House Extensions Old Street
Single storey rear and double storey extensions in Old Street, 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
Extension work in Old Street looks different from the terraced-street norm. Around Old Street 99% of homes are flats, in post-war blocks, new-build towers and converted warehouses, and GS Renovation also works on the occasional period house that survives on the older EC1 streets. We handle foundations, steelwork, roofing and fit-out, and we are honest about what Islington Council will and will not allow on a given building.
In Old Street, 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 Old Street: 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 Old Street
Old Street range: choose above
Extending houses near Old Street
Where a genuine house survives on the older streets around Old Street, a rear or side-return extension can turn a cramped ground floor into an open-plan kitchen-diner. We dig and pour foundations sized to the ground conditions, install the steel beams that carry the existing rear wall, and tie the new roof into the old. Every opening is designed by a structural engineer and inspected under building regulations.
Whether the work is permitted development or needs a full planning application depends entirely on the property. A modest single-storey rear extension may fall under permitted development, but a flat above, previous additions or an Article 4 direction can remove those rights, and conservation area status restricts them, requiring permission from Islington Council. We check your title and location first, then advise on the right application, made on your designer's drawings, rather than guessing and risking enforcement.
Housing in Old Street
By the valuation list's count, Old Street holds about 6,800 homes, 1% houses and 99% flats; by age, 16% were built before 1919, 5% between the wars and 76% since 1945. Where most homes are flats, a flat in Old Street has no householder permitted development rights, so extending one needs planning permission and the freeholder's consent.
Extending a home in Old Street usually means extending a flat
With 99% of Old Street homes being flats, an extension here is nearly always an extension to a flat: enclosing part of a terrace, building out at ground level into a yard, or adding a room onto a flat roof. Islington Council says you need to apply for full planning permission to add an extension or conservatory to a flat. There is no permitted development route to try first. The freeholder's consent is needed as well, because the external walls and the ground or roof being built on are often not part of the flat itself.
For the 1% of Old Street homes that are houses, the rules are those for houses, and the St Luke's conservation area straddles Whitecross Street and Old Street. In any conservation area a side extension, a rear extension of more than one storey, a roof extension or external cladding needs planning permission. A single-storey rear extension within the size limits can still be permitted development, unless an Article 4 direction removes it. Islington has issued article 4 directions in 40 of its 42 conservation areas to prevent some minor alterations, which can bring the new windows and doors into planning.
Extending apartments around Old Street
Most Old Street homes are flats, and extending a flat is a different discipline. Outward expansion is usually impossible, so we focus on what leasehold allows: enclosing a balcony, reconfiguring internal volume, or adding a mezzanine where a converted warehouse offers the ceiling height. Each option depends on the lease, the freeholder's licence to alter and the structural capacity of the existing floor, which the engineer we appoint confirms.
Any external change to a new-build or conversion in EC1 typically needs both the freeholder's consent and, where it alters the building's appearance, planning permission from Islington Council. We coordinate with the managing agent on access, working hours and protection of common parts, and we keep neighbouring leaseholders informed. The building regulations side, from structure to insulation and fire separation, is inspected and signed off by building control as part of the job.
Kitchen extensions in Old Street
99% of homes in Old Street are flats, and a flat has no householder permitted development, so a ground-floor flat's kitchen extension needs planning permission from Islington Council and the freeholder's consent. With so few houses here, the realistic kitchen gain in most Old Street homes is a better layout inside the flat rather than an extension. The fit-out is priced on its own page, kitchen renovation in Old Street; the build figures are in the table above. Double storey extensions belong to the few houses here.
- Planning applications and permitted development assessments
- Foundations, groundworks and steel frames
- Trial holes to set foundation depth near drains and trees
VOA Council Tax stock of properties, March 2025, for Old Street & St Luke's. Counts rounded by the VOA.
Why Old Street Homeowners Choose GS Renovation
An Old Street extension is as much a permissions puzzle as a building one. GS Renovation reads the lease, the planning position and the structure together, then delivers foundations, steel, roof and fit-out with one accountable team. Our founder's 30+ years on the tools mean fewer surprises, cleaner approvals and a finish that suits these conversions and new-builds.
- Fully insured, with cover in place on every site
- Insulation and thermal detailing to current regulations
- Permitted development checked before you pay for a planning application
Built a new extension at rear of property. Laid foundations, drainage, raised floor, new roof and completed all fixtures and interior decoration…
George always kept to commitments and arrived on time. He offered helpful suggestions during his initial visit and promptly provided a reasonably…
Saaid is the best craftsman I have worked with. He knows what he is doing from the very beginning. He has a great knowledge of construction…
FAQ
Frequently Asked Questions about House Extensions Old Street
Can I get a fixed price for house extensions at an EC1 address?
Fixed pricing is the default for house extensions in Old Street, not the exception. What prevents it is real uncertainty about the structure at the EC1 address, and then GS Renovation prices the investigation first and the job afterwards, within £2,000 to £2,800 per m² for a rear extension (indicative). Once it is done, the build follows its set sequence: drainage under the footprint is diverted before foundations are poured.
Can I extend my flat in an Old Street block or conversion?
Sometimes, but the options differ from a house. Outward extension is rarely possible, so we look at enclosing balconies, reconfiguring space or adding a mezzanine where ceiling height allows. Any change needs the freeholder's licence to alter, and external alterations may need planning permission from Islington Council. We check the lease and structure first, then advise honestly on what is achievable.
Does permitted development let me extend my Old Street flat?
No. Permitted development rights for extensions belong to houses, never to flats or maisonettes, so any outward addition to a flat needs a planning application to Islington Council. With the VOA recording 99% of local homes as flats, most owners here start from that position. The lease normally requires the freeholder's consent as well, and building regulations apply whatever the planning route.
I own one of the few houses near Old Street: how far can I extend without planning?
An attached house can usually add a single-storey rear extension up to 3 m deep under permitted development, and more under the prior approval route. Conservation area status removes side extension rights. Houses are only a tiny share of homes here, so check that previous alterations have not already used those rights. Building regulations approval is needed either way.
What notices apply when digging foundations near neighbouring Old Street buildings?
On tight EC1 plots the answer usually involves the Party Wall Act. A trench within 3 metres of the building next door that reaches lower than its footings triggers a month's written notice. Next door may agree in writing; if they object, surveyors are appointed and their award governs the dig. Serving it while the drawings are still being finished stops the notice delaying the start.
What does building control check on an extension to an Old Street house?
Every stage that will later be hidden. Foundations are inspected before concrete, drainage before it is covered, and structural steel before boxing. Insulation must meet current Part L standards, so walls, floor and roof are seen as they go in. Where the extension crosses or sits near a public sewer, the water company's consent is needed first, which can change the footprint.
Which Islington building control fee band applies to a modest Old Street extension?
Islington's Table 1 domestic charges have a band for an extension up to 40 sq m, so the fee follows the floor area on the drawings. A flat with common areas cannot use a building notice, so an extension to such a flat goes through full plans, where the same total is split into a plan charge and an inspection charge. We measure the area from the drawings before the application goes in, so the correct band is paid first time.
Does a tree near an Old Street extension need Islington's agreement before it is cut back?
In a conservation area, you have to tell the council first. In an Islington conservation area you must give the Council six weeks notice in writing before any work is carried out to prune or fell a tree. If roots or branches are in the way of foundations or scaffold, that notice sits on the critical path. We check the trees around the footprint on the first visit and build the six weeks into the start date.
When should an Old Street owner book Islington pre-application advice for an extension?
Before the full drawings, once there is a sketch worth discussing. Islington offers householder pre-application written advice with a site visit, and follow-up advice later. An officer on site sees the neighbours' windows and how the extension sits in the conservation area. Islington's planning pre-application fees increased on 2 January 2025, so we check the current charge when the booking is made.
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