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 Ruislip?
In Ruislip, a dormer loft conversion typically costs £62,500–£88,500 for a typical rear dormer with en-suite, including VAT at 20% (standard rate). The guide for Ruislip reflects typical costs in London, roughly 30% above the UK-wide figure. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| A typical rear dormer with en-suite | £62,500–£88,500 |
| Higher specification | £88,500–£110,500 |
What moves the price most:
- Dormer size and roof structure
- Scaffolding and access
- Fire safety upgrades to the existing house
- En-suite or bathroom
Your exact price depends on the survey and drawings. The guide price tool gives a quick range in the meantime.
Do you need planning permission for a dormer loft conversion in Ruislip?
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.
We check this for your address before design work starts, so there are no surprises later.
What we handle
From survey to sign-off, the job normally involves:
- Insulation, plastering, electrics and plumbing
- Party wall notices for shared walls
- Building control completion certificate
- Drawings and structural calculations
- Steel beams and new floor joists
- Dormer structure, roof covering and windows
How long does it take?
Allow 6 to 9 weeks on site. Design and approvals come first and typically take 6 to 12 weeks, depending on the approval route.
Building in Ruislip
Many London boroughs have conservation areas and detailed design guides, so early design advice saves time at the planning stage.
We work across Ruislip and neighbouring areas such as Pinner, Northolt and Uxbridge. Postcodes we cover in Ruislip include HA4.
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
Permissions sorted
Applications, building control and neighbour arrangements, all before the start date.
- 04
Construction and completion
We build, put right any snags and hand over the building control certificate.
Questions about dormer loft conversions in Ruislip
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.
Does a dormer loft conversion need planning permission?
A rear dormer is often permitted development in England, provided the extra roof volume is within 40 cubic metres on a terraced house or 50 on a semi-detached or detached house, and it does not face the road. Front dormers and houses in conservation areas usually need an application.
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.
How much does a dormer loft conversion cost in Ruislip?
In Ruislip, a dormer loft conversion typically costs £62,500–£88,500 for a typical rear dormer with en-suite, including VAT at 20% (standard rate). Your fixed price depends on the survey and drawings.
Do you build dormer loft conversions in Ruislip?
Yes. We build dormer loft conversions across Ruislip, including postcodes HA4. Every project starts with a free home visit.