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Doors & Windows

Sash window restoration, bifold doors and secure external doors, fitted with period properties and conservation requirements in mind.

Doors & Windows by GML Construction in North London

Sash windows are usually worth restoring, not replacing

Original timber sash windows are often in better structural condition than they look, and full replacement isn't always necessary — or even permitted, if the property's in a conservation area. We assess whether restoration or draught-proofing genuinely solves the problem before quoting a full replacement.

Where replacement is the right call, we fit like-for-like timber sash windows on period properties rather than uPVC, which conservation areas typically won't approve for street-facing elevations.

What's included

  • Timber sash window restoration and draught-proofing
  • Like-for-like sash window replacement for conservation areas
  • Bifold and sliding door installation on extensions
  • Secure external door fitting, including composite doors
  • Double glazing upgrades where permitted

Bifolds and modern openings on period homes

Bifold doors are common on rear extensions, and we design the opening to work with the rest of the property's proportions rather than as an incongruous modern addition. This usually comes up as part of a wider extension project.

01

Site Visit & Quote

Free, no-obligation assessment and a fixed written quote.

02

Plan the Work

Materials, timeline and any permissions confirmed before we start.

03

Carry Out the Job

One site manager, our own trades, start to finish.

04

Handover

Final walkthrough and snagging before we call it done.

Common questions

Can I replace sash windows with uPVC?

On conservation-area properties, usually not on street-facing elevations — planning rules typically require timber or timber-effect replacements. We'll confirm what applies to your specific property.

Is it cheaper to restore or replace sash windows?

Restoration is often more cost-effective than people expect, particularly if the timber frame is sound — we'll give you an honest comparison rather than default to recommending replacement.

Do bifold doors need planning permission?

Usually not if they're replacing an existing opening of similar size, but this depends on the property and whether it's part of a wider extension. We'll confirm at the quote stage.

Draughty sash windows or planning a new opening? Let's take a look.