Building an ensuite can add value – but do you have the space? These are the minimum measurements you need to squeeze one in

If you can squeeze an en-suite or supplementary bathroom upstairs, you can add between three and six per cent to the value of your home. Typical outlay starts around £3,500 (depending on size, fittings and work needed).

However, the added value and improved household functionality only work if you have enough room to accommodate an en-suite without seriously compromising the size and functionality of your bedroom.

'Successful small bathrooms and en-suites are shaped by proportion and restraint, rather than size alone. There’s no fixed rule about what must go into a space - it’s about deciding what you really need and what can be optional,' says James Lentaigne, creative director at Drummonds. 'The practicalities should always be guided by an experienced plumber or contractor, who can advise on drainage, heating, lighting and ventilation. That said, thinking creatively early on makes a huge difference.'

How small is the minimum for a bathroom?

The question of ‘how small is too small’ is up for debate.

‘The smallest space I’ve worked with was around H2600mm xW850mm x D1900mm,’ says Matthew Kallum, founder of Kallums Bathrooms. ‘This was only really functional as a wet room and contained a wall-hung toilet – like this from B&Q – wall-hung basin and underfloor heating. I also had an option with a bath in this room using one of Bette's 1050mm x 650mm squat baths with a shower over it.

The minimum size is really dictated by what you want to contain within the room and how much flexibility you have in terms of layout.

What are the best measurements for an ensuite?

For a clearer size guide, Soma Pillay, bathroom specialist at Bathroom City, recommends ‘a floor space of 0.7m x 1.3m for a compact cloakroom with a toilet and small basin, but 0.8m x 1.4m offers a more comfortable layout, particularly where doors open outwards or slide neatly out of the way.'

'For wet rooms, the absolute minimum is around 1.5m x 1m, allowing enough clearance for safe movement and effective drainage,' says Soma Pillay.

'In its purest form, a wet room has no internal separations, meaning the entire space is exposed to water during showering - something that’s particularly common in more compact layouts,' adds Luke, designer at Ripples Tunbridge Wells. 'Walk-in shower ideas , by contrast, introduce a glass screen or partition to create a clearer sense of separation. As a general guide, for shower rooms aim for a footprint of around 1700mm x 900mm, with the door centred on the longer wall, which allows for a comfortable and well-proportioned showering space.'

If you want to include a shower or bath, look to create a room of around 2m x 2m. This will give you enough space to navigate the room and will ensure that fixtures and fittings don't feel crammed in.

What size fittings should I buy?

Keeley Sutcliffe highlights the importance of focusing on how the space functions once the fittings are in place, rather than becoming obsessed with square footage.

‘Basins around 350 to 400mm wide remain practical for everyday use without overwhelming the room, while showers are generally most comfortable from around 800mm sq, even though smaller options exist,’ she says.

‘Baths can be reduced to around 1500mm in length, provided the surrounding layout allows safe access and movement, but you can get models as small as 1360mm,' says Keeley from BC Designs. BC Designs' Penny – available from Robert Dyas – features a generous slipper design but has a footprint of just W750mmxD1360mm.

Smaller models are available, but practicality becomes compromised. Wherever possible, visit a showroom – especially when purchasing showers and baths – so you can judge the size in relation to yourself.

How to design an ensuite to maximise space?

‘Thoughtful planning can unlock surprising flexibility in a small bathroom layout, from introducing subtle partitions to reworking how different zones sit next to each other,' says James Lentaigne, creative director at Drummonds.

Once you’ve got your proposed room size, Soma advises ‘laying everything out to scale on paper, or using masking tape on the floor, helps to visualise how the space will actually feel, not just how it looks on a plan. Allow at least 600mm in front of toilets and basins, and consider door openings, towel rails and storage early on.’

For added versatility, companies like Renovate with Reno offer digital tools that allow you to get a feel for the space and rearrange essentials. They can also help you play with colour combinations and finishes.

How to save space?

Don’t overlook the choice of door, as even a few saved inches can make all the difference. Pocket doors slide apart rather than swinging into the room, allowing you to make the most of the available space on either side of the door are many kits available that can be integrated when building stud walls.

Barn-style doors – like this from B&Q – are easier to install retroactively and bring a country-style aesthetic to the room. Or forgo a door altogether – a curtain can screen a bathroom entrance and has luxurious appeal for the en suite to an adult bedroom. However, this is not an option that’s compatible with wet rooms that don’t have a shower screen to contain water splashes.

As well as maximising physical space, design choices can also make a small bathroom look bigger. Mirrored walls and splashbacks can visually double the sense of space, making even the most compact room feel less claustrophobic. This effect is amplified by the way the mirrors will reflect light (whether natural or artificial) into the room. Other design choices, such as glass shower screens – like this from B&Q – rather than solid walls or curtains, and floating basins and toilets, promote a sense of openness by keeping all available floor space visible.