London Flat Bathroom Renovation: Planning Guide for 2025

Bathroom Renovation in a London Flat: A Complete Planning Guide

Bathroom renovations are one of the most requested works in London flats. Done well, they add value and transform daily life. Done poorly, they cause disputes with freeholders, building regs non-compliance, and water ingress into the flat below. Here is how to plan the project correctly.

Do You Need Planning Permission?

In the vast majority of cases, bathroom renovation inside a flat does not require planning permission. It falls within permitted development as internal alteration. However, planning permission may be required if:

• The property is a listed building (any internal works require listed building consent)
• The renovation involves moving or creating a window or external opening
• The flat is in a conservation area and the works affect the external appearance

Always check with your local London borough planning department if the property is listed or in a conservation area. Camden, Islington, Kensington and Chelsea, and Westminster all have large conservation area footprints covering significant proportions of their housing stock.

Building Regulations

Building regulations do apply to bathroom works in certain circumstances:

• Electrics — any new electrical work in a bathroom is notifiable under Part P. This includes adding a new socket, fitting a heated towel rail with a fused spur, or installing an extractor fan wired to the lighting circuit. Work must be carried out by a Part P registered electrician or notified to building control.
• Structural changes — removing or altering a load-bearing wall to reconfigure a bathroom requires a structural engineer's calculation and building control approval.
• Drainage alterations — relocating a toilet or changing the position of a soil stack requires building regs compliance under Part H (drainage) and Part M (access).
• Ventilation — a bathroom without an openable window requires mechanical ventilation extracting at 15 litres per second minimum (30 l/s for a shower room), connected to or triggered by the light switch and with a 15-minute overrun.

Leasehold Consent

Before any bathroom renovation in a leasehold London flat, read your lease. Most long residential leases require the freeholder's written consent before carrying out alterations. The freeholder may charge a licence fee (typically £500–£1,500 in London) and may impose conditions including use of approved contractors and method of floor waterproofing. Doing works without consent is a breach of the lease and can complicate remortgage and sale.

Wet Room vs Shower Enclosure

The choice between a wet room (fully tiled, tanked, no enclosure) and a shower enclosure has practical implications in a flat:

• Wet rooms require a tanked waterproofing membrane applied to the floor and walls before tiling. In a timber-joisted floor, the subfloor must be assessed for deflection — excessive movement will crack grout and eventually the waterproofing. Wet rooms add approximately £300–£600 to the waterproofing cost but eliminate the need for an enclosure (saving £200–£800).
• Shower enclosures are simpler, less prone to waterproofing failure if poorly installed, and easier to retrofit without structural assessment. They are the lower-risk choice in period London flats with suspended timber floors.

Realistic Costs in London (2025)

• Basic refurbishment (replace suite, retile, new flooring): £4,000–£7,000
• Mid-range renovation (reconfigure layout, wet room conversion, underfloor heating): £8,000–£15,000
• High specification (bespoke vanity units, heated floors, designer fixtures, full replumb): £15,000–£30,000+

Typical Timeline

A standard bathroom renovation in a London flat takes 7–14 working days once materials are on site. Allow four to eight weeks lead time for bespoke tiles, sanitary ware, and vanity units. Add two to four weeks for leasehold consent if required. A realistic project planning window from decision to completion is eight to twelve weeks.