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 Swanley?
In Swanley, a dormer loft conversion typically costs £54,000–£76,000 for a typical rear dormer with en-suite, including VAT at 20% (standard rate). Prices across the South East are typically 12% above the UK average for this kind of work, which is reflected in the range for Swanley. 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 biggest cost drivers are:
- En-suite or bathroom
- Dormer size and roof structure
- Scaffolding and access
- Staircase position
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 Swanley?
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.
Where work involves a shared wall, building on the boundary, or digging foundations within 3 metres of a neighbour’s building and deeper than its foundations (or within 6 metres for deeper work), the Party Wall etc. Act 1996 applies and notices must be served before work starts.
Our first visit includes a check of your planning history, so you know the route before paying for drawings.
What we handle
Handled as part of most dormer loft conversions:
- New staircase and fire-safe escape route
- Drawings and structural calculations
- Measured survey and head-height check
- Party wall notices for shared walls
- Building control completion certificate
- Steel beams and new floor joists
How long does it take?
Allow 6 to 9 weeks on site. Allow time beforehand for drawings and approvals, usually 6 to 12 weeks.
Building in Swanley
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.
From BR8 outwards, we take on projects throughout Swanley and the surrounding parts of Kent.
How it works
- 01
Visit and measured survey
A free visit to understand the project, check access and take measurements.
- 02
Drawings and written quote
We prepare the design and give you a written, itemised quote with inclusions and exclusions.
- 03
Permissions sorted
Applications, building control and neighbour arrangements, all before the start date.
- 04
Build and handover
Work follows the agreed programme, with inspections along the way and a completion certificate at the end.
Questions about dormer loft conversions in Swanley
How much does a dormer loft conversion cost in Swanley?
In Swanley, 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.
How long does it take?
Usually 6 to 9 weeks on site.
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 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.
Who approves a dormer loft conversion in Swanley?
Planning matters in Swanley go to the council covering your address, and the work needs building control approval. We prepare and submit the applications for you.