Mansard Roof Extensions in Mortlake

Mortlake FAQ for mansard roof extensions

Do I need planning permission for mansard roof extensions in Mortlake?

Most mansard roof extensions projects in Mortlake fall under Permitted Development if the property is a house (not a flat), not listed, and not in a conservation area. Richmond upon Thames has no borough-wide Article 4 Direction. We confirm eligibility free at the site survey.

How much does mansard roof extensions cost in Mortlake?

Drawings: fixed fee from £1,575 (Mansard Roof Extensions). Construction cost is separate and depends on size, finish and structural complexity. For victorian and edwardian terraces (typical of Mortlake), expect £45,000–£85,000 build cost for a standard rear extension or loft, more for mansards or basements.

How long does the mansard roof extensions process take in Mortlake?

12–14 weeks from first call to Richmond Council planning decision. Site survey week 1, design weeks 2–3, validation 1–2 weeks, statutory 8-week determination.

What property types are common in Mortlake?

Mortlake is characterised by victorian and edwardian terraces. We've delivered mansard roof extensions for every period represented here — the design choices vary significantly by stock.

Will my application succeed in Mortlake?

Our first-time approval rate in Richmond upon Thames is 98%. Pre-application advice from Richmond Council is built into our process when the case is borderline (conservation area, Article 4, listed).

Which postcode districts around Mortlake do we cover for mansard roof extension work?

Every Mortlake postcode district we draw in, the stock that dominates it and the authority that validates a mansard roof extension there. Mortlake fees below are the statutory England rates for 2026, not mansard roof extension estimates.

Postcode	Area	Dominant stock	What it means for a mansard roof extension
SW14	Mortlake / East Sheen	Victorian and Edwardian terraces	Mortlake / East Sheen sits wholly inside SW14, so Richmond Council validates every mansard roof extension submitted from an SW14 address.
TW9	Richmond	Georgian terraces, Victorian villas	Neighbouring Richmond, where mansard roof extension work is handled by the same Richmond Council case officers.
TW1	Twickenham	Georgian fragments, Victorian terraces, Edwardian villas	Neighbouring Twickenham, where mansard roof extension work is handled by the same Richmond Council case officers.
TW9	Kew	Georgian and Edwardian villas	Neighbouring Kew, where mansard roof extension work is handled by the same Richmond Council case officers.
SW13	Barnes	Georgian villas, Edwardian terraces	Neighbouring Barnes, where mansard roof extension work is handled by the same Richmond Council case officers.
SW14	East Sheen	Edwardian villas, 1930s semi-detached	Neighbouring East Sheen, where mansard roof extension work is handled by the same Richmond Council case officers.
TW11	Teddington	Edwardian villas, Victorian terraces	Neighbouring Teddington, where mansard roof extension work is handled by the same Richmond Council case officers.
TW12	Hampton	Georgian villas, Edwardian terraces, 1930s semi-detached	Neighbouring Hampton, where mansard roof extension work is handled by the same Richmond Council case officers.
TW2	Whitton	1930s semi-detached	Neighbouring Whitton, where mansard roof extension work is handled by the same Richmond Council case officers.
TW10	Ham	Georgian villas, post-war estates	Neighbouring Ham, where mansard roof extension work is handled by the same Richmond Council case officers.

Which Mortlake neighbourhoods suit a mansard roof extension best?

Roof pitch, wall build-up and plot depth change every few Mortlake streets, and each one changes what a mansard roof extension can achieve at that address.

Mortlake (SW14) — Victorian and Edwardian terraces defines Mortlake, where victorian and edwardian terraces set what a mansard roof extension can do. A mansard on a Victorian terrace almost always needs full planning permission across SW14. Any Mortlake mansard roof extension is validated by Richmond Council, with Mortlake station the usual Mortlake reference point on the site plan.
Near Mortlake: East Sheen (SW14) — mansard roof extension work in East Sheen means edwardian villas, 1930s semi-detached. East Sheen is Edwardian villas, 1930s semi-detached. Edwardian parapets give a mansard a clean base line throughout SW14. Richmond Council decides the East Sheen application, and Sheen Lane anchors the East Sheen location plan.
Near Mortlake: Teddington (TW11) — a mansard roof extension in Teddington starts from edwardian villas, victorian terraces, and Teddington reads as Edwardian villas, Victorian terraces. A mansard on a Victorian terrace almost always needs full planning permission in TW11. Richmond Council assesses Teddington mansard roof extensions against its own Teddington character guidance, and the location plan we draw for Teddington references Teddington Lock.
Near Mortlake: Hampton (TW12) — Georgian and Edwardian villages defines Hampton, where georgian villas, edwardian terraces, 1930s semi-detached set what a mansard roof extension can do. Mansards read as original on Georgian terraces across TW12. Any Hampton mansard roof extension is validated by Richmond Council, with Hampton Court Palace the usual Hampton reference point on the site plan.
Near Mortlake: Whitton (TW2) — 1930s semi-detached defines Whitton, where 1930s semi-detached set what a mansard roof extension can do. Mansards are rare on 1930s stock — the hipped roof form works against across TW2. Any Whitton mansard roof extension is validated by Richmond Council, with Whitton station the usual Whitton reference point on the site plan.
Near Mortlake: Ham (TW10) — Georgian common, post-war estate defines Ham, where georgian villas, post-war estates set what a mansard roof extension can do. Mansards read as original on Georgian terraces across TW10. Any Ham mansard roof extension is validated by Richmond Council, with Ham Common the usual Ham reference point on the site plan.
Near Mortlake: Richmond (TW9, TW10) — Georgian centre, riverside conservation defines Richmond, where georgian terraces, victorian villas set what a mansard roof extension can do. Mansards read as original on Georgian terraces across TW9. Any Richmond mansard roof extension is validated by Richmond Council, with Richmond Green the usual Richmond reference point on the site plan.

What local planning policy applies to a mansard roof extension in Mortlake?

How designation changes a Mortlake mansard roof extension: Richmond Council maintains 72 conservation areas, including Ham Common, Richmond Green, Kew Green. Inside any of them a Mortlake mansard roof extension cannot rely on permitted development, and the route becomes a £258 householder application determined in 8 weeks rather than a £120 prior approval in 6 weeks. Richmond Green sets the tone for Mortlake casework.

Article 4 and your Mortlake mansard roof extension: Richmond Council has made no borough-wide direction, so permitted development for a mansard roof extension in Mortlake generally survives outside Mortlake conservation areas and listed curtilages. A Lawful Development Certificate at £129 is how a SW14 owner records that a mansard roof extension was lawful.

Mortlake housing stock: Georgian in Richmond Green and Twickenham; Edwardian villas in Barnes and East Sheen; 1930s semi-detached in Whitton; riverside cottages along the Thames. Highest conservation area coverage in London; Royal Parks and Thames corridor add heritage layers; design quality heavily scrutinised. Read that before choosing a mansard roof extension route in Mortlake — construction, not postcode, sets what is achievable. Mansard roof extensions in Mortlake start at £1,575 on a fixed fee, or £1,750 for the Complete package covering both Richmond Council submissions.

What happens if a Mortlake property sits on a boundary?

Hounslow — cross the Mortlake boundary and Hounslow Council takes the mansard roof extension instead, applying 30 conservation areas of its own around W3. We re-price mansard roof extensions at the Mortlake edge because Hounslow policy and Richmond upon Thames policy rarely align on mansard roof extension depth.
Kingston upon Thames — adjoining Mortlake, with 22 conservation areas centred on KT1. A mansard roof extension on the far side of the Mortlake line is determined by Kingston Council, so the Mortlake quote for mansard roof extensions is checked against Kingston upon Thames guidance before it is issued.
Wandsworth — adjoining Mortlake, with 45 conservation areas centred on SW8. A mansard roof extension on the far side of the Mortlake line is determined by Wandsworth Council, so the Mortlake quote for mansard roof extensions is checked against Wandsworth guidance before it is issued.
Hammersmith and Fulham — adjoining Mortlake, with 45 conservation areas centred on W6. A mansard roof extension on the far side of the Mortlake line is determined by Hammersmith & Fulham Council, so the Mortlake quote for mansard roof extensions is checked against Hammersmith and Fulham guidance before it is issued.

Sources for this Mortlake mansard roof extension page: borough policies maps and conservation-area registers (2025–26), Royal Mail postcode district boundaries, the Town and Country Planning (Fees for Applications) (England) Regulations, the Town and Country Planning (General Permitted Development) (England) Order 2015 as amended, and the Party Wall etc. Act 1996.