Knowing how to design a cloakroom is mostly about accepting that you are solving an engineering problem before a decorating one. A downstairs WC is the smallest room in a London house and the one with the least room for error: get the drainage, the door swing or the head height wrong and no amount of expensive wallpaper rescues it. Get them right and you have added the single most useful room in a family home, and one of the few places where you can be genuinely bold.
The same considered approach we bring to a utility room or a hallway applies here, only with tighter tolerances.
Start with the drainage, not the plan
This is the decision that determines everything else, and the one homeowners leave until last. A WC needs to reach the soil stack, and it wants to do so by gravity: a conventional connection is silent, needs no electricity and essentially never fails. Find where your stack runs before you decide where the room goes, because a cloakroom sited two metres from the stack is a different project, and a different budget, from one sited eight metres away.
When gravity is genuinely impossible, a macerator makes an otherwise unusable location work. Be clear-eyed about the trade: it is audible, it depends on power, and it will not tolerate anything beyond paper, which in a household with children is a matter of when rather than if. A macerator is a solution to a problem, not a free choice. Pay for the drainage survey first and let the answer tell you where the room can go.
The space you actually need
As a practical minimum, around 800mm wide by 1400mm long will take a WC and a small basin with a door that opens. The mistake is to measure only the fittings. You need roughly 600mm of clear floor in front of the pan to stand up and turn, and that clear space is the difference between a room that works and one where you edge sideways past the basin.
Below the practical minimum, the levers are:
- An outward-opening or sliding door, which buys back the entire door swing. The single most effective move in a tight cloakroom.
- A corner basin, or a shallow wall-hung one, some as slim as 250mm front to back.
- A concealed cistern in a stud wall, which loses you around 150mm of depth but gains a shelf and a much calmer look.
- A wall-hung WC, which frees the floor beneath it and makes the room read as larger. It needs a supporting frame, so decide early.
Under the stairs: the head height trap
Under the stairs is the classic location and it works, provided you site the room around the slope rather than the floor plan. The rule is simple and constantly ignored: put the WC where the ceiling is highest, and the basin, or nothing at all, where it is lowest. A pan positioned under the low end of a staircase produces a room you cannot stand up in, which is discovered at first fix, when it is expensive.
Stand in the space and mime it before anything is built. If your head touches the underside of a stair tread while you are seated, the plan is wrong regardless of how neat it looks on paper.
The kitchen myth, and the rules that do apply
Two regulations matter here, and one widespread belief is simply wrong.
The myth first: people are routinely told a downstairs toilet cannot open into a kitchen. In a home, it can, with a door. Approved Document G requires that a room containing a WC is separated from a kitchen or food preparation area, and in dwellings that separation is a door. A ventilated lobby is not needed. The stricter rule, where a WC must not communicate directly with a room where food is prepared, comes from workplace regulations covering food businesses, and it has been repeated so often that it is now folklore about houses. It is worth knowing, because in a small terrace the kitchen wall is sometimes the only place the room can go.
Ventilation genuinely does apply. Most cloakrooms are internal, so an extractor is the answer, and Approved Document F sets an intermittent extract rate of 6 litres per second for sanitary accommodation. Where there is no openable window, the fan needs controls that keep it running for at least 15 minutes after the room is vacated. Budget for the overrun model. The cheapest fan on the shelf will not have it, and a cloakroom with poor extract is unpleasant in a way that reflects on the whole house.
Building control interprets, so confirm your specifics with them or your designer rather than with a forum.
Be bold: this is the room for it
Here is the part that makes a cloakroom enjoyable rather than merely functional. It is small, visually separate from everywhere else, and nobody spends more than two minutes in it. That combination means a pattern or colour that would exhaust you in a living room is perfect here. A dramatic wallpaper, a deep saturated paint, a strong tile: the room is a moment, not a place you live.
It is also cheap to be brave. Two or three rolls covers most cloakrooms, so a paper you could never justify across a bedroom becomes affordable. This is the one room in a London house where restraint is usually the wrong instinct, and it is the room guests are guaranteed to see on their own.
Where to spend and where not to:
- Spend on the tap and the door handle. They are the only things anyone touches, the room is small enough that they dominate, and a good tap in a tiny room is affordable in a way it is not in a family bathroom.
- Spend on lighting. A single central downlight is the default and it is unflattering. A wall light beside or above a mirror is transformative.
- Spend on the mirror, which does double duty by making the room feel larger.
- Do not overspend on the WC itself. Beyond a decent flush and a soft-close seat, the returns fall away quickly.
- Do not tile floor to ceiling by default. Half-height panelling with paint or paper above is usually warmer, cheaper and more interesting.
The details that get forgotten
- Somewhere to put a phone or a handbag. A narrow shelf, the top of a concealed cistern, anything. Its absence is felt immediately.
- A door that does not open onto a dining table. Worth planning around at concept stage, not discovering at first fix.
- Hooks. It is called a cloakroom for a reason, and coats have to live somewhere in a house without a hallway cupboard.
- Access to the stopcock or isolation valves, if they end up boxed in behind the new work.
- A hard-wearing floor. It is the room nearest the front door, so it takes wet shoes and grit all winter.
The honest summary
A cloakroom is a small room that behaves like a large project, because the drainage, the head height and the ventilation are all fixed constraints you discover rather than decide. Resolve those three first, keep 600mm of clear floor, and then spend your energy on the tap, the light and a wallpaper you would never dare use anywhere else. It remains the best value room in a London house: two square metres that change how a family lives in the whole ground floor.
If you are weighing up the wider project, see our guide to interior designer costs in London, or start from the Vertigo Interiors homepage.
Frequently Asked Questions
What is the minimum size for a downstairs cloakroom?
As a practical minimum, around 800mm wide by 1400mm long will take a WC and a small basin and still let the door open. Below that you are into corner basins and outward-opening or sliding doors. Remember the space is not just the fittings: you need roughly 600mm of clear floor in front of the WC to stand and turn comfortably.
Can a downstairs toilet open directly into a kitchen?
In a home, yes, with a door. Approved Document G requires that a room containing a WC is separated from a kitchen or food preparation area, and in dwellings that separation is a door: a ventilated lobby is not needed. The stricter no-direct-access rule people often quote comes from workplace regulations for food businesses, not from the rules governing your house. Confirm your specifics with building control.
Does a cloakroom need a window or an extractor fan?
It needs ventilation, and an extractor is the usual answer since most cloakrooms are internal. Approved Document F sets an intermittent extract rate of 6 litres per second for sanitary accommodation. Where there is no openable window, the fan needs controls that keep it running for at least 15 minutes after the room is vacated, so budget for the overrun model rather than the cheapest fan.
Do I need a macerator for a downstairs toilet?
Only if you cannot reach the soil stack by gravity. A conventional gravity connection is always the better outcome: it is silent, needs no power and rarely fails. A macerator makes an otherwise impossible location work, but it is noisy, depends on electricity and is intolerant of anything beyond paper. Pay for the drainage survey before you commit to a position.
Where is the best place for a downstairs cloakroom?
Under the stairs is the classic answer, and it works if the head height suits the WC position: put the pan where the ceiling is highest, not where the plan looks tidiest. Otherwise, look for dead space near the existing soil stack, and try to avoid a door that opens straight into a dining or sitting area.
Should you use bold wallpaper in a small cloakroom?
It is one of the few rooms where you genuinely should. A cloakroom is small, nobody lingers, and it is visually separate from the rest of the house, so a pattern that would overwhelm a living room reads as confident here. It is also cheap to be brave: two or three rolls covers most cloakrooms.