House Extensions Welling
Single storey rear and double storey extensions in Welling, 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 plans and builds extensions across Welling, working with the 1930s semi-detached and interwar houses that give DA16 its character. Those generous plots and side accesses suit rear kitchen extensions and side extensions particularly well. We handle the foundations, steelwork, roof and full fit-out as one managed project.
In Welling, 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 Welling: 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 Welling
Welling range: choose above
Rear and side extensions on Welling plots
The wide, deep gardens common to Welling's interwar semis are ideal for single storey rear kitchen extensions that open the kitchen onto the garden, and the side access many of these houses retain makes a side extension or wrap-around addition genuinely practical. We start with proper foundations and groundworks sized to the ground conditions on your plot, then build up in blockwork to match the existing brickwork and rooflines of the 1930s streetscape.
Double storey extensions add a bedroom and often an en-suite above a larger kitchen below, which suits families staying put in DA16 rather than moving on. We install the steel beams that carry the new openings, tie the new structure into the original house correctly, and complete the roof works so the finished extension reads as part of the original interwar home rather than an afterthought bolted on the back.
Housing in Welling
The valuation list shows roughly 4,020 homes in the Welling statistical area, of which 5% are pre-1919, 76% interwar and 18% post-1945, split 21% flats to 78% houses. 56% of homes here are semi-detached; a rear extension on a semi in Welling digs beside the attached neighbour, so one party wall notice is usual.
What Bexley's 2026 design guide means for a Welling semi
Bexley adopted the Design Guide SPD Part 2, which includes Building Alterations and Extensions guidance, on 29 June 2026. For a terraced or semi-detached dwelling it says an extension should typically not exceed 3.5m deep. 15% of Welling homes are terraced and 58% semi-detached or detached, so for the attached houses that depth is the starting point for a planning application. A scheme drawn earlier to a deeper footprint should be looked at again before it is submitted.
The guide also says a single-storey extension should not exceed 4m at its highest point, with an eaves height of no more than 3m. On a Welling semi, where the neighbour's rear windows sit close to the boundary, those numbers shape the roof more than the room. A flat roof with a lantern keeps the eaves low along the party line while still bringing light into the middle room. We set the roof form at the start, because it decides where the steel goes and how the walls are built up.
Planning and party walls in Welling
An extension may fall under permitted development or it may need a full planning application to Bexley Council, and which route applies depends on the size, the height and whether your property sits under any restrictions. Many modest single storey rear extensions in Welling proceed under permitted development, up to 3 metres deep on a semi, or 6 metres through the prior approval route, while larger, double storey or more prominent schemes need consent. We advise honestly on the likely route before you commit and coordinate the drawings with your architect or technician either way.
Whichever planning route applies, the building work itself must meet building regulations, with foundations, steel, insulation and drainage all inspected and signed off. Because these are semi-detached houses, extensions near the shared boundary usually trigger the Party Wall Act, so you serve notice on the neighbour as building owner in good time, and we supply the drawings it needs. Getting the planning, the building control and the party wall matters aligned early keeps a Welling extension moving without avoidable delays.
Kitchen extensions in Welling
74% of the houses in Welling are semi-detached or detached, which usually leaves room for a kitchen extension across the full rear width, with a steel beam over the opening into the house. The fit-out is priced on its own page, kitchen renovation in Welling; the build figures are in the table above.
Side return extensions in Welling
Side returns belong to Victorian and Edwardian terraces, and only 5% of homes in Welling 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 Welling
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 Welling often needs planning permission from Bexley Council. With 58% of homes here semi-detached or detached, the side of the house is often an option too. Bexley has 23 conservation areas across the borough and special controls apply to buildings in them (council source). Our double storey extension page explains the build, at £1,800 to £2,600 per m² across both floors.
- Trial holes to set foundation depth near drains and trees
- Roof works and structural alterations at roof level
- Party wall process explained, and the extension built to the award
VOA Council Tax stock of properties, March 2025, for the Welling statistical area, one of several statistical areas covering DA16. Counts rounded by the VOA.
Trusted House Extensions in Welling
Welling homeowners choose GS Renovation because we manage the whole extension under one roof, from the first foundation to the final coat of paint. We know how Bexley Council handles permitted development and full applications, and how the party wall rules affect semis. With our founder's 30+ years on the tools, you deal with one team that stands behind the result.
- Free, no-obligation quotations
- Drainage diverted or built over with the right approval in place
- Garden levels and access made good where the build meets outside
Built a new extension at rear of property. Laid foundations, drainage, raised floor, new roof and completed all fixtures and interior decoration…
Giorgio is an excellent and intelligent workman, and with very reasonable prices! He installed a kitchen extractor fan in a complicated situation…
George was brilliant. Lovely bloke, very reasonably priced and a perfectionist to boot. He completed our small kitchen renovation with care and great…
FAQ
Frequently Asked Questions about House Extensions Welling
Is a cheap house extensions quote in Welling worth taking?
Before accepting a cheap house extensions quote in Welling, check what has been left out. Low quotations tend to be light on approvals and reinstatement, and work done without Bexley Council building control sign-off becomes expensive when the DA16 property is sold. The market range is £2,000 to £2,800 per m² for a rear extension (indicative); a figure far below it has usually skipped a step in the sequence: the steel into the house is designed before the rear wall comes down.
Will my Welling rear extension need planning permission?
Many single storey rear extensions on Welling's interwar semis fall within permitted development, so no planning application is needed, but larger, double storey or more prominent schemes usually require consent from Bexley Council. Either way the work must meet building regulations. We assess your specific plot and advise on the correct route before any drawings are finalised. A listed building is the exception: work that affects its character, inside or out, including an extension or taking out a wall or chimney breast, needs listed building consent from Bexley Council, and doing it without consent is a criminal offence.
Do I need party wall notices for a rear extension on my Welling semi?
Very likely. A wall built along the boundary with the attached house needs notice, and digging the new foundation within 3 metres of their house to below its footings needs one month's notice, which shallow interwar foundations make probable. Your neighbour can consent or dissent; dissent means surveyors and an award. Serving early keeps the start date secure.
What if drains run under my planned Welling extension?
A pair of semis often shares a drain run at the back, and where it serves more than one house it may be a public sewer, needing the water company's consent before you build over or near it. Access points must stay reachable, so a manhole may move or be added. The runs are camera surveyed before drawings are finished so the foundation design reflects them.
How does a new extension open into my Welling house?
Through the old rear wall, which is carried on a steel beam designed by the engineer and set on padstones once props are in. The shell and roof are usually built first so the house stays closed, with the wall removed late in the programme. Bexley Council's building control inspects the steel before it is boxed in, alongside the foundations, drainage and insulation stages.
Does my Welling extension have to meet insulation standards?
Yes. Part L applies to every extension, so the new floor, walls and roof reach current insulation standards whether or not planning was needed, and large glazed doors or rooflights have to be balanced by the rest of the design. The interwar rooms beside it, with older walls and floors, will feel colder than the new space unless their heating or insulation improves at the same time.
Can a Welling semi use prior approval instead of the design guide depth?
It can be a separate route. The larger home extension scheme is a prior approval process under permitted development, and Bexley offers a Fast Track fee for a decision within 20 working days of validation. It carries its own limits and neighbour consultation, only works where permitted development rights survive on the house, and is not available in a conservation area. Check that first, then compare it with a planning application judged against the design guide.
Does a shared drain behind a Welling semi change the building control route?
Yes. In Bexley a building notice cannot be used for construction or extension over or within 3m of a drain, sewer or disposal main controlled by Thames Water, and a run serving both halves of a pair is normally one of those. The extension then goes to Bexley as full plans, with the decision taking five to eight weeks, so the drain survey belongs at the very start of the design.
Can Bexley give written advice on a Welling extension before an application?
Yes, through its Category G pre-application service for householder proposals, with a written response or a meeting and written response. Without a meeting, Bexley provides the written response within 15 working days of receiving the request. It is worth doing where a Welling scheme goes beyond the design guide depth or height, since the answer arrives before the drawings are finalised and the structural engineer we appoint is instructed.
Every Service, One Team
More GS Renovation Services in Welling
One team for every GS Renovation service in Welling:
Same Service, Nearby Areas
House Extensions Near Welling
We carry out house extensions across Welling and the surrounding areas. Explore a nearby location:
Ready to Start Your Welling Project?
Free, no-obligation quote for house extensions in Welling.