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 Mill Hill?
In Mill Hill, a mansard loft conversion typically costs £84,500–£123,500 for a typical rear mansard, including VAT at 20% (standard rate). The guide for Mill Hill reflects typical costs in London, roughly 30% above the UK-wide figure. 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 |
The main things that change the cost:
- Roof covering: natural slate costs more
- Front, rear or both
- Bathrooms and finishes
- Party wall surveyor fees
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 Mill Hill?
Approvals for a mansard loft conversion in Mill Hill 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.
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.
We check this for your address before design work starts, so there are no surprises later.
What we handle
What we take care of:
- Planning drawings and application
- New roof structure, slate or tile covering and lead work
- Dormer windows
- Party wall notices to both neighbours
- Building control sign-off
- Staircase and fire-safe escape route
How long does it take?
The build itself usually takes 9 to 12 weeks on site, after planning approval. Before that, surveys, drawings and approvals usually take 3 to 4 months, longer if the council asks for changes.
Building in Mill Hill
Space is at a premium in London, so homeowners often build out into the side return or up into the roof rather than move.
From NW7 outwards, we take on projects throughout Mill Hill and the surrounding parts of Greater London.
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 pricing
Design options, then a fixed quote based on the chosen drawings and 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 mansard loft conversions in Mill Hill
Can I stay at home?
Usually. The new roof is built under a temporary cover so the house stays dry.
How long does a mansard loft conversion take in Mill Hill?
Typically 9 to 12 weeks on site, after planning approval. Design and approvals beforehand usually take 3 to 4 months.
Does a mansard need planning permission?
Almost always, because it changes the roof shape. Councils assess it against local design guidance.
Why choose a mansard over a dormer?
A mansard gives more usable floor space and a neater appearance from the street, but costs more and needs planning permission.
How much does a mansard loft conversion cost in Mill Hill?
In Mill Hill, 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.