Costs and planning
Adding an en-suite: space, drainage and building warrants
To add an en-suite you need enough space for a shower, toilet and basin, a waste route to the soil stack, an extractor fan and safe electrics. In a house in Scotland, an en-suite and its drainage can usually be added without a building warrant, but in a flat a new en-suite usually needs one. This guide walks through each step.
What does a new en-suite need?
| Need | Why it matters | What to check |
|---|---|---|
| Space | Room to use each fitting comfortably | A shower, toilet and basin, plus the door swing |
| Drainage | A toilet needs a route to the soil stack | Distance and fall to the stack |
| Ventilation | Clears steam and prevents mould | At least 15 l/s extraction, or another option in Standard 3.14 |
| Electrics | Fan, lighting and any electric shower | Fitted and certified by a registered electrician |
| Water supply | Enough pressure for the shower | Pressure and flow at the survey |
Do you need a building warrant?
In a house, Scotland's building regulations allow an en-suite, including its drainage, to be added without a warrant, as long as the work does not affect a separating wall, the structure or how waste water leaves the building. In a flat, a new en-suite usually needs a warrant. Your council's building standards team makes the final call. Read our building warrant guide.
Where can an en-suite go?
- Part of a large bedroom, separated by a stud wall.
- A box room or large cupboard next to the bedroom.
- A loft conversion, fitted out once the loft is built.
- The closer to the soil stack, the simpler the drainage.
Ventilation and windowless en-suites
Many en-suites have no window, so the extractor fan does all the work. Scotland's Standard 3.14 asks for mechanical extraction of at least 15 litres per second, a continuous fan, or a passive stack system. See our bathroom ventilation guide.
How we build en-suites
We refit existing en-suites and build new ones in bedrooms, box rooms and lofts. We check the drainage at the free survey, decide case by case where there is no gravity route, and handle the building warrant if one is needed. Most en-suites take 1 to 2 weeks. See our en-suite installation service.
Sources
- Scottish Government: Domestic Technical Handbook, 0.5 Work not requiring a warrant
- Scottish Government: Domestic Technical Handbook, 3.14 Ventilation
Figures from other organisations are theirs, not our prices. Check each source for the latest version.
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How much space do you need for an en-suite?
There is no single minimum. A shower, toilet and basin can fit into a surprisingly small space, such as a box room or the end of a bedroom, as long as each can be used comfortably and the door does not clash with them. The waste route matters as much as the floor area. We measure at the free survey and tell you honestly whether it will work.
Do you need a building warrant for an en-suite in Scotland?
In a house, usually not, as long as the work does not affect a separating wall, the structure or how waste water leaves the building. In a flat, a new en-suite usually needs a warrant. Your council's building standards team makes the final decision. If a warrant is needed, we handle the application, and work starts once it is approved.
Can an en-suite go anywhere in the house?
Not always. A toilet needs a reliable waste route to the soil stack with enough fall, so the closer the en-suite is to the stack, the simpler the job. Where there is no gravity route, a pumped waste is sometimes possible, but not always suitable. We check the route at the survey and decide case by case. Any pump is shown on your quote.
Does an en-suite need a window?
No, but it does need good ventilation. Scotland's Standard 3.14 asks for mechanical extraction of at least 15 litres per second for a bathroom or shower room, a continuous extract fan, or a passive stack system. In a windowless en-suite, the fan does all the work, so it needs to be the right size and properly ducted outside. A window helps with light.