Why a 40m² Studio Flat in London Costs £220,000—When the Real Build Cost Is Only £40,000

Are buyers really paying £160,000 just for paperwork, middlemen, and an old fit-out? London homeowners already know extensions, studios, and small builds are expensive to buy. But very few people realise how cheap they are to build.

A standard studio-sized space (40m² — the England & Wales national minimum studio size) has a real construction cost of about:

  • £15,000 — Strip foundations
  • £12,500 — External and internal cavity walls
  • £12,500 — Flat or pitched roof frame
  • ≈ £40,000 total for the entire structural build

Even with a full fit-out — electrics, plumbing, insulation, plastering, flooring, kitchen, bathroom — you are still in the range of £55,000–£58,000.

So why does a tiny, old, dated studio sell for £220,000?

Why is the market charging £160,000 more for something that costs £40k to build from scratch?

Let’s break this down using the same logic we apply daily when delivering rear extensions, side extensions, wraparound extensions, and double-storey extensions across London.


1. Build Cost ≠ Market Cost

London property is not priced based on the cost to construct foundations, walls, and roof frames.
It’s priced based on:

  • Scarcity
  • Demand
  • Planning restrictions
  • Mortgage culture
  • London postcode
  • Historic inflation

Nothing to do with construction.

We know this because we build full 3m, 4m, 5m and 6m rear extensions, wraparounds, and double-storey additions every week.
We see the real prices:

Cavity walls? Cheap.

Roof structure? Cheap.

Foundations? Cheap.

Paperwork + transaction system + land cost? Insane.

The market price of a studio flat, extension, or small unit is driven by everything except the cost to build it.


2. People Aren’t Paying for Bricks — They’re Paying for Layers of Middlemen

A studio that costs £40k to build but sells for £220k includes:

❌ Mortgage fees

❌ Estate agents
❌ Lawyers & conveyancing
❌ Stamp duty
❌ Planning history
❌ Developer profit
❌ Land cost
❌ Bureaucracy
❌ Old building “market value”

None of this adds structure.
None of it adds strength.
None of it adds engineering.

When we build extensions, we deliver everything under one roof:

**✔ Design

✔ Planning support
✔ Structural engineering
✔ Foundations
✔ Walls
✔ Roof frame
✔ Building control
✔ Project sequencing
✔ Final build**

There are no middle layers, which is why your build cost stays consistent and controlled.

If property resales worked like construction does, studios would not cost £220k.


3. Even the Fit-Out Doesn’t Justify the Price Gap

Let’s be realistic:
A full fit-out for 40m² — including bathroom, kitchen, electrics, flooring and plastering — costs:

👉 £10,000–£18,000 depending on finish level.

So even on the high end:

  • £40,000 full structural build
  • £15,000 premium fit-out
  • £55,000 total

Yet the same unit sells for £220,000.

That is £165,000 of non-construction cost.


4. Our Extensions Prove the Real Cost of Building Space

Look at the types of work we deliver daily:


🧱 Rear Extensions (3m, 4m, 5m, 6m)

Open-plan kitchen/living areas
Structural steel installation
Foundations, walls, roof frames
Cohesive finishes matching the original house
Planning + building control + engineering
Single contractor, fixed price


🧱 Side Extensions

Turn wasted side space into usable internal rooms
Utility rooms, dining areas, kitchen expansions
Structural tying-in to existing house
Delivered end-to-end with planning + engineering
One contractor = no hidden surprises


📐 Wraparound Extensions

Full-width rear + side transformation
Resets home flow & increases footprint
Consistent foundation-to-roof design
Cohesive material matching
Managed from drawings to final construction


🛠️ Double-Storey Extensions

Expand both floors in one build
More bedrooms, bathrooms, landing space
Bigger ground-floor living areas
Integrated structural design
Built seamlessly into the existing home


These projects teach us something very important:

👉 The physical act of building is not expensive.
👉 The “London property market system” is what inflates cost.

The same structural components repeated in extensions are the same ones needed to build a studio:

🧱 Walls

Dense block or brick
Insulation
Cavity build-up
Lintels
Load-bearing capacity

🏗️ Roof Frame

Timber joists
50×150 / 50×195 / 50×225 depending on span
300–400mm centres
Full waterproofing & support layers

◻️ Foundations

600mm–900mm strip footing
Designed for 5 t/m² soil bearing
Simple, predictable, fast

📐 Technical Engineering

Structural calculations
Drawings
Connection details
Support layouts
Building control-ready

🧰 Construction Oversight

On-site supervision
Material spec compliance
Sequenced build
Quality control & reporting

All of this — put together — still totals around £40,000–£55,000 for a 40m² structure.


5. The Big Question: Why Pay £160,000 for Nothing Structural?

If the walls, roof, foundations, and structure cost:

👉 £40,000

And the fit-out costs:

👉 £15,000

Then what exactly is the other:

👉 £160,000

going toward when buying a studio?

The answer is simple:

Because London buyers are paying for the system — not the building.

Not the walls.
Not the roof.
Not the foundations.
Not the insulation.
Not the design.
Not the engineering.

They’re paying for a market machine built on fees, land value, and mortgage culture.


Conclusion: Build Space for £40k Instead of Buying It for £220k

Today, homeowners finally have a new option:

✔ Build a 40m² extension
✔ Use a standardised structural design
✔ Fixed cost
✔ Full engineering
✔ Full compliance
✔ One contractor
✔ No layers
✔ No inflated middlemen costs

A structure is cheap.
A London property is not.

So the real question is:

If it costs £40,000 to build a studio-sized space… why pay £220,000 for an old one?

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