Bathroom
renovation
in Swiss Cottage, NW3
Designers, Architects, Engineers & Builders Under One Roof.
One Studio. One Contract. One Team.
Most Swiss Cottage bathrooms sit in tall houses or shared blocks, so the run of the waste pipe and the extract decides the layout before the tiles do.
Putting in a new Swiss Cottage bathroom that brings fresh plumbing, or rewiring close to the bath or shower, may need building regulations approval, according to GOV.UK.
Many houses here are tall: on Fitzjohn's Avenue they are mostly four or five storeys, and Netherhall Gardens reaches five and six.
So our first job is to lift a few floorboards and trace the soil stack, because in a house of that height the stack decides where a WC can sit.
Sources: GOV.UK: Building regulations approval, Camden: Fitzjohns/Netherhall Conservation Area Character Appraisal and Management Plan (December 2022)
What needs building control
Swapping an existing bath, WC, basin or sink for a new one is among GOV.UK's exempt works, but new circuits round a bath or shower are not.
Under the Water Fittings Regulations, a bath taking more than 230 litres to the middle of its overflow cannot go in until the water supplier has been told and has agreed.
Our quotations list which items will be notified, so the certificates arrive as expected instead of being chased after handover.
Sources: GOV.UK: when you don't need building regulations approval, The Water Supply (Water Fittings) Regulations 1999, regulation 5
Extract fans and windowless rooms
When a bathroom is refitted, Approved Document F says any fan already there stays or is replaced, and is tested to confirm it works.
A room that never had ventilation need not gain any, unless the new work would leave the building further from the ventilation rules than it was.
For an inner bathroom with no window we fix the duct route, to an outside wall or an approved riser, before the ceiling goes up.
Source: Approved Document F, Volume 1: Dwellings (2021 edition)
Soil pipes, vents and the front wall
In South Hampstead, the design guide published under the Swiss Cottage name sends soil and vent pipes to side or back walls, and a fresh one on the front needs permission and will be resisted.
Camden's Home Improvements guidance asks across the borough for new pipework on side and rear walls, grouped neatly, and in conservation areas makes a pipe on a highway-facing wall a planning matter.
Camden's factsheet for that conservation area asks that any new service be invisible from the street.
Along Eton Avenue, Belsize's statement also brings external ducts and air handling units under planning control.
Sources: Camden: Swiss Cottage Conservation Area Design Guide (updated June 2026), Camden Council: Home Improvements, Camden Planning Guidance (January 2021), Camden: Swiss Cottage Conservation Area, what the new planning measures mean for you (Article 4(1) factsheet, 1 September 2010, updated June 2026), Camden: Belsize Conservation Area Statement (agreed 20 November 2002), Camden: Belsize Conservation Area Statement (agreed 20 November 2002)
Bathrooms in leasehold flats
LEASE points out that a 'no cutting of external walls' clause would block a new hole in the wall, even one for a pipe.
Where the landlord owns the floor, running underfloor heating through someone else's flat needs the landlord's permission.
Leaseholders carrying out works have to keep noise reasonable and leave shared stairs and corridors clean and passable.
Whatever a lease says, it is unlawful for a landlord to demand a premium for agreeing to non-structural alterations that need consent.
In a mansion block we agree the hours for noisy stripping-out with the managing agent, and send neighbours a note naming the days the water will be off.
Source: LEASE: Alterations and home improvements
Windows, glass and the bathroom wall
Stained, etched or leaded glass ought always to be retained and mended with a specialist's advice, Camden's guide says, and some bathroom windows still have it.
Adding secondary glazing for warmth requires no permission; its meeting rails should sit in line with the old window's glazing bars.
For a flat on the South Hampstead side, a replacement bathroom window in a new material or pattern is a planning matter wherever it is.
Sources: Camden: Swiss Cottage Conservation Area Design Guide (updated June 2026), Camden: Swiss Cottage Conservation Area, what the new planning measures mean for you (Article 4(1) factsheet, 1 September 2010, updated June 2026)
A bathroom that stays watertight
Before a tile goes down, the floor is tanked and the shower tray or former is set to its fall, so a slow leak can never find the ceiling beneath.
Removable panels for traps and valves are drawn into the design rather than cut later, and the isolating valves are placed where the next plumber will find them.
If the house has only one bathroom, a working WC is kept in service every night until the job is finished.
Fitting a bathroom into an older house
In the Elsworthy area, the appraisal notes that many houses divided into flats in and after the war have since become single houses again.
When a house that was once flats is put back together, we look at which of its old bathrooms sit over each other and keep those, since stacked rooms share one waste run.
An en-suite carved from a large bedroom is planned around the chimney breast and the window, so the room left behind is still well proportioned.
Under a sloping roof, the bath or shower goes where the ceiling is highest and the basin and WC take the lower side.
Source: Camden: Elsworthy Road Conservation Area Appraisal and Management Strategy (adopted 14 July 2009)
Questions about Swiss Cottage bathrooms
Will building control need to see my Swiss Cottage bathroom?
Possibly, if new plumbing or new electrics near the bath or shower are involved; straight swaps are exempt.
Could the soil stack go down the street side of my house?
Not without permission in a conservation area, and in South Hampstead Camden will resist it.
What ventilation does a windowless bathroom in NW3 need?
Keep or replace any fan that was there; if there was none, add ventilation only where the work would otherwise reduce compliance.
Can the freeholder charge me for agreeing to my new bathroom?
Not a premium for non-structural alterations, according to LEASE.
Are there rules for a very large bath?
Above 230 litres the water supplier has to be told and must agree before it goes in.
What does a bathroom renovation in Swiss Cottage cost?
The run of the waste pipe and the extract decides the layout in most Swiss Cottage bathrooms, whether in a tall house or a shared block, and those two routes account for much of the cost. How far the pipes travel, what the floor will take and how materials reach an upper storey all count, and in a block so do the lease and the managing agent. We visit first, then agree the scope and specification with you before giving a written quotation.
Sources: GOV.UK: Building regulations approval, GOV.UK: when you don't need building regulations approval, Camden Council: Home Improvements, Camden Planning Guidance (January 2021), Camden: Swiss Cottage Conservation Area Design Guide (updated June 2026), Approved Document F, Volume 1: Dwellings (2021 edition), LEASE: Alterations and home improvements, The Water Supply (Water Fittings) Regulations 1999, regulation 5
Related pages
Sources
- GOV.UK: Building regulations approval
- Camden: Fitzjohns/Netherhall Conservation Area Character Appraisal and Management Plan (December 2022)
- GOV.UK: when you don't need building regulations approval
- The Water Supply (Water Fittings) Regulations 1999, regulation 5
- Approved Document F, Volume 1: Dwellings (2021 edition)
- Camden: Swiss Cottage Conservation Area Design Guide (updated June 2026)
- Camden Council: Home Improvements, Camden Planning Guidance (January 2021)
- Camden: Swiss Cottage Conservation Area, what the new planning measures mean for you (Article 4(1) factsheet, 1 September 2010, updated June 2026)
- Camden: Belsize Conservation Area Statement (agreed 20 November 2002)
- Camden: Belsize Conservation Area Statement (agreed 20 November 2002)
- LEASE: Alterations and home improvements
- Camden: Elsworthy Road Conservation Area Appraisal and Management Strategy (adopted 14 July 2009)
Guides & Local Reading
More Services in Swiss Cottage
Book a feasibility visit
Visit our studio or invite us to survey your home. We’ll assess scope, discuss design possibilities and provide an honest budget framework.
Consultation
We survey your property, discuss your vision and provide a clear budget framework.