House Extensions Morden
Single storey rear and double storey extensions in Morden, planning, structure and build under one contract.
- Rated 4.9 from 31 reviews on MyBuilder
- Single-storey rear extension from £40,000
- Free site survey, itemised quote
GS Renovation builds extensions across Morden, adding kitchen extensions and rear extensions to the interwar terraces and semis that fill SM4. Most houses have room at the rear, and semis often at the side too, and with our founder's 30+ years on the tools, we manage groundworks, steelwork, roofing and fit-out as one continuous project.
In Morden, a single-storey rear extension typically starts from £40,000, or £2,000 to £2,800 per m² (indicative London ranges, Architecture for London, Resi, MyBuilder and Checkatrade, 2026). GS Renovation Ltd, a building contractor based in Potters Bar, does the work in Morden: the structural engineer we appoint designs the structure, we build it, and building control signs it off.
Price guide
| Work | Indicative London range |
|---|---|
| Single-storey rear extension | from £40,000 |
| Rear extension, per m² | £2,000 to £2,800 |
| Side return, per m² | £2,400 to £3,200 |
| Wraparound, per m² | £2,400 to £3,200 |
| Double storey, per m² | £1,800 to £2,600 |
| Basement extension | see the basement page |
Indicative London ranges (Architecture for London, Resi, MyBuilder and Checkatrade, 2026), not a quotation. Prices checked September 2026. Full breakdown: Extension Costs & Planning.
Quick estimate for Morden
Morden range: choose above
Kitchen and rear extensions in Morden
On a Morden terrace the usual project is a single-storey kitchen extension across the back of the house, joining the old kitchen and the back room into one kitchen-diner that opens onto the garden. On a semi with side access, a side or wrap-around extension can add more without swallowing the whole garden. We dig and pour foundations to suit the ground, tie the new walls into the existing structure, and fit steel beams where the old external wall is opened up to join old and new space.
A rear extension across the back of the house works well where families want to bring the kitchen, dining and living areas together and open onto the garden. We handle the roof, whether a warm flat roof with rooflights or a pitched tie-in, the glazing, and the full internal finish, so you deal with one team from the first trench to the final coat of paint.
Housing in Morden
The valuation list shows roughly 9,990 homes in Morden, of which 2% are pre-1919, 81% interwar and 17% post-1945, split 25% flats to 75% houses. 64% of homes here are terraced; a rear extension on a terrace in Morden digs foundations close to both neighbours, so notices to both are normal.
Floor area bands and inspection stages for a Morden extension
Merton sets its building control charge for an extension by floor area, with one band for extensions between 10m2 and 40m2 and another for extensions over 40m2 up to 300m2. A single storey kitchen extension across the back of a Morden terrace can sit in the first band. Add a side infill on an end of terrace or a semi, or a second storey, and it can move into the second. Measure the floor area on the drawings before the application goes in, so the fee paid matches the extension being built and nothing has to be topped up later.
Merton's example inspection stages for an extension include excavation for foundations, oversite, and new walls with below ground drainpipes. On a Morden plot each of those is a hold point. The trench waits open until it has been seen, the oversite waits before the slab is cast, and the new drain runs stay uncovered until they have been checked. Book the concrete, the slab and the backfill around those visits, and keep a day of slack after each, so a late inspection does not leave a ready-mix lorry waiting at the kerb.
Planning and permitted development in Morden
Many single storey rear extensions on Morden houses fall under permitted development, which means no full planning application to Merton Council; a lawful development certificate is optional but worth having as proof for a future sale. Larger projects, double storey additions, or work on a property in a conservation area can need full planning permission. We advise honestly on which route your house falls under before you commit.
Whatever the planning position, every extension has to meet building regulations for foundations, structure, insulation, drainage and fire safety, and Merton building control inspects at each stage. Where the new build affects the shared party wall with your neighbour, you serve the notices under the Party Wall Act as building owner, with the drawings we supply. Planning and building regs are separate approvals, and we keep both on track from start to finish.
Side return extensions in Morden
Side returns belong to Victorian and Edwardian terraces, and only 2% of homes in Morden predate 1919, so they are the exception here; most extensions run across the full rear width instead. Our side return extension page covers the build in detail, with build rates of £2,400 to £3,200 per m².
Double storey extensions in Morden
Under permitted development a two-storey rear extension can go no more than 3 metres beyond the original rear wall and must stay at least 7 metres from the rear boundary, and in a conservation area it is not permitted development at all. Many gardens are too short for the 7 metre rule, so a double storey extension in Morden often needs planning permission from Merton Council. On the 64% of homes that are terraced, the neighbours' windows usually decide the depth. Merton's immediate Article 4 Direction for small HMOs in 13 wards, including Lower Morden, Wimbledon Park and Wimbledon Town, started on 24 March 2026 (council source). Our double storey extension page explains the build, at £1,800 to £2,600 per m² across both floors.
- Wrap-around extensions and infills
- Full fit-out, finishing and making good
- Planning applications and permitted development assessments
VOA Council Tax stock of properties, March 2025, for Morden Central, Lower Morden and St Helier North. Counts rounded by the VOA.
Why Morden Homeowners Choose GS Renovation
GS Renovation is a natural fit for Morden extensions because we self-deliver the structural core, the foundations, the steel and the roof, rather than subcontracting the hard parts. We guide you through permitted development or a Merton planning application, give you the drawings for the party wall notices, and finish the interior properly. Our founder's 30+ years of extensions mean fewer surprises and a build that adds real value.
- Garden levels and access made good where the build meets outside
- Weathertight shell reached before the fit-out begins
- Itemised pricing, so you can see what every stage costs
Built a new extension at rear of property. Laid foundations, drainage, raised floor, new roof and completed all fixtures and interior decoration…
George was brilliant. Lovely bloke, very reasonably priced and a perfectionist to boot. He completed our small kitchen renovation with care and great…
George always kept to commitments and arrived on time. He offered helpful suggestions during his initial visit and promptly provided a reasonably…
FAQ
Frequently Asked Questions about House Extensions Morden
What does the house extensions quotation for a Morden home cover?
A Morden quotation for house extensions sets out scope, programme and price on one document, within £2,000 to £2,800 per m² for a rear extension (indicative). It shows what is done, in what order and at what cost, and the order is not arbitrary: the steel into the house is designed before the rear wall comes down. Exclusions are stated plainly rather than left to be discovered once work starts at the SM4 property.
Does my Morden extension need planning permission or is it permitted development?
It depends on the size and position. Many single storey rear and side extensions on Morden's interwar houses are permitted development, so no full application to Merton Council is required, though a lawful development certificate is wise. Double storey work, extensions near a boundary or in a conservation setting usually need planning permission. Either way, building regulations always apply, and we confirm your route before quoting.
How deep will the foundations be for an extension on Morden's clay?
Deeper than people expect when trees are near. Many interwar suburbs sit on shrinkable clay, and mature trees drawing water from it make the ground swell and shrink with the seasons. The structural engineer sets the foundation depth from the soil type and the distance to trees, sometimes calling for piles or a reinforced raft, and building control checks the open trench. Dig a trial hole early so the depth is known before the design is fixed.
Does digging foundations for a Morden extension need neighbour notice?
It can, even when nothing touches their wall. The Party Wall etc. Act 1996 requires one month's notice if you excavate within 3 metres of a neighbour's building to below its foundations, which on terraced Morden plots is common. They may agree or dissent and a dissent leads to a surveyor's award. If the extension also sits on the boundary line, a separate notice covers that wall.
How do I keep the middle room light after extending my Morden house?
Bring light in from above. An extension pushes the rear wall of a Morden house outward, which leaves the old dining room further from any window. Rooflights close to the existing house, or a lantern over the join, send daylight back into the middle of the plan. Glazing affects the insulation calculation, so rooflight sizes are fixed at design rather than added later.
At what stages does building control visit a Morden extension?
At each point where work is about to be covered up. Typical visits are the open foundation trenches, the damp-proof course and oversite, drainage before backfilling, the steel bearings where the old wall comes out, and insulation before plaster. Merton Council or your inspector then issues the completion certificate. Missing a stage can mean opening finished work, so the site programme is built around them.
Could a Morden extension be liable for the Community Infrastructure Levy?
Only a large one. In Merton, a permission for any new dwelling or at least 100 square metres of new-build gross internal area will usually become liable for CIL. A single storey rear extension on a Morden house is normally well under that. Merton's effective CIL residential rate for Mitcham, Morden and West Barnes is above its original rate, so if a scheme is heading towards that floor area, check the liability before the planning application goes in.
Does a Morden extension in the Upper Morden Conservation Area take longer to approve?
If it needs planning permission, yes. The Upper Morden Conservation Area was designated by Merton Council in 1986, and Merton's fast track householder decision is up to 46 days from validation inside a conservation area, against up to 30 days outside one. A side extension or a two storey rear extension there needs an application, while a modest single storey rear extension can still be permitted development. Where an application is needed, plan on the longer figure and hold long lead orders until the decision.
What if a Morden extension comes within 3 meters of a public sewer?
The building control route narrows. In Merton a full plans submission must be made before work starts if the proposed extension is within 3 meters of a Thames Water sewer, and a building notice is not available for those works. That rules out starting on a building notice while the drawings catch up. Apply on full plans with the drainage details included, so the approval and the Thames Water process run in step.
Every Service, One Team
More GS Renovation Services in Morden
One team for every GS Renovation service in Morden:
Same Service, Nearby Areas
House Extensions Near Morden
We carry out house extensions across Morden and the surrounding areas. Explore a nearby location:
Ready to Start Your Morden Project?
Free, no-obligation quote for house extensions in Morden.