House Extensions & Loft Conversions in Barnet
Award-winning design & build from your local team in Finchley N3. Extensions, loft conversions, renovations & architecture across High Barnet, East Barnet, Friern Barnet, Whetstone & Totteridge.
LABC Awards
Winners 2024
200+ Reviews
4.7 / 5 Rating
NFB Members
LABC Partners
Award-Winning Design & Build in Barnet
The Only Design & Build Company You Need in Barnet If you’re planning a house extension, loft conversion, or renovation in Barnet, you already know the market is crowded. London-wide firms will cover your area but don’t know your street. Loft conversion specialists can’t build your extension.
Extension companies outsource the architecture. You end up either compromising on local knowledge or coordinating multiple companies and hoping they all deliver. LCCL Construction solves both problems.
We’re a complete design and build company based in Finchley N3 — 10 minutes from Barnet. Our in-house team includes architects, structural engineers, project managers, and experienced builders. When you work with us, you get one team that knows Barnet inside out, one point of contact, and one company accountable for every aspect of your project from first sketch to final finish.
Unlike London-wide firms that spread themselves across 30+ boroughs, LCCL is concentrated in Barnet, North London, and Hertfordshire. Our team is on your doorstep. We’re working on properties across High Barnet, East Barnet, Friern Barnet, Whetstone, Totteridge, New Barnet, and Oakleigh Park every single week.
We know Barnet Council’s planning officers. We know which conservation areas have Article 4 Directions. We know the estate management trust rules in Hampstead Garden Suburb and Totteridge.
We know what a 1930s Whetstone semi looks like from the inside, because we’ve extended and converted dozens of them.
Why Barnet Homeowners Choose LCCL
What Makes LCCL Different From Every Other Builder in Barnet One company, every service — House extensions, loft conversions, renovations, architecture, new builds — all delivered by one in-house team. No subcontractors you’ve never met turning up on site. No coordinating between an architect, a builder, and a structural engineer. One team handles everything.
LABC Award Winners 2024 — The LABC Building Excellence Award recognises the highest standards in construction and building regulation compliance in the UK.
200+ reviews, 4.7 out of 5 — Not 20 reviews. Not 50. Over 200 verified reviews from real homeowners across Barnet, North London, and Hertfordshire. That’s a track record you can trust.
20+ years of experience — We’ve been building in Barnet for over two decades. We’ve seen every type of property, every planning challenge, and every structural surprise. There’s nothing we haven’t handled.
10-year LABC warranty — Every project comes with an optional 10-year warranty underwritten by LABC — the UK’s largest network of building control professionals. That’s not a company guarantee that disappears if we close. It’s an independent warranty backed by a national body.
NFB members and LABC Registered Partners — We’re members of the National Federation of Builders and registered partners of the Local Authority Building Control scheme. These aren’t paid directory listings — they’re earned through consistently high standards.
Our Services
Design and build under one roof, Architecture, planning, construction, and finishing — managed by one team, from start to finish.
- HOUSE EXTENSIONS
House Extensions in Barnet
A house extension is the smartest investment a Barnet homeowner can make. In a borough where the average semi-detached house price exceeds £700,000, the stamp duty alone on buying a bigger property can cost more than a well-designed extension. And you stay in the area you love, in the home you know, with space designed exactly around how your family lives.
LCCL Construction specialises in house extensions across Barnet. We deliver every type — single-storey rear extensions, side return extensions, wraparound extensions, double-storey side and rear extensions, and basement conversions. Every extension includes our full design and build service: in-house architecture, structural engineering, planning submissions, construction, and finishing. One team, one quote, one company accountable for the result.
Types of Extension We Deliver in Barnet
Rear Extensions The most popular project in Barnet. Under the larger home extension scheme, semi-detached properties can extend up to 6 metres from the rear wall (8 metres for detached) subject to a prior approval notification to Barnet Council. This gives you enough space for a substantial kitchen-diner or open-plan living area. The prior approval process takes 42 days, and we handle every step. For properties not using prior approval, a standard 3-metre rear extension usually falls under permitted development with no application needed.
Side Return & Wraparound Extensions If your Barnet home has a narrow side alley running alongside the kitchen to the garden, you’re sitting on wasted space. A side return extension fills this gap, and when combined with a rear extension in a wraparound layout, creates a dramatically larger ground floor. This is transformative for Victorian and Edwardian terraced properties in East Barnet, New Barnet, and Friern Barnet — where side returns are common but the kitchen can feel impossibly cramped.
Double-Storey Extensions Maximum additional space — rooms on both ground and first floor. In Barnet, double-storey extensions require full planning permission and must comply with the 45-degree rule to protect neighbours’ light and privacy. Our architects design two-storey proposals that meet Barnet Council’s requirements while maximising your usable space.
Basement Conversions & Extension Costs
Basement Conversions For larger detached properties in Totteridge, Arkley, and parts of High Barnet, basement conversions offer substantial additional space without altering external appearance — particularly valuable in conservation areas. Complex but highly rewarding, with LCCL managing the entire process including underpinning, waterproofing, and building control compliance.
How Much Does a House Extension Cost in Barnet? Extension costs depend on size, type, and specification. Here are typical costs for Barnet including our full design and build service: All prices are detailed quotes including in-house architecture, structural engineering, all construction, project management, building control, and optional 10-year LABC warranty. No extras, no surprises.
- LOFT CONVERSIONS
Loft Conversions in Barnet
A loft conversion is the single best investment most Barnet homeowners can make. You already own the space — it’s sitting above your head right now, empty. A well-designed loft conversion adds a full bedroom and en-suite bathroom, increases your property value by 15 to 25 percent, and gives your family the space it needs without the cost, stress, and upheaval of moving house.
Barnet’s housing stock is perfectly suited to loft conversions. The borough is dominated by Victorian terraces, Edwardian semis, 1930s suburban houses, and Arts and Crafts properties — all with steeply pitched roofs and generous ridge heights that create excellent conversion potential. We’ve converted hundreds of lofts across High Barnet, East Barnet, Friern Barnet, Whetstone, New Barnet, and Totteridge, and we know exactly what works for each property type.
Types of Loft Conversion We Deliver
Rear Dormer — The most popular conversion in Barnet. A flat-roofed extension from the rear roof slope creates a spacious room with full standing headroom. Ideal for a master bedroom with en-suite. Typically falls under permitted development — no planning application needed.
Hip-to-Gable — Extends the sloping hip at the side of the roof into a vertical gable wall, creating significantly more internal space. Particularly popular in Barnet because of the high number of semi-detached and detached properties with hipped roofs. Combined with a rear dormer, adds 30 to 40 square metres.
Mansard — Raises the party wall and constructs a new roof with a near-vertical front slope. Creates the maximum possible space but requires full planning permission from Barnet Council. Most common in terraced properties in East Barnet and New Barnet.
L-Shaped Dormer — Combines a rear dormer with a side dormer, creating an L-shaped extension that maximises floor area. Perfect for larger properties where you want two rooms plus a bathroom in the loft.
How Much Does a Loft Conversion Cost in Barnet? Loft conversion costs in Barnet depend on the type of conversion, the size of your property, and the specification you choose. As a guide: All prices include: in-house architectural design, structural engineering, building control, project management, all construction, and optional 10-year LABC warranty. No hidden extras.
Planning Permission for Loft Conversions in Barnet
Most loft conversions in Barnet qualify under permitted development rights, meaning no formal planning application is required. You will need a Lawful Development Certificate from Barnet Council to confirm compliance — our architects prepare all drawings and submit this on your behalf. However, if your property is within one of Barnet’s 16 conservation areas, the rules change significantly. 10 of these conservation areas have Article 4 Directions that remove permitted development rights for roof alterations.
This means even a standard rear dormer may need full planning permission. The key conservation areas affecting loft conversions in Barnet include: Monken Hadley — Article 4 Direction in force, Totteridge — Article 4 Direction in force plus Totteridge Manor Association trust controls, Mill Hill — Article 4 Direction in force, Wood Street (High Barnet) — Article 4 Direction in force, Hampstead Garden Suburb — Article 4 Direction in force plus HGS Trust additional controls, Moss Hall Crescent — Article 4 Direction in force, Hendon (The Burroughs) — Article 4 Direction in force.
Our architects have specific experience navigating planning applications in all of these areas. We know what Barnet Council will approve, we know the conservation officer’s expectations, and we design proposals that satisfy both planning policy and trust requirements first time.
- RENOVATIONS
Home Renovations & New Builds in Barnet
Not every project is a loft conversion or extension. Sometimes a property needs a complete rethink — structural walls moved, layouts reconfigured, kitchens and bathrooms rebuilt, electrics and plumbing modernised, insulation upgraded to current standards. That’s a full renovation, and it’s what transforms a tired house into a home you’re proud to live in.
We Specialise in Barnet’s Property Types Victorian terraces (East Barnet, New Barnet) — Opening up cramped ground floors, converting cellars, upgrading solid-wall insulation, restoring original features while adding modern comfort. Edwardian & 1930s semis (High Barnet, Whetstone) — Reconfiguring layouts for modern family life, adding en-suites, replacing dated kitchens and bathrooms, improving energy efficiency.
Arts & Crafts homes (Hampstead Garden Suburb) — Sensitive restoration using traditional materials and methods. Working within trust requirements while discreetly modernising interiors. Post-war properties (across the borough) — Full structural modernisation, insulation upgrades, new heating systems, contemporary finishes that bring the property into the 21st century.
New builds & knock-down-rebuilds — Complete project management from demolition through to handover. In-house architecture, planning, construction, and finishing.
- ARCHITECTURE
Architectural Services in Barnet
Every LCCL project starts with design. Our in-house architects create detailed drawings for loft conversions, extensions, renovations, and new builds across Barnet. The critical advantage of having architects within the same company as the build team: your design is always buildable, costed accurately, and optimised for efficient construction.
No beautiful drawings that blow the budget when priced. No redesigns halfway through. No surprises.
Our Architectural Service Covers Initial site survey and feasibility assessment Concept designs and 3D visualisations Full planning drawings for submission to Barnet Council Building regulation drawings and structural engineering Party wall documentation (Party Wall etc. Act 1996) Heritage statements for Barnet’s conservation areas Lawful Development Certificate applications Pre-application advice consultations with Barnet Council planning For properties in conservation areas with Article 4 Directions or subject to estate trust controls, our architects have specific experience designing proposals that satisfy both standard planning requirements and the additional restrictions.
We’ve successfully obtained approvals in Monken Hadley, Totteridge, Mill Hill, Hampstead Garden Suburb, and other restricted areas across Barnet.
- LOCA PLANNING EXPERTISE
Planning & Local Knowledge — Barnet
Local Planning Authority
The London Borough of Barnet is the local planning authority for all areas. Applications are submitted through the Planning Portal and assessed against the Barnet Local Plan (updated Spring 2025) and the London Plan. Pre-application advice is available from Barnet Council and can significantly improve approval chances for complex projects.
Conservation Areas
Barnet has 16 designated conservation areas. 10 have Article 4 Directions restricting permitted development rights.
Article 4 Directions
If your property falls within a conservation area, even minor external alterations — including loft dormers, replacement windows, and boundary walls — may require formal planning permission. Proposals are assessed against each conservation area’s Character Appraisal and Management Strategy, and applications often require a Heritage Statement.
Estate Trust Controls
Properties in Hampstead Garden Suburb and parts of Totteridge are subject to additional estate management trust approval beyond standard planning. The Hampstead Garden Suburb Trust requires approval for extensions, window replacements, and even minor external changes. These additional approvals run alongside (not instead of) the normal planning process.
Typical Planning Timescales
Lawful Development Certificate: approximately 8 weeks from submission. Householder planning application: 8-week target decision. Prior approval (larger home extension): 42-day notification period. Full planning application: 8–13 weeks depending on complexity. Building control: inspections throughout construction, final sign-off at completion.
How It Works — Your Project in 6 Steps 1. Free Consultation — Call us on 020 8037 7332 or book online. We’ll visit your Barnet property, discuss your ideas, assess feasibility, and give you honest advice. No sales pressure. No obligation. 2. Design & Quote — Our architects create concept designs, 3D visualisations, and a detailed specification. You get a comprehensive quote with a full breakdown — not an estimate that grows. You know exactly what you’re paying before you commit. 3. Planning & Approvals — We submit all necessary applications to Barnet Council, handle building regulation drawings, structural engineering, and party wall notices. You don’t chase paperwork — we do. 4. Construction — Our experienced build team starts on site. Your dedicated project manager keeps you informed with regular updates. We turn up when we say we will, and we keep the site clean and safe.
Building Control Sign-Off
LABC inspectors attend at each key stage. At completion, you receive your building control completion certificate and optional 10-year LABC warranty. 6. Handover — We walk through every detail with you. Any snagging is addressed immediately. You move into your transformed home. We don’t disappear — we’re based 10 minutes away and we stand behind our work.
Frequently Asked Questions
Do I need planning permission for a loft conversion in Barnet?
Most loft conversions in Barnet fall under permitted development and don’t need a planning application. The exceptions: properties in conservation areas with Article 4 Directions (Monken Hadley, Totteridge, Mill Hill, Hampstead Garden Suburb, and others), mansard conversions, and front-facing dormers. We assess your property specifically and handle all necessary approvals.
How much does a loft conversion cost in Barnet?
Costs range from £45,000 for a standard rear dormer to £90,000+ for an L-shaped or mansard conversion. Our prices include in-house architectural design, structural engineering, all construction, and optional LABC warranty. We provide detailed quotes — transparent pricing with no hidden extras — final costs confirmed once designs and structural requirements are agreed.
How long does a house extension take in Barnet?
Single-storey rear extensions: 10–14 weeks on site. Double-storey: 14–20 weeks. Add 8–12 weeks pre-construction for design, planning approval, and building regulation drawings. We provide a detailed timeline specific to your project at quotation stage.
Do you handle planning applications with Barnet Council?
Yes — completely. Our in-house architects prepare all drawings and documentation and submit directly to Barnet Council. This includes planning applications, Lawful Development Certificates, prior approval notifications, and heritage statements for conservation areas. We manage the entire process and liaise with planning officers throughout.
What’s included in your price?
Everything. Architectural design, structural engineering, planning submissions, building control, project management, all construction labour and materials, and optional 10-year LABC warranty. We don’t charge extras for things other companies add on later. Your comprehensive quote covers the complete project.
Areas We Cover
Based in Finchley N3, serving London and Hertfordshire.
North London and Hertfordshire
Barnet | Finchley | Hendon | Muswell Hill | Edgware | Enfield | Borehamwood | Potters Bar | Watford | St Albans
Across London
Hampstead | St Johns Wood | Islington | Kensington & Chelsea | Fulham | Clapham | Richmond | Putney & Wandsworth | Crouch End | Stoke Newington | Highgate | Ealing | Notting Hill | Camden | Queens Park