Adding a bathroom to a garden room, and what it really involves

How much space to allow

A compact WC and basin can fit into roughly one metre by one and a half. A shower room needs closer to two metres by one and a half to be usable without soaking the door.

Remember the space comes out of your room, not out of thin air. On a small footprint, a shower room can take a quarter of the floor, which sometimes makes a slightly larger building the better decision.

Getting the waste away

This is the decision that shapes the cost. Gravity to an existing drain is ideal but depends on levels and distance. Where that is not possible, a pumped macerator or a small pumping station moves waste to the house drainage.

Water supply and freezing

A supply is usually taken from the house, laid at sufficient depth to be below frost, and fitted with an isolation valve so the garden building can be shut down and drained if it is unused in winter.

Hot water is normally a small point of use electric heater or an instantaneous electric shower. That keeps the pipework short and avoids losing heat down a long run from the house.

Ventilation and finishes

A shower room in a well sealed building must have mechanical extraction or you will be dealing with condensation and mould within a season. Fit an extract with an overrun and duct it properly to the outside.

Finishes need to handle steam: a tanked and tiled shower area, a moisture resistant board substrate and a paint suitable for humid rooms. We renovate bathrooms in houses as part of our services, and the same standards apply out here, with the difference that a garden building has fewer places for moisture to disperse.

Regulations

Adding sanitary facilities and drainage brings building regulations into the project, covering the drainage work, ventilation and the electrical installation. It does not automatically make the building a dwelling, and a WC does not turn a garden office into an annexe, but the works themselves need doing properly and certifying.

Garden room with toilet and shower: planning the layout

A garden room with toilet plan usually works best with the wet room against the wall nearest the house drain. That keeps the waste run short, lets the shower room borrow a small window or rooflight, and leaves the glazed side of the building free for the main room.

Keep the door to the shower room out of the line of sight from the main glazing, and allow for a towel rail and somewhere to put clothes. Those small details are what make a garden room with shower and toilet feel like part of the design rather than a cupboard added later.

Adding a kitchen as well

A garden room with kitchen facilities uses the same water supply and waste route, so a sink or kitchenette next to the shower room shares most of the pipework. Once a building has a kitchen, a bathroom and a bed, it is being used as separate accommodation, which is an annexe with a different planning position altogether.

What decides the cost of a garden room with bathroom

The cost of a garden room with a bathroom depends far more on the drainage than on the sanitaryware. The distance to the nearest foul drain, whether the levels allow gravity or need a pump, the route for the water supply and the hot water method are the big variables. Finishes such as tiling and the extract fan come after.

Because those items vary so much from garden to garden, the itemised written quote prices the building and the bathroom as separate lines, so you can see exactly what the toilet or shower adds before deciding.