Estiquote

Local costs · South East · September 2026

How much does an extension cost in Milton Keynes?

A mid-range 25 m² single-storey extension in Milton Keynes costs about £72,500 to £89,500 including VAT, or £2,900 to £3,600 per m² at South East prices. Milton Keynes charges £840 for building control on a 10 to 40 m² extension (full plans, including VAT): about the same as the typical council (£840). With design, a structural engineer, building control and a 15% contingency, budget £89,500 to £115,000.

By Estiquote · Prices reviewed · Council fees from Milton Keynes's published schedule · How we calculate

Work out your project in Milton Keynes

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Typical prices in Milton Keynes

Mid-range finish, South East prices, including VAT. The budget adds design and engineering fees, Milton Keynes's building control charge and a 15% contingency.
ProjectBuilding workBudget to plan for
Single-storey extension, 25 m²£72,500 to £89,500£89,500 to £115,000
Double-storey extension, 40 m²£105,000 to £132,000£128,000 to £167,000
Dormer loft conversion, 30 m²£65,000 to £80,000£80,500 to £102,000
Kitchen, medium£9,700 to £17,200£11,100 to £19,800
Bathroom refit£6,500 to £9,800£7,500 to £11,300

Building prices in South East run about 15% above the UK average outside London. Kitchens and bathrooms vary less from place to place than extensions and lofts.

Building control fees in Milton Keynes

Milton Keynes council charges including VAT (plan and inspection combined)
WorkCharge
Extension up to 10 m² (full plans)£666
Extension 10 to 40 m² (full plans)£840
Larger extension, 40-60 m² (full plans)£1,254
Extension 10 to 40 m² (building notice)£923
Loft conversion up to 40 m²£1,254
Garage conversion£552

Milton Keynes charges £840 for building control on a 10 to 40 m² extension (full plans, including VAT): about the same as the typical council (£840). Source: Milton Keynes's building control charges, Not clearly stated: page cites 1 April 2025; page last updated 1 August 2026. Inc VAT ("Charges include VAT unless otherwise stated").

Private approved inspectors set their own prices and are often competitive, so it is worth asking one or two for a quote as well. See how Milton Keynes compares with every council we checked.

Notes on Milton Keynes's schedule

Own schedule. Loft figure is with dormer (without dormer 957.60).

Planning

If your extension needs planning permission, a householder application in England costs £548. Many single-storey rear extensions are permitted development and need no application, and a lawful development certificate (£274) confirms it.

Other councils in South East

Building control for a 10 to 40 m² extension:

Questions people ask

How much does an extension cost in Milton Keynes?

A mid-range 25 m² single-storey extension in Milton Keynes costs about £72,500 to £89,500 including VAT for the building work, or £2,900 to £3,600 per m², based on South East prices reviewed in September 2026. With fees and a 15% contingency, budget £89,500 to £115,000.

How much is building control in Milton Keynes?

Milton Keynes charges £840 (including VAT) for a 10 to 40 m² extension (full plans), according to its published schedule (Not clearly stated: page cites 1 April 2025; page last updated 1 August 2026).

How much does a loft conversion cost in Milton Keynes?

A mid-range 30 m² dormer loft conversion in Milton Keynes costs about £65,000 to £80,000 including VAT for the building work, and about £80,500 to £102,000 with fees and a 15% contingency.

Before you get quotes