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Single
Story
Extensions Leeds

Specialist single storey extension builders in Leeds. The most cost-effective way to add significant ground-floor space to your home — including rear extensions, kitchen extensions, wraparound builds and side returns. Cobin Contractors handles all structural steelwork in-house, including RSJ beams, goalpost frames and Building Control coordination. We serve homeowners across Leeds, Headingley, Chapel Allerton, Roundhay, Adel, Moortown, Horsforth, Alwoodley and surrounding areas.
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8m

Max depth — detached homes with prior approval

6m

Max depth — semi-detached / terraced homes with prior approval

100%

Steel in-house — no subcontracting

Free

Site survey — Leeds homeowners

Permitted development — quick guide

Detached

Up to 4m depth — no planning needed

Standard PD. Up to 8m with Prior Approval (Larger Home Extension scheme). Max height 4m.

Semi / terrace

Up to 3m depth — no planning needed

Standard PD. Up to 6m with Prior Approval. Party Wall Act may apply. Max eaves 3m within 2m of boundary.

Wraparound

L-shaped — rear and side combined

Goalpost steel frame typically required. Maximises ground-floor footprint on terraces and semis. Prior Approval applies above standard PD limits.

Conservation

Additional restrictions apply

Harrogate Stray area and Ilkley — Article 4 Directions may remove PD rights. Full planning often required. We check at survey.

All types

Building Regulations — always required

Every single storey extension needs Building Control approval regardless of Permitted Development status.

Building Control Certified

Structural Steel In-House

Free Surveys — 24hr Response

Leeds Based

Fixed Price Quotes

What is a single storey extension

THE MOST VERSATILE WAY
to Add GROUND-FLOOR SPACE

A single storey extension is a ground-floor structural addition built to the rear, side or flank of your property — extending your home outward at one level, without adding another floor above. It is one of the most practical ways for Leeds homeowners to create more usable living space, including larger kitchen-diners, extended living rooms, utility areas, home offices and garden-facing family spaces.
Unlike a double storey extension — which usually involves more planning, structural complexity and disruption — a single storey extension can often qualify under Permitted Development Rights. This allows many Leeds homeowners to extend without a full planning application, depending on property type, depth, height, boundary position and any local planning restrictions.

Cobin Contractors builds single storey extensions across Leeds on detached, semi-detached and terraced properties — from Victorian terraces in Headingley and Chapel Allerton to larger family homes in Roundhay, Adel, Alwoodley, Moortown and Horsforth. All structural steelwork — including RSJ beams, goalpost frames and padstones — is handled in-house by our own team, under one contract and one Building Control completion certificate.

GET A FREE SITE SURVEY ACROSS LEEDS →

01

MOST COMMONLY BUILT UNDER PERMITTED DEVELOPMENT

Single storey extensions are one of the extension types most likely to qualify under Permitted Development Rights — meaning no full planning application, no planning fee and no standard eight-week determination period in many cases. Detached homes can usually extend up to 4m as standard, while semi-detached and terraced homes can usually extend up to 3m. Larger extensions may be possible through Prior Approval.

02

ADAPTABLE TO ANY GROUND-FLOOR USE

Single storey extensions are not limited to kitchens. Across Leeds, we build extensions for open-plan kitchen-diners, living rooms, dining rooms, utility areas, home offices and family spaces. The new space is designed around how your household actually uses the ground floor — not just how much square footage you want to add.

03

LOWER DISRUPTION THAN A FULL DOUBLE STOREY BUILD

A single storey extension is usually simpler and less disruptive than a double storey extension. There is no first-floor structural connection, less scaffolding and fewer upstairs works. A typical single storey extension in Leeds can often be completed in around 8–12 weeks from breaking ground, depending on size, access, structure and specification.

04

STRUCTURAL STEELWORK IN-HOUSE — NO SUBCONTRACTORS

Almost every open-plan single storey extension requires RSJ steel beam installation when the original rear wall or an internal load-bearing wall is removed. Cobin Contractors handles beam specification, structural calculations, steel supply and installation as part of the extension build — not subcontracted, not treated as a separate contract.

Extension types

FOUR TYPES OF
SINGLE STOREY EXTENSION

A single storey rear extension is the most common extension type for Leeds homeowners. It extends the back of the property into the garden and creates more usable space behind the original house. Rear extensions are commonly used for kitchen expansion, open-plan kitchen-diner creation, living room enlargement and better garden connection. They work well on terraced, semi-detached and detached homes across Leeds.

01

Most common

Single Storey Rear Extension

A single storey rear extension is the most common way to add ground-floor space to a Leeds home. It extends the back of the property into the garden and is often used to create a larger kitchen, open-plan kitchen-diner, extended living room or better connection to outdoor space. Rear extensions work well on terraced, semi-detached and detached homes across Leeds. Where the original rear wall is opened, RSJ steel beam installation is usually required to support the structure above.

Permitted Development

RSJ installation

Flat / pitched roof

Open plan

02

Most transformative

Open-Plan Kitchen-Diner Extension

An open-plan kitchen-diner extension combines a single storey rear extension with internal load-bearing wall removal. This creates a larger, brighter and more connected space across the back of the home. This type of extension usually requires structural steelwork, including an RSJ beam across the original rear wall opening. If an internal supporting wall is removed, a second beam may also be needed.

RSJ installation

Load bearing wall removal

Bi-fold doors

Lantern roof

03

Maximum footprint

Wraparound Extension

A wraparound extension combines a rear extension with a side return extension to create an L-shaped layout. It is one of the best ways to maximise ground-floor space on Leeds terraced and semi-detached homes. Because the rear and side of the property are opened together, wraparound extensions often require goalpost steel frames to create a wide, open-plan layout without unnecessary internal supports.

L-shaped plan

Goalpost steel frame

Side return

Prior Approval

04

Side extension

Side Return Extension

A side return extension uses the narrow side passage, side access area or unused space beside the home. It is especially useful where the existing kitchen or dining area feels narrow, dark or disconnected. Side return extensions are common on Leeds terraced and semi-detached homes. They can be built as standalone extensions or combined with a rear extension to create a full wraparound layout.

Garage conversion option

Structural steel

Planning may apply

Detached properties

NOTE ON PERMITTED DEVELOPMENT  Permitted Development rules can allow many single storey rear extensions in Leeds to be built without a full planning application, but this depends on property type, extension depth, height, boundary position and whether any local restrictions apply. Detached homes can usually extend further than semi-detached and terraced homes. Larger single storey extensions may require Prior Approval, and some Leeds properties may need full planning permission if Permitted Development rights are restricted. Cobin Contractors checks your planning route during the free site survey and confirms the current position before you commit to the build.

Single storey vs double storey

CHOOSING THE RIGHT
EXTENSION TYPE
FOR YOUR PROPERTY

The decision between a single storey and double storey extension depends on what space you need, your Leeds property type, your planning position, rear garden depth, budget and timeline. For many Leeds homeowners, a single storey extension is the better choice when the main goal is to create more ground-floor living space — such as a larger kitchen-diner, extended living room, utility area or open-plan family space. A double storey extension is more suitable when you also need extra bedrooms, bathrooms or first-floor space.

 

FactorSingle Storey ExtensionDouble Storey Extension
Planning — most casesOften Permitted Development — no application neededFull planning application usually required
Depth limitsUp to 8m detached / 6m semi-terrace (Prior Approval)Up to 3m PD if 7m+ from rear boundary
Programme8–12 weeks from breaking ground (typical)16–24 weeks from breaking ground (typical)
DisruptionGround floor only — limited roof and first-floor worksSignificant first-floor works — temporary roof, scaffolding
Space addedGround floor onlyGround floor and first floor simultaneously
Value returnStrong — open-plan kitchen-diners in high demandStrong — additional bedrooms add significant value
Structural complexityRSJ beam(s) for wall openings — manageableMore complex — first-floor connections, temporary works
Conservation areasArticle 4 Directions may apply — full planning possibleFull planning always required in conservation areas
For most Leeds homeowners whose primary need is expanded ground-floor living space — especially open-plan kitchen-diners, extended living areas and better garden access — a single storey extension is usually the fastest, simplest and most planning-accessible route. If your goal is to add bedrooms, bathrooms or increase both floors at the same time, a double storey extension may be the better long-term option. Cobin Contractors checks your property, planning position and structural requirements during the free survey before recommending the right extension route.

Property types

SINGLE STOREY EXTENSIONS FOR
every LEEDS PROPERTY

The structural, planning and design approach for a single storey extension depends on your property type. Cobin Contractors builds single storey extensions across Leeds for detached homes, semi-detached homes, terraced houses and older brick or stone properties.

Detached Houses

Maximum Permitted Development Flexibility

Detached houses across Leeds, Harrogate, Ilkley and Baildon have the greatest Permitted Development flexibility for kitchen extensions — up to 4m standard PD, up to 8m with Prior Approval. No party wall implications in most cases and foundations typically straightforward on established suburban plots.
  • Architectural design and planning drawings — in-house
  • Structural engineer calculations for foundations, steelwork and roof
  • Planning application submission and party wall coordination
  • Foundations, footings and below-DPC masonry
  • Full cavity wall construction and RSJ steelwork
  • First-floor joists, roof structure and tie-in to existing
  • Render, brick-match or stone finish to match existing
  • Interior plasterwork, first and second fix, decoration

Semi-Detached Houses

MOST COMMON IN LEEDS

Semi-detached homes make up a large part of Leeds housing stock and are one of the most common property types for single storey rear extensions, side extensions and open-plan kitchen-diner projects. Standard Permitted Development usually allows up to 3m rear projection, with up to 6m possible through Prior Approval. Party Wall Act requirements may apply where excavation, foundations or structural work sit close to the shared boundary.
  • Architectural design and planning drawings — in-house
  • Structural engineer calculations for foundations, steelwork and roof
  • Planning application submission and party wall coordination
  • Foundations, footings and below-DPC masonry
  • Full cavity wall construction and RSJ steelwork
  • First-floor joists, roof structure and tie-in to existing
  • Render, brick-match or stone finish to match existing
  • Interior plasterwork, first and second fix, decoration

Terraced Houses

Victorian Stock — Leeds Inner Suburbs

Victorian terraced houses across Headingley, Chapel Allerton, Roundhay and inner Leeds are well-suited to rear kitchen extensions. Standard PD is 3m, rising to 6m with Prior Approval. Party Wall Act implications are common on both sides — neighbouring properties on terraces are served notices before any structural work begins.
  • Architectural design and planning drawings — in-house
  • Structural engineer calculations for foundations, steelwork and roof
  • Planning application submission and party wall coordination
  • Foundations, footings and below-DPC masonry
  • Full cavity wall construction and RSJ steelwork
  • First-floor joists, roof structure and tie-in to existing
  • Render, brick-match or stone finish to match existing
  • Interior plasterwork, first and second fix, decoration

Yorkshire Stone Properties

Ilkley, Harrogate & Baildon

Stone properties across Ilkley, Harrogate and Baildon require specific expertise for kitchen extensions. We source matching Yorkshire millstone grit and Magnesian limestone from regional suppliers for external elevations. Planning authorities in Harrogate conservation areas and Ilkley require material matching — we advise and liaise with local planning officers where needed.
  • Architectural design and planning drawings — in-house
  • Structural engineer calculations for foundations, steelwork and roof
  • Planning application submission and party wall coordination
  • Foundations, footings and below-DPC masonry
  • Full cavity wall construction and RSJ steelwork
  • First-floor joists, roof structure and tie-in to existing
  • Render, brick-match or stone finish to match existing
  • Interior plasterwork, first and second fix, decoration

Planning guide 2026

Permitted Development,
Prior Approval &
What You Actually Need

Planning rules for single storey extensions in Leeds are based on national Permitted Development legislation, not just local council preference. The same core depth and height limits apply across England, but your property type, boundary position, conservation status and previous alterations can affect whether your extension qualifies. The most important distinction most homeowners miss is this: Permitted Development and Building Regulations are separate requirements.
Permitted Development tells you whether you need planning permission. Building Regulations confirm whether the structure is safe, insulated, ventilated, drained and legally compliant. You may be able to build a single storey extension under Permitted Development with no full planning application, but you still need Building Control approval.
Prior Approval under the Larger Home Extension scheme allows some Leeds homeowners to extend beyond standard Permitted Development depth limits. The local authority notifies neighbouring properties for a 42-day consultation period. If no valid objections are raised, the extension may proceed. Cobin Contractors checks your planning route during the free survey and confirms whether your Leeds property is likely to need Permitted Development, Prior Approval or full planning permission before you commit to the build.
FULL PLANNING GUIDE FOR LEEDS →
Property Type Standard PD Depth Prior Approval Depth
Detached house 4m 8m
Semi-detached house 3m 6m
Terraced house 3m 6m
Conservation area Check locally Full planning likely

4m

Max height — single storey

Where the extension comes within 2m of the rear boundary, eaves height cannot exceed 3m. Ridge must not exceed the existing roof height.

50%

Max garden coverage rule

All extensions and outbuildings combined must not cover more than half the area of land surrounding the original house — measured from the original house footprint.

LDC

Lawful Development Certificate

Not legally required to build under PD, but strongly recommended. Formal confirmation from your local planning authority that the kitchen extension is lawful — protects you on sale and removes uncertainty with solicitors.

Art.4

Article 4 Directions — Harrogate & Leeds

Parts of Harrogate — particularly around The Stray and historic village centres — and some parts of Leeds and Ilkley have Article 4 Directions that remove standard PD rights. We check at survey before you commit to any planning approach.

Structural steelwork

ALMOST EVERY single storey
EXTENSION NEEDS A STEEL BEAM.
WE INSTALL OURS IN-HOUSE.

When a single storey extension opens up the ground floor — removing the original rear wall or creating a structural opening between the existing room and the new space — a Universal Beam, commonly called an RSJ, is usually required to carry the load above. Any structural opening into a load-bearing wall usually needs engineer calculations, correct beam specification, padstones and Building Control inspection before the steelwork is concealed.
Most extension builders subcontract structural steelwork to a separate contractor. Cobin Contractors does not. Our in-house structural team handles beam specification, structural calculations, steel supply, installation and Building Control coordination on every single storey extension we build in Leeds.

RSJ beam installation — openings over ~1m

Any structural opening into a load-bearing wall may require a Universal Beam, also known as an RSJ. On single storey rear extensions, this is usually the beam that spans the original rear wall opening, allowing the existing room and new extension to become one open-plan space without unnecessary internal supports.

Goalpost steel frames for large openings

On wraparound extensions or large open-plan rear wall removals, a goalpost steel frame may be required. This usually includes two vertical steel columns supporting one horizontal steel beam, creating a wide, column-free opening across the rear or side of the property.

Material matching — stone, brick and pointing

Under Permitted Development, external materials should match the existing house as closely as possible. For Leeds properties, this often means matching facing brick, stonework, roof tiles, render, mortar colour and pointing style so the extension feels like part of the original home.

Floor continuity — existing to new

Running the same floor finish from the existing room into the new single storey extension creates a more seamless layout. This requires careful floor-level planning between the original structure and the new extension slab, especially when the goal is an open-plan kitchen-diner or living space.

Natural light strategy — rooflights and glazing

Deep single storey extensions can feel dark if they rely only on rear-facing glazing. Rooflights, lantern roofs and well-positioned doors or windows help bring natural light into the centre of the new space and improve the feel of the room throughout the day.

Thermal Performance — Leeds Homes

A well-insulated single storey extension should feel warm, efficient and comfortable throughout the year. Wall insulation, roof insulation, glazing specification and airtightness all affect long-term energy performance, especially during colder Leeds winters.
structural steelwork services →

Building Regulations

WHAT BUILDING REGULATIONS
COVER ON A Single Storey EXTENSION

Building Regulations are separate from planning permission. Every single storey extension in Leeds requires Building Control approval, whether the project is built under Permitted Development, Prior Approval or full planning permission. Building Control checks that the extension is structurally safe, properly insulated, ventilated, drained and compliant before final sign-off. Cobin Contractors manages the Building Regulations process as part of every single storey extension we build in Leeds.

Part A — Structure

Part A covers the structural safety of the extension. This includes foundations, load-bearing walls, RSJ steel beams, padstones and the structural connection between the existing house and the new extension. Engineer calculations are required where walls are removed, openings are widened or steel beams are installed. Building Control usually inspects foundations and structural steelwork before they are covered.

Part B — Fire Safety

Part B covers fire safety within the new and altered areas of the home. This can include fire protection to structural steel beams, smoke detection, escape routes and fire-safe construction details. Where RSJ beams are installed, they usually need to be encased in fire-rated plasterboard before final finishing.

Part C — Damp Proofing

Part C covers damp protection and moisture control. This includes damp proof course continuity, ground conditions, wall junctions and protection where the new extension meets the original property. This is especially important on older Leeds homes where existing walls, floors and drainage may need careful assessment before construction starts.

Part F — Ventilation

Part F covers ventilation for new and altered spaces. If the extension includes a kitchen, extract ventilation is required. Windows, doors and trickle vents may also be assessed to make sure the new space has suitable airflow and does not create condensation or ventilation issues elsewhere in the home.

Part H — Drainage

Part H covers foul water, surface water and roof drainage. New foundations must not damage existing drain runs, and any drain diversion needs to be checked before work continues. On Leeds homes, drainage routes are assessed during the survey and early construction stages so the extension can be built safely around existing pipework.

Part L — Energy Efficiency

Part L covers insulation, heat loss, glazing performance and energy efficiency. Walls, roofs, floors, windows and doors must meet current thermal performance standards. Large areas of glazing, such as bi-fold doors, sliding doors or rooflights, may require additional assessment to make sure the extension remains compliant and efficient.
Cobin Contractors submits the Building Regulations application, coordinates inspections and manages the final completion certificate for your single storey extension in Leeds. You do not need to deal directly with Building Control, structural engineers or separate steel contractors. We manage the process as part of the build.

Design guidance

DESIGN CONSIDERATIONS FOR
LEEDS
SINGLE STOREY EXTENSIONS

Single storey extensions involve more design decisions than many homeowners expect. The right choices can turn a basic extra room into a space that genuinely improves how the ground floor works. For Leeds homes, the best design depends on property type, existing layout, garden position, natural light, structural openings, roof choice and how the new space connects with the original house.

Roof type — flat, pitched or lantern

Flat roofs are common on Leeds single storey extensions because they allow rooflights and lantern roofs to bring natural light into the middle of the room. Pitched roofs can suit detached homes, traditional properties and houses where the existing rear elevation works better with a pitched design. Lantern roofs are popular for open-plan kitchen-diners because they add height, daylight and a more premium finish.

Rear glazed opening — bi-fold, sliding or French doors

The rear glazed opening has a major impact on how the extension feels and how it connects to the garden. Bi-fold doors open fully and create a strong indoor-outdoor connection. Sliding doors give a cleaner glass-to-frame ratio and work well for modern layouts. French doors are a more cost-effective option and often suit traditional Leeds properties.

Structural calculations — Eurocode 3 standard

Building Control will not approve structural steelwork without proper engineer calculations. These calculations confirm the correct RSJ beam size, padstone specification and load transfer. Cobin Contractors handles structural calculations as part of the extension process, so the steelwork, design and Building Control approval stay coordinated.

Padstones — load distribution

Padstones are required where RSJ beams bear into supporting walls. They spread the load from the steel beam into the masonry below. Correct padstone sizing is essential for Building Control approval and long-term structural safety, especially where large openings are created for open-plan kitchen-diner layouts.

Fire-rated plasterboard — Building Regulations Part B

Structural steel beams must be protected before they are covered. In most cases, exposed steelwork needs to be encased in fire-rated plasterboard to meet Building Regulations Part B. Building Control usually inspects the steel installation before it is concealed.

Party Wall Act — structural implications

On terraced and semi-detached homes in Leeds, foundation excavation, steelwork and wall removal near a shared boundary may trigger Party Wall Act requirements. Cobin Contractors identifies potential Party Wall issues during the initial survey, before you commit to the structural approach or final build plan.

Where we build

SINGLE STOREY EXTENSIONS ACROSS
LEEDS

We build single storey extensions across the full Leeds e region. Each area carries its own planning context, typical property types and structural considerations — all of which we assess and advise on at your free site survey.

LS1 – LS29

Leeds

Headingley, Chapel Allerton, Roundhay and central Leeds.

LS1–LS29

Harrogate

Harrogate town, Pannal, Starbeck and surrounding villages.

BD17

Baildon

Baildon​ — stone and brick detached

LS29

ILKLEY

Yorkshire stone property specialists

LS8

ROUNDHAY

Leeds — Victorian and Edwardian semis

LS16

ADEL

Leeds suburb — detached and semi-detached

LS16

BRAMHOPE

Village — detached stone and brick

BD • LS • HG • WF

WEST YORKSHIRE

Full county coverage

All Yorkshire

YORKSHIRE

Wider regional coverage

House Extensions

House Extensions

Cobin Contractors is a House extension specialist in Leeds. From single-storey kitchen extensions to full double-storey builds, all structural steelwork is handled in-house. Serving Leeds, Harrogate, Baildon, Ilkley and surrounding areas.
View House extensions →

Rear Extensions

Rear Extensions

The most common single storey extension type in Leeds Full detail on planning, structural steelwork, property types and permitted development for rear extensions on detached, semi-detached and terraced properties.
View rear extensions →

KITCHEN Extensions

KITCHEN Extensions

Specialist kitchen extension builders across Leeds. Open-plan kitchen-diners, rear wall structural alterations, RSJ beam installation — all structural steelwork handled in-house. 

View KITCHEN extensions →

FAQs

SINGLE STOREY EXTENSION
FAQs

The real questions Leeds homeowners ask before committing to a single storey extension — answered clearly, without sales language.
Ask us a question →
How much does a single storey extension cost in Leeds in 2026?
A typical single storey extension in Leeds can vary depending on size, structure, access, roof type, glazing, drainage, internal finish and whether load-bearing walls need to be removed. Smaller rear extensions usually cost less, while open-plan kitchen-diner extensions with RSJ steelwork, rooflights, bi-fold doors or larger structural openings sit toward the higher end. Cobin Contractors provides fixed-price quotes after a free site survey.
Not always. Many single storey rear extensions can be built under Permitted Development if they stay within the required depth, height, boundary and design limits. Larger extensions may need Prior Approval, and some Leeds homes may need full planning permission if Permitted Development rights are restricted or removed.
A typical single storey extension in Leeds takes around 8–12 weeks from breaking ground, depending on size, access, structural complexity, drainage, roof type and internal specification. More complex open-plan layouts, wraparound extensions or projects with major structural wall removal can take longer.
You may need Party Wall notices if your extension involves excavation, foundations or structural work close to a shared boundary. This is common on terraced and semi-detached homes in Leeds. Cobin Contractors identifies potential Party Wall issues during the initial survey.
In many cases, yes. A single storey extension usually causes less disruption than a double storey build. However, there may be temporary disruption when the rear wall is opened, services are moved, drainage is adjusted or kitchen areas are disconnected.
A well-designed single storey extension can add strong value by creating more usable ground-floor space, especially a larger kitchen-diner, open-plan living area or better connection to the garden. The value depends on your Leeds property type, location, build quality, layout and finish.
Yes. Cobin Contractors handles RSJ beam installation, load-bearing wall removal, goalpost frames, padstones, structural calculations and Building Control coordination in-house. You do not need to arrange a separate steel contractor.
Yes. After the free site survey and feasibility review, Cobin Contractors provides a written fixed-price quote before work begins. The quote is based on your property, structure, access, planning route, specification and Building Control requirements.

Free design assessment

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Your single Storey?

Book a free, no-obligation site assessment. We will visit your property, review planning feasibility and send you a written feasibility report with an indicative budget within 5 working days.
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