London Flat Bathroom Renovation: Complete Planning Checklist

Complete Bathroom Renovation Checklist for London Flats

Renovating a bathroom in a London flat involves more parties and more approvals than renovating a house. Leasehold obligations, freeholder consent requirements, and shared building infrastructure all add complexity that can catch flat owners off guard. This checklist covers every stage from initial planning to final snagging.

Stage 1: Consents and Approvals

Leasehold and Freeholder Requirements

• Read your lease in full. Most London flat leases require freeholder consent for any alterations to the flat, particularly those affecting pipework, drainage, or the fabric of the building.
• Identify whether the bathroom wet wall, soil stack, or drainage pipes are communal infrastructure. If they are, any work affecting them requires formal freeholder approval and possibly a Licence to Alter.
• Submit a formal application to the freeholder or managing agent describing the scope of work before any work begins. Keep copies of all correspondence.
• Check whether your lease requires you to use approved contractors. Some London leasehold properties require freeholder-approved tradespeople for plumbing and drainage work.
• Confirm whether a Party Wall Agreement is needed if structural work is planned near a shared wall.

Building Regulations

• Determine whether your project requires Building Regulations notification. Major changes to drainage, electrical installations, or structural elements all require notification.
• Appoint a local authority building inspector or approved inspector if required.
• Ensure any electrical work is carried out by a Part P registered electrician who can self-certify their work.

Stage 2: Design and Specification

Layout and Measurements

• Measure the bathroom accurately, including ceiling height, window positions, and door swing arc.
• Identify the location of the soil stack and waste pipe connections. These are fixed points that constrain WC and basin placement.
• Confirm hot and cold water supply routes and whether pressure is adequate for your chosen shower type.
• Check ceiling height for any over-bath shower screens or wetroom installations.

Fixture Selection

• Select sanitary ware: WC, basin, bath or shower tray, and shower enclosure or wetroom.
• Confirm that selected fixtures comply with Part G water efficiency requirements (WC maximum 6 litres per flush, basin taps maximum 6 litres per minute).
• Select shower valve type: thermostatic is strongly recommended for safety, particularly in flats where incoming water pressure may fluctuate.
• Choose taps and waste fittings and confirm compatibility with your water pressure system.
• Select tiles, flooring, and any heated floor system.
• Specify heated towel rail and confirm electrical or plumbing connection type.

Ventilation

• Confirm whether the bathroom has an openable window. If not, mechanical extract ventilation is mandatory under Part F.
• Select an extract fan rated at a minimum of 15 litres per second for a bathroom with a shower or bath.
• Plan the duct route. In a flat, the duct cannot discharge into a communal void and must terminate at an external wall or through the roof with freeholder approval.

Stage 3: Pre-Works Preparation

• Isolate the water supply to the bathroom. Locate the isolation valves on the hot and cold supplies and test that they operate.
• Protect flooring outside the bathroom from damage during deliveries and works.
• Arrange temporary access to another bathroom or shower facility for the duration of works.
• Confirm delivery dates for all fixtures, tiles, and equipment before the start date to avoid delays mid-project.
• Check that the flat has adequate access for bulky items such as a bath or wetroom former.

Stage 4: First Fix (Behind the Walls)

• Carry out any structural work: strengthening floors for a heavy bath, fitting additional noggins for wall-hung sanitary ware.
• Complete demolition: remove old fixtures, tiles, and floor coverings. Check the condition of the substrate before proceeding.
• Rough-in plumbing: run hot and cold supplies to new positions, fit new waste pipes with correct falls, connect to soil stack.
• Rough-in electrical: run circuits for fan, underfloor heating, shaver socket, and any wall lighting.
• Install underfloor heating elements if specified, following manufacturer guidelines for heating mat or pipe spacing.
• Apply waterproof membrane (tanking) to all wet areas: shower floor, shower walls to at least 1800mm, around bath rim.

Stage 5: Tiling and Flooring

• Prepare substrate: check for flatness, fix any movement, apply primer as specified by tile adhesive manufacturer.
• Install floor tiles before wall tiles to allow wall tiles to sit cleanly above the floor.
• Use flexible tile adhesive in wet areas. Confirm adhesive and grout are rated for continuous wet immersion in the shower zone.
• Leave expansion joints at all internal corners and at the junction between wall and floor tiles. Fill with silicone, not grout.
• Allow adhesive and grout to cure fully before exposing to water (minimum 24 hours for adhesive, 24 hours for grout).

Stage 6: Second Fix Plumbing and Electrical

• Connect WC, basin, bath, and shower tray waste connections.
• Install shower valve, hand set, and overhead rose.
• Connect hot and cold supplies to basin taps, bath taps, and shower valve.
• Install heated towel rail and connect to supply.
• Fit extract fan and connect to switched live circuit with overrun timer.
• Complete electrical second fix: fit switches, shaver socket, and any recessed lighting using IP-rated fittings appropriate to the bathroom zone.

Stage 7: Final Commissioning and Snagging

• Turn on water supply slowly and check all joints and connections for leaks with the system pressurised.
• Test WC flush and basin waste operation.
• Test shower at minimum and maximum temperature settings to confirm thermostatic valve operates correctly.
• Test extract fan operation and confirm it runs on timer overrun after the switch is turned off.
• Test underfloor heating if installed.
• Inspect all silicone lines: they should be clean, continuous, and free from voids. Re-do any that have gaps.
• Check all tile grout lines for consistency and missing grout. Touch up as needed.
• Clean all surfaces, remove tile adhesive residue, and fit mirror and accessories.
• Obtain completion certificate from building inspector if applicable.
• Provide the managing agent or freeholder with evidence of completion and compliance if required by your Licence to Alter.