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Adding a toilet or shower to a garden room
A toilet turns a garden room into somewhere you can spend the whole day. It's also the single biggest jump in cost and red tape, so it's worth knowing what's involved before you commit.
The short answer: expect to pay around £3,000 to £8,000 for a toilet, basin and shower with drainage, plus building regulations fees. Drainage is usually the biggest cost.1
What it costs
| Item | Typical cost |
|---|---|
| Connecting to mains drainage | £1,500 to £3,000 |
| Toilet | £500 to £1,500 |
| Basin and pipework | £300 to £800 |
| Shower | £500 to £2,000 |
| Hot water | £500 to £1,500 |
| Building regulations approval | £200 to £500 |
Source: MyBuilder price guide, October 2026.1
Drainage is the deciding factor
Waste needs to flow downhill to a drain, so the distance and fall from the room to your nearest drain decides most of the cost. If the room sits lower than the drain or a long way from it, you may need a pump, which adds cost and something else to maintain. Ask a plumber to look at the drainage route before you fix the room's position.
Approvals
New drainage and plumbing normally need building regulations approval, even when the building itself is exempt. Put the fees in your budget.1
When it tips into needing planning permission
A toilet on its own doesn't usually change the planning position for an office or studio. What matters is use. Once a room is set up for someone to sleep or live in it, with a bedroom, kitchen and bathroom, it starts to look like separate living accommodation, and that needs planning permission.2 If that's your plan, you're really building a granny annexe, and you should talk to your council early.
Questions people ask
Can I put a toilet in my garden room without planning permission?
A toilet alone in an office, gym or studio doesn't usually need planning permission, but it will normally need building regulations approval for the drainage. If the room becomes somewhere to live, it will need permission.2
How much does it cost to add a toilet to a garden room?
Typically £3,000 to £8,000 with drainage, depending on the distance to your nearest drain.1
Related guides
Sources
- MyBuilder, Garden room cost price guide, updated 21 October 2026. UK price ranges for garden rooms, foundations, electrics, plumbing and fees.
- Planning Portal (England), Outbuildings: mini guide. Permitted development limits for outbuildings.