Small bathrooms are not scaled-down big bathrooms. They are a different design problem. In a large room you arrange fittings. In a small one you are solving a packing puzzle where several of the pieces are fixed by the building and one wrong decision — usually the door — costs you the whole scheme.
Central London has an enormous supply of small bathrooms, and they got small in identifiable ways. Mansion block flats built with one bathroom for a household with staff. Georgian and Victorian houses carved into flats, where a bathroom was fitted into a box room, a return, or the space under a stair. Post-war blocks with a compact internal bathroom and no window at all. Each of those gives you a different set of fixed points, and knowing which one you are in tells you where to start.
Start with what cannot move
Before drawing anything, establish four things. Everything else is decoration.
The soil stack
Your WC needs a connection to a stack, and the connection needs fall. In a mansion block the stack is usually in a shared riser and it is not moving — the riser serves the flats above and below you, and altering it is not your decision alone. In a conversion the stack is often on an external rear wall, which means the WC wants to be near that wall. You can move a WC away from a stack, but the waste run has to fall, and that fall has to fit inside your floor depth. In a period conversion with shallow joists it frequently does not, which pushes you towards raising the floor or fitting a pumped waste. Both are legitimate. Both have consequences. See plumbing for the drainage detail.
The floor depth
How much build-up you have between the top of the joists or slab and the finished floor level you can live with. This governs whether a waste can run where you want, whether underfloor heating fits, whether a wet floor can be formed, and whether the door still opens. Concrete slabs in blocks are usually not to be cut. Timber joists can sometimes be notched within limits, and sometimes cannot — that is a structural question, not a plumbing preference.
The door
In a small bathroom the door swing is often the largest single consumer of floor area, and it is frequently the cheapest thing to change. An inward-opening door sterilises a quarter-circle of the room that you then cannot put anything into. Changing the hinge side, hanging it to open outward, or fitting a pocket or sliding door can transform a layout. Two cautions: a door opening outward into a narrow hall can be a nuisance or worse, and in a listed building the door and its architrave may themselves be part of what is protected. Check before you commit.
The window, or the absence of one
An internal bathroom with no window is entirely normal in London and entirely workable, but it makes mechanical extraction non-negotiable rather than optional. Part F covers ventilation, and it applies whether you like the look of a grille or not. Extraction and condensation are covered properly in our ventilation guide, and the point to absorb at design stage is that the duct route needs to exist before the ceiling is closed up.
Where the space actually goes
People assume small bathrooms are lost to the bath. Usually they are lost to circulation, boxing and swing.
- Boxing. A stack boxed in generously, a pipe run boxed the full width of a wall because it was easier — these quietly eat hundreds of millimetres. Reboxing tightly, or building a shallow full-width duct that gives you a shelf as compensation, often recovers real space.
- Pedestals and cisterns. A pedestal basin and a close-coupled WC take floor. Wall-hung fittings free the floor visually and make cleaning easier, but they need a frame and a chase in the wall, and the frame needs somewhere to live. That is a first-fix decision.
- Swing. The door, and any hinged shower door. Both can be designed out.
- Dead corners. Small rooms accumulate corners nothing fits into. Bespoke joinery beats a standard cabinet every time in a room like this.
Bath, shower, or an argument about resale
The bath-versus-shower question in a one-bathroom flat is a real one, and it is not only about how you wash. In a family-sized flat, removing the only bath narrows the tenant and buyer pool. In a pied-à-terre or a one-bed, it usually does not. Landlords should think about the letting audience rather than their own preference.
If you keep the bath, a shorter bath with a proper over-bath screen and a decent thermostatic shower is a serious option in a small room, and far better than a full-length bath crammed in with no room to stand. If you go shower-only, the choice between a tray-and-enclosure and a fully tanked wet floor is a construction decision, not a style one — floor depth, waterproofing and the neighbour below all bear on it. Our wet room versus shower enclosure guide sets out the trade-off, and tanking explains what has to be right underneath either.
Making a small room read as bigger
Some of this is genuine and some of it is folklore. What actually works in the flats we see:
- Fewer, larger tiles. Fewer grout lines calm a small room. The catch is that large-format tiles are unforgiving of an out-of-true wall, so the substrate has to be prepared properly — that is where the time goes, and it is why our tiling pricing is driven by preparation as much as area. Period walls are almost never flat.
- Run the same floor tile through, uninterrupted. Breaks and thresholds chop a small floor into smaller pieces.
- Wall-hung everything. Seeing the floor run under the fittings is the single most effective trick in the book.
- Recess rather than protrude. A tiled niche in the shower wall replaces a rack you would otherwise walk into. Plan it at first fix — it has to miss the studs, the pipes and, in solid walls, the wall itself.
- Layered light. One central fitting flattens everything. Mirror lighting, a low-level light and a downlight or two give the room depth. All of it engages Part P and the bathroom zones, so it is designed at first fix and installed to BS 7671 — see electrical.
- A big mirror. Cheap, and it works.
- Heated towel rail on a wall you were not using. Or, better, keep the walls clear and put the heat in the floor — our underfloor heating guide covers what it needs.
Storage: the thing small bathrooms are really short of
A small bathroom usually fails on storage rather than on floor area. Two people's daily kit, towels, cleaning things and the spare loo roll have to live somewhere, and if they have nowhere to live they live on the floor, on the cistern and on the edge of the bath — which makes a well-designed room look like a badly designed one within a fortnight.
The space to mine is vertical and shallow. A mirrored cabinet recessed into a stud wall gives depth you were not using. A full-height narrow cupboard in the dead corner beside the door holds more than a wide low unit and takes almost no floor. If you box a stack, box it once, box it tightly, and put a shelf on top of it rather than pretending it is not there. A vanity that spans the basin wall gives you a worktop and a cupboard for the price of the floor the basin was taking anyway — though remember that a vanity fixes your basin position, so it wants to be decided before first fix, not after.
Bespoke joinery is usually the right answer in a room like this, because standard units are sized for rooms that are not this one. The economics are less painful than people expect once you account for how much of a small room a badly fitting standard unit wastes.
What goes on the floor
Tile is the default and for good reason: it tolerates water, it is easy to keep clean, and it works over underfloor heating. If you are running a floor finish through from a hallway for continuity, be careful — most leases have something to say about floor finishes and acoustic performance in flats, and engineered timber in a bathroom is a specification decision rather than a free choice. Our wood flooring page covers where timber is and is not sensible; in a small windowless bathroom, tile is usually the calmer answer.
The leasehold layer
Almost every small London bathroom is in a flat, and that means the lease has an opinion. Most leases require freeholder or managing agent consent for alterations, typically as a formal licence to alter, and typically triggered by exactly what a small-bathroom redesign wants to do: move waste, touch a wall, change a floor finish. Many freeholds in Central London sit with large estates whose requirements vary considerably, so read your lease and speak to your managing agent before you commit to a layout. Our consent guide and licence to alter guide explain the usual shape of it. If your flat is in a listed building, internal works affecting special character generally need listed building consent too.
There is also the neighbour below. In a small internal bathroom, everything you do is directly above somebody's ceiling. That raises the stakes on waterproofing and on how you fix a floor, and it is worth being conservative about both.
Questions worth answering before you draw
- Where is the stack, and how much fall do I actually have?
- What is under the floor — timber or slab — and how much build-up can I afford?
- Can the door swing change, and is the door itself protected?
- Is there a duct route for extraction, and where does it terminate?
- Am I keeping a bath, and what does the audience for this flat expect?
- What does my lease say about floor finishes and waste?
How we approach it
We survey the room before we design it, because in small bathrooms the fixed points decide the scheme and you cannot see the fixed points in a photograph. Then you get a fixed quote against a defined scope — bathroom refurbishment starts from £2,800, tiling from £55/m², and larger refurbishment is per quotation. One point of contact, trades sequenced by us, protection down from the first day, and the flat left clean.
Send photographs of the room, including the ceiling and the wall the WC sits on, and tell us what is above and below you. That tells us more than the dimensions do.