Basement Conversions · SW16 Streatham
SW16 spans Lambeth and Croydon; Lambeth controls the Telford Park and Leigham Court conservation areas around Streatham.
If your property sits elsewhere in the borough, the borough-wide page for basement conversions in Lambeth covers the same service across every ward.
Basement conversions and lowering existing cellars in Streatham add space without touching the roofline — valuable on SW16's period houses around Streatham, Norbury, Streatham Hill, Furzedown. Lambeth Council reviews structural, drainage and flood-risk impact, and a Party Wall award plus a Thames Water build-over agreement are usually required. We coordinate the structural engineer and the waterproofing design.
Full architectural technology service for basement digs and cellar conversions in Streatham — structural underpinning design, waterproofing strategy, Party Wall coordination, planning where required, and building regulations through to completion certificate.
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 basement conversion drawings 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 basement conversion drawings 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: SW16 spans four boroughs. Only 64.3% of its 2025 sales sat in Lambeth, with sales also recorded in Croydon, Merton and Wandsworth, so one council's numbers cannot describe the whole district. For SW16 itself: 978 sales, median £467,500. 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.
Desktop study plus measured survey assessing existing foundations, ground conditions, water table level and underpinning viability for your Streatham property.
New-build basements and lightwell extensions need planning permission. Cellar conversions of existing space are usually Permitted Development. We confirm the route and submit where needed.
Underpinning sequence drawings, reinforced concrete design, temporary works strategy — all to Eurocode with chartered engineer sign-off.
BS 8102:2022 compliant — cavity drain, cementitious tanking or membrane system specified for Streatham's ground conditions and water table.
Full Plans application to Lambeth Council Building Control or an approved inspector covering structure (Part A), fire safety (Part B), damp-proofing (Part C), ventilation (Part F) and thermal performance (Part L).
Almost every Streatham basement triggers Party Wall notices. We also manage Thames Water Build Over Agreements where within 3m of a public sewer.
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 basement conversion drawings 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.
Householders often approach us after a neighbour used a different council. Our full range is set out 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 basement conversion there. SW16 fees below are the statutory England rates for 2026, not basement conversion estimates.
| Postcode | Area | Dominant stock | What it means for a basement conversion |
|---|---|---|---|
| SW16 | Streatham / Norbury | Edwardian terraces, post-war flats | Streatham / Norbury is split at SW16. Either Lambeth Council or Wandsworth Council or Merton Council or Croydon Council can determine a basement conversion here, so the SW16 address is checked against both policies maps first. |
| SW16 | Streatham | Edwardian terraces, post-war flats | Streatham sits inside SW16; basement conversion proposals here are determined by Lambeth Council. |
| SE11 | Kennington / Vauxhall | Georgian terraces, post-war estates | Adjoining district to SW16, also inside Lambeth for basement conversion purposes. |
| SE24 | Herne Hill | Victorian villas, Edwardian terraces | Adjoining district to SW16, also inside Lambeth for basement conversion purposes. |
| SE27 | West Norwood / Tulse Hill | Victorian terraces, Edwardian villas | Adjoining district to SW16, also inside Lambeth for basement conversion purposes. |
| SW2 | Brixton Hill / Tulse Hill | Victorian terraces, post-war estates | Adjoining district to SW16, also inside Lambeth for basement conversion purposes. |
| SW11 | Battersea / Clapham Junction | Victorian terraces, mansion blocks | Adjoining district to SW16, also inside Wandsworth for basement conversion purposes. |
| SW12 | Balham | Victorian and Edwardian terraces | Adjoining district to SW16, also inside Wandsworth for basement conversion purposes. |
| SW15 | Putney / Roehampton | Edwardian terraces, Victorian villas, mansion blocks | Adjoining district to SW16, also inside Wandsworth for basement conversion purposes. |
| SW17 | Tooting / Earlsfield | Edwardian terraces | Adjoining district to SW16, also inside Wandsworth for basement conversion purposes. |
Roof pitch, wall build-up and plot depth change every few SW16 streets, and each one changes what a basement conversion can achieve at that address.
How designation changes a SW16 (Streatham / Norbury) basement conversion: Lambeth Council maintains 64 conservation areas, including Streatham Hill, Clapham Common, Herne Hill. Inside any of them a SW16 (Streatham / Norbury) basement conversion cannot rely on permitted development, and the route becomes a £548 householder application determined in 8 weeks rather than a £249 prior approval in 6 weeks. Kennington sets the tone for SW16 (Streatham / Norbury) casework.
What Article 4 removes near SW16 (Streatham / Norbury): Borough-wide Article 4 for HMO conversions; plus office-to-residential restrictions. Before pricing a basement conversion we check whether the SW16 address is inside the mapped area, because Lambeth Council draws the SW16 (Streatham / Norbury) boundary street by street rather than across the whole of SW16 (Streatham / Norbury).
The building fabric around SW16 (Streatham / Norbury): 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. A basement conversion in SW16 (Streatham / Norbury) is scoped against that stock first, because it decides whether the scheme runs as permitted development, a £274 Lawful Development Certificate, or a full £548 application to Lambeth Council.
How designation changes a SW16 (Streatham / Norbury) basement conversion: Wandsworth Council maintains 45 conservation areas, including Nightingale Triangle, Wandsworth Common, Clapham Common West. Inside any of them a SW16 (Streatham / Norbury) basement conversion cannot rely on permitted development, and the route becomes a £548 householder application determined in 8 weeks rather than a £249 prior approval in 6 weeks. Magdalen Park sets the tone for SW16 (Streatham / Norbury) casework.
What Article 4 removes near SW16 (Streatham / Norbury): Article 4 for HMO conversions covering the whole borough. Before pricing a basement conversion we check whether the SW16 address is inside the mapped area, because Wandsworth Council draws the SW16 (Streatham / Norbury) boundary street by street rather than across the whole of SW16 (Streatham / Norbury).
The building fabric around SW16 (Streatham / Norbury): 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. A basement conversion in SW16 (Streatham / Norbury) is scoped against that stock first, because it decides whether the scheme runs as permitted development, a £274 Lawful Development Certificate, or a full £548 application to Wandsworth Council.
Sources for this SW16 basement conversion 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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