Kitchen Extensions Lewisham

A kitchen extension in Lewisham is shaped less by taste than by the plot. Terraced houses make up 31% of the borough's homes and semi-detached or detached houses only 8%, so a kitchen extension here is far more often a terrace job: a single storey addition across the back, sometimes with the side return folded in. Lewisham's own extensions guidance sets the depth and the height on the boundary, and a public drain within 3 metres of the house brings a build over agreement before any digging. We plan the structure, the drainage and the new kitchen as one programme.

In Lewisham, a rear kitchen extension of about 30 square metres typically costs £45,000 to £97,500 excluding VAT, or £60,000 to £100,000 for a side return (indicative London ranges, Resi, MyBuilder and Checkatrade, 2026). GS Renovation Ltd, a building contractor based in Potters Bar, does the work in Lewisham: the structural engineer we appoint designs the foundations and steel, we build the room and fit the kitchen, and a registered electrician certifies the electrics.

How deep a Lewisham kitchen extension can go on a terrace

Lewisham's Alterations and Extensions SPD, adopted on 24 April 2019, is the document your designer draws against, and it answers the depth question directly: rear extensions on terraced or semi-detached properties should generally be no more than 3m deep. That figure is guidance for a planning application, so a longer scheme needs a reason the officer can accept, such as a neighbour who has already built out further. Settle the depth before the steel is drawn, because it fixes where the new rear wall and its foundation sit.

The same SPD adds a second test that matters on the short gardens behind a Victorian row: an extension should never take up more than half the depth of the original rear garden or yard. On a Lewisham terrace with a shallow yard, that half line can bite before the 3m figure does. Measure from the original rear wall, not from any lean-to or conservatory added later, because the test is the original garden.

Housing in Lewisham

Lewisham's housing, as the Council Tax list records it, is about 133,910 homes: 40% houses, 60% flats, with 34% pre-1919, 18% interwar and 45% built since 1945. Most homes here are flats, and only a ground floor flat in Lewisham with its own garden can extend its kitchen.

Boundary height, roof lights and the look from next door

Where the extension sits on the party boundary, the Lewisham SPD says an extension up to 3m long should generally be no more than 3m high on that line. That limit steers the roof design: a flat roof with a parapet, or a mono pitch that rises away from the neighbour, keeps the wall on the boundary low while the ceiling inside climbs toward the house. Your designer sets the falls and the parapet detail at this stage, and we build to those drawings.

Roof glazing is how a deep kitchen gets daylight, and the SPD is specific where it meets the old house: rooflights should ideally be flush and never project more than 150mm above the original roof slope. That rule bites where a scheme adds rooflights to the pitched roof of the retained back addition or the main house. Glazing in the new flat roof is judged as part of the extension design instead. We order glazing only once the planning drawings are fixed, since lead times run to weeks.

Public sewers behind Lewisham terraces and the build over agreement

Before any digging in Lewisham, find out where the public sewer runs. Lewisham's building control guidance says you must apply for a build over agreement before doing any works if your home is within 3 metres of a public drain or 1 metre of a public lateral drain. On a terrace a drain shared by several houses often crosses the back yards, and a shared run of that kind is usually a public sewer. The agreement comes from the sewerage company rather than building control, and a CCTV survey of the run settles where it goes early.

Where Lewisham is the building control body, it also uses a full plans application for any new proposal to build above or within 3 metres of a drain or sewer. That rules out the quicker building notice route, where work can start within 48 hours. That changes the paperwork order: drawings go to building control with the drainage detail resolved, and it pays to have the decision back before the ground is opened. A registered building control approver is the other route. In practice the foundation may need to bridge the pipe with a lintel or go deeper beside it, and that choice is made on paper first.

Steel, inspections and fitting the kitchen in one Lewisham programme

Opening the back of a Lewisham house into a new kitchen means a steel beam across the old rear wall, sized by the structural engineer we appoint and set on padstones. Lewisham Building Control's typical inspection stages include commencement, excavation, foundations, damp proof course, drains inspection and testing, insulation and completion. Where Lewisham is the building control body, we book each visit as the stage is reached, so concrete is not poured and insulation is not boarded over before the inspector has seen it.

Running the kitchen fit out in the same programme saves a second round of disruption. First fix plumbing and electrics go in while the walls are open, the floor screed is laid with any underfloor heating, and the units are templated once the plaster is dry. A registered electrician certifies the new circuits. The Lewisham completion inspection then covers the finished room rather than a shell. Snagging is walked with you before the final visit.

• New kitchen circuits, with Part P certification from a registered electrician
• Rear, side return and wraparound kitchen extensions
• Utility rooms and larders at the back of the extension

VOA Council Tax stock of properties, March 2025, for all 37 statistical areas in Lewisham. Counts rounded by the VOA.

Related reading for Lewisham homeowners planning kitchen extensions: kitchen renovation in Lewisham, our Lewisham area guide, a wraparound kitchen-diner, the Party Wall Act on a boundary build, our London kitchen extensions page and Side Return or Rear Extension.

Trusted Kitchen Extensions in Lewisham

We take a Lewisham kitchen extension from the approved drawings to a working kitchen with one team and one programme. The founder, Abdelaaziz Saaid, brings more than three decades on site, and he visits before pricing to check the rear wall, the yard and the drainage route. You get a written quotation after that visit and a written programme showing when each inspection falls. Your designer handles the planning drawings and the structural engineer we appoint handles the steel; we build to both and keep the site tidy for the neighbours.

• Honest updates if a date or a detail has to move
• Drains surveyed by camera before the footprint is fixed
• Old kitchen kept in use until the new shell is weathertight

Reviewed jobs near Lewisham

1 MyBuilder review from Crofton Park, with each customer's own job title:

• Replace small section of wooden worktop, sink, tap and gas hob, Crofton Park, 17 Apr 2024 (5 out of 5)

Read all 31 on our reviews page.

Checked by Abdelaaziz Saaid, founder and director of GS Renovation Ltd (Companies House no. 14611254). Structural design is by the consulting engineer appointed to your project.