Extension Architectural Designer · Pinner & London
Extension Architectural Designer in Pinner
Pinner's local architectural design studio for rear extensions, loft conversions, planning permission, Principal Designer support, house extension design and 3D visualisation — designed here, approved here, built here.
Based at 159 Christchurch Ave, Harrow
Pinner homes, understood
Pinner isn’t one kind of street. It’s three kinds of homes layered on top of each other — and each comes with different possibilities and different rules.
The village core
Around the High Street and Church Lane, Pinner is still a medieval village: timber-framed buildings from the 15th century, the Grade II* church of St John the Baptist, and streets Harrow Council calls “a remarkable survival of a medieval village”. Much of it is the Pinner High Street Conservation Area, with listed buildings throughout.
What it means: extensions here are possible, but they almost always need a full planning application. Materials and detailing matter, and the council’s conservation officers are closely involved from the start.
The Metroland semis and detached houses
Between the wars, Pinner grew fast around the Metropolitan line: the mock-Tudor and Edwardian semis and detached houses most Pinner homeowners live in today, on wide, leafy plots.
What it means: this is Pinner’s classic extension and loft stock. Generous rear gardens suit single-storey and double-storey rear extensions, and the hipped roofs on 1930s semis are exactly what hip-to-gable loft conversions are made for. Many projects here fall under permitted development — but check your street’s rules first (see the routes below).
The protected garden suburbs
Pinnerwood Park, West Towers and Pinner Hill were designed as garden suburbs — and are now protected as conservation areas. West Towers is the only complete Metroland estate designated in the borough; Pinner Hill’s detached houses sit in large, green plots with a semi-rural feel.
What it means: beautiful streets, stricter rules. Article 4 directions remove many permitted development rights here — in parts of Pinnerwood Park and West Towers, even dormers, roof alterations and replacement windows need planning permission. Check before you design.
We check which Pinner your home sits in during the free consultation — before any design work starts. (See also: Planning permission in Pinner)
Which planning route applies to your home?
Every Pinner project takes one of four routes. Which one depends on your house, your street, and what you want to build.
Permitted development
Many single-storey rear extensions and loft conversions on Pinner’s Metroland houses need no application at all, provided they meet the national rules on size, height and materials. If you want that confirmed in writing, we can obtain a Certificate of Lawful Development for you. The national rules are explained in the government’s own guidance: When is permission required?
Prior approval
A larger single-storey rear extension — up to 6 metres for a terraced or semi-detached house, up to 8 metres for a detached house — does not need a full application, but it does need prior approval from Harrow Council, including a neighbour consultation.
Full planning application
Double-storey extensions, most work in conservation areas, and anything outside the permitted development limits goes to Harrow Council as a full application. The statutory period is 8 weeks; most applications are decided within 6–10 weeks, and preparing drawings and documents takes 3–5 weeks before submission. In conservation areas, the council also consults its Conservation Officer and the Conservation Area Advisory Committee.
Check first in Pinner
Conservation area + Article 4
Pinner has 13 conservation areas — and five of them have Article 4 directions removing permitted development rights: Pinner High Street, East End Farm, West Towers, Pinnerwood Park and Pinner Hill. In the Pinnerwood Park core and in West Towers that includes dormers and roof alterations; across those areas it also covers front walls, fences and gates. If your street is on this list, assume permission is needed until we have checked your exact address. The council’s own guidance for all 13 areas is the Pinner Conservation Areas SPD.
New since June 2026: converting a house into a small HMO now needs planning permission anywhere in the borough, including Pinner, under a borough-wide Article 4 direction.
What we handle for you: measured survey, concept design, planning drawings, the full application pack, and all correspondence with Harrow Council through to decision. If you’ve had a refusal, we assess appeal prospects honestly.
Our services in Pinner
Rear extensions in Pinner
Wide plots and long rear gardens are Pinner’s gift: single-storey, double-storey and wraparound extensions that open the back of a Metroland semi into one kitchen-living space.
Explore service →Loft conversions in Pinner
Hip-to-gable and dormer conversions made for 1930s hipped roofs — with one warning: in West Towers and the Pinnerwood Park core, dormers need planning permission first.
Explore service →Planning permission in Pinner
Full applications, permitted development advice, lawful development certificates and appeals, handled end to end with Harrow Council — including conservation-area applications across Pinner’s 13 conservation areas.
Explore service →Principal Designer (CDM) support
Health and safety compliance for your build, from pre-construction information to site oversight, under the CDM 2015 regulations.
Explore service →House extension design
The full design service for bigger remodels: layouts rethought, not just rooms added.
Explore service →3D Visualisation
See your extension before you commit: realistic visuals of your design, inside and out.
Explore service →Every project starts with a free consultation. After we’ve seen your property, you get a fixed-fee proposal in writing — no hourly billing, no surprise invoices, and no published price lists: every home is different, so every fee is quoted on the actual job.
Project snapshots
A few examples of what that looks like in practice:
Rear extension
Open-plan kitchen space with an exposed brick wall — the classic rear extension layout.
Loft conversion
A calm loft bedroom with a stone feature wall under the roof.
Open-plan kitchen
Kitchen and living space combined in one open-plan room.
Extendopedia in numbers
Extendopedia is based in Harrow and works across the borough, Pinner included. The numbers below are the studio’s record to date.
| Metric | Result |
|---|---|
| Projects delivered | 180+ |
| Years in Harrow | 9 |
| First-time approval rate | 95% |
| Average client rating | 4.9/5 |
[TO CONFIRM: owner to confirm the 95% approval rate applies to Harrow Council applications specifically].
Based here: 159 Christchurch Ave, Harrow HA3 8NS — our actual studio, a short drive from Pinner.
Hours: Mon–Fri, 9am–5pm · Phone: +44 7353 860797 · Email: info@extendopedia.co.uk · More about Extendopedia
Areas we serve around Pinner
We work across Pinner and the neighbourhoods around it:
- Pinner Village
- Pinner Green
- Hatch End
- Pinner Hill
- West End
- North Harrow
- Rayners Lane
- Eastcote
Based in Harrow, working across the borough — our Harrow guide is live. A Stanmore guide is next; Wembley and Ealing follow.
The spaces we design
Examples of the kinds of spaces we design — open-plan kitchen-living rooms, calm loft bedrooms, homes that open onto their gardens.
Brick houses, quiet streets
Traditional brick homes on a quiet residential street.
Detached house and garden
A detached brick house with its garden and driveway.
Dining space
A dining area within an open-plan kitchen extension.
Want to see more? Browse our portfolio.
Working with us
One team from first sketch to final sign-off. No handovers, no surprises. Here is the exact process we follow for every project.
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Free consultation
We visit your home, listen to what you need, and tell you honestly what’s achievable: planning route, realistic timeline, whether it’s worth proceeding.
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Fixed-fee proposal
After the site visit, you get a written fixed fee for the design stage. Nothing is billable until you approve it.
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Measured survey
Every wall, door, window and level drawn to scale.
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Concept design
Two or three layout options, tested against how you live.
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Planning
Full application pack prepared and submitted to Harrow Council; we handle all correspondence. (See also: Planning permission in Pinner)
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Building regulations
The technical compliance set your builder and inspector need.
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Site support
Queries answered through the build, details clarified, health and safety coordinated.
Pinner FAQs
Can I extend my Pinner home under permitted development?
Often yes — on Pinner’s Metroland streets, many rear extensions and loft conversions meet the national permitted development rules. But Pinner also has 13 conservation areas, and five of them have Article 4 directions that remove those rights street by street. We check your exact address during the free consultation and tell you which route applies before you commit to anything. (See also: Planning permission in Pinner)
I live in Pinnerwood Park or West Towers — can I still convert my loft?
Usually yes, but not under permitted development: in those estates, dormers and roof alterations need planning permission first, because Article 4 directions protect the original roofscape. Designs that respect the estate’s character stand the best chance — Harrow Council’s own design guides for these areas cover loft conversions specifically, and we design to them.
Do I need permission to change my front wall, fence or gate — or to pave my front garden?
In the Pinner High Street, East End Farm, Pinnerwood Park and Pinner Hill conservation areas, yes: Article 4 directions mean gates, fences and walls need planning permission. In the Pinnerwood Park core, creating hard surfacing for parking in a front or side garden needs permission too. Elsewhere in Pinner, normal permitted development rules usually apply — we confirm for your address.
How long does Harrow Council take to decide?
The statutory period for householder applications is 8 weeks. Straightforward cases are often decided sooner, and most applications are decided within 6–10 weeks; conservation-area cases can take the full period, because the council consults its Conservation Officer and the Conservation Area Advisory Committee. Before submission, allow 3–5 weeks for us to prepare drawings and documents.
We’re in a conservation area — can we still extend?
Usually yes, but you’ll likely need a full planning application rather than permitted development, and the design must respect the area’s character. In its Pinner appraisals, the council’s consistent steer is extensions at the rear, subservient in scale, in materials that match the original house — that’s how we design them.
Do you handle building regulations as well as planning?
Yes. Planning permission asks “may you build it?” Building regulations ask “is it built safely and compliantly?” We prepare both — most clients use us for the full journey.
Do I need a Principal Designer for my project?
For most home extension and loft projects with more than one contractor, yes — the CDM 2015 regulations require one, and it’s usually us: we coordinate health and safety from the first design decisions through the build. (See also: Principal Designer (CDM) support)
How much will my project cost?
Our design fee is fixed and quoted in writing after we’ve seen your property — every home is different, so we don’t publish price lists. Build costs go directly to your contractor; we’ll give you a realistic range once we’ve assessed the job.
Start with a free consultation
Tell us about your project — a rough idea is enough. We’ll visit, assess feasibility honestly, and confirm a fixed fee in writing. No obligation, no sales pitch.
Extendopedia · 159 Christchurch Ave, Harrow HA3 8NS · info@extendopedia.co.uk · Mon–Fri 9am–5pm