Home extensions

Extensions that enhance, not just enlarge

A well-designed extension is never an afterthought. At Gresford Architects, extensions are an opportunity to reimagine how homes across Oxford, the Cotswolds, the Chilterns, London and the wider South East are lived in, experienced and loved. From the terraced houses of Jericho to Cotswold stone cottages and suburban semis in North London, each project is rooted in its context and designed for lasting value.

As a RIBA Chartered Practice, ARB-registered architects, members of the Passivhaus Trust and the Society for the Protection of Ancient Buildings (SPAB), we bring award-winning experience to the challenge of extending homes with care. Our projects — from The Deerings (RIBA East Award, 2018; RIBA House of the Year longlist) to The Great Barn — demonstrate how thoughtful interventions can both respect heritage and transform modern living.

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What is extension design?

Extension design is the art of expanding and upgrading a home in ways that elevate both form and function. For us, it is more than “adding on” — it is about creating interventions that feel as if they were always meant to be there.

We specialise in:

  • Kitchen and living extensions that transform dark ground floors into social, light-filled hubs.
  • Two-storey additions to suburban houses, unlocking flexible layouts and improved circulation.
  • Contemporary glass and timber pavilions, opening heritage cottages to their gardens.
  • Extensions to listed buildings, balancing conservation with bold but sensitive new design.

Our approach to extensions

Understanding your home and ambitions

Every extension begins with listening. We study how you live — frustrations, routines, aspirations — and uncover the untapped potential of your existing home.

Contextual harmony

Extensions must feel seamless. We analyse daylight, solar gain, views, materials and movement. Using daylight analysis and solar modelling, we ensure that new spaces are light, balanced and energy-efficient.

Sustainable, fabric-first upgrades

An extension is also an opportunity to improve the whole home. We integrate airtightness continuity, thermal bridge modelling (Ψ-values), and triple glazing, alongside natural, vapour-open materials to protect older walls.

Moisture and structural integrity

Where new meets old, we design carefully for moisture control (using WUFI hygrothermal modelling) and structural load. Steelwork, foundations and junction detailing are resolved with both safety and elegance in mind.

Planning and permissions

We guide you through the complexities of permitted development rights, full planning permission and Listed Building Consent. Our experience with authorities such as Oxford City Council and Cotswold District Council ensures applications are evidence-based and persuasive.

Collaborative clarity

Extensions are personal journeys. We work with you, specialist craftspeople, and consultants in a transparent, iterative process. Visualisations and models help translate complexity into clarity at every stage.

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Our extension process:
 Briefing → Site + daylight analysis → Concept design → Planning/heritage strategy → Technical detailing → On-site QA → Post-occupancy evaluation (POE).

Learn more about our sustainable approach

Extension projects in action

Modern extension with patterned brickwork, large glass door opening to interior, small side window, brick buildings background, surrounded by plants, architecture by Gresford Architects.
Modern extension with patterned brickwork, large glass door opening to interior, small side window, brick buildings background, surrounded by plants, architecture by Gresford Architects.

Ickburgh Road — a light-filled kitchen/dining extension transformed a dark ground floor into the social heart of the home.

Modern grey extension with large glass sliding doors, interior visible, brick building in background, architecture by Gresford Architects
Modern grey extension with large glass sliding doors, interior visible, brick building in background, architecture by Gresford Architects

Graham Street — a timber-and-glass pavilion added light and openness while respecting the building’s vernacular charm.

A small modern extension with large glass windows and a patio, surrounded by greenery and traditional brickwork, architecture by Gresford Architects.
A small modern extension with large glass windows and a patio, surrounded by greenery and traditional brickwork, architecture by Gresford Architects.

Lavender Grove — a two-storey rear extension reconfigured circulation, upgraded thermal performance, and maximised garden views.

Bright dining area with large sliding glass doors opening to a garden, featuring a wooden table, chairs, and open shelving, architecture by Gresford Architects.
Bright dining area with large sliding glass doors opening to a garden, featuring a wooden table, chairs, and open shelving, architecture by Gresford Architects.

Albyn Road — a two-storey rear extension reconfigured circulation, upgraded thermal performance, and maximised garden views.

Why choose Gresford Architects for your extension?

  • Expertise in sensitive transformations — From Oxford terraces to rural farmhouses and London townhouses, we deliver extensions that enhance rather than overshadow.
  • Sustainability at the core — Extensions are a chance to improve energy use across the whole home. Our fabric-first upgrades deliver measurable reductions in energy bills and improved comfort.
  • Heritage and planning expertise — Our membership of SPAB and our track record with listed buildings position us as experts in heritage-sensitive design.
  • Award-winning credibility  — The Deerings achieved RIBA East Award recognition and was longlisted for RIBA House of the Year. Our projects feature in Dezeen, Grand Designs Magazine, The Spaces, and The Modern House.
  • End-to-end partnership — From feasibility studies to final snagging, we act as your advocate — aligning budgets, performance and design vision throughout.

Transform your home with thoughtful design

If you are considering an extension — whether a subtle addition or a bold reimagining — we can help you explore what is possible.

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Frequently Asked Questions

Do I need planning permission for an extension?

Some smaller projects fall under permitted development rights, but many require planning permission — especially in conservation areas or for listed buildings.

How much does a house extension cost?

Budgets typically range from £100,000 to £500,000+, depending on scope, complexity and finishes. We provide detailed cost plans during feasibility

What types of extensions do you design?

From kitchen/dining spaces to two-storey additions and heritage-sensitive pavilions, we design across all scales.

Can extensions be added to listed buildings?

Yes, with Listed Building Consent. Our work on The Great Barn shows how heritage character can be preserved while improving liveability.

How long does an extension take?

Most projects run 9–18 months from design to completion, depending on permissions and build scale.

Do extensions add value to a property?

Yes. Extensions typically enhance both liveability and resale value, particularly when designed with energy efficiency and long-term adaptability in mind.

How do you ensure old and new blend seamlessly?

Through material integrity, contextual analysis and precision detailing. We believe in the marriage of the poetic and the practical — restoring the character of the old while introducing contemporary interventions that feel timeless.

What is the difference between a contemporary vs traditional extension?

Contemporary designs often use glass, steel and timber to create contrast and light, while traditional extensions blend more closely with existing materials. We advise on both approaches depending on context and client aspirations.

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