TL;DR — Key Facts
- Dormer loft conversion: £45,000 – £65,000 (inner London borough)
- Mansard conversion: £70,000 – £110,000
- Velux conversion: £25,000 – £38,000
- Planning permission: Generally available for rear dormers
- Conservation areas: 20 in Greenwich
What does a Greenwich loft conversion cost, and will it pass?
Greenwich is the harder end of London on both counts. Its Datahub set records 2,296 rear dormer applications at 64% approved and 1,700 loft conversions at 67%, while the borough approved just 70.7% of all householder applications it decided.
| Measure | Greenwich | Outcome |
|---|---|---|
| Rear dormer applications in the Datahub | 2,296 | 64% approved |
| Loft conversion applications in the Datahub | 1,700 | 67% approved |
| Mansard applications in the Datahub | 144 | 53% approved |
| Householder decisions | 2,301 | 70.7% approved |
| Lawful development certificates issued | 1,228 | — |
| Conservation areas | 14 | 884 hectares |
Sources: Datahub rows from the Planning London Datahub, retrieved 15 August 2026 — phrase-matched descriptions, comparable within Greenwich only; decision figures from MHCLG PS1 and PS2, twelve quarters to March 2026; conservation areas from planning.data.gov.uk, retrieved 1 September 2026. Build costs on this page are our own 2026 London range, not a published statistic.
What does a Greenwich loft cost by roof type?
Once the budget works, the next step is the drawing set: loft conversions in Greenwich.
Loft conversion build costs in Greenwich depend primarily on the type of conversion. As an inner London borough, Greenwich sits in the mid-range of London loft conversion pricing.
Loft conversion build costs in Greenwich
These figures are build costs only and do not include professional fees (architect, structural engineer, Party Wall surveyor) or council fees. The actual cost will depend on the size of your loft, the specification of the fit-out, the structural complexity, and access constraints.
A standard dormer loft conversion typically adds 20-30 square metres of living space, while a mansard can add 30-50 square metres with full standing head height throughout. The additional floor area and value uplift typically exceeds the cost of the conversion, making loft conversions one of the most cost-effective home improvements in Greenwich.
Which loft type suits Greenwich properties?
Eltham's interwar semis take the standard hip-to-gable and rear dormer. The Victorian terraces of East Greenwich and Charlton generally have height for a rear dormer alone. Georgian property in the town centre is a mansard proposition at best and frequently not a conversion candidate at all, given the combination of listed status and the World Heritage setting.
Dormer loft conversions
Greenwich has extensive streets of terraced housing, making rear dormer loft conversions the most popular option. A flat-roof rear dormer on a Victorian or Edwardian mid-terrace can add 20-30 square metres of living space. Rear dormers on terraced houses generally fall under Permitted Development, provided they do not exceed the highest part of the existing roof and are set back from the eaves. Properties in conservation areas may need full planning permission for dormers visible from the highway.
Mansard loft conversions
Mansard conversions replace the existing roof slope with a near-vertical front and a shallow-sloped top, creating a full additional storey. Mansard conversions always require planning permission as they alter the roofline. In Greenwich, mansard conversions are assessed on a case-by-case basis, with design quality, streetscene impact, and conservation area status being key considerations. Mansard conversions are more expensive than dormers but create significantly more usable floor area with full standing head height throughout.
Hip-to-gable and dormer combinations
The semi-detached and detached properties in Greenwich often have hipped roofs, which limit the usable loft space. A hip-to-gable conversion extends the hipped end to a full gable, combined with a rear dormer to maximise floor area. This combination can add 25-35 square metres. Hip-to-gable conversions on semi-detached properties may fall under Permitted Development, though the gable extension must not extend beyond the plane of the existing house front.
Velux (rooflight) conversions
A Velux or rooflight conversion is the simplest and most affordable option, suitable where there is already sufficient head height in the existing loft space. Rooflights are installed into the existing roof slope without changing its shape. This type of conversion almost always falls under Permitted Development and is particularly suitable for properties in Greenwich's 20 conservation areas where changes to the roofline may not be acceptable. The trade-off is less usable floor area compared to a dormer or mansard.
Does a Greenwich loft need planning permission?
In Greenwich the deciding factor is often not your roof but the view past it. Maritime Greenwich is a UNESCO World Heritage Site, and development affecting its setting — including protected views across the park and the river — is assessed against the site's outstanding universal value. A dormer that would be unremarkable in Eltham can be refused in East Greenwich for that reason alone. Outside the town centre the borough is ordinary outer London.
Permitted Development for lofts
Most rear dormer and Velux loft conversions fall under Permitted Development and do not require a planning application. The key PD conditions are:
- The dormer must not exceed the highest part of the existing roof
- The dormer must be set back at least 200mm from the eaves
- Materials must be similar in appearance to the existing house
- No verandas, balconies, or raised platforms
- Side-facing windows must be obscure-glazed and non-opening below 1.7m
- Volume limit: 40 cubic metres for terraced houses, 50 cubic metres for others
Conservation areas
Greenwich has 20 conservation areas, including Greenwich Town Centre (World Heritage Site), Blackheath, Charlton, Eltham Park. In conservation areas, Permitted Development rights for loft conversions are more restricted. Front-facing dormers and side-facing dormers visible from the highway generally require planning permission. Rear dormers may still qualify as PD, but the conservation officer may have views on materials and design. Mansard conversions in conservation areas are assessed against the area's character appraisal and management plan.
Mansard planning permission
A mansard alters the roof's form and height and needs permission on that basis. In Greenwich the additional question is the World Heritage Site: a roof addition visible in a protected view of Maritime Greenwich is assessed against the site's outstanding universal value, which is a heavier test than design policy. In Eltham, none of that applies and a hip-to-gable is usually the better-value form anyway.
Greenwich publishes a pre-application scale of its own. Within the World Heritage Site and its setting the enquiry is worth buying, because the heritage assessment is difficult to anticipate and the borough approves only 70.7% of householder applications (MHCLG planning statistics, retrieved 1 September 2026). In Eltham and Thamesmead it rarely changes the outcome.
Our drawing fees for loft conversions in Greenwich
At Architectural Drawings London. Our MCIAT chartered architectural technologists prepare everything needed for planning submission (where required) and building regulations approval.
Drawing fees for loft conversions
Every package includes a measured survey, existing and proposed floor plans and elevations, roof plan, sections, and a site plan. For mansard conversions, we also prepare a design and access statement and streetscene elevation. Our fees are 30% below typical London architect rates for the same scope of work.
We cover all Greenwich postcodes: SE3, SE7, SE9, SE10, SE18, SE28.
Frequently asked questions
How much does a loft conversion cost in Greenwich?
Loft conversion costs in Greenwich vary by type. A rear dormer loft conversion typically costs £45,000 to £65,000. A mansard conversion costs £70,000 to £110,000. A Velux (rooflight only) conversion costs £25,000 to £38,000. These are build costs only.
Do I need planning permission for a loft conversion in Greenwich?
Outside the 20 conservation areas, usually — Greenwich has no borough-wide Article 4 Direction and issued 1,228 lawful development certificates in three years (MHCLG planning statistics, retrieved 1 September 2026). Within the World Heritage Site and its setting, treat the permitted development position as a starting point rather than an answer, because the heritage assessment can bear on work that is technically permitted. Mansards require an application in every case.
What is the minimum head height for a loft conversion in Greenwich?
Eltham's interwar semis reach it at the apex and want the hip converted to make the floor work. The Victorian terraces of East Greenwich and Charlton generally have more to play with. Georgian property in the town centre is a different exercise, where the roof may not be alterable at all.
Do I need a Party Wall Agreement for a loft conversion in Greenwich?
On the terraced and semi-detached stock, yes. Two clear months of notice are needed before anyone seats a beam in the shared wall or builds it up, under the 1996 party wall statute. Riverside new-build is generally flats, where the roof is common parts and the question is a leasehold one before it is a party wall one. Check what the lease demises first.
Can I get a mansard loft conversion approved in Greenwich?
Greenwich assesses mansard applications on a case-by-case basis. Greenwich Council will consider the impact on the streetscene, conservation area status, design quality, and any existing precedents on your street.
