Residential specialism

Mansard roof extensions in London.

All five mansard variants — rear-only, full, L-shape, mansard + dormer hybrid, or roof-only conversion. Conservation Area and Article 4 mansard planning specialism, slate-matched designs, Heritage Statements and officer negotiation built in. Drawings, Building Regs, structural calcs and Party Wall — fixed fee from £1,575, MCIAT chartered.

Get a free quote → What's included

From £1,575 fixed fee council-ready drawing review All London boroughs £2m PI insured

Mansard roof extension drawings with conservation area heritage design for London terrace

What's included

Fully end-to-end, nothing extra to add.

Conservation area design review

We check against your borough's mansard design guide (Islington, Camden, Hackney, Tower Hamlets all publish them) and design to match.

Heritage Statement

Required for conservation areas — demonstrates the mansard respects the character and townscape of the terrace.

Street elevation massing

Accurate photomontage showing how the mansard sits alongside your neighbours — often decisive at committee.

Party Wall and structural

Mansards invariably trigger Party Wall notices. Structural package includes new ridge, tie beams, floor joists.

Planning submission & agent service

Full liaison with planning officer, committee representation if called in.

Full building regs package

Part L thermal, Part B fire (mansards require careful fire-escape consideration), Part E acoustic.

Five mansard variants, one decision

Rear-only, full, L-shape, hybrid or roof-only — which suits your terrace?

London mansard roof extensions divide into five recognised patterns. The right one depends on terrace position (mid or end), street precedent, conservation area status, Article 4 direction, and how much additional floor area you actually need. Below is the plain-English decision matrix — every variant almost always needs Full Planning permission, not Permitted Development, because mansards alter the existing roof line.

Rear-only mansard

The most common London mansard. Slate-clad rear slope at 70°, hidden from the street so often the only mansard form approved in conservation areas. Full Planning (8-week determination); LPAs in Islington, Hackney, Camden, Tower Hamlets routinely approve where the design guide is followed. Typical added floor area 22–28m². Best for: Victorian and Georgian terraces in conservation areas.

drawings from£1,575

Full mansard (front + rear)

Rare and planning-sensitive. Slate slopes on both front and rear pitches, small symmetrical sash dormers to the street. Almost never approved in conservation areas without strong street precedent. Best chance: where the rest of the terrace already has full mansards. Typical added floor area 28–36m². Full Planning, often committee-level.

drawings from£1,750

L-shape mansard

Mansard above the main roof combined with a flat-roof addition over the rear back-addition (the "L"). Effectively a full extra floor — common on Victorian terraces where the rear outrigger already steps down. Full Planning, sometimes with a separate Householder application. Typical added floor area 30–38m². Best for: maximising a 5-bed conversion on a 4-bed terrace.

drawings from£1,950

Mansard + dormer hybrid

Rear mansard combined with a small side dormer or rooflight bank. Sensible on end-of-terrace and semi-detached properties where the side elevation can carry additional light. Full Planning, occasionally with PD-route side rooflights to keep elevation reads simple. Typical added floor area 24–30m². Best for: end-of-terrace Victorian or Edwardian.

drawings from£1,750

Roof-only mansard upgrade

You already have a loft conversion (dormer or hip-to-gable) and want to upgrade the rear slope to a true mansard for full headroom. Existing structure usually stays; new slate slope and revised parapet line. Full Planning, but a faster path because most of the loft already exists. Typical added headroom: 0.4–0.6m across the whole rear room. Best for: 1990s/2000s loft conversions being modernised.

drawings from£1,575

Six weeks, five stages

From first site visit to submitted application.

Most London mansard roof submissions complete in 25–32 working days from instruction. The council then takes 8 weeks on a Householder Planning application — longer if it goes to committee, which is more common on mansards in conservation areas than on standard rear extensions. Building Regulations Full Plans, structural design and Party Wall coordination all run in parallel so the contractor has a complete pack on day one of the build.

Site survey & measured roof drawings

Days 1–4 — measured existing roof survey, parapet and chimney heights, photographic record of the terrace, conservation area and Article 4 check.

Concept design & heritage assessment

Days 5–11 — mansard variant selected, slate and lead detailing matched to neighbours, street-context massing study, Heritage Statement drafted.

Full planning + Design and Access Statement

Days 12–22 — proposed plans, elevations, street-scene CGI, Design & Access Statement, Heritage Statement finalised, Planning Portal lodgement.

Building Regs, structural & Party Wall

Days 23–32 — Part L thermal, Part B fire-escape, Part E acoustic; new ridge beam, floor joists and tie-rod calcs; Party Wall notices drafted to both flanks.

Tender & build support

Post-approval — competitive tender pack to three London mansard specialists, on-site queries answered through slate works, lead flashings and internal fit-out.

Sample drawing set

A real London mansard submission, page by page.

Anonymised drawings from a rear-only mansard roof extension to a Victorian terrace in a Camden conservation area. Householder Planning approved at delegated officer level in 9 weeks with Heritage Statement and slate-matched detailing, followed by Full Plans Building Regulations submission with chartered structural sign-off on a new ridge beam, tie rods and reinforced floor joists.

Comparative mansard roof variant elevations — rear-only, full and L-shape mansard sample drawing London conservation area — Mansard variant comparison · 1:100 · A3

L-shape mansard loft conversion proposed elevation and floor plan — anonymised London Victorian terrace sample — L-shape mansard proposed plan · 1:50 · A3

Street-scene photomontage showing slate-matched mansard alongside neighbouring terrace — London conservation area planning sample — Street-scene context · photomontage · A3

Section through proposed rear mansard with ridge beam, tie rods and Part L insulation build-up — London sample drawing — Section through mansard · 1:20 · A2

Want the full PDF set? Start a free quote and we’ll email a redacted sample matching your mansard variant.

Fixed fees — 30% below London architects

Mansard roof drawings, priced honestly.

Essentials mansard

Planning drawings + Heritage Statement — rear-only or roof-only upgrade.

from£1,575

London architect: £2,400–£3,200

Measured roof survey + existing drawings
Proposed plans, elevations & sections
Heritage Statement & street-scene context
Householder Planning submission

Start Essentials →

Complete mansard

Planning + Building Regs + structural calcs — full L-shape or hybrid ready.

from£2,250

London architect: £3,400–£4,800

Everything in Essentials
Full Building Regs pack (Part L, B, E, M)
Structural calcs — ridge beam, tie rods, joists
Slate & lead detail drawings
Agent service until decision

Start Complete →

Premium mansard

Planning + BR + structural + 3D visuals + Party Wall + tender support.

from£3,150

Architects: £5,200–£8,500+

Everything in Complete
3D photo-real street-scene visuals
Party Wall notices drafted & served
Competitive tender pack — 3 mansard specialists

Discuss Premium →

Real London mansard projects

Recent mansard roof extensions.

Three featured mansard submissions across inner London. Planning references verifiable on each council’s public portal — full case studies publishing shortly.

Camden Conservation Area mansard

Victorian terrace, NW1, inside a designated conservation area. Slate-matched rear-only mansard at 70° pitch with timber sash-style dormers and reinstated stock-brick parapet. Householder Planning approved first time at delegated level with Heritage Statement. 26m² added; loft master suite with ensuite.

ApprovedCase study soon

Westminster mansard with rear dormer

Georgian terrace, W1. Hybrid mansard combining a rear slate slope with a small side dormer for additional light to the new bathroom. Approved at committee after officer recommendation, with strict slate sample sign-off and lead flashing detail conditions. 32m² of new floor area across the new full-height storey.

ApprovedCase study soon

Islington L-shape mansard

Victorian terrace, N1, with existing rear back-addition. Wraparound rear ground-floor extension below, L-shape mansard above with new ridge beam and tie rods designed by chartered structural engineer. Full Planning approved with the borough’s mansard design guide cited section-by-section. 36m² added.

ApprovedCase study soon

Mansard Roof FAQs

Common questions.

Every case is different. Call +44 7592 201 353 for a five-minute chat.

Start a free quote →

Will a mansard be approved in my conservation area?

It depends on the borough policy and the terrace context. Islington, Hackney and Tower Hamlets all allow mansards in many conservation areas following their design guides. Westminster is stricter. We advise case-by-case at the feasibility stage.

What's the ideal mansard pitch?

70° at the front slope is typical — steep enough to maximise floor area while reading as a roof rather than a full storey. Front dormers are usually small and symmetrical.

Can I have a mansard if the rest of the terrace doesn't?

Often yes, but councils favour applications supported by the wider street. Where precedents exist nearby — common in Islington, Hackney — approval is far more likely.

How much headroom does a mansard give me?

Full-height — typically 2.3–2.5m ceiling from the new floor. Unlike a dormer, which gives partial head height, a mansard is a full additional storey.

What about lightwells and windows?

Conservation area mansards use small, proportioned, timber-framed sash-style windows on the mansard face, set back behind a parapet. Flat rooflights for the flat roof portion. We design to match the terrace.

Mansard roof extensions in London.

Quick facts · Mansard Roof Extensions in London

Fully end-to-end, nothing extra to add.

Conservation area design review

Heritage Statement

Street elevation massing

Party Wall and structural

Planning submission & agent service

Full building regs package

Rear-only, full, L-shape, hybrid or roof-only — which suits your terrace?

Rear-only mansard

Full mansard (front + rear)

L-shape mansard

Mansard + dormer hybrid

Roof-only mansard upgrade

From first site visit to submitted application.

Site survey & measured roof drawings

Concept design & heritage assessment

Full planning + Design and Access Statement

Building Regs, structural & Party Wall

Tender & build support

A real London mansard submission, page by page.

Mansard roof drawings, priced honestly.

Essentials mansard

Complete mansard

Premium mansard

Recent mansard roof extensions.

Camden Conservation Area mansard

Westminster mansard with rear dormer

Islington L-shape mansard

Common questions.

Mansard Roof by borough

Other services we offer

Planning Drawings

Building Regs Drawings

Loft Conversions

House Extensions

Watch: Mansard Roof Extensions in action

Get a callback in 30 minutes

Ready to start your mansard roof?

Before you go…