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 Welling?
In Welling, a mansard loft conversion typically costs £84,500–£123,500 for a typical rear mansard, including VAT at 20% (standard rate). That range is adjusted for London, where domestic building work typically costs around 30% above the national average. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| A typical rear mansard | £84,500–£123,500 |
| Higher specification | £123,500–£154,500 |
Your quote will depend mainly on:
- Front, rear or both
- Roof covering: natural slate costs more
- Party wall surveyor fees
- Scaffolding on busy streets
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 mansard loft conversion in Welling?
Approvals for a mansard loft conversion in Welling follow the rules for 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
On a typical mansard loft conversion we handle:
- Structural design and calculations
- Building control sign-off
- Staircase and fire-safe escape route
- Planning drawings and application
- Dormer windows
- New roof structure, slate or tile covering and lead work
How long does it take?
Allow 9 to 12 weeks on site, after planning approval. Design and approvals come first and typically take 3 to 4 months, depending on the approval route.
Building in Welling
Space is at a premium in London, so homeowners often build out into the side return or up into the roof rather than move.
Our Welling coverage includes postcode districts DA16, and we also work in nearby places such as Bexleyheath, Sidcup and Eltham.
How it works
- 01
Survey and brief
We visit, discuss your ideas and budget, and survey the property or site at no cost.
- 02
Drawings and written quote
We prepare the design and give you a written, itemised quote with inclusions and exclusions.
- 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 Welling
How long does it take?
Around 9 to 12 weeks on site, plus 2 to 3 months for planning and party wall matters beforehand.
How much does a mansard loft conversion cost in Welling?
In Welling, a mansard loft conversion typically costs £84,500–£123,500 for a typical rear mansard, including VAT at 20% (standard rate). Your fixed price depends on the survey and drawings.
Does a mansard need planning permission?
Almost always, because it changes the roof shape. Councils assess it against local design guidance.
Can I stay at home?
Usually. The new roof is built under a temporary cover so the house stays dry.
Do you build mansard loft conversions in Welling?
Yes. We build mansard loft conversions across Welling, including postcodes DA16. Every project starts with a free home visit.