Full architectural technology service for basement digs and cellar conversions in Lewisham — structural underpinning design, waterproofing strategy, Party Wall coordination, planning where required, and building regulations through to completion certificate.
A basement conversion drawings package in Lewisham, where the stock is largely Victorian and Edwardian terraces across Brockley, is the full measured-survey-to-submission drawing set London Borough of Lewisham needs in order to determine an application: existing and proposed plans, elevations and sections at 1:100 and 1:50, a location and site plan, and the supporting statements the case officer asks for.
Prepared and reviewed by the chartered technologist team at Architectural Drawings London — MCIAT chartered, £2m PI insured.Last reviewed 2026-08-03.
Full architectural technology service for basement digs and cellar conversions in Lewisham — structural underpinning design, waterproofing strategy, Party Wall coordination, planning where required, and building regulations through to completion certificate.
Housing stock in Lewisham: Victorian and Edwardian terraces across Brockley, Honor Oak, Forest Hill; 1930s semi-detached in Catford and Hither Green; post-war mixed in Deptford.
Character: Generally permissive planning compared to central boroughs; loft conversions and side-return extensions routinely approved under PD.
Desktop study plus measured survey assessing existing foundations, ground conditions, water table level and underpinning viability for your Lewisham 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 Lewisham's ground conditions and water table.
Full Plans application to Lewisham 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 Lewisham basement triggers Party Wall notices. We also manage Thames Water Build Over Agreements where within 3m of a public sewer.
Single planning or regs submission.
Planning + building regs + structural.
Listed, conservation, complex sites.
Move the controls for an indicative figure. It anchors your budget — it is not a quote. Every project is priced after a free survey.
Build costs are separate and quoted by your contractor. See our published fees.
Every Lewisham postcode district we draw in, the stock that dominates it and the authority that validates a basement conversion there. Lewisham fees below are the statutory England rates for 2026, not basement conversion estimates.
| Postcode | Area | Dominant stock | What it means for a basement conversion |
|---|---|---|---|
| SE13 | Lewisham / Hither Green | Victorian terraces, post-war flats | SE13 covers Lewisham / Hither Green only; Lewisham Council handles the basement conversion, and Lewisham / Hither Green case officers apply the SE13 conservation-area map. |
| SE14 | New Cross | Victorian and Edwardian terraces across Brockley | SE14 covers New Cross only; Lewisham Council handles the basement conversion, and New Cross case officers apply the SE14 conservation-area map. |
| SE23 | Forest Hill / Honor Oak | Victorian villas, Edwardian terraces | Forest Hill / Honor Oak sits wholly inside SE23, so Lewisham Council validates every basement conversion submitted from an SE23 address. |
| SE26 | Sydenham | Victorian villas, Edwardian terraces | SE26 straddles a boundary: Sydenham addresses fall to Lewisham Council or Bromley Council, so confirm which authority validates the basement conversion before submitting SE26 drawings. |
| SE3 | Blackheath / Kidbrooke | Georgian villas, Victorian terraces | A basement conversion in Blackheath / Kidbrooke may land with Greenwich Council or Lewisham Council — SE3 crosses the boundary, and the SE3 policies map decides it street by street. |
| SE4 | Brockley | Victorian and Edwardian terraces | SE4 covers Brockley only; Lewisham Council handles the basement conversion, and Brockley case officers apply the SE4 conservation-area map. |
| SE6 | Catford / Bellingham | 1930s semi-detached, post-war flats | A basement conversion at an SE6 address in Catford / Bellingham is determined by Lewisham Council under its own Local Plan policies for Catford / Bellingham. |
| SE8 | Deptford | Georgian terraces, post-war estates, new-build | A basement conversion at an SE8 address in Deptford is determined by Lewisham Council under its own Local Plan policies for Deptford. |
Roof pitch, wall build-up and plot depth change every few Lewisham streets, and each one changes what a basement conversion can achieve at that address.
Conservation areas covering Lewisham: Lewisham Council runs 30, and Blackheath, Deptford High Street, Forest Hill are the ones Lewisham owners meet most. A basement conversion inside a Lewisham conservation area loses permitted development, so the Lewisham submission is a householder application at £548 decided in 8 weeks — not a £249 prior approval decided in 6 weeks. In Deptford High Street a basement conversion is judged on the street elevation first.
No blanket Article 4 over Lewisham: Lewisham Council has not withdrawn permitted development across Lewisham, so a basement conversion outside a Lewisham conservation area usually keeps it. The £274 Lawful Development Certificate is still the document a SE4 owner wants on file.
The building fabric around Lewisham: Victorian and Edwardian terraces across Brockley, Honor Oak, Forest Hill; 1930s semi-detached in Catford and Hither Green; post-war mixed in Deptford. Generally permissive planning compared to central boroughs; loft conversions and side-return extensions routinely approved under PD. A basement conversion in Lewisham 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 Lewisham Council.
Sources for this Lewisham 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.
Direct answers to the questions Lewisham homeowners ask every week about basement conversion drawings.
Start a free quote →Converting an existing cellar to habitable space in Lewisham usually does not require planning permission — it is an internal alteration. However, excavating a new basement, adding lightwells, or lowering floor levels to create a new storey typically does require planning. Lewisham does not have a borough-specific basement policy beyond the national framework — basement conversions are generally permissible subject to structural, drainage and flood-risk considerations. Thames Water Build Over Agreements apply where you're within 3m of a public sewer.
Basements are the most expensive way to add space in Lewisham, per square metre, because of underpinning, waterproofing and temporary works — all sequential and all engineered. Our package covers planning where required, building regulations, structural design and the BS 8102 waterproofing specification. See our fees.
Most properties in Lewisham can support a basement conversion, provided foundations are deep enough or can be underpinned, the water table is manageable, and there are no significant tree root or drainage constraints. Victorian and Edwardian houses in Lewisham often have existing cellars that can be deepened. We assess suitability at the initial survey.
BS 8102:2022 requires a waterproofing strategy appropriate to the site's water table and ground conditions. In Lewisham, this typically means a Type C cavity drain membrane system (most reliable), sometimes combined with Type A barrier protection. The strategy must be specified by a qualified waterproofing designer — included in our package.
A typical Lewisham basement conversion takes 6–12 months to build once drawings are approved. Our architectural package takes 5–8 weeks from instruction to Building Control submission. The longer build time reflects the sequential underpinning process, which must proceed in careful stages.
If your property sits on a boundary, here are the neighbouring options.
We cover every architectural technology service in Lewisham with one chartered team.
A construction-ready drawing package compliant with every Approved Document — Part A structure, Part B fire, Part L thermal, Part M accessib...
Every loft type across every Lewisham roof line — dormer, mansard, hip-to-gable, L-shape, Velux. LDC or full planning route, building regula...
The whole spectrum — rear extensions, side returns, wraparounds, double-storey, basement digs. Planning-led design with detailed technical p...
Lewisham's most space-efficient loft solution when PD-route dormers are blocked. Our chartered team designs mansards that get approved in Le...
Turn your unused Lewisham garage into a bedroom, home office or open-plan kitchen-diner. Planning route assessment, full building regulation...
Chartered structural engineer calculations for every residential intervention in Lewisham — steel beams, lintels, pad foundations, wall remo...
Measured surveys across Lewisham — floor plans, elevations and sections to ±3mm accuracy. Leica Disto laser + BLK360 point-cloud scanning, A...
End-to-end Party Wall Act 1996 service for Lewisham — Section 1, 3 and 6 notices, schedule of condition surveys, party wall award coordinati...
London's most popular loft type — the full-width rear dormer. Planning or Permitted Development route assessed for your Lewisham property, b...
Leave your number and an Architectural technologist will call you back within 30 minutes during working hours.
No obligation. No sales pressure. Just expert advice about basement conversion drawings in Lewisham.
Free quote in 60 seconds. No hourly billing. MCIAT chartered.
Get my free quote →
