What is a mansard loft conversion?
A mansard loft conversion rebuilds the roof with a nearly vertical slope (about 72 degrees) and a flat top, effectively adding a new storey. Small dormer windows sit within the steep slope. Mansards are common on period terraces in towns and cities.
How much does a mansard loft conversion cost in Wellingborough?
In Wellingborough, a mansard loft conversion typically costs £62,000–£90,000 for a typical rear mansard, including VAT at 20% (standard rate). Prices across the East Midlands are typically 5% below the UK average for this kind of work, which is reflected in the range for Wellingborough. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| A typical rear mansard | £62,000–£90,000 |
| Higher specification | £90,000–£112,500 |
What moves the price most:
- Front, rear or both
- Party wall surveyor fees
- Number of dormers and lead work
- Roof covering: natural slate costs more
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 mansard loft conversion in Wellingborough?
Whether you need planning permission depends on your house and its location in England. In England a mansard almost always needs planning permission because it changes the roof shape. Many councils publish design guidance for mansards on terraced streets, and some streets are more likely to be approved where neighbours already have one.
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
The work we manage on a mansard loft conversion:
- Dormer windows
- Structural design and calculations
- New roof structure, slate or tile covering and lead work
- Insulation, electrics, plumbing and plastering
- Party wall notices to both neighbours
- Building control sign-off
How long does it take?
Expect 9 to 12 weeks on site, after planning approval. Allow time beforehand for drawings and approvals, usually 3 to 4 months.
Building in Wellingborough
The East Midlands has a mix of red-brick terraces, inter-war semis and newer estates, so rear extensions and garage conversions are common projects.
We work across Wellingborough and neighbouring areas such as Rushden, Kettering and Northampton. Postcodes we cover in Wellingborough include NN8.
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 pricing
Design options, then a fixed quote based on the chosen drawings and specification.
- 03
Approvals in place
We handle planning, building control and neighbour notices before work starts.
- 04
Build and handover
Work follows the agreed programme, with inspections along the way and a completion certificate at the end.
Questions about mansard loft conversions in Wellingborough
How long does it take?
Around 9 to 12 weeks on site, plus 2 to 3 months for planning and party wall matters beforehand.
Do I need party wall agreements?
Yes, mansards on terraced houses almost always involve both party walls.
Who approves a mansard loft conversion in Wellingborough?
Planning matters in Wellingborough go to the council covering your address, and the work needs building control approval. We prepare and submit the applications for you.
Can I stay at home?
Usually. The new roof is built under a temporary cover so the house stays dry.
How much does a mansard loft conversion cost in Wellingborough?
In Wellingborough, a mansard loft conversion typically costs £62,000–£90,000 for a typical rear mansard, including VAT at 20% (standard rate). Your fixed price depends on the survey and drawings.