Almost every bathroom project in a Central London flat begins with the same question, usually asked too late: do I actually need permission for this? The answer is in your lease, and it usually turns on a single distinction — whether you are replacing what is there, or altering the flat.
That line is blurrier than it sounds, and it is where people get into trouble.
The distinction that decides everything
Take out a bath and put a new bath in the same place, on the same waste, with the same layout. That is closer to replacement, and many leases would not treat it as an alteration requiring consent — though yours might, so check.
Take out a bath and put in a walk-in shower where the bath was, move the WC to the other wall, and re-run the waste across the room to reach the stack. That is an alteration. Most leases require the freeholder's or managing agent's consent for alterations, particularly where soil and waste pipes are affected, and this proposal affects them squarely.
The trap is that projects migrate. They start as "just a new suite" and end up moving the WC by 400mm because the new vanity does not fit otherwise. The moment the waste changes, you are in different territory. Decide honestly, at the design stage, which project you are doing.
What typically triggers a consent requirement
- Moving the soil or waste connection. The most common trigger, and the most consequential. This is the one to check first.
- Relocating the WC. Almost always a waste question and often a structural one, because a WC needs a short, generously-falling run to the stack.
- Removing or altering walls. Including walls you have been assured are "just a stud".
- Changing the floor build-up. Tiling on a floor that was previously boarded and carpeted adds weight and changes the acoustics — and many leases have covenants about floor coverings.
- Underfloor heating. New wet or electric services within a floor.
- Moving a bathroom into a room that was not one. A different proposition entirely — new drainage, new ventilation, and often a firm no if it would sit over a neighbour's habitable room.
- Anything touching the riser. The stack is usually not yours.
Whether these apply to your flat is a lease question. Leases in the same block can differ. Read yours or ask your solicitor; the managing agent should confirm the position in writing.
Why waste is the whole game
People assume the constraint on a bathroom is space or budget. In a flat, the constraint is gravity.
Waste runs by gravity, at a fall. A WC needs a large-diameter run over a short distance to the stack, and it needs that run to be within the floor void or boxed at low level. In a mansion block with timber floors, the void might be shallow, the joists run the wrong way, and notching or drilling them beyond permitted limits is not an option — that is structure, and structure is not in your demise.
So the geometry decides. Sometimes a layout that looks perfect on a drawing simply cannot be built without either raising the floor, which changes door heights and thresholds, or boxing at a height that ruins the room, or moving the stack, which is not yours to move. Our plumbing page covers the trade side, and our bathroom refurbishment page explains how we work through this — set prices, and bathrooms from £2,800.
This is also why an honest contractor will say no to some layouts. A macerator is sometimes offered as the answer. It has its place, but it is a pump with a lease-relevant failure mode, and freeholders are frequently unenthusiastic about it. Ask before you design around one.
The one below you
Every decision in a flat bathroom is really a decision about the flat below. Your floor is their ceiling. Your waste run passes over their rooms. A leak in your shower tray becomes their problem, quickly and expensively, and then the freeholder's, and then the insurers'.
This is why freeholders' surveyors scrutinise waterproofing, falls, and pipework detailing above everything else, and why the specification matters far more than the tile you have chosen. Tanking properly, forming falls properly, pressure-testing before covering anything up, using accessible isolation — these are the things that keep a bathroom out of the block's incident log. Our tiling work starts from £55/m², but the tiling is the last 10% of the job and the least of its risks.
Making an application that gets answered
Freeholders' surveyors are assessing risk. Give them what they need to assess it and the process gets shorter.
- An existing layout drawing and a proposed layout drawing. Even simple ones.
- Where the waste currently connects and where it will connect, with the fall shown.
- The floor build-up, including any acoustic layer.
- The waterproofing specification.
- Any electrical work proposed, and confirmation it will be certified.
- Ventilation — where the extract goes, and how.
- The contractor, their insurance, working hours, access and waste arrangements.
- Whether anything structural is touched, and if so, the structural design.
Expect to be responsible for the freeholder's reasonable professional and legal costs of dealing with the application; the arrangements vary, so ask at the outset. Expect the consent, if granted, to be a formal document with conditions. Do not rely on a verbal or informal approval — when you sell, a buyer's solicitor will ask for the paperwork, and its absence is a real problem at the worst possible moment.
Our guide to a licence to alter in a mansion block covers the mechanics of that process in more depth.
What consent conditions usually mean for the build
Consent is rarely a blank cheque. Where a licence is granted it commonly carries conditions about how the works are carried out — insurance, hours, protection, notice, and an obligation to complete within a period and to a standard. Some conditions bear directly on the specification: an acoustic layer under a hard floor, a particular waterproofing approach, or a requirement that the works are inspected.
Read those conditions before you accept a builder's programme, and make sure the builder has read them too. A condition requiring that the flat below be protected, or that works stop at a certain hour, is not administrative noise — it is a term you have agreed to, and breaching it while holding the licence is worse than never having applied. Our maintenance and refurbishment work in blocks is run on that basis as a matter of course.
Consents that are not your freeholder's
Consent from the freeholder is not the only permission in play, and it does not substitute for the others.
Bathrooms engage Building Regulations — Part F for ventilation, Part G for sanitation and hot water, and Part P for the electrics — regardless of what your lease says. That is set out in building regulations for bathrooms. If your building is listed, works affecting its special character typically need listed building consent, and internal features can be caught — see listed building consent for bathrooms. If work affects a party structure, the Party Wall etc. Act 1996 may apply — see party wall agreements for flat refurbishment.
How the block itself constrains the job
Beyond the lease, the building has its own rules. In blocks around Marylebone, Mayfair and Fitzrovia, and in the mansion stock of St John's Wood, Maida Vale and Little Venice, expect some combination of: restricted noisy working hours, contractor sign-in with the porter, a booked and protected service lift, no skip, and waste out by bag on a schedule. In the converted terraces of Bayswater and Paddington there may be no lift and no porter at all, which is a different problem — everything up and down a narrow staircase past other people's front doors.
These rules do not change what you can build, but they change the programme and the price, and any contractor who has not asked about them has not started thinking about your job yet.
Sequencing that actually works
Read the lease. Settle the layout, honestly, including the waste. Get drawings. Apply for consent. Get the licence. Then book the work. Then strip out, first fix, test, certify, waterproof, tile, second fix, snag.
Reversing any two of those steps is how a six-week bathroom becomes a six-month argument. The one genuinely irreversible mistake is starting work that needs consent without it — that puts you in breach, and the remedy is at the freeholder's discretion.
How we handle it
We will tell you at the quoting stage where we think consent is likely to be needed, and we will not quietly build something that puts you in breach of your lease. We give a fixed quote before starting, work to the block's rules, and leave the place clean. Bathrooms start from £2,800 — see the bathroom page for what that covers, or send photos and any drawings through the quote form or WhatsApp.
This is practical guidance, not legal advice. Your lease governs, and leases vary. Confirm the position with your solicitor or managing agent.