The single most expensive mistake made in Central London flats is starting work before consent exists. It is expensive in two directions: the work stops, and the relationship with the freeholder — which you will need again — starts from a bad place. This page explains how the licence-to-alter process generally works in mansion blocks, what tends to trigger it, and how to plan around it.
One warning before anything else. Leases differ. Two flats in the same block, granted in different decades, can contain materially different covenants. Freeholders differ too. Nothing here can tell you what your lease says. Read it, or have your solicitor read it, and ask your managing agent to confirm the position in writing.
Why a flat is not a house
You do not own a mansion flat in the way you own a house. You own a long lease: a contract that grants you possession of a defined demise for a term, subject to covenants. Those covenants almost always restrict what you may alter.
The demise itself is narrower than most owners assume. Typically it stops somewhere around the internal surfaces. The structure, the main walls, the floors and ceilings as structural elements, the exterior and often the windows may sit with the freeholder or be shared. So when you take up a floor, or chase a wall, or move a soil pipe, you are frequently working on something that is not fully yours.
Most leases require the freeholder's consent for alterations — commonly documented as a licence to alter, which is a formal deed. Structural work, works affecting soil and waste pipes, changes to floor finishes, and anything touching common parts or services are the usual triggers. Whether your specific proposal needs consent is a question for the lease.
What tends to trigger it in practice
- Moving or altering waste. Relocating a WC, a bath or a kitchen sink changes where the waste picks up and where it discharges. This one is consent territory in most leases, and it is the most common reason a bathroom project stalls.
- Removing or altering walls. Even a wall that appears non-structural may be doing something. Nobody can tell from a photograph.
- Floor finishes. Many leases in mansion blocks contain covenants about carpet, or about keeping floors covered, precisely because of noise transmission between flats. Replacing carpet with timber or stone is a classic consent trigger — see our wood flooring page for how the build-up and acoustic layer affect this.
- Underfloor heating and wet systems in floors. New services in a floor void raise structural, acoustic and leak-risk questions all at once.
- Windows, external elements, plant. Almost always outside the demise, and frequently subject to planning or heritage control as well.
- Electrical and heating alterations. Where they interact with communal risers or the intake, they need discussion regardless of what the lease says about electrics.
How the process usually runs
Typically it goes something like this. You approach the freeholder or the managing agent with a proposal. They will usually want drawings and a specification — not a paragraph, but something a professional can assess. The freeholder generally appoints a surveyor to review it, and you would normally expect to be responsible for the freeholder's reasonable professional and legal costs of dealing with your application. What those costs are, and how they are handled, varies; ask up front rather than discovering later.
If the proposal is acceptable, a licence to alter is drawn up and completed. It commonly sets out what is permitted, conditions attached to it, and obligations about the manner of the works, insurance, reinstatement and completion. Then, and only then, you start.
Do not treat a friendly email from a managing agent as consent. Consent under most leases is a formal thing. An informal go-ahead is worth very little if the freeholder changes, the block is sold, or you come to sell your flat and a buyer's solicitor asks for the licence.
What the freeholder's surveyor is actually looking for
It helps to understand that the surveyor is not trying to obstruct you. They are protecting the building and the freeholder's interest, and they are looking at a short list of things:
- Structure. Is anything load-bearing being touched, and if so, is there proper structural design behind it?
- Water. Anything that could leak into a flat below is treated seriously, because in a block, leaks are the freeholder's problem too. Waterproofing, falls, drainage and pipework detailing get scrutinised.
- Noise. Floor build-ups, plant, extract fans. Blocks live and die by noise complaints.
- Fire and compartmentation. Anything through a floor, a ceiling or a compartment wall.
- Services. Whether the proposal loads the communal services or interferes with the riser.
- The manner of the works. Hours, access, protection of common parts, waste removal, insurance.
A proposal that answers those questions before they are asked moves faster than one that does not. That is the whole trick.
The mansion block reality
Blocks in St John's Wood, Maida Vale, Little Venice and the Bayswater streets are typically late-Victorian to inter-war, with solid masonry, timber floors, and services that have been added rather than designed. The blocks also run on rules — porters, service lifts, sign-in books, working hours, waste routes. Those rules do not appear in your lease. They are the block's management arrangements, and they are just as capable of stopping your job.
Practical consequences worth planning for:
- Hours. Many blocks restrict noisy work to defined hours on weekdays only. That changes the programme, not just the day.
- Lift. Booking, protection, weight limits. Everything in and out goes this way, including your bath and your waste.
- Waste. There is often no skip permit available and nowhere to put one. Waste leaves in bags, by lift, on a schedule.
- Protection. Common parts protection is usually a condition. It is also basic professionalism.
- Neighbours. The flat below is the one that matters most, because everything you do to a floor happens to their ceiling.
Many freeholds in this part of London sit with large estates and long-established landlords, and their licence-to-alter requirements, forms and standards vary considerably. We are not going to characterise any particular estate's process — check your lease and ask your managing agent what theirs involves.
Timing: plan backwards
The most common planning error is to book a contractor and then apply for consent. Reverse it. Consent processes take time — drawings, surveyor review, legal drafting, execution — and the honest answer to "how long?" is that it depends entirely on the freeholder, the complexity, and how complete your application is. We will not invent a timescale. Ask the managing agent what their process involves at the outset, and build the programme from that answer.
Within the works, sequence matters too. Consent, then strip out, then first fix, then test and certify, then finish. Our refurbishment page sets out how we run that, and where a bathroom is involved the specifics are in bathroom refurbishment and freeholder consent for a bathroom refurbishment.
Retrospective consent, and why it is a bad plan
Some owners do the work and deal with the consequences later. It is worth being clear about what that risks. A breach of covenant is a breach whether or not anyone notices at the time, and the freeholder's remedies are set out in the lease. Even where a freeholder is willing to regularise matters afterwards, they are negotiating from a position of total strength, and you are paying for that.
The other cost arrives at sale. Buyers' solicitors ask for the licence for any alteration that appears to have been made. If you cannot produce it, the transaction slows while indemnity insurance or retrospective consent is explored, and it slows at the point where you have the least leverage and the most to lose. Consent obtained properly at the right time is cheap by comparison.
The other consents that may run alongside
A licence to alter is a contractual permission from your landlord. It is not planning permission, it is not Building Regulations approval, and it is not listed building consent. These are separate systems and none of them substitutes for another.
- If the building is listed, works affecting its special character typically need listed building consent — see listed building consent for bathrooms.
- If it is in a conservation area, additional planning controls generally apply — see conservation area rules in Central London.
- Building Regulations apply to the work itself regardless of the lease — see building regulations for bathrooms.
- Works to a shared wall or structure may be notifiable under the Party Wall etc. Act 1996 — see party wall agreements for flat refurbishment.
Four different permissions, four different bodies, four different timelines. In flats around Mayfair, Marylebone and Fitzrovia, it is entirely normal for three of the four to apply to one bathroom.
What a good contractor contributes
Not the consent itself — that is a matter between you, your freeholder, and usually a solicitor and an architect or surveyor. What we contribute is the technical content that makes an application credible and the discipline that keeps the licence's conditions satisfied on site: a defined scope, the right floor build-up, proper waterproofing, sensible service routes, protection of common parts, working within the block's hours, and waste handled the way the building requires.
We give set prices and a fixed quote before starting, and one point of contact — which matters more than it sounds when a porter, a managing agent and a downstairs neighbour all have opinions. Send your drawings or photographs through the quote form or on WhatsApp, or read more about the areas we work in on our areas page.
This is practical guidance, not legal advice. Your lease governs. Confirm the position with your solicitor or managing agent before committing to anything.