urban levels. Insurance: most London home insurers do not require PAS 24 windows but offer 5–10% premium discounts where they are installed.

Aluminium vs Timber Windows London 2026 | Builderr

Aluminium window systems and London applications

Aluminium windows have dominated the contemporary London extension market since approximately 2015 — particularly for rear extensions, bifolds, sliding doors and steel-look (Crittall-style) glazing. Major systems used in London: Reynaers (Belgian, premium spec, MasterPatio, MasterLine 8 and SL38 sliding doors, CS86-LS for slim casement); Schuco (German, high-performance, AWS 65, FWS 50 curtain walling, ASS 70 sliding); AluK (UK-manufactured, mid-spec, F82, optio); SAPA (Norwegian, value-mid spec); Smart Systems (UK, popular with installers, Visoglide sliding, Alitherm 600 casement). Typical applications: (1) Bifold doors — Reynaers SL/CF 77, Schuco ASS 70 FD, AluK Optio Bifold — at 4.8m bifold wall cost £8,500–£14,000 supply & install. (2) Slim sightline casements for rear extensions — Reynaers MasterLine 8 (62mm sightline) at £950–£1,400/m². (3) Crittall-style internal screens — AluK F82 with bronze powder coat, £1,100–£1,800/m². (4) Lift-and-slide doors — Reynaers SL38 or Schuco ASS 70.HI — premium at £14,000–£22,000 for a 4–6m opening. Aluminium U-values: typical thermally-broken aluminium 1.2–1.6 W/m²K (Reynaers MasterLine 8: 1.2); high-performance triple-glazed 0.8 W/m²K. Reynaers CF 77 bifold: 1.4 W/m²K. Lifecycle: 30+ years; powder coat finish stable for 25+ years; minimal maintenance.

Timber window systems and London applications

Timber windows remain essential for heritage replacement, conservation area replacement, and contemporary timber-frame contemporary designs. Major timber window manufacturers used in London: Mumford & Wood (Conservation range — accoya engineered timber sashes and casements; Conservation Plus for high-spec); George Barnsdale (UK manufacturer, sash specialists, BRE certified); Westbury (premium accoya sash and casement); Bereco (mid-spec accoya); Lomax + Wood (high-spec engineered timber); Norrsken (Scandinavian high-performance triple-glazed timber). Typical applications: (1) Heritage replacement sash windows — Mumford & Wood Conservation, accoya, slim sightline, slim DG — £2,500–£4,200 per window installed for a typical Victorian first-floor sash; conservation area officer's preferred option. (2) Bespoke timber casements for conservation contemporary rear extensions — £1,400–£2,200 per m². (3) Engineered timber bifolds — less common but available (Sunfold Systems, ID Systems Aluk-clad timber) at £14,000–£22,000 for a 4–5m bifold. Timber U-values: high-spec engineered triple-glazed timber 0.8–1.0 W/m²K (best in class); accoya double-glazed sash 1.3–1.5 W/m²K; standard softwood double glaze 1.6–1.8 W/m²K. Accoya is the dominant timber species for new London window manufacture — acetylated radiata pine with a 50-year above-ground durability guarantee. Maintenance: factory-finished timber requires repaint every 8–12 years (microporous finish) — typically £400–£800 per window when due.

When to choose timber vs aluminium vs composite

Choice framework for a London renovation: Conservation area / Article 4 / Listed building → Timber (Mumford & Wood, George Barnsdale, Westbury). Conservation officers will reject uPVC and typically reject aluminium for replacement of historic sashes; new contemporary rear extensions in conservation areas may permit aluminium for the new element while heritage windows on the host are kept timber. Listed buildings: timber sash replacement requires Listed Building Consent — like-for-like replacement is the default route. Modern contemporary extension (no conservation constraint) → Aluminium (Reynaers, Schuco, AluK) for slim sightlines, large openings, bifolds and sliders. Aluminium dominates new-build and contemporary extension specifications for visual reasons (slim profile, dark anthracite finish, large pane sizes) and acoustic/thermal reasons (sealed unit performance plus high air tightness). Period property with contemporary rear extension → Hybrid spec: timber sash restoration or like-for-like timber replacement on the host property + aluminium bifold/sliding doors on the rear extension. This is the dominant Builderr approach across 60%+ of London renovation projects. Composite (aluminium-clad timber) → Premium hybrid for clients wanting timber warmth inside + aluminium maintenance-free outside. Velfac, IDsystems, Sunfold Systems. Cost premium ~30% over aluminium-only; suits high-spec contemporary or contemporary heritage projects.

Cost comparison: 3-bed Victorian terrace renovation

Worked example — a 3-bed Victorian terrace renovation in Hackney with rear extension. Existing windows: 8 sash windows (front + side), 2 casements (rear), 1 bay window (front). Plus new rear extension requires: 4.8m bifold + 2 casement + 1 rooflight (rooflight priced separately). Option A — all timber: Mumford & Wood Conservation sash replacement for 8 sashes at £2,800 each = £22,400; 2 timber casements rear of host £3,800; bay window timber 3-sash £8,500; new extension timber casements 4m² £4,800; new extension timber bifold 4.8m £18,500 (premium). Total timber: £58,000. Option B — host timber + extension aluminium (Builderr default for conservation areas): host as Option A (£34,700); new extension Reynaers MasterLine 8 casement 4m² £4,800; bifold Reynaers CF 77 4.8m £11,500. Total: £51,000. Option C — host sash restoration + extension aluminium: sash restoration whole house £24,000 (vs £22,400 replacement); rear of host aluminium casement 4m² £4,800; bay window restoration £8,500; rear extension as Option B (£16,300). Total: £53,600 — and preserves all original glass. Option D — all aluminium (only if conservation officer permits): host elevation aluminium £28,000 (often refused in CAs); bay window aluminium £6,500; rear extension £16,300. Total: £50,800 — lowest cost but reputational/CA risk on the host. Builderr typical recommendation: Option C (host sash restoration + extension aluminium) — best long-term value, planning-safe, preserves heritage.

Aluminium vs Timber Windows in a London Renovation: Which Is Better?