Can You Fit A Toilet Under The Stairs? | Considerations & Advice

If you’re looking at upgrading your home and potentially adding value to your property or even just helping to avoid that morning rush and queue outside the bathroom. You may be considering installing a toilet under the stairs. But is that even possible?

In this post, I’ll answer whether you can have a toilet under the stairs and what you’ll need to consider as well as answer some popular questions about the topic.

Let’s dive in!

Can I have a toilet under my stairs?

Yes! In many homes across the UK, it is possible to add a toilet in the space under your stairs. It is a popular upgrade for many homes built in the 19th and early 20th century before multiple bathrooms became the standard for family-sized homes.

If your stairs seem to take up a lot of floor space on the ground floor, you may have enough room to fit in a toilet and basin.

While this sounds like an easy and affordable means to add an extra bathroom to your home, the average cost for this project starts at around £3,000 and can run up to £15,000.

An ambitious DIY homeowner could tackle the job, but many people will want to hire a contractor for the plumbing and electrical. You may be taking down at least one wall, updating the floor, installing ventilation, and connecting the toilet waste.

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Before you start opening up walls, it is wise to do a little research for your under-stairs toilet project.

  • Is there enough space and access?  The room under the stairs should be about two metres tall, one metre deep, and one and a half metres wide. Consider how the ceiling slopes. Can you sit on a toilet and stand up without bumping your head?

    Also, think about how the door will work. Will it swing out into the hall? A sliding door may be a smarter choice. You are more likely to find enough room going through the side of the stairs. With a little creativity, it is possible to squeeze a toilet in at the back of the stairs.

  • Where is the water supply? Both the toilet and the basin will need at least access to cold water. If you have a kitchen nearby, it is possible to divert water to the new WC. If you have a basement, running new pipes is simple. Concrete floors and masonry walls may present challenges best tackled by a contractor.

  • How will the toilet connect to the main waste? Your home has a main waste that sends all waste to the sewer or septic tank. Your toilet under the stairs will need to connect to that waste. Will the waste go under the floor or do you need a macerator toilet with a pump to send waste to the drain?

  • How will the toilet room be ventilated? Building regulations require that every bathroom have either a window or an extractor fan. A fan must be ducted directly to the outside, so you can’t just cut a hole in the wall between the bathroom and the kitchen. 

  • Lighting the toilet room: Even if you have a window, the new WC will need an overhead light. It can either use a pull chain or a switch mounted outside the room. A lighted mirror will do double duty without causing a tall guest to bump their head on a ceiling-mount light.

  • Flooring and Tiles: It is wise to install at least a waterproof floor in this tiny bathroom. While you are at it, simply tiling the entire space will protect your home from possible water damage.

Benefits Of Having A Toilet Under The Stairs

Extra Facilities: Having that extra toilet during the morning rush can be a life saver. Especially for larger families all trying to get through the bathroom before work and school. It can also come in handy during any family get-togethers or events at home when toilet facilities are in high demand!

Accessibility: If your only other bathroom and toilet are upstairs, having a downstairs toilet can be a very handy and helpful addition for any elderly (or less able) visitors that may struggle to climb the stairs. However, it’s probably not going to be big enough for wheelchair users.

Privacy: Adding an additional toilet downstairs (under the stairs) means that guests won’t have to use your private bathroom. So no need to fear about that dirty pile of clothes on the floor!

Toilet under stairs dimensions
Toilet under stairs dimensions

How To Maximise The Space

Your understairs toilet addition will likely be a study in compact home design. In order to give your guests enough space for comfort, look at short projection or wall-hung toilets with a hidden cistern. These can give you as much as 20 cm for extra knee room compared to traditionally sized toilets.

Also, think about where the basin will fit and how somebody will get around it to reach the toilet. There are corner-mounted, slim, and wall-hung basins that use less space while still providing a good wash.

There are even basins built into the top of some toilets, so you only need enough square metres for a single piece of sanitaryware.

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Do you need planning permission for under-stairs toilets? 

If all you are doing is upgrading the space under your stairs to a toilet room, you won’t need planning permission. However, if you are doing a more major extension or renovation, then you may need a permit. A quick call to your local council will ensure you don’t receive an enforcement notice after you thought you were done.

Do toilets under stairs need extractor fans?

Yes, you will need to have adequate ventilation for your under-stairs toilet room. The extractor fan must be vented directly to the outside and should be wired to the light switch.

If your stairs are located in the middle of the home, you will need to add ducting for the extractor fan. If the stairs are on an outside wall, you can opt to add a small window instead of an extractor fan.

Does a toilet under the stairs add value to a property?

Yes, on average adding just a two-piece cloakroom to any home can increase its value by as much as 5%. With the average home in the UK currently costing around £280,000. You could potentially see its resale value rise by £5k-£14k by simply adding a toilet and small basin under the stairs.

This is based on the assumption that there is a full-sized bathroom elsewhere (preferably upstairs) in the property.

Is a Saniflo toilet under the stairs the best option?

It all depends on the construction of your home. If you have no easy way to run plumbing under the floor or behind the walls for your under-stairs toilet, a Saniflo toilet provides a smart option.

It has a pump and macerator that can actually push waste uphill or over an extended distance to connect with the main waste pipe in your home. This allows you to add a toilet in an otherwise impossible location.

A Saniflo or macerating toilet can cost between £800 and £1400 with installation costs higher than a traditional toilet. But, you won’t be paying to knock down walls or cut into floors. So it may save you thousands for the entire project.

Talk to your builder or plumber about what your best option might be.

What is the minimum size for a toilet room?

The minimum size for a toilet room (or toilet under the stairs) is approximately 70cm wide x 130cm long. However, to make it a more functional and comfortable space, you ideally want your toilet under stairs dimensions to have a little bit of a larger footprint around 80cm x 140cm.

Either way, the door will typically have to open outward or be a sliding (pocket) door in order to fit everything inside and access the room.

Final Thoughts…

There you have it! Everything you need to know if you’re considering having a toilet under the stairs.

It may not be possible for every household and it may be more of a challenge than you initially thought. However, it is completely possible to install a small cloakroom under the stairs and it could bring some great benefits to your home life as well as your property’s resale value.


Michael R

Michael is a KBB designer from the UK. He's been designing and project managing new Kitchen, Bedroom and Bathroom installations for over eight years now, and before that, he was an electrician and part of a KBB fitting team. He created The Bathroom Blueprint in early 2020.