Can you have a garden room with a bathroom?

A toilet changes how you use a garden room. You don’t have to walk back to the house in the rain, and a studio or gym with a shower becomes far more useful. It is also the single most expensive extra you can add, so it is worth understanding what is involved before you ask for quotes.

What a garden room bathroom usually includes

Most garden room bathrooms are small shower rooms, often built into one end of the room behind a stud wall. A typical layout fits in about 1.2 by 2 metres:

• a toilet
• a small basin
• a shower tray or wet floor with a screen
• an extractor fan and a heated towel rail

Some people only want a toilet and basin. That saves space and a little money, because the shower and hot water are the parts that need the most power and plumbing.

How water and drainage get to the room

The bathroom fittings are the easy part. The work that decides the price happens underground.

Water supply

Cold water comes from the house through a pipe laid in a trench, usually alongside the electric cable. The pipe needs to be deep enough, or well enough insulated, not to freeze in winter. Hot water usually comes from an electric water heater or an electric shower inside the room, rather than from the house boiler.

Drainage

Waste needs to reach a drain. The cheapest case is a manhole or drain run close to where the room will sit, with enough fall for the waste to flow by gravity. The further away the drain, and the more ground there is to dig through, the more it costs.

If the room sits lower than the drain, or a gravity run is not possible, the alternative is a pump. A macerator toilet grinds and pumps waste through a narrow pipe. Building regulations only allow a macerator toilet where there is also a toilet that drains by gravity, so check with the builder and building control early if you are relying on one.

What a garden room bathroom costs

Price guides put the extra cost of a bathroom at roughly £3,000 to £9,000 on top of the room itself. Our cost calculator uses £4,000 to £8,000 as the typical range.

What pushes the price up:

• a long distance to the nearest drain
• hard ground, paths or patios to dig through
• needing a pump instead of gravity drainage
• a full-size shower and better-quality fittings

What keeps it down:

• placing the room close to an existing drain
• a toilet and basin only, with no shower
• planning the bathroom from the start, not adding it later

Planning permission and building regulations

Planning permission

Adding a bathroom does not by itself mean you need planning permission. What matters is how you use the room. A garden office, studio or gym with a toilet is still “incidental” to the house and can usually be built under permitted development.

Using it as a bedroom or separate home is different. A room with a bathroom that someone sleeps in is treated as living accommodation, and that needs planning permission. Our planning guide covers the size and height limits as well.

Building regulations

New drainage and sanitary fittings are covered by building regulations, even when the room itself is small enough to be exempt. In practice that means the drainage should be done by someone who can show it meets the rules, and the electrics for the shower and water heater need Part P certification. Ask the builder who will deal with building control and what certificates you will get at the end.

Things to ask the builder

When you get quotes for a garden room with a bathroom, ask each builder to put these in writing:

1. Where they will connect to the drains, and how far the run is.
2. Whether drainage is by gravity or a pump.
3. How the water pipe is protected from frost.
4. How hot water is supplied, and the power it needs.
5. Who handles building control and which certificates you get.
6. Whether the bathroom is a fixed price or an estimate that could change once they dig.

Ask for the bathroom as its own line in the quote. That makes it easier to compare builders and to see what you would save without it.

Is it worth it?

If you will spend whole days in the room, a toilet is often the extra that makes it work. It is especially useful for:

• garden offices used every working day
• gyms, where a shower saves walking through the house
• studios used for teaching or by clients
• rooms used by older relatives during the day

If you only use the room for a few hours at a time and the back door is close, the money may be better spent on size, insulation or better doors.

If you’re planning a garden room with a toilet or shower in Sheffield, tell us in the quote form. The builder can then check the drain position on their first visit.