House Extensions Bloomsbury
Single storey rear and double storey extensions in Bloomsbury, 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
Extending a home in Bloomsbury means working within one of London's most protected settings, where Georgian and Regency townhouses in WC1 sit inside Camden's conservation areas. GS Renovation builds extensions across North London, backed by its founder's 30+ years on the tools, handling foundations, steelwork, roofs and fit-out while navigating the planning and party wall demands these period properties bring.
In Bloomsbury, 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 Bloomsbury: 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 Bloomsbury
Bloomsbury range: choose above
Rear and side-return extensions in Bloomsbury
The most common extension in Bloomsbury opens up the rear of a townhouse at lower-ground or garden level, sometimes infilling a narrow side return to widen a cramped kitchen. The garden squares are communal, so the plot behind a terrace house is usually small and enclosed by neighbours on three sides. We dig and lay foundations to suit the ground and neighbouring structures, install the steel beams the opening needs, and tie the new roof and walls into the existing period fabric.
Because so much of WC1 is listed or within a conservation area, an extension here is far more likely to need a full planning application to Camden Council than to fall under permitted development, and a listed property will need listed building consent as well. We advise honestly on which route applies before you commit. Where neighbours are affected you, as building owner, serve the party wall notices, or your surveyor does, since excavation near a shared wall almost always triggers the Act; we give you the drawings and programme they need.
Housing in Bloomsbury
Of the 14,890 homes the valuation list records in Bloomsbury, 49% were built before 1919, 13% between the wars and 37% since 1945; 97% are flats and 3% are houses. Where most homes are flats, a flat in Bloomsbury has no householder permitted development rights, so extending one needs planning permission and the freeholder's consent.
Extending a Bloomsbury house under the conservation area appraisal
With 3% of Bloomsbury homes being terraced houses, a rear extension here is a job for a small number of owners, each on a plot hemmed in by neighbours. The Bloomsbury Conservation Area appraisal and management strategy, adopted in April 2011, is used to assess planning applications in the area, and a planning application for alterations in a Camden conservation area must include a heritage statement. For an extension that statement should explain what the rear elevation contributes, what the new work would cover and how the materials relate to the original brick.
Pre-planning application advice is where the design gets tested before it is expensive to change. Camden's Level 2 homeowner advice covers multiple or more complex works, such as more than one extension or two storey rear extensions, so a scheme of that kind belongs there rather than at Level 1. Bring the heritage statement in draft, a measured survey and photographs of the neighbouring rear elevations. What comes back at that stage should shape the drawings before the structural engineer we appoint sizes any steel or foundations.
Adding space to Bloomsbury period homes
Where the ground floor cannot grow, some Bloomsbury owners look at the roof instead. In a conservation area the roof line matters enormously, so a dormer, mansard or extra storey is a design and planning question for your architect and Camden's planners before it is a building one. Our part is the ground-floor and rear work and the structural alterations inside the house, with the building regulations detail that goes with them: floors, steel, insulation, escape and fire separation.
For owners of leasehold flats in Bloomsbury's mansion blocks, structural extension is usually limited, but reconfiguring space and improving the layout is often possible with the freeholder's licence to alter and the managing agent's agreement. Whichever type of property you own, we manage the whole extension as one project, from coordinating the drawings and applications with your architect through groundworks, superstructure and roofing to a complete internal fit-out, so you deal with a single team throughout.
Kitchen extensions in Bloomsbury
97% of homes in Bloomsbury are flats, and a flat has no householder permitted development, so a ground-floor flat's kitchen extension needs planning permission from Camden Council and the freeholder's consent. With so few houses here, the realistic kitchen gain in most Bloomsbury homes is a better layout inside the flat rather than an extension. The fit-out is priced on its own page, kitchen renovation in Bloomsbury; the build figures are in the table above. Double storey extensions belong to the few houses here.
- Drainage diversion and build-over agreements with the water authority
- Flat and pitched roofs with rooflights or lanterns
- Single and double storey extensions
VOA Council Tax stock of properties, March 2025, for Fitzrovia East & Bloomsbury West, Holborn, St Giles & Bloomsbury South and King's Cross & Bloomsbury North. Counts rounded by the VOA.
Why Choose GS Renovation in Bloomsbury
Homeowners across WC1 choose GS Renovation because extending a Bloomsbury period home demands both building skill and a steady hand with Camden's planners and party wall matters. With our founder's 30+ years on the tools, we join foundations, steel, roof and fit-out into one accountable project, keep the work tidy in an occupied home, and deliver space that respects the building's character.
- Materials priced at options, so you choose the finish
- Permitted development checked before you pay for a planning application
- Building control inspected at foundation, damp course and steel stages
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 Bloomsbury
Which parts of a house extensions project in Bloomsbury cost the most?
Which part of a house extensions project in Bloomsbury costs most depends on the house, which is why the survey comes first. In older stock reinstatement often outweighs the structural element; a newer WC1 property is the other way round. GS Renovation prices the two separately within £2,000 to £2,800 per m² for a rear extension (indicative), so phasing is possible, provided the order holds: drainage under the footprint is diverted before foundations are poured.
Will my Bloomsbury extension need planning permission or is it permitted development?
In much of Bloomsbury the answer leans towards planning permission, because the area's conservation status and the number of listed buildings restrict permitted development rights that apply elsewhere. A listed home also needs listed building consent. We assess your specific property against Camden's rules early, so you know the likely route before spending on detailed design, and we coordinate with your architect or designer on the application either way.
Can I extend my flat in Bloomsbury?
Rarely, and never under permitted development, which covers houses only. Flats are 97% of Bloomsbury's dwellings, so most extension questions here are really about adding space inside. Any extension to a flat needs full planning permission from Camden Council, the freeholder's written consent, and building regulations approval. Other flats in the building will usually have a say too.
Is a mansard or roof extension possible on a Bloomsbury building?
Sometimes, though the roofline is closely guarded. In a conservation area any dormer or mansard is designed to sit with the rest of the street, and a listed building adds consent on top of planning. Structurally, the walls below must carry the new storey, so the engineer checks them first, and an extra floor changes the fire escape arrangements for every flat beneath it.
What extra consent does an extension to a listed Bloomsbury house need?
Listed building consent, alongside planning permission from Camden Council. A listed WC1 townhouse is judged on how the addition affects its historic fabric and setting, so designs are often lightweight and clearly later than the house. Building regulations apply whatever the planning route, including Part L insulation for the new walls, floor and roof, with inspections before anything is covered.
Will digging foundations for a Bloomsbury extension involve the neighbours?
In a terrace, almost always. The Party Wall Act gives adjoining owners a month's warning where trenches within 3 metres of their house go deeper than its footings, and building a wall astride the boundary brings in the Act too. Georgian houses can sit on shallow brick footings, so the engineer designs the new foundation around them, and building control sees the trenches before concrete.
Does a Bloomsbury rear extension trigger Camden's Community Infrastructure Levy?
Only if the scheme adds 100 square metres of new floorspace or an extra dwelling, which is when Camden's levy applies. Camden adopted its current charging schedule on 30 October 2020. Measure the new floorspace of the whole scheme against that threshold before planning is submitted, not room by room, because a rear addition combined with other new space in the same application is judged as one proposal.
Can a tree in a Bloomsbury garden hold up an extension programme?
Yes. In a conservation area Camden requires six weeks' notice before work to any tree with a trunk diameter of more than 75mm at a height of 1.5 metres. A tree near the line of the new foundations, including one next door whose roots or crown need cutting back, falls under that rule. Give the notice as soon as the footprint is fixed, so the six weeks run while the drawings are finished rather than after.
Does the floor area of a Bloomsbury extension change Camden's building control charge?
Yes. Camden's Schedule 2 residential charges are set in bands, and one band covers an extension of a dwelling, including basements, exceeding 10m2 but not exceeding 60m2. Check the final internal area against the band edges before the drawings are frozen, because a small change in depth can move a scheme across one. The schedule gives the total for a building notice, so ask which figure applies to the route you are using.
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