Kitchen Extensions Harrow

52% of homes in Harrow date from 1919 to 1939 and 39% are semi-detached or detached, so a kitchen extension here is often added to an interwar semi or detached house. On those plots the choice is a full-width rear addition or a wraparound. Where it needs planning permission, the Residential Design Guide limits its height on the boundary and, through the two for one rule, how far it can go deeper. We set out the footings, drainage, steel and roof, then fit the kitchen in the same programme so one team hands over a finished room.

In Harrow, 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 Harrow: 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 rear kitchen extension can go on a Harrow semi

On a Harrow semi that needs a planning application, the Residential Design Guide sets the depth before the brief does. The guide caps a flat-roofed single storey rear extension abutting a neighbour at a 3 metre height on the boundary, or 3.5 metres at the mid-point of a pitched roof. Under its two for one rule, any extra rear depth must be set in from the side boundaries by twice the extra depth you want, so the deeper part of the kitchen is narrower than the part nearest the house.

That trade decides the layout before the kitchen designer starts. If you want a long island and a wide opening to the garden, the set-in may pull the deeper part of the addition off the party side and leave a strip of the old patio against the neighbour. We check the footprint against both rules at the survey, then agree where the sink, hob and doors sit so the drainage and the steel land where the plan needs them.

Housing in Harrow

On the valuation list Harrow counts about 96,870 homes, 38% flats and 62% houses; 10% predate 1919, 52% are interwar and 38% post-war. 31% of homes here are semi-detached; a semi in Harrow can take its kitchen extension across the back and round into the side passage, which leaves room for a utility behind the kitchen.

Prior approval for a deeper extension in Harrow

A larger single storey rear extension on a Harrow house can go through prior approval instead of a householder planning application, but not on Article 2(3) land such as a conservation area. Harrow's prior approval page says the limit rises from 3 metres to 6 metres for terraced or semi-detached houses and to 8 metres for detached houses. The process includes consulting the immediate neighbours and can last 42 days, and under permitted development a single storey rear extension cannot exceed four metres in height.

For the programme this means the neighbour consultation sits in front of the start date, so order of work is fixed only once the council has responded. Prior approval covers the planning side alone. The structure, drainage and glazing still go to building control, and the structural engineer we appoint sizes the steel over the new opening in the rear wall. We book the groundworks once both answers are in, so the dig does not stall halfway.

Roof lights and glazing in Pinner conservation areas

If your house is in one of the Pinner conservation areas with a roof direction, rooflights need planning permission. An Article 4 direction for all houses in West Towers Conservation Area requires planning permission for any other alteration to the roof, including rooflights. In the Pinnerwood Park Estate Conservation Area core area, Article 4 directions bring dormer windows, rooflights and gabling existing hipped roofs under planning control too. Show every rooflight, on the extension and on the main roof, on the drawings that go to planning before the structural drawings are finished.

Glazing near a boundary has its own limit across the borough when an application is assessed. Harrow's design guide says large windows in the wall of a side extension within 3m of a boundary are unacceptable, and conservatories that close to a boundary would normally need brick flank walls or solid panels. For a wraparound that means the light comes from the roof and the garden end, not the flank. We order glazing only after the approved drawings fix sizes and positions.

Drains, inspections and sign-off for a Harrow kitchen extension

Drainage can decide the building control route for a Harrow kitchen extension. Where Harrow is the building control body and the new walls go over or within 3m of a public drain or sewer, Harrow requires a full plans application, not a building notice, so the drawings are checked before the footings are dug. A kitchen on the back of the house often moves the sink and the gully, which is why we trace the runs at the survey. A build-over also needs the sewer owner's agreement.

Where Harrow is the building control body, its surveyors visit site on weekdays between 10 in the morning and 3 in the afternoon. They also offer a same-day inspection, subject to surveyor availability, if you phone before 9:00. We plan the foundation, drainage and pre-plaster stages around that window so the trades are not left idle. At the end the applicant must submit a completion notice under Regulation 16(4a), or the completion certificate is withheld, so we keep the paperwork moving with the snagging.

• Soil stack and gully rerouting beneath the new floor
• The kitchen itself fitted under the same contract as the build
• Rear, side return and wraparound kitchen extensions

VOA Council Tax stock of properties, March 2025, for all 30 statistical areas in Harrow. Counts rounded by the VOA.

Work in Harrow rarely sits on its own, so you may also want kitchen renovation in Harrow, our Harrow area guide, fitting the kitchen itself, how building control inspects an extension, how we handle kitchen extensions across London and Planning a Kitchen Island.

Why Choose GS Renovation in Harrow

A kitchen extension is two projects, a structure and a kitchen, and delays often come from the gap between them. We run both as one programme in Harrow: survey and measured drawings, groundworks and drainage, steel and roof, first fix, plastering, then the kitchen, worktops and decorating. The structural engineer we appoint sizes the steel, a registered electrician certifies the wiring, and you deal with one contact from the first dig to the final clean.

• Kitchen layout agreed before the foundations, so the services land in the right place
• Our own trades on site rather than a chain of subcontractors
• Old kitchen kept in use until the new shell is weathertight

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.