Extending a period Islington terrace means working within conservation constraints and tight urban plots. TrustBuilt Projects builds rear, side-return and lower-ground (basement) extensions across Barnsbury, Canonbury and Highbury (N1, N5, N7).
Islington's Georgian and Victorian terraces sit on tight plots, often with small rear gardens and shared boundaries, so extensions here are about clever use of space — a rear or side-return extension to open up the ground floor, or a lower-ground (basement) extension where the garden can't be lost. The right answer depends on the plot and the conservation status.
With Barnsbury, Canonbury and the other Islington conservation areas covering much of the borough — plus a lot of Grade II listed Georgian housing — permitted development often doesn't apply. Extensions are typically planning-led, and listed properties need listed building consent. We design to the local policy from the outset.
Lower-ground extensions and light-well works are common in N1 because they add space without touching the protected garden or street elevation. They're more involved structurally, so we lead with proper survey and structural design before any pricing.
Islington extension costs run above the London average — driven by conservation detailing, tight access and the higher proportion of structural and lower-ground work. Typical ranges:
| Project type | Typical cost | Timeline |
|---|---|---|
| Rear extension (single-storey) | £55,000 – £90,000 | 14–18 weeks |
| Side-return extension | £60,000 – £95,000 | 14–20 weeks |
| Lower-ground / basement extension | from £120,000 | 24–36 weeks |
| Listed / heritage-led extension | from £90,000 | 18–26 weeks |
Every project is quoted in writing after a free site visit — these ranges are a guide only.
Usually yes, but it's planning-led rather than permitted development. The council looks closely at materials, glazing and how the extension sits against the original house. We design to Islington's conservation policy and manage the application for you.
Listed Georgian houses can often still be extended sensitively, but it needs listed building consent and a design that protects the historic fabric. We coordinate the consent, heritage statement and works to keep everything compliant.
Where the garden is small and protected, going down rather than out is often the only way to add real space — and in Islington's market the value uplift can justify it. It's a bigger structural job, so we start with a full survey and structural design before pricing.
A single-storey rear or side-return extension typically runs 14–20 weeks; basement and listed works take considerably longer. The planning stage adds time up front, which we build into the timeline.
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