Mansion blocks are the defining residential stock of large parts of Central London — Marylebone, Bayswater, Maida Vale, St John's Wood and beyond. Solid, generously planned, built to last, and built at a time when a large flat needed one bathroom because the household had staff who did not use it.
Which is why so many of them are being refurbished, and why the work is so consistently misunderstood. A mansion block bathroom is not technically difficult. It is constrained — by a riser you did not design, a lease you did not write, a building with its own rules, and a neighbour whose ceiling is your floor. Understand the constraints and the job is calm. Ignore them and you will meet them anyway, later, more expensively.
The riser decides your layout
Start here, because everything else follows. Your soil stack almost certainly runs in a communal riser, serving the flats above and below. It is not yours. It cannot be moved, because moving it is not a decision one flat gets to take, and in most blocks the riser is common parts in any case.
So your WC has to connect to that stack, with proper fall, within the depth of your floor. Which in a mansion block is usually a concrete slab you are not cutting into. That leaves you building any fall up on top of the slab — which raises the floor, and a raised floor has consequences for the door, the threshold and possibly the lease.
The honest conclusion is that in most mansion block flats the WC wants to stay near where it is. You can move it. It costs, it may need a pumped or macerating waste, and the macerator is a mechanical item that needs power, servicing and access forever. Sometimes that is worth it. Often the better trade is to accept the WC position and spend the money on everything else in the room. Our plumbing page covers the drainage side, and small bathroom design covers working within fixed points.
There is a second riser question worth asking early: where does your extraction go? Many mansion block bathrooms are internal, with no window, which makes mechanical extraction non-negotiable under Part F. If the only route out is a long horizontal duct to an external wall, the fan has to be selected for that actual route rather than off a shelf, and the duct has to be rigid, supported and properly terminated. This is the commonest failure in these flats. See ventilation and condensation.
The lease, and the licence to alter
Most leases require freeholder or managing agent consent for alterations, typically through a formal licence to alter. The triggers are usually precisely what a bathroom refurbishment wants to do: alter soil or waste, affect structure, or change floor finishes. Many leases in these blocks also carry requirements about floor coverings and acoustic performance, which matters the moment you plan to tile a floor that was carpeted.
Many freeholds in Central London sit with large estates, and their licence requirements, information demands and timescales vary considerably. Do not assume, and do not rely on what a neighbour tells you they did in 1998. Read your lease, write to your managing agent early, and expect them to want to know what you are doing before they agree to it. Our licence to alter guide and freeholder consent guide set out the usual shape of the process. If the block is listed — a good number are, and many sit in conservation areas — internal works affecting special character generally need listed building consent as well.
The point to internalise: consent does not usually dominate the cost. It routinely dominates the calendar. Start it weeks before you want to start work, not the week before. Our programme guide explains where it lands.
The flat below
Everything you build is directly above somebody's ceiling, and that changes the risk calculus in a way that people from houses do not immediately feel.
It raises the stakes on waterproofing. A wet room in a mansion block is a lovely thing and a higher-variance thing — it is a system whose integrity depends entirely on how the corners, junctions and the drain collar were detailed. A well-made tray is a manufactured, tested object with few and known weak points. Neither is wrong; they are different risk profiles, and above a neighbour's ceiling that is worth thinking about honestly. See wet room versus enclosure and tanking.
It also raises the stakes on noise and on drilling. Slabs carry sound. Fixings go somewhere. And it means the neighbour is a stakeholder in your programme whether or not either of you wanted that — which is a good argument for telling them what you are doing and when, before they hear it through the floor.
Getting in and out
This is where mansion block jobs consume time that a house never spends.
- No skip. Nowhere to put one, and often no permit that would help. Strip-out waste comes out in bags, by hand, in trips, and goes with a licensed carrier.
- Parking that does not exist. Deliveries are planned, timed and sometimes carried a distance. A pallet of stone is not a casual arrival.
- The lift. Blanketed, sometimes booked, sometimes with limits on what may go in it. In some blocks materials go up the stairs instead, which is a different day entirely.
- Common parts. Protected before anything moves, and cleaned every day. The hall is the neighbours' hall.
- The porter. Where a porter is involved, they are the gatekeeper — access, deliveries, notice, and often the person who tells you what the building actually expects. Worth treating as a colleague rather than an obstacle.
- Hours. Most blocks restrict working hours, and many restrict noisy work to a narrower window still. A shorter productive day lengthens the calendar without adding an hour of labour.
None of this is anyone being difficult. It is what a shared building is. But it is real, and a quote that has not accounted for it is not cheaper — it is just less honest about what it is going to do to your neighbours.
What we find when the walls come open
These flats are old and they have been altered. Expect old supply pipe, sometimes lead. Expect wiring and a consumer unit that were adequate for a flat with fewer demands than yours. Expect previous work of unknown provenance, particularly where a bathroom was squeezed in during a conversion. Expect tiles bedded in sand-and-cement thick enough to be holding the wall together, and expect the wall behind them to be less flat than you hoped — which is exactly why large-format tile and stone need real preparation before the first one goes on. See tiling, from £55/m².
Bathrooms engage Part F for ventilation, Part G for sanitation and hot water, and Part P for electrics; our electrical work is to BS 7671 and starts from £80. The regulations guide covers what applies. Landlords should note that rented homes require an EICR at least every five years under the Electrical Safety Standards in the Private Rented Sector (England) Regulations 2020 — a refurbishment is the moment to sort anything that would become a finding.
Working with the building rather than against it
There is one more thing worth saying, because it saves more grief than any technical decision on this page. A mansion block is a community with a memory, and a refurbishment is a temporary imposition on everybody who lives in it. How you handle that determines whether the next six weeks are uneventful.
Tell the managing agent what you are doing and when, in writing, before you start rather than after somebody complains. Tell the neighbours either side and directly below — particularly below — and give them a rough programme and a way to reach someone if something goes wrong. Most complaints in these blocks are not really about noise; they are about noise that arrived without warning and had no obvious end date. A neighbour who knows the drilling stops on Friday is a different neighbour from one who does not.
Keep the common parts genuinely clean rather than technically covered. Dust in a communal hall is what residents notice and remember, and it is what gets a job talked about at the next residents' meeting. And keep to the permitted hours precisely, including the first day, because the first day is when everyone is deciding what sort of job this is going to be.
None of that is soft. It is the difference between a licence application that goes smoothly and one that acquires conditions, and between a block that tolerates your works and one that scrutinises them.
What to establish before you start
- Where the riser is, and whether the WC can realistically move.
- What your floor is, and how much build-up you have.
- What the lease says about floor finishes, waste and structure.
- Who the managing agent is, and what their licence process involves.
- Where extraction can terminate.
- The building's working hours, lift rules and delivery arrangements.
- Whether the stopcock is findable, and whether it turns.
How we run them
Survey first — including the riser, the floor and the route in, because those set the job. Then a fixed quote against a defined scope, then work. We deal with the managing agent, the porter and the access arrangements rather than leaving them for you, and the protection goes down before the first tool comes out. Bathroom refurbishment starts from £2,800, wood flooring from £30/m², and wider refurbishment is per quotation. We work across Marylebone, Bayswater, Maida Vale and St John's Wood, where this stock is concentrated — the full list is on our areas page.
Send photographs of the room, tell us which floor you are on and who your managing agent is. Those two facts tell us more about the job than the dimensions do.