What is a rooflight loft conversion?
A rooflight loft conversion (sometimes called a roof window conversion) keeps the existing roof shape and adds roof windows that sit flush with the slope. The floor is strengthened, a staircase is added and the space is insulated and finished.
How much does a rooflight loft conversion cost in Sunbury-on-Thames?
In Sunbury-on-Thames, a rooflight loft conversion typically costs £33,500–£50,500 for a typical rooflight conversion, including VAT at 20% (standard rate). That range is adjusted for the South East, where domestic building work typically costs around 12% above the national average. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| A typical rooflight conversion | £33,500–£50,500 |
| Higher specification | £50,500–£63,000 |
The biggest cost drivers are:
- Staircase position
- Floor and roof strengthening
- Number of roof windows
- Storage and finishes
A guide range is only a starting point: the guide price tool gives an instant figure for your size, and a free survey turns it into a fixed quote.
Do you need planning permission for a rooflight loft conversion in Sunbury-on-Thames?
The approval route for Sunbury-on-Thames is set by planning law in England. In England roof windows are permitted development if they project no more than 15 centimetres from the roof slope and side-facing windows are obscure-glazed. Listed buildings need consent.
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.
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 rooflight loft conversions:
- Floor joists and any steel beams
- Insulation between and under rafters
- Head-height survey
- Staircase and fire-safe escape route
- Electrics, heating and plastering
- Drawings and structural calculations
How long does it take?
The build itself usually takes 4 to 6 weeks on site. Before that, surveys, drawings and approvals usually take 6 to 12 weeks, longer if the council asks for changes.
Building in Sunbury-on-Thames
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 KT12 outwards, we take on projects throughout Sunbury-on-Thames and the surrounding parts of Surrey.
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
Design and fixed quote
Drawings, structural calculations and an itemised, fixed price for the agreed specification.
- 03
Approvals
Planning or permitted development confirmation, building regulations and any party wall matters.
- 04
Build and handover
Work follows the agreed programme, with inspections along the way and a completion certificate at the end.
Questions about rooflight loft conversions in Sunbury-on-Thames
Do you build rooflight loft conversions in Sunbury-on-Thames?
Yes. We build rooflight loft conversions across Sunbury-on-Thames, including postcodes KT12 and TW16. Every project starts with a free home visit.
Can I have a bathroom?
Yes, where there is enough head height at the shower or bath position.
How much does a rooflight loft conversion cost in Sunbury-on-Thames?
In Sunbury-on-Thames, a rooflight loft conversion typically costs £33,500–£50,500 for a typical rooflight conversion, including VAT at 20% (standard rate). Your fixed price depends on the survey and drawings.
What about fire safety?
The same escape rules apply as for any loft conversion, so a protected stairway and smoke alarms are typically needed.
How much head height do I need?
Around 2.2 metres or more from the top of the ceiling joists to the ridge is a good starting point. Insulation and new floor joists reduce the height.