Project-managed refurbishment & building, London Covering all London boroughs 07498 597339
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Modern home extension on London property
Construction — London

Home
Extension
London.

Single and double storey extensions designed, built and finished to your specification. We manage planning, structural engineering, build and all finishing trades — one team, one contract.

Free
Survey & quote
Full service
Design to completion
All London
Boroughs covered
Our options
Every job is different. Contact us for a free quote tailored to your property.
Single storey rear extension
Up to 4m depth, basic specification, planning included
Single storey — high spec
Bifold doors, lantern roof, underfloor heating, premium finishes
Double storey extension
Two floors, structural engineering and planning included
Side return extension
Common in terraced houses, filling the side return passage
Wraparound extension
Combined rear and side return for maximum ground floor open-plan living space
Request a free quote →

Congestion charge may apply for central London postcodes.

About home extensions

Extending your
London home.

A well-designed home extension can add significant value to a property while providing the additional living space that London's often-cramped housing stock needs. Rear extensions, side returns and double storey additions are among the most common projects we undertake.

We handle the full project from concept design through to planning permission, structural engineering, build and all finishing trades including electrics, plumbing and plastering. This avoids the complexity and risk of managing multiple contractors.

Most single storey rear extensions fall within Permitted Development rights and do not require full planning permission, though a Lawful Development Certificate is advisable. Double storey extensions almost always require planning consent, which we manage on your behalf.

Why choose us

Why London
homeowners choose us.

01
Full project management

We manage design, planning, structural engineering and all construction trades. You have a single point of contact throughout — no coordinating between an architect, structural engineer and separate builders.

02
Planning expertise

We have experience with planning applications across all London boroughs and know what different councils typically require. We manage the application on your behalf.

03
Fixed-price contracts

Once the design is agreed and planning obtained, you receive a fixed-price build contract. Contingencies for discovered structural issues are clearly defined upfront.

04
All trades in-house

Our own teams carry out blockwork, roofing, plastering, electrics and plumbing. Specialist trades such as steelwork are subcontracted to trusted partners.

What's included

Complete
project.

Concept design
Initial drawings and 3D visualisation so you can see the proposed extension before committing
Planning application
Full planning application managed on your behalf, including all drawings and supporting documents
Structural engineering
Structural calculations for steel beams, foundations and any load-bearing modifications
Groundworks & foundations
Excavation and reinforced concrete foundations specified to structural engineer's design
Blockwork & roofing
External walls, flat or pitched roof structure and weatherproofing installed by our teams
Windows & doors
Supply and fitting of bifold, French or sliding doors and windows to your specification
First & second fix trades
Plumbing, electrics, plastering and floor finishing by our own teams
Decoration
Final decoration of all new surfaces, leaving the extension ready to furnish
How it works

Design to
completion.

01
Consultation & design
We visit, take measurements and produce initial concept drawings for your review and approval.
02
Planning & engineering
We submit the planning application and commission structural engineering calculations simultaneously.
03
Build
Construction commences once planning is approved — groundworks, structure, roof and all internal trades.
04
Handover
Final inspection and snag list addressed. Building Regulations sign-off obtained and all certificates handed over.
Common questions

Questions
answered.

Do I need planning permission for a rear extension?
Many single storey rear extensions fall under Permitted Development, particularly in houses (not flats). However, Article 4 directions in some London boroughs remove PD rights — we advise case by case.
How long does an extension take?
A single storey extension typically takes 12–16 weeks from groundworks start to completion. Double storey extensions take 20–28 weeks. Planning permission adds 8–12 weeks before build commencement.
Can I stay in the house during construction?
Yes — we sequence the work to maintain access to the rest of the property wherever possible. There will be periods of increased noise and dust, but most clients remain in residence throughout.
Does an extension add value?
A well-specified extension in London typically adds 10–20% to a property's value, often significantly more than the construction cost, particularly for kitchen-diner extensions that improve the quality of family living space.
What is a Party Wall Agreement?
If your extension is within 3m of a neighbour's property or involves work to a shared wall, you'll need a Party Wall Agreement. We can refer you to a qualified Party Wall surveyor.
London-wide service

Start planning
your extension.

Get in touch

Request a callback.

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Message us
Call GMAS — 07498 597339