Service
House Extensions London
Rear, side-return, side and double-storey house extensions across London and within the M25, delivered to issued architectural drawings and structural information with Building Control coordination.
House extensions built around your property and plans
TopBuild UK builds house extensions across London and locations within the M25. Our genuine portfolio includes single-storey rear extensions, side and back extensions, double-storey side extensions, glazed additions and extensions delivered alongside loft conversions or wider house renovations.
We work to the drawings and specification issued by your architect or design team, coordinating foundations, drainage, masonry, roof construction, glazing, structural openings and the internal work included in the agreed scope.
Where the design needs structural steel, the beams and supporting details follow the structural engineer's calculations. All structural work is backed by our 10-year guarantee, with the quotation defining the work and finishes included.
Types of house extension we build
- Single-storey rear extensions
- Side-return and side extensions where the property and design allow
- Double-storey side extensions
- Combined side and back extensions
- Glazed, flat-roof and pitched-roof extension designs
- Extensions delivered with loft conversions or wider refurbishment
- 10-year guarantee on structural work
Our house extension construction process
- 1
Site visit and brief
We review the property, access and proposed extension, then discuss the drawings, specification and finish expected.
- 2
Project information review
We review the issued architectural information, planning position, structural calculations and Building Control route relevant to the project.
- 3
Quotation and scope
A clear quotation sets out the construction work, services and finishes included, together with any information still required before starting.
- 4
Site preparation and foundations
The site is prepared before excavation, foundations and below-ground work proceed to the project information and inspection requirements.
- 5
Structure and envelope
Walls, structural openings, engineer-specified steelwork, floors, roof construction, windows and external doors form the extension shell.
- 6
Services and internal work
The plumbing, electrics, insulation, plastering, joinery and finishes included in the agreed scope are coordinated through the build.
- 7
Inspections and handover
Required inspections are accommodated at the relevant stages, followed by the agreed completion work, documentation and 10-year structural guarantee.
Planning route
Planning permission and permitted development
Some house extensions can be permitted development when the property, design and all relevant limits and conditions qualify. Other extensions require householder planning permission. Previous alterations, property type, planning conditions, Article 4 directions and location can affect which route is available.
TopBuild UK does not provide legal planning advice or submit planning applications. We build to the drawings and consents prepared for the project, working alongside your architect or planning consultant. The planning route should be confirmed with the appropriate professional or local planning authority before construction begins.
Design and compliance
Architects, structural engineers and Building Control
The architect or designer prepares the layout and construction information. Where foundations, beams, columns or other structural elements require calculations, the structural engineer designs those elements and issues the details for construction.
Building Regulations approval is separate from planning permission. House extensions generally require Building Regulations consideration and inspections at relevant stages. We coordinate our work with the issued design information and the project's Building Control route, without presenting ourselves as the designer or approval body.
Areas covered
House extensions across London and the M25
Our genuine extension portfolio includes work in Hampstead, London Fields, Kilburn, Winchmore Hill, Kennington, Fulham, Herne Hill and Woolwich, alongside projects in Chigwell within the M25.
Each property has different access, neighbouring constraints, existing construction and design requirements. We assess the actual site and issued information before defining the construction scope and quotation.
Trust and guarantee
Why choose TopBuild UK for your extension?
A successful extension depends on coordinated construction, clear project information and careful integration with the existing property.
Genuine extension experience
Our project photography documents rear, side, double-storey, glazed and steel-framed extensions delivered across London and within the M25.
Coordinated construction
We work alongside architects, structural engineers and Building Control, delivering the agreed structural work and wider construction scope.
10-year guarantee
All structural work is backed by our 10-year guarantee, with the included work and finishes set out in the quotation.
Frequently asked questions
What types of house extension do you build?
Our genuine project portfolio includes single-storey rear extensions, side and back extensions, double-storey side extensions, glazed additions and extensions combined with loft conversions or full refurbishment.
Do I need planning permission for a house extension?
That depends on the property, previous alterations, location and proposed design. Some projects require householder planning permission, while others may qualify for permitted development. Your architect, planning consultant or local planning authority should confirm the route for the specific property.
Can a house extension be permitted development?
Some extensions can be permitted development if every relevant limit and condition is satisfied and the property's rights have not been restricted. This is project-specific and should be checked before work begins.
Do I need an architect for an extension?
Extension projects need suitable drawings and construction information. We work to information prepared by your architect or design team and do not replace their design or planning role.
When is a structural engineer required?
A structural engineer is normally involved where the design requires calculated foundations, beams, columns, structural openings or other load-bearing alterations. We install those elements to the engineer's issued drawings and calculations.
Does a house extension need Building Regulations approval?
Building Regulations approval is separate from planning permission, and house extensions generally require Building Regulations consideration. The appropriate application and inspection route should be established for the individual project.
Can you install the steelwork for an extension?
Yes. We install engineer-specified beams, columns and structural frames as part of extension projects. Detailed information about this service is available on our Steel Beam Installation page.
Can you combine an extension with a loft conversion or refurbishment?
Yes. Our genuine projects include extensions delivered alongside loft conversions and wider house remodelling. The quotation and programme are prepared around the combined scope.
What affects the cost of a house extension?
Cost depends on size, structure, access, ground conditions, glazing, roofing, services, internal specification and the amount of remodelling involved. We review the drawings and property before preparing a fixed-price quotation for the agreed scope.
Is extension work guaranteed?
All structural work on the extension carries our 10-year guarantee. The quotation confirms the work and finishes included.
Which areas do you cover?
We build extensions across London and locations within the M25. Our existing extension projects include Hampstead, London Fields, Kilburn, Winchmore Hill, Kennington, Fulham, Herne Hill, Woolwich and Chigwell.
Our work
Recent extensions
Genuine TopBuild UK extension projects
Planning a house extension in London?
Tell us about the property and share any drawings you already have. We will review the scope and come back with the next steps for a fixed-price quotation.
10-year structural guarantee · No obligation