Extension Cost · Hackney

How much does an extension cost in Hackney?

Hackney sits toward the top of the national range, and specification is what put it there — a design-led market where the glazing, steel and finish packages move cost more than the floor area does. A single-storey rear here runs from a shell figure around £3,930 per m² to an all-in nearer £6,470, with the design-led end pushing past it.

Cost your Hackney extension See a sample report

The figure you find isn't the figure you pay

As everywhere, most cost guides quote a shell rate — the bare build. It is not what lands on your account. Calibrated to Hackney, a single-storey rear looks like this per square metre.

The headline
you find

£3,930

Shell only — structure, roof, envelope. Per m².

What you
actually pay

£6,470

All-in with a fitted kitchen, fees, contingency and VAT. Per m².

On a typical 30 m² rear in Hackney, that is roughly £190,000 to £215,000 all-in — against a shell headline nearer £120,000. The difference is the fit-out, the professional fees, the contingency and the VAT the shell figure never included. Where in that range you land depends heavily on the property.

Figures calibrated from BuildLens South East build data — around 10% above the regional baseline — priced on current day rates and live merchant pricing (2026). The all-in assumes an entry-level bespoke kitchen from local joinery; a higher kitchen tier moves it further.

Why Hackney sits above the national range

Hackney's reputation lags its reality. The borough's cost drivers today are those of a premium design market, and the budget-borough assumptions people arrive with are usually a decade out of date.

A design-led market

Hackney extensions skew architectural: structural glazing, exposed steel, crittall-style screens, polished concrete. Cost here moves with specification more than area — two identical footprints can land £40,000 apart on the glazing and finishes package alone, which is exactly the reference-class trap an average conceals.

De Beauvoir and the conservation streets

De Beauvoir Town, London Fields and the borough's other conservation areas bring the usual controls on external alterations. The Victorian terrace grid does the volume, with the period overhead that always implies.

Tight sites, tight access

Side returns and rear knock-throughs on terrace streets mean access through the house, skips on permits, and preliminaries that climb with the postcode's density.

Where the money goes, itemised. The full anatomy of an extension — substructure through fit-out — and how BuildLens builds the number from method and live pricing, sits on the main extension cost page. This page is the Hackney calibration of it.

Extension cost — the full breakdown →

Common questions about extension cost in Hackney

How much does a single-storey rear extension cost in Hackney?

Calibrated to Hackney, the shell runs around £3,930 per m² and the all-in — with a fitted kitchen, fees, contingency and VAT — nearer £6,470. A typical 30 m² rear therefore lands roughly £190,000 to £215,000 all-in. The figure depends heavily on the specific property, which is what a desktop analysis of your address sets out.

Why do Hackney quotes differ from the national averages online?

Because most published figures are shell rates without fit-out, fees, contingency or VAT — and because they know nothing about Hackney: specification packages that move cost faster than floor area, and the terrace-access preliminaries the borough's density imposes. The quote is usually not high; the headline was incomplete for this property in this place.

Why do Hackney extension quotes vary so widely for the same size?

Specification. Hackney is a design-led market, and the glazing, steelwork and finishes packages that define its extensions can move the same footprint by tens of thousands of pounds. Quotes that look inconsistent are usually pricing different specifications — which is why comparing them needs every quote set against the same itemised scope.

What pushes a Hackney extension over budget?

The property and the fit-out, usually — a kitchen or bathroom specified above the budget it was set against, and the local conditions above surfacing mid-job instead of being priced upfront. Both are predictable once the specific property is assessed, which is exactly what a BuildLens report does before you commit.