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 Ilford?
In Ilford, a mansard loft conversion typically costs £84,500–£123,500 for a typical rear mansard, including VAT at 20% (standard rate). Prices across London are typically 30% above the UK average for this kind of work, which is reflected in the range for Ilford. 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 biggest cost drivers are:
- Front, rear or both
- Roof covering: natural slate costs more
- Scaffolding on busy streets
- Bathrooms and finishes
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 mansard loft conversion in Ilford?
Before anything is built in Ilford, we confirm which approvals apply 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.
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.
At the survey we check your house’s planning history and any restrictions, and tell you which route applies.
What we handle
On a typical mansard loft conversion we handle:
- Dormer windows
- Party wall notices to both neighbours
- Building control sign-off
- Structural design and calculations
- New roof structure, slate or tile covering and lead work
- Planning drawings and application
How long does it take?
Build time is typically 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 Ilford
Space is at a premium in London, so homeowners often build out into the side return or up into the roof rather than move.
Projects in Ilford (IG1, IG4 and IG5) 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
Approvals
Planning or permitted development confirmation, building regulations and any party wall matters.
- 04
Construction and completion
We build, put right any snags and hand over the building control certificate.
Questions about mansard loft conversions in Ilford
Do you build mansard loft conversions in Ilford?
Yes. We build mansard loft conversions across Ilford, including postcodes IG1, IG4 and IG5. Every project starts with a free home visit.
Does a mansard need planning permission?
Almost always, because it changes the roof shape. Councils assess it against local design guidance.
How much does a mansard loft conversion cost in Ilford?
In Ilford, 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.
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 long does it take?
Around 9 to 12 weeks on site, plus 2 to 3 months for planning and party wall matters beforehand.