En Suite Bathroom Guide

An en suite is the most common bathroom addition we are asked about, and the one where planning matters most, because you are trading bedroom space for it permanently. Get the dimensions, the drainage and the acoustics right and it adds real value to daily life. Get them wrong and you have a cramped shower and a bedroom that feels smaller.

How much space you genuinely need

The absolute minimum for a usable shower en suite is around 900mm by 1700mm, giving an 800mm square shower, a short projection toilet and a compact basin in a line. That works, but it is tight and there is nowhere to put a towel. A more comfortable arrangement needs about 1.2 metres by 2 metres, which allows a 1000mm shower, a proper vanity and a towel rail. Plan on paper with the door swing drawn in, because a door opening inwards into a small en suite can render a third of the floor unusable.

Where to take the space from

• The corner of the bedroom. Simplest, and best taken from the corner nearest the existing soil stack.
• A built in wardrobe run. Often already 600mm deep, so extending to 1200mm costs you less bedroom than starting from scratch.
• The landing or a box room. Preserves the bedroom entirely, though it may create an awkward corridor.
• Over the stairs. Workable in some layouts, but headroom must be checked carefully before anything is promised.

Whatever you take, check the bedroom still works afterwards. A double bed plus 700mm of walking space on at least one side is the test most people apply without realising it.

Drainage, the decisive constraint

The toilet needs a 110mm waste with a consistent fall of about 18mm to 20mm per metre to reach the soil stack. Within two to three metres this is usually straightforward. Beyond that, the options are to reposition or add a stack on an external wall, or to use a macerator or pumped waste unit. Gravity is always better where it can be achieved, since it is silent and mechanically simple. In a loft conversion, the vertical drop to the existing stack usually helps, but boxing the run through the floor below needs planning.

Shower and basin wastes at 40mm and 32mm are far more flexible and rarely dictate the layout.

Noise, the thing people forget

An en suite shares a wall with a bed. Address it at build stage:

1. Acoustic mineral wool in the stud wall, not just the void.
2. Two layers of plasterboard on the bedroom side, staggered joints.
3. A solid core door with acoustic seals rather than a hollow one.
4. An inline fan sited in the loft with only a grille in the ceiling.
5. A slow fill or delayed action inlet valve on the cistern.
6. Clip pipework properly and insulate the runs to stop noise transmitting through the structure.

Ventilation without a window

Most en suites are internal, so mechanical extraction is not optional. Duct it outside through a soffit or roof tile vent, use rigid ducting, choose a fan sized above the 15 litres per second minimum and fit a humidity sensor with an overrun. Leave a 10mm gap under the door so replacement air can reach the room. A steamy en suite with poor extraction will put moisture straight into the bedroom.

Water pressure with two bathrooms

Adding an en suite means two showers potentially running at once. On an unvented cylinder or a high output combi that is usually fine. On a gravity system it very often is not, and the honest answer may be that a system upgrade should be part of the project. We measure pressure and flow at survey so this is known before you commit.

Making a small en suite feel good

Continuous flooring, wall hung fittings, a large mirror, warm 3000K lighting and one full height tiled wall with painted plaster elsewhere. A clear glass screen rather than an enclosure with a door. Underfloor heating instead of a low level radiator, freeing the wall for a slim towel rail. These are small choices that make 1.5 square metres feel deliberate rather than squeezed.

Get yours planned and priced

We will measure the bedroom, check the stack and the joists, tell you honestly whether the space works, and give you a fixed written price within 24 hours. All stud work, plumbing, tiling, joinery and electrics carried out in house by our own insured fitters.

Common questions