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 Cambridgeshire?
In Cambridgeshire, a dormer loft conversion typically costs £51,000–£72,000 for a typical rear dormer with en-suite, including VAT at 20% (standard rate). Building costs in the East of England run about 6% above the UK average, and the figures for Cambridgeshire are adjusted to reflect that. 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:
- Fire safety upgrades to the existing house
- Scaffolding and access
- Built-in storage and finishes
- En-suite or bathroom
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 dormer loft conversion in Cambridgeshire?
The approval route for Cambridgeshire is set by planning law 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.
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:
- Insulation, plastering, electrics and plumbing
- Steel beams and new floor joists
- Drawings and structural calculations
- Building control completion certificate
- Party wall notices for shared walls
- Measured survey and head-height check
How long does it take?
Build time is typically 6 to 9 weeks on site. Allow time beforehand for drawings and approvals, usually 6 to 12 weeks.
Building in Cambridgeshire
Across the East of England, 1930s and post-war semis, newer estates and rural cottages all feature, each with different extension and loft options.
Towns we cover in Cambridgeshire include Peterborough, Cambridge, Wisbech, St Neots, Huntingdon and March.
How it works
- 01
Survey and brief
We visit, discuss your ideas and budget, and survey the property or site at no cost.
- 02
Design and fixed quote
Drawings, structural calculations and an itemised, fixed price for the agreed 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 Cambridgeshire
How long does it take?
Usually 6 to 9 weeks on site.
How much does a dormer loft conversion cost in Cambridgeshire?
In Cambridgeshire, 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.
Do you build dormer loft conversions in Cambridgeshire?
Yes. We build dormer loft conversions across Cambridgeshire, including postcodes CB1, CB10, CB2, CB21 and CB22. Every project starts with a free home visit.
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.
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.