What is a dormer loft conversion?
A dormer loft conversion adds a box-shaped structure to the rear roof slope, creating vertical walls and full headroom across most of the new room. It is the most common loft conversion in the UK because it works on terraced, semi-detached and detached houses.
How much does a dormer loft conversion cost in Ashford, Surrey?
In Ashford, a dormer loft conversion typically costs £54,000–£76,000 for a typical rear dormer with en-suite, including VAT at 20% (standard rate). We start from a UK-wide guide and adjust it for the South East, where labour and materials are typically about 12% above average. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| A typical rear dormer with en-suite | £54,000–£76,000 |
| Higher specification | £76,000–£95,000 |
The main things that change the cost:
- Dormer size and roof structure
- Built-in storage and finishes
- Fire safety upgrades to the existing house
- En-suite or bathroom
For a figure based on your own measurements, try the guide price tool, then book a free home visit for a fixed quote.
Do you need planning permission for a dormer loft conversion in Ashford, Surrey?
Whether you need planning permission depends on your house and its location in England. In England a rear dormer is often permitted development if the extra roof volume is no more than 40 cubic metres on a terraced house or 50 on other houses, it does not face the road, sits no higher than the ridge and is set back from the eaves, with matching materials and obscure-glazed side windows. Balconies, front dormers and work in conservation areas need planning permission.
Building regulations approval comes from the council’s building control service or a registered building control approver. The work is inspected at key stages, such as foundations, drainage and insulation, and a completion certificate is issued at the end.
At the survey we check your house’s planning history and any restrictions, and tell you which route applies.
What we handle
Handled as part of most dormer loft conversions:
- Party wall notices for shared walls
- Dormer structure, roof covering and windows
- New staircase and fire-safe escape route
- Insulation, plastering, electrics and plumbing
- Drawings and structural calculations
- Building control completion certificate
How long does it take?
Expect 6 to 9 weeks on site. Before that, surveys, drawings and approvals usually take 6 to 12 weeks, longer if the council asks for changes.
Building in Ashford, Surrey
The South East has a broad mix of housing, from Victorian terraces in the towns to post-war semis and newer estates, so extension types vary street by street.
We work across Ashford and neighbouring areas such as Staines, Feltham and Sunbury-on-Thames. Postcodes we cover in Ashford include TW15.
How it works
- 01
Free visit
We look at the property, talk through what you want and measure up. There is no charge and no obligation.
- 02
Drawings and written quote
We prepare the design and give you a written, itemised quote with inclusions and exclusions.
- 03
Approvals
Planning or permitted development confirmation, building regulations and any party wall matters.
- 04
Construction and completion
We build, put right any snags and hand over the building control certificate.
Questions about dormer loft conversions in Ashford, Surrey
How much head height do I need?
Ideally at least 2.2 metres from the top of the ceiling joists to the underside of the ridge. Less can still work with a dormer, but we check this at the survey.
How much does a dormer loft conversion cost in Ashford?
In Ashford, a dormer loft conversion typically costs £54,000–£76,000 for a typical rear dormer with en-suite, including VAT at 20% (standard rate). Your fixed price depends on the survey and drawings.
What fire safety is required?
Building regulations require a safe escape route. Converting a two-storey house to three storeys usually means a protected stairway with fire doors to habitable rooms and mains-wired smoke alarms.
How long does a dormer loft conversion take in Ashford?
Typically 6 to 9 weeks on site. Design and approvals beforehand usually take 6 to 12 weeks.
Do I need a party wall agreement?
In England and Wales, if the conversion cuts into or builds on a shared wall, notices must be served under the Party Wall etc. Act 1996.