A typical price
6 × 4.5 m
- London (outer)
- £47,700 to £61,100
- South East
- £46,100 to £59,100
- Midlands
- £44,100 to £56,400
- North of England
- £43,500 to £55,600
7 × 5 m
- London (outer)
- £52,000 to £66,500
- South East
- £50,200 to £64,300
- Midlands
- £48,000 to £61,400
- North of England
- £47,300 to £60,500
8 × 5.5 m
- London (outer)
- £56,700 to £72,600
- South East
- £54,800 to £70,100
- Midlands
- £52,300 to £67,000
- North of England
- £51,500 to £66,000
| Size | London (outer) | South East | Midlands | North of England |
|---|---|---|---|---|
| 6 × 4.5 m | £47,700 to £61,100 | £46,100 to £59,100 | £44,100 to £56,400 | £43,500 to £55,600 |
| 7 × 5 m | £52,000 to £66,500 | £50,200 to £64,300 | £48,000 to £61,400 | £47,300 to £60,500 |
| 8 × 5.5 m | £56,700 to £72,600 | £54,800 to £70,100 | £52,300 to £67,000 | £51,500 to £66,000 |
Including VAT, for: rear dormer, new stairs, fire doors, carpet. Priced 6 October 2026 on published UK rates. A guide, not a quote.
More than it looks
The middle-size job above is 40 tasks, about 8 weeks on site:
- Prep and strip-out · 1
- Structure · 8
- Roof and windows · 7
- First fix: pipes and cables · 4
- Plaster, insulation, floors · 6
- Finishes and second fix · 14
Plus site costs: scaffold, skips, building control, party wall notices, engineer’s calculations, site toilet, insurance, supervision, dust protection, cleaning, electrical certificate.
- It’s structural: steels and a floor, designed by an engineer.
- A new floor means fire doors on the stairs and linked alarms.
- Steels on a shared wall mean notices to the neighbours.
What changes the price
Dormer size
- Why it moves the price
- More floor, roof and wall
- Ask
- “How big is the dormer?”
Stairs
- Why it moves the price
- May mean moving a wall below
- Ask
- “Where do the stairs go?”
An en-suite
- Why it moves the price
- Adds plumbing and tiling
- Ask
- “Is a bathroom included?”
Roof and windows
- Why it moves the price
- Matching tiles, window choice
- Ask
- “What have you priced?”
| What | Why it moves the price | Ask |
|---|---|---|
| Dormer size | More floor, roof and wall | “How big is the dormer?” |
| Stairs | May mean moving a wall below | “Where do the stairs go?” |
| An en-suite | Adds plumbing and tiling | “Is a bathroom included?” |
| Roof and windows | Matching tiles, window choice | “What have you priced?” |
Paperwork and certificates
- Building regulations sign-off
- Engineer’s calculations
- Party wall notices
Questions to ask for this job
- Who does the drawings?
- Is scaffold included, and for how long?
- Will we need to move out?
What would your job cost?
Describe it, and see a typical price for your area. Then ask builders who do this work.
Read next
How we wrote this
Written by Structa; prices from Structa’s engine, 6 October 2026. The rules come from the official pages below. General information, not legal advice.
- Planning Portal: common projects (England) (checked 6 October 2026)
- GOV.UK: When you need building regulations approval (checked 6 October 2026)
- GOV.UK: Party walls and building work (checked 6 October 2026)