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 Stevenage?
In Stevenage, a dormer loft conversion typically costs £51,000–£72,000 for a typical rear dormer with en-suite, including VAT at 20% (standard rate). Prices across the East of England are typically 6% above the UK average for this kind of work, which is reflected in the range for Stevenage. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| A typical rear dormer with en-suite | £51,000–£72,000 |
| Higher specification | £72,000–£90,000 |
The biggest cost drivers are:
- Built-in storage and finishes
- En-suite or bathroom
- Scaffolding and access
- Dormer size and roof structure
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 Stevenage?
Before anything is built in Stevenage, we confirm which approvals apply 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.
If the answer is not clear-cut, we can apply for formal confirmation before you commit to the build.
What we handle
On a typical dormer loft conversion we handle:
- Steel beams and new floor joists
- Insulation, plastering, electrics and plumbing
- Measured survey and head-height check
- Building control completion certificate
- Drawings and structural calculations
- Dormer structure, roof covering and windows
How long does it take?
Expect 6 to 9 weeks on site. Allow time beforehand for drawings and approvals, usually 6 to 12 weeks.
Building in Stevenage
Many towns in the East of England have estates built since the 1970s, where garage conversions and rear extensions are popular.
Projects in Stevenage (SG1) are surveyed in person before we quote, so the price reflects your actual property.
How it works
- 01
Visit and measured survey
A free visit to understand the project, check access and take measurements.
- 02
Design and pricing
Design options, then a fixed quote based on the chosen drawings and specification.
- 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 Stevenage
Who approves a dormer loft conversion in Stevenage?
Planning matters in Stevenage go to the council covering your address, and the work needs building control approval. We prepare and submit the applications for you.
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 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 Stevenage?
In Stevenage, a dormer loft conversion typically costs £51,000–£72,000 for a typical rear dormer with en-suite, including VAT at 20% (standard rate). Your fixed price depends on the survey and drawings.
Will I need to move out?
No. Most of the work is done from scaffolding and the roof. The new staircase is formed near the end, which causes a few days of disruption.