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Independent UK planning guide

Single-storey extension costs in the UK

Add ground-floor space with foundations, structure, weatherproofing, services and internal finishes.

Get site-specific quotes

Typical UK range

£2,200–£3,500/m²

Straightforward jobs

From £40,000

Typical site time

3–6 months

Build the allowance

How to read this price

Starting allowance

For a straightforward, accessible job with a standard specification.

From £40,000

Typical UK project

An early planning range before a tradesperson inspects the property.

£2,200–£3,500/m²

Likely programme

Site time varies with preparation, sequencing, approvals and drying periods.

3–6 months

These figures are early UK planning allowances. They are not a substitute for an itemised quotation after inspection.

Control the variables

What can change the quote?

Ground conditions and foundations

Steelwork and structural openings

Access, scaffolding and waste

Glazing, services and room specification

Before accepting a quote

Ask for these details in writing

  • Labour, materials and VAT
  • Preparation and protection
  • Access equipment and waste
  • Named provisional allowances
  • Testing and certification
  • Programme and payment stages
  • Making good and decoration
  • Warranty and snagging process

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