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How much does it cost to build a 150m² house?

Short answer

Applying Build It magazine’s 2026 rates to 150 m² of gross internal floor area gives a construction cost of about £375,000 to £450,000 for an average self build. A simple, self-managed build could be around £330,000, and a high-spec one £480,000 or more. That’s construction only, excluding land, professional fees, connections and contingency.

The arithmetic

Build It’s 2026 guide gives an average self build rate of £2,500 to £3,000 per m² of gross internal floor area (GIA), from about £2,200 for simple self-managed builds to above £3,200 for high-end detailing. Multiplied by 150 m²:

LevelBuild It 2026 rate per m²x 150 m²
Low (simple, self-managed)about £2,200about £330,000
Typical (average self build)£2,500 to £3,000£375,000 to £450,000
High (high-end detailing)£3,200+£480,000+

This is our arithmetic on Build It’s figures, not a quote, and it doesn’t account for how VAT applies to your project.

What a 150m² home usually looks like

150 m² is a common size for a self built family home. Typical examples:

  • A three or four bedroom, two storey house with an open plan kitchen and living space.
  • A larger three bedroom bungalow or a chalet bungalow with rooms in the roof.
  • A replacement dwelling on a plot where an older, smaller house is coming down.

Where the build route matters most

At this size the choice of who runs the build makes a real difference in pounds. Build It uses a 150 m² house as its own example: with a main contractor it suggests around £375,000 to £450,000, and says self managing the trades could bring that to roughly £300,000 to £360,000, about 20% less. That saving is real, but it comes with your time, your risk and your coordination.

Build It also says a professional project manager typically costs 5% to 7% of build cost. On a £400,000 build that is £20,000 to £28,000 (our arithmetic). Some people find that a fair trade for keeping a self managed project on track.

The construction system matters too. BuildStore notes timber construction costs more than brick and block in the early stages, because you pay for the whole system up front, which affects your cash flow even if the total is similar.

What’s not in these figures

  • Land, plus stamp duty and legal costs on the purchase
  • Architect, structural engineer, surveys, planning and building control fees
  • Structural warranty and site insurance
  • Service connections
  • Any garage, driveway and landscaping
  • Finance costs and temporary accommodation
  • Contingency: Penrith Building Society asks for evidence of a 15% contingency

See the full list in what’s not included in the cost per m².

How to refine your 150m² estimate

  1. Decide your build route first. Main contractor, self managed or project managed changes which part of Build It’s range applies to you.
  2. Pick a construction system and ask suppliers how their payments fall, not just the total.
  3. Look hard at the open plan space. Big spans and large areas of glazing in the kitchen and living area are common at this size and can push cost up.
  4. Get a ground investigation. Foundations are one of the biggest unknowns early on.
  5. Swap estimates for quotes stage by stage. Watch the high end of your range, not the low.

How Self Build Budget helps

The free ranged estimate gives you a low and high figure for your floor area, quality and region. On the Standard plan you can store quotes side by side and see the projected cost for each line, so if a quote comes in above estimate you see it before the money goes. The Professional plan adds a 26-week cash-flow forecast, useful if your construction system front loads payments.

Questions people also ask

Is £400,000 enough for a 150m² self build? For construction alone, it sits within Build It’s 2026 average band applied to 150 m². You’d still need land, fees, connections and contingency on top.

How much cheaper is self managing a 150m² build? Build It suggests around 20%, which on its own 150 m² example is roughly £375,000 to £450,000 down to £300,000 to £360,000.

Is 150m² big enough for four bedrooms? Often, in a two storey layout, though bedroom sizes and living space will be modest compared with larger homes.

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