Mansard Roof Extensions · SW16 Streatham
SW16 spans Lambeth and Croydon; Lambeth controls the Telford Park and Leigham Court conservation areas around Streatham.
This page covers one part of the borough. For the full picture — fees, timelines and the council's current position — read mansard roof extensions in Lambeth.
A mansard roof extension adds a full storey behind a new sloping front face — a strong option on SW16's terraces in Streatham where a standard dormer is too small. Lambeth Council scrutinises mansards on townscape and precedent, especially within Telford Park, Streatham Lodge, Leigham Court; we design to the borough's roof guidance with a Heritage Statement where the setting requires it.
Streatham's most space-efficient loft solution when PD-route dormers are blocked. Our chartered team designs mansards that get approved in Streatham conservation areas — with heritage statements and planning officer negotiation built in.
Across Streatham, Norbury, Streatham Hill, Furzedown in SW16, the dominant property is victorian and edwardian terraces and bay-fronted semis, with mansion blocks and larger villas around streatham and norbury. That stock shapes what mansard roof extensions looks like here: the right approach for a period terrace differs from a mansion-block flat or a new-build, and Lambeth Council judges each on design quality and neighbour impact. We survey the specific Streatham property, confirm the planning route — Permitted Development, a Lawful Development Certificate, or full planning — and draw a council-ready set tailored to the SW16 streetscape.
Housing stock in SW16: Victorian and Edwardian terraces and bay-fronted semis, with mansion blocks and larger villas around Streatham and Norbury.
Within the district: Streatham, Norbury, Streatham Hill, Furzedown.
Streets we know in SW16: the Streatham Hill and Telford Park roads, Mount Ephraim Lane and the Furzedown streets. Each road has its own building line, boundary treatment and precedent that Lambeth Council weighs when assessing a mansard roof extensions scheme.
Conservation areas: Telford Park, Streatham Lodge, Leigham Court. Inside these, most external work needs full planning and a Heritage Statement.
Getting around SW16: Streatham, Streatham Hill and Streatham Common rail to Victoria and London Bridge.
Regeneration: Streatham falls within or beside the Streatham town centre regeneration, which shapes local planning policy and design expectations.
Property values: Price-paid entries for SW16 number 978 in 2025, midpoint £467,500 and 2.1% below the previous year. Our borough breakdown lists three types for Lambeth: semi-detached at £1,065,000, terraced at £880,000 and flats at £470,000. Contains HM Land Registry data (c) Crown copyright and database right 2026
Borough character: Mix of dense Victorian residential and post-war estate; strong conservation area coverage; generally design-led planning decisions.
We check against Lambeth Council's mansard design guide and design to match the terrace.
Required for Streatham's conservation areas — demonstrates the mansard respects character and townscape.
Accurate photomontage showing how the mansard sits alongside neighbours — often decisive at Lambeth Council committee.
Mansards invariably trigger Party Wall notices in Streatham's dense terraced streets. Structural package includes new ridge, tie beams, floor joists.
Full liaison with Lambeth Council planning officer, committee representation if called in.
Part L thermal, Part B fire (critical on mansards), Part E acoustic separation.
Single planning or building-regs submission.
Planning + building regs + structural.
Listed, conservation or complex sites.
Yes. The Victorian and Edwardian terraces and bay-fronted semis around Telford Park and Furzedown suit side-return and rear extensions plus loft conversions, much of it within Permitted Development outside the conservation areas, confirmed with a Lawful Development Certificate. We confirm the route and draw to Lambeth's checklist.
SW16 straddles the boundary — Streatham and Streatham Hill sit in Lambeth, while Norbury falls into Croydon. The two councils apply different conservation and householder controls, so we confirm your exact authority before quoting and submit accordingly.
Usually yes — a hip-to-gable plus rear dormer on the semis, within the volume allowance and confirmed by a Lawful Development Certificate, provided you're not in the Telford Park or Leigham Court conservation areas. We check the constraints for your road and draw it for Building Control.
With SW16 houses around £700,000-£1m and Streatham's town-centre regeneration improving the area, a well-designed rear extension or loft adds family space worth comfortably above the build and drawing cost.
Lambeth Council charges its own statutory application fee (currently £548 for a householder planning application, £610 for a full application). We quote the drawings as one fixed price and the free site survey covers every SW16 address.
For a SW16 project across Streatham, Norbury, Streatham Hill, Furzedown, expect roughly 3–4 weeks from instruction to submission: week 1 the measured survey, weeks 2–3 the drawings and your revisions, then validation and the statutory determination by Lambeth Council (8 weeks for a householder application). We carry the Streatham application through every officer query to the decision.
Streatham (SW16) sits primarily in Lambeth, so applications are decided by Lambeth Council. Conservation areas within SW16 include Telford Park, Streatham Lodge, Leigham Court, where full planning and a Heritage Statement are required. We confirm the planning route for your exact address before quoting.
Almost always. Any structural work behind mansard roof extensions in Streatham — new openings, steel beams, loft floors, foundations — needs Building Regulations approval covering structure (Part A), fire escape (Part B) and insulation (Part L), submitted to Lambeth Council Building Control or an approved inspector. On SW16's typically terraced and semi-detached stock, a Party Wall notice to adjoining neighbours is normally required before the steelwork. We coordinate both as part of the Complete package.
In value terms, yes. The bigger risk is an unapproved or non-compliant scheme — which is why council-ready drawings and a clean Building Control sign-off matter on SW16 homes.
Moving, or weighing up a site in the next borough along? Here is the complete service list for SE5, SE19, SE21, SE24, SE27, SW2, SW4 and SW9.
Pick a slot that suits you. No obligation and no sales pressure, just straight answers on your planning route.
Every SW16 postcode district we draw in, the stock that dominates it and the authority that validates a mansard roof extension there. SW16 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 |
|---|---|---|---|
| SW16 | Streatham / Norbury | Edwardian terraces, post-war flats | SW16 straddles a boundary: Streatham / Norbury addresses fall to Lambeth Council or Wandsworth Council or Merton Council or Croydon Council, so confirm which authority validates the mansard roof extension before submitting SW16 drawings. |
| SW16 | Streatham | Edwardian terraces, post-war flats | Streatham sits inside SW16; mansard roof extension proposals here are determined by Lambeth Council. |
| SE11 | Kennington / Vauxhall | Georgian terraces, post-war estates | Adjoining district to SW16, also inside Lambeth for mansard roof extension purposes. |
| SE24 | Herne Hill | Victorian villas, Edwardian terraces | Adjoining district to SW16, also inside Lambeth for mansard roof extension purposes. |
| SE27 | West Norwood / Tulse Hill | Victorian terraces, Edwardian villas | Adjoining district to SW16, also inside Lambeth for mansard roof extension purposes. |
| SW2 | Brixton Hill / Tulse Hill | Victorian terraces, post-war estates | Adjoining district to SW16, also inside Lambeth for mansard roof extension purposes. |
| SW11 | Battersea / Clapham Junction | Victorian terraces, mansion blocks | Adjoining district to SW16, also inside Wandsworth for mansard roof extension purposes. |
| SW12 | Balham | Victorian and Edwardian terraces | Adjoining district to SW16, also inside Wandsworth for mansard roof extension purposes. |
| SW15 | Putney / Roehampton | Edwardian terraces, Victorian villas, mansion blocks | Adjoining district to SW16, also inside Wandsworth for mansard roof extension purposes. |
| SW17 | Tooting / Earlsfield | Edwardian terraces | Adjoining district to SW16, also inside Wandsworth for mansard roof extension purposes. |
Roof pitch, wall build-up and plot depth change every few SW16 streets, and each one changes what a mansard roof extension can achieve at that address.
Conservation areas covering SW16 (Streatham / Norbury): Lambeth Council runs 64, and Clapham Common, Herne Hill, Brixton Road are the ones SW16 (Streatham / Norbury) owners meet most. A mansard roof extension inside a SW16 (Streatham / Norbury) conservation area loses permitted development, so the SW16 (Streatham / Norbury) submission is a householder application at £548 decided in 8 weeks — not a £249 prior approval decided in 6 weeks. In Herne Hill a mansard roof extension is judged on the street elevation first.
Article 4 and your SW16 (Streatham / Norbury) mansard roof extension: Borough-wide Article 4 for HMO conversions; plus office-to-residential restrictions. At a SW16 address that matters twice over, because Lambeth Council applies the direction unevenly across SW16 (Streatham / Norbury) — we read the SW16 (Streatham / Norbury) policies map for the exact SW16 address before quoting mansard roof extensions.
What SW16 (Streatham / Norbury) is built from: Victorian terraces in Clapham, Brixton, Herne Hill; Edwardian villas; 1930s and post-war estates in parts of Streatham; Georgian in Kennington. Mix of dense Victorian residential and post-war estate; strong conservation area coverage; generally design-led planning decisions. That mix decides the mansard roof extension route in SW16 (Streatham / Norbury) more than the postcode does, and it is what a Lambeth Council case officer reads first. A householder application costs £548 paid to Lambeth Council direct, with 8 weeks to a decision once validated.
Conservation areas covering SW16 (Streatham / Norbury): Wandsworth Council runs 45, and Tonsley, Magdalen Park, Nightingale Triangle are the ones SW16 (Streatham / Norbury) owners meet most. A mansard roof extension inside a SW16 (Streatham / Norbury) conservation area loses permitted development, so the SW16 (Streatham / Norbury) submission is a householder application at £548 decided in 8 weeks — not a £249 prior approval decided in 6 weeks. In Tonsley a mansard roof extension is judged on the street elevation first.
Article 4 and your SW16 (Streatham / Norbury) mansard roof extension: Article 4 for HMO conversions covering the whole borough. At a SW16 address that matters twice over, because Wandsworth Council applies the direction unevenly across SW16 (Streatham / Norbury) — we read the SW16 (Streatham / Norbury) policies map for the exact SW16 address before quoting mansard roof extensions.
What SW16 (Streatham / Norbury) is built from: Extensive Victorian terraced streets — the classic London side-return extension opportunity; Edwardian villas around the commons; 1930s semi-detached in Southfields. Family-oriented, high side-return extension and loft conversion rates; planning department experienced with Victorian terrace modifications. That mix decides the mansard roof extension route in SW16 (Streatham / Norbury) more than the postcode does, and it is what a Wandsworth Council case officer reads first. A householder application costs £548 paid to Wandsworth Council direct, with 8 weeks to a decision once validated.
Sources for this SW16 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.
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