House Extensions · SE23 Forest Hill
Fixed-fee house extension drawings for Forest Hill, Honor Oak, Perry Vale, Horniman in the SE23 postcode, drawn by an MCIAT-chartered architectural technologist and submitted to Lewisham Council. SE23 is decided by Lewisham Council. Forest Hill and Honor Oak are hilly, leafy Victorian/Edwardian suburbs with strong loft and rear-extension demand; conservation areas cover the better villa streets near the Horniman and London Road, while the bulk of the terraced and semi stock keeps permitted-development rights.
MCIAT chartered drawings for planning, building regs, lofts and extensions — fixed fees 30% below typical London architects. Tell us what you need and we’ll reply the same working day.
House extensions in Forest Hill are dominated by single-storey rear and side-return additions on SE23's victorian and edwardian terraces and villas across, with double-storey and wrap-around schemes where the plot allows. Lewisham Council weighs depth, height and neighbour daylight; many extensions across Forest Hill, Honor Oak, Perry Vale, Horniman are Permitted Development, which we confirm with a Lawful Development Certificate before you build.
The whole spectrum — rear extensions, side returns, wraparounds, double-storey, basement digs. Planning-led design with detailed technical phase, ideal for victorian and edwardian terraces and villas across typical of Forest Hill.
Across Forest Hill, Honor Oak, Perry Vale, Horniman in SE23, the dominant property is victorian and edwardian terraces and villas across forest hill and honor oak, larger detached houses on the hills, and 1930s semis towards perry vale. That stock shapes what house extension drawings looks like here: the right approach for a period terrace differs from a mansion-block flat or a new-build, and Lewisham Council judges each on design quality and neighbour impact. We survey the specific Forest Hill property, confirm the planning route — Permitted Development, a Lawful Development Certificate, or full planning — and draw a council-ready set tailored to the SE23 streetscape.
Housing stock in SE23: Victorian and Edwardian terraces and villas across Forest Hill and Honor Oak, larger detached houses on the hills, and 1930s semis towards Perry Vale.
Within the district: Forest Hill, Honor Oak, Perry Vale, Horniman.
Conservation areas: Forest Hill, Honor Oak, Horniman / London Road. Inside these, most external work needs full planning and a Heritage Statement.
Getting around SE23: Forest Hill and Honor Oak Park (Overground and Southern).
Property values: approx £600k–£1.2m for houses, £375k–£600k for flats (Land Registry, 2024) — a useful gauge of the build value an extension or loft adds in SE23.
Borough character: Generally permissive planning compared to central boroughs; loft conversions and side-return extensions routinely approved under PD.
Measured existing survey, photographic record, Article 4 and conservation check specific to Forest Hill before we quote.
2–3 design options at concept stage — alternative layouts, glazing, roof forms.
Site location plan, existing and proposed plans, elevations, sections, D&AS where required.
Part L thermal, Part B fire, Part M accessibility, structural strategy.
Steel beam, foundation, lintel design. Chartered engineer sign-off.
Party Wall notices where needed; Thames Water Build Over Agreement where within 3m of a public sewer.
Single planning or building-regs submission.
Planning + building regs + structural.
Listed, conservation or complex sites.
Most do. The Victorian and Edwardian terraces and semis across Forest Hill and Honor Oak in SE23 generally keep permitted-development rights for single-storey rear extensions and rear dormer lofts, decided by Lewisham Council, provided they're outside the local conservation areas. The hilly plots sometimes raise overlooking and retaining-wall issues we design around. We check your address against Lewisham's conservation layer first.
Parts are. Lewisham designates conservation areas in Forest Hill and Honor Oak, typically covering the grander villa streets near the Horniman Museum and London Road, while most of the terraced and 1930s semi stock sits outside. Inside a conservation area, loft dormers and external alterations need full planning and a Heritage Statement. We map your specific Forest Hill or Honor Oak street before relying on PD.
Forest Hill and Honor Oak SE23 have a lot of larger Victorian and Edwardian semi-detached and detached villas, which often take a hip-to-gable plus rear dormer for a full extra floor, or a substantial rear dormer on terraces. The sloping sites mean we pay attention to ridge heights and neighbour overlooking. We design to the roof type and confirm whether full planning or a Lawful Development Certificate applies.
Our fixed fee for house extension drawings in Forest Hill starts at £1,225 — no hourly billing. With Forest Hill property at approx £600k–£1.2m for houses, £375k–£600k for flats (Land Registry, 2024), the professional drawing fee is a small fraction of the value the work adds to SE23's victorian and edwardian terraces and villas across. Lewisham Council charges its own statutory application fee on top (currently £258 for a householder planning application, £578 for a full application). We quote the drawings as one fixed price and the free site survey covers every SE23 address.
For a SE23 project across Forest Hill, Honor Oak, Perry Vale, Horniman, 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 Lewisham Council (8 weeks for a householder application). We carry the Forest Hill application through every officer query to the decision.
Forest Hill (SE23) sits primarily in Lewisham, so applications are decided by Lewisham Council. Article 4 in force in the borough: No. Conservation areas within SE23 include Forest Hill, Honor Oak, Horniman / London Road, 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 house extension drawings in Forest Hill — 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 Lewisham Council Building Control or an approved inspector. On SE23'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. With Forest Hill (SE23) property at approx £600k–£1.2m for houses, £375k–£600k for flats (Land Registry, 2024), a well-designed extension or loft typically returns more than it costs in added floor area and sale value, while our fixed drawing fee from £1,225 keeps the professional cost predictable. 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 SE23 homes.
From £840.
From £840.
From £1,225.
From £1,575.
From £995.
From £1,950.
From £350.
From £540.
From £450.
From £1,225.
Pick a slot that suits you. No obligation and no sales pressure — just straight answers on your planning route, fixed fee and timescale.
Every SE23 postcode district we draw in, the stock that dominates it and the authority that validates a house extension there. SE23 fees below are the statutory England rates for 2026, not house extension estimates.
| Postcode | Area | Dominant stock | What it means for a house extension |
|---|---|---|---|
| SE23 | Forest Hill / Honor Oak | Victorian villas, Edwardian terraces | SE23 covers Forest Hill / Honor Oak only; Lewisham Council handles the house extension, and Forest Hill / Honor Oak case officers apply the SE23 conservation-area map. |
| SE23 | Forest Hill | Victorian villas, Edwardian terraces | Forest Hill sits inside SE23; house extension proposals here are determined by Lewisham Council. |
| SE23 | Honor Oak | Victorian villas, Edwardian terraces | Honor Oak sits inside SE23; house extension proposals here are determined by Lewisham Council. |
| SE4 | Brockley | Victorian and Edwardian terraces | Adjoining district to SE23, also inside Lewisham for house extension purposes. |
| SE6 | Catford / Bellingham | 1930s semi-detached, post-war flats | Adjoining district to SE23, also inside Lewisham for house extension purposes. |
| SE8 | Deptford | Georgian terraces, post-war estates, new-build | Adjoining district to SE23, also inside Lewisham for house extension purposes. |
| SE12 | Lee / Grove Park | mixed stock | Adjoining district to SE23, also inside Lewisham for house extension purposes. |
Roof pitch, wall build-up and plot depth change every few SE23 streets, and each one changes what a house extension can achieve at that address.
Conservation areas covering SE23 (Forest Hill / Honor Oak): Lewisham Council runs 30, and Forest Hill, Hither Green, Lee Green are the ones SE23 (Forest Hill / Honor Oak) owners meet most. A house extension inside a SE23 (Forest Hill / Honor Oak) conservation area loses permitted development, so the SE23 (Forest Hill / Honor Oak) submission is a householder application at £258 decided in 8 weeks — not a £120 prior approval decided in 6 weeks. In Blackheath a house extension is judged on the street elevation first.
Article 4 and your SE23 (Forest Hill / Honor Oak) house extension: Lewisham Council has made no borough-wide direction, so permitted development for a house extension in SE23 (Forest Hill / Honor Oak) generally survives outside SE23 (Forest Hill / Honor Oak) conservation areas and listed curtilages. A Lawful Development Certificate at £129 is how a SE23 owner records that a house extension was lawful.
The building fabric around SE23 (Forest Hill / Honor Oak): 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 house extension in SE23 (Forest Hill / Honor Oak) is scoped against that stock first. Our SE23 (Forest Hill / Honor Oak) fixed fee starts at £1,225; the £1,750 Complete package runs the SE23 (Forest Hill / Honor Oak) scheme through Lewisham Council planning and building control in one go.
Sources for this SE23 house 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.
Free fixed quote in 60 seconds. From £1,225. MCIAT chartered.
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