— LMDEC · South & West London · Since 2014
House extensions in South London.
More room for family life. A clearer route from the first drawing to the final finish.
LMDEC builds rear, side-return, wraparound and two-storey house extensions across South and West London. Our director and project manager coordinate site teams and specialist trades, so your new space and the existing house are planned as one project.
— What we build
Choose the space your home needs.
Rear extensions
Bring the kitchen, dining area and garden together. We coordinate the structural opening, roof design, drainage, glazing and internal finishes so the new room connects properly to the house.
Side-return extensions
Make use of the passage beside a rear addition. The crucial decisions are often the boundary detail, rooflight layout, drainage route and how daylight reaches the middle of the home.
Wraparound extensions
Combine a side infill with a rear addition to reshape the ground floor. Plan the structure, circulation, storage and garden connection together before settling the kitchen layout.
Two-storey extensions
Add accommodation on both levels where the site and planning position allow it. Upper-floor layout, roof junctions and the relationship with neighbouring windows need attention from the outset.
— Before the drawings go further
Which planning route fits your property?
| Your starting point | What to establish next |
|---|---|
| A house with a modest rear extension | Check the original footprint, earlier additions and every applicable permitted development limit. |
| A larger single-storey rear extension | The larger-home-extension route requires prior approval and is not available on designated land such as conservation areas. |
| A side extension in a conservation area | Householder planning permission is required; check the relevant appraisal and any additional controls. |
| A flat, maisonette or listed property | Do not assume householder permitted development applies. Establish the relevant planning, heritage and ownership consents. |
Check the Planning Portal extension guidance. Planning, Building Regulations, party wall matters and ownership consent are separate checks.
— A buildable scope
A drawing is the start of the specification.
Structure & groundworks
Confirm the structural design, foundation assumptions, access for excavation and the sequence for opening up the existing house. Record what remains an allowance until conditions are exposed.
Drainage & services
Locate drains before fixing the footprint. Agree who obtains any sewer approval, whether a chamber must move, and how heating, power, ventilation and hot water serve the new space.
Kitchen & glazing
Agree kitchen supply and installation responsibilities, opening sizes, rooflights and glazing specifications before orders. A generous opening on a drawing needs a coordinated structural and installation detail.
The rooms you already have
Include making good, flooring transitions, decoration, alarm changes and alterations outside the extension. These should be visible in the quotation rather than discovered during the build.
— Budget & specification
What does a house extension cost?
£70k–£160k
Indicative LMDEC extension budget guide, excluding VAT.
Use this as a starting range, not a price for a particular size or extension type. Complex structures, premium glazing, extensive work to the existing house or a higher specification can take a project beyond it.
The written quote defines the kitchen allowance, finishes, structural work and exclusions. Professional and statutory fees are identified separately; a 10% contingency is shown separately rather than hidden in the headline.
Compare the same scope: shell-only and fully finished prices are not equivalent. Our renovation cost estimator can help structure an initial budget discussion.
— The programme
One coordinated project, from visit to handover.
- Site visit and brief. Walk through the proposed space, access, existing services and your priorities.
- Design and approvals. Work with your architect and engineer to resolve the construction information and approval responsibilities.
- Written scope and quote. Agree inclusions, allowances, exclusions, stage payments and decisions needed before work begins.
- Construction and communication. Coordinate trades, inspections and deliveries; track the programme and site photographs through your Client Portal.
- Handover and aftercare. Complete snagging and collect the relevant certificates and manuals. A two-year workmanship warranty and six-month return visit are included.
We set the construction programme against the actual scope and procurement lead times. Planning, neighbour matters and pre-construction design are scheduled separately from time on site.
— Our work
Built around the way you live.
See our completed work and client reviews. Over fifty verified five-star reviews on Google, Trustindex and Yell.
— Local knowledge
Start with the rules for your address.
House extensions in Wandsworth →
LP5, address-specific Article 4 controls, neighbour daylight and the questions to resolve before a side-return or rear-extension quote.
We also work in Balham, Clapham, Wimbledon, Richmond, Croydon and the surrounding South and West London areas. Share your postcode and drawings so we can discuss your particular property.
Planning more than an extension? Explore loft conversions and full house refurbishments.
— Common questions
House extensions — your questions.
Do I need planning permission for a house extension?
It depends on the existing property, the size and position of the addition, earlier extensions and local restrictions. Some houses retain permitted development rights; flats and maisonettes do not have the same householder rights. Check the route before commissioning a final design.
Can you work with my architect’s drawings?
Yes. We can price and build from your architect’s drawings and coordinate with your structural engineer. Before work starts we agree the construction details, specification, responsibilities and any outstanding approvals.
Can an extension and full refurbishment be carried out together?
Yes. We can coordinate the extension, structural alterations and refurbishment in one programme. The quote separates the new addition from work to existing rooms, so you can see where the budget is going.
Can we stay at home during the extension?
That depends on the scope, access and whether a safe kitchen, bathroom and protected living area can remain available. We discuss the disruptive stages and any temporary move before agreeing the programme.
What should I send before a site visit?
Send the property address, existing and proposed drawings if available, planning decisions, structural information, target start date and your budget including or excluding VAT. Photographs of the rear elevation and access route are useful too.
Who manages my extension?
Our director and project manager coordinate site teams and specialist trades. Core trades are kept in-house, with gas and electrics by our regular Gas Safe and NICEIC registered subcontractors. Your Client Portal keeps the programme, photographs and project information together.
— Your next step
Let’s talk about the house you want to live in.
Send your address, drawings if you have them, and the changes you want to make. Tell us your target start date and whether your budget includes VAT, the kitchen and professional fees.
A fixed-price quote within 48 hours of our site visit.
— Sources & review
Check the documents behind the advice.
Planning sources checked 18 October 2026. Rules depend on the property and proposal; use the current documents and address-specific records with your designer.