House Extensions · SW20 Raynes Park
Merton applies suburban householder control across SW20, with a conservation pocket around Cottenham Park; a settled family market.
The borough-level guide to house extensions in Merton sets out how the same work is handled across the rest of the authority.
House extensions in Raynes Park are dominated by single-storey rear and side-return additions on SW20's inter-war and edwardian semis and detached houses, with double-storey and wrap-around schemes where the plot allows. Merton Council weighs depth, height and neighbour daylight; many extensions across Raynes Park, West Wimbledon, Cottenham Park, Motspur Park fringe 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 inter-war and edwardian semis and detached houses typical of Raynes Park.
Across Raynes Park, West Wimbledon, Cottenham Park, Motspur Park fringe in SW20, the dominant property is inter-war and edwardian semis and detached houses around raynes park and west wimbledon, with larger houses toward wimbledon common. 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 Merton Council judges each on design quality and neighbour impact. We survey the specific Raynes Park property, confirm the planning route — Permitted Development, a Lawful Development Certificate, or full planning — and draw a council-ready set tailored to the SW20 streetscape.
Housing stock in SW20: Inter-war and Edwardian semis and detached houses around Raynes Park and West Wimbledon, with larger houses toward Wimbledon Common.
Within the district: Raynes Park, West Wimbledon, Cottenham Park, Motspur Park fringe.
Streets we know in SW20: the Cottenham Park roads, Coombe Lane, Grand Drive and the West Barnes streets. Each road has its own building line, boundary treatment and precedent that Merton Council weighs when assessing a house extension drawings scheme.
Conservation areas: Cottenham Park, Wimbledon West Side fringe. Inside these, most external work needs full planning and a Heritage Statement.
Getting around SW20: Raynes Park and Motspur Park rail to Waterloo, plus Wimbledon nearby for the District line and tram.
Property values: around £400,000 for a flat and £800,000-£1.3m for a house — a useful gauge of the build value an extension or loft adds in SW20.
Borough character: Wimbledon is heavily conservation-controlled; outer Merton (Morden, Mitcham) is permissive.
Measured existing survey, photographic record, Article 4 and conservation check specific to Raynes Park 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.
Yes. The inter-war and Edwardian semis and detached houses around Cottenham Park and Grand Drive suit rear, side and double-storey extensions plus loft conversions, much of it within Permitted Development outside the conservation area, confirmed with a Lawful Development Certificate. We confirm the route and draw to Merton's checklist.
Often, on the wider semi and detached plots around Coombe Lane — a two-storey side or rear extension, subject to Merton's design and neighbour-amenity policy on side-space and daylight. We design within those limits and produce the planning and Building Regulations drawings together.
Usually yes on the semis — a hip-to-gable plus rear dormer within the volume allowance, confirmed by a Lawful Development Certificate, provided you're not in the Cottenham Park conservation area. We check the constraints for your road and draw it for Building Control.
With SW20 houses around £800,000-£1.3m and direct rail links to Waterloo, a rear extension or loft adds family space worth comfortably above the build and drawing cost. SW20 is a sought-after family suburb.
With Raynes Park property at around £400,000 for a flat and £800,000-£1.3m for a house, the professional drawing fee is a small fraction of the value the work adds to SW20's inter-war and edwardian semis and detached houses. Merton Council charges its own statutory application fee on top (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 SW20 address.
For a SW20 project across Raynes Park, West Wimbledon, Cottenham Park, Motspur Park fringe, 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 Merton Council (8 weeks for a householder application). We carry the Raynes Park application through every officer query to the decision.
Raynes Park (SW20) sits primarily in Merton, so applications are decided by Merton Council. Conservation areas within SW20 include Cottenham Park, Wimbledon West Side fringe, 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 Raynes Park — 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 Merton Council Building Control or an approved inspector. On SW20'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 Raynes Park (SW20) property at around £400, 000 for a flat and £800, 000-£1.3m for a house, a well-designed extension or loft typically returns more than it costs in added floor area and sale value. 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 SW20 homes.
If your site sits close to the edge of the borough, it is worth checking the authority next door. Browse everything we do in SW16, SW17 and SW19.
Pick a slot that suits you. No obligation and no sales pressure, just straight answers on your planning route.
Every SW20 postcode district we draw in, the stock that dominates it and the authority that validates a house extension there. SW20 fees below are the statutory England rates for 2026, not house extension estimates.
| Postcode | Area | Dominant stock | What it means for a house extension |
|---|---|---|---|
| SW20 | Raynes Park | Victorian villas, Edwardian terraces | Raynes Park sits wholly inside SW20, so Merton Council validates every house extension submitted from an SW20 address. |
| SW20 | Wimbledon | Victorian villas, Edwardian terraces | Wimbledon sits inside SW20; house extension proposals here are determined by Merton Council. |
| SW19 | Wimbledon / Colliers Wood | Victorian villas, Edwardian terraces | Adjoining district to SW20, also inside Merton for house extension purposes. |
| SM4 | Morden | 1930s semi-detached, post-war flats | Adjoining district to SW20, also inside Merton for house extension purposes. |
| CR4 | Mitcham | 1930s semi-detached, post-war estates | Adjoining district to SW20, also inside Merton for house extension purposes. |
Roof pitch, wall build-up and plot depth change every few SW20 streets, and each one changes what a house extension can achieve at that address.
SW20 (Raynes Park) conservation designations: there are 28 across Merton Council, Wimbledon Common, Wimbledon Village, John Innes among them. Designation costs a SW20 (Raynes Park) owner the permitted-development route: a house extension then needs a £548 householder application over 8 weeks, in place of the £249 prior approval route that takes 6 weeks. Mitcham Cricket Green is the SW20 (Raynes Park) designation that most often changes a house extension design.
No blanket Article 4 over SW20 (Raynes Park): Merton Council has not withdrawn permitted development across SW20 (Raynes Park), so a house extension outside a SW20 (Raynes Park) conservation area usually keeps it. The £274 Lawful Development Certificate is still the document a SW20 owner wants on file.
The building fabric around SW20 (Raynes Park): Victorian villas in Wimbledon; Edwardian terraces in Tooting and Colliers Wood; 1930s semi-detached in Morden and Raynes Park; post-war flats in Mitcham. Wimbledon is heavily conservation-controlled; outer Merton (Morden, Mitcham) is permissive. A house extension in SW20 (Raynes Park) 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 Merton Council.
Sources for this SW20 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.
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