Turn your understairs space into a cloakroom

Turn your understairs space into a cloakroom

Having a toilet downstairs is very convenient and adds value to your property. Let’s make that typical underused space work harder for you and your home. 

Planning and Building Control to turn your understairs space into a cloakroom

This is the most annoying part of home renovations, but it’s important to make sure your house is safe and complies with all the requirements to avoid future problems. 


You will need to check with your Council only if you are planning to add a window on an external wall. This can be especially limiting if you are living in a Conservation area too. Otherwise, internal works like converting your understairs space into a cloakroom don’t require planning consent. 

Who can help you

If you are making further work around the house, your Architect should be able to help you out with the application. Otherwise, you can get a draftsman or an architectural technician to do the drawings for you to submit them directly to the Council. 

Building Control

You will need to submit a Building Control application when you are making changes to the plumbing and ventilation of a space. If you are just replacing fixtures, you don’t need to apply. 

A Building Control application will require a simple drawing of the new cloakroom indicating some dimensions and details of how you are planning to connect the drainage, sanitary water, providing ventilation and lighting. This space will probably have to comply with Part E (soundproofing), Part F (ventilation), Part G (sanitary water), and Part H (drainage) of the Building Regulations. 

Who can help you

If you are making further work around the house, your Architect or Main Contractor should be able to help you out with the application. When you are only making this small change at home you can get a self-certified electrician and plumber. They work following the building regulations and can provide a certificate demonstrating that the works comply.

Will I be able to connect with the drainage system?

The first step is to find out if you have a soil pipe close by. You might have a kitchen or utility next to the staircase or you might have a bathroom right off the landing. Find out where is the vertical pipe that is collecting waste from your sinks, toilets, etc and how far you would be from it the future toilet and wash hand basin. 

If they are rather far, you might still be able to connect to the existing drainage using a stub stack. This is a half-height pipe with a valve that allows air to come into the drainage system to avoid blockages. The first step is always to analyse the existing system, but as a last resort, you could ultimately install a macerating toilet.

Who can help

Since being able to connect to the drainage system is practically the most important thing from a toilet, I would recommend starting with bringing a drainage contractor home to have a visual inspection of your drainage system. A contractor specialised in drainage would be also used to do this type of work and will let you know about your possibilities. Remember to always contact a self-certified contractor to make sure the works will comply with the building regulations. A plumber specialises in the sanitary water income whilst a drainage contractor specialises in waste coming out of the property, so make sure you contact the right contractor.

stub stack in cloakroom
Stub stack system - At Mizen Design & Build

How do I ventilate the cloakroom?

Ventilation is always required in wet areas like bathrooms, utilities, kitchens, etc. You will need to install a mechanical extract fan to extract humidity if you don’t have a window. The fan will need to extract 15l/s and will need to be connected to the exterior through a pipe. If you don’t have space between the floorboards or the ceiling of the adjacent room, you can bring the ceiling down with a soffit and take advantage to introduce new lighting features like downlights or LEDs in that room. You will also need to leave a small gap between the door and the flooring to allow for some air to come in. This is because the extractor fan is constantly taking the air out of the room and you would be out of the air if we only extract air.

What layout works best?

The width of the toilet will be determined by the width of the stairs, so there is not much that you can do about it. Generally, it makes more sense to locate the toilet under the sloping ceiling and the wash hand basin just in front of the door or in the corner. For private reasons, it’s best to have the toilet on a side of the door and face first a wash hand basin. In terms of dimensions, you could take into consideration the following.

  • 1.4m min behind the toilet to allow for a person to seat comfortably.
  • 1.8m in front of the toilet to avoid clashing your head when you approach the toilet.
  • 0.9m minimum from the edge of the toilet to the opposite wall to make sure a person can approach it.
There are always storage corners that could be used, but try to keep it simple. Another important thing to consider is the size of the wash hand basin. You will probably be better off with a hand rinse sink because they are smaller. A floating storage unit or not storage unit at all would be best to keep the place looking as ample as possible. There is also an option combining toilet and wash hand basin that is a really good space saver.
blue and pink cloakroom
These Three Rooms
toilet cloackroom traditional
Big Bathrooms Shop
cloackroom with wall paper
Rachel Havill

What lighting can I install in a cloakroom?

Although pendant lamps are very pretty, it’s best to avoid them in cloakrooms. The ceiling will generally be lower than in the rest of the house and you will want to have the least amount of items interfering in front of you. My suggestion would be to go for downlights or lamps attached to the ceiling or wall.

blue toilet with terrazzo
FizzPop Interiors


Bring a drainage contractor home to have a look at possibilities to connect to the existing drainage. Make sure you use self-certified professionals to advise you about building control and contact the right professional if you also need to apply for planning permission. 

Think carefully about what you are going to do with the ventilation and the rest is only the fun part, the design, and decoration of the space. 

I hope this has been useful, and please let me know if you have any questions writing it down in the comments. 

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